The CPD Book Volume Two 2023

ELECT RICIAN &INSTALL ER

THE BUSINESS MAGAZINE FOR THE ELECTRICAL TRADE

THE C P D B OOK I VOLUME TWO

SECTION 1

8 ‘Codebreaking’ the latest on-site finds from electricians on the job

11 The requirements for the installation of equipment in meter boxes

14 Looking at the relationship between the Electricity at Work Regulations and BS 7671

16 LS0H cable: how does it work and how should you tackle it?

18 The importance of surge protection in complex installations

21 A look at some of the changes that were introduced with the May 2023 Corrigendum

22 What tests should be carried out as part of routine fire alarm maintenance and checks?

25 Overvoltage protection: how does the Corrigendum alter things?

SECTION 2

29 Recommendations around the use of insulation piercing connectors on meter tails

32 The requirements that apply to the design and maintenance of emergency lighting systems

34 ‘Codebreaking’ the latest on-site finds from electricians on the job

36 What does the Open Charge Point Protocol (OCPP) mean for EV installations?

39 Which cable management systems will help avoid corrosion in certain environments?

42 Getting the full details on the May 2023 Corrigendum

44 The implications of voltage imbalance on the electrical supply of an installation

SECTION 3

47 A look at the problems facing designers who may be specifying heavy current using equipment connected to consumer units

50 The considerations that electrical professionals need to make when installing equipment in medical locations

52 Earthing and bonding: understanding their different, but equally important, functions within an installation

54 Advice on the best ways to avoid false alarms

56 Earth electrodes and the relevant code of practice associated with their application

58 ‘Codebreaking’ the latest on-site finds from electricians on the job

60 The importance of providing additional fire protection following the mandated use of AFDDs

SECTION 4

62 Identifying some of the real hidden costs of inefficient cable calculations

64 How to verify the electrical continuity of protective bonding conductors in commercial and/or industrial locations

66 ‘Codebreaking’ the latest on-site finds from electricians on the job

68 How do fire rated downlights work and what is the legislation governing their use?

70 When do you need to use an intended departure?

72 What are inrush currents, who do they cause problems, and how can they be measured?

SECTION 5

75 Key considerations when installing RCDs

78 Addressing some of the common questions around EV charge point installations and maintenance

80 Earthing and bonding: what are the differences?

83 What is interoperability lighting and why is it important?

84 How do you measure the resistance of a cable, and how do you calculate the resistance of a standard 1.5 mm fire alarm cable?

86 ‘Codebreaking’ the latest on-site finds from electricians on the job

88 A look at the safety considerations installers should be aware of when dealing with Li-ion battery energy storage systems (BESSs)

W O R K T H R O U G H E A C H S E C T I O N A N D E A R N 5

C P D C R E D I T s ( o r 5 h o u r s o f l e a r n i n g )

T O WA R D S YO U R P R O F E S S I O N A L R E C O R D !

continuing professional development (CPD) can be broadly defined as any type of learning you undertake which increases your knowledge, understanding and experiences of a subject area or role

To help professionals to better document and prove this process, the CPD Book contains content and articles that have been checked, verified and accredited by a third-party specialist organisation

Collectively, the content within this specially designed publication has been deemed worthy of 5 CPD credits, or 5 hours’ worth of CPD, with each individual section providing 1 credit, or 1 hours’ worth of CPD.

Once this content has been consumed, readers will have the

opportunity to scan a QR code which will provide a bespoke, downloadable certificate that can be used as part of a professional’s ongoing CPD record

DO NOT SCAN THE QR CODE UNLESS YOU HAVE READ ALL OF THE CONTENT WITHIN EACH SECTION!

A large element of CPD involves self-certification and relies on professionals being honest about what they have actually read, consumed and digested A QR code has been placed with the final article in each of the five learning sections within this publication and ONLY once you have read ALL of the articles within each section, should you then scan the code to receive your bespoke certificate

By skipping any of these steps, you’re not just cheating the system, but yourself and your fellow professionals at the same time!

NEW USERS – ACCESS YOUR BESPOKE CPD CERTIFICATE IN FIVE STEPS

1. Read ALL of the content and articles included within the five sections

2. Find the QR code with the last article in each section and scan

3 Enter your email address

4. Fill out your details on the contact form

5. Download your certificate for use as part of your annual CPD record

PREVIOUS USERS – ACCESS YOUR CPD CERTIFICATE IN FOUR STEPS

1. Read ALL of the content and articles included within the five sections

2. Find the QR code with the last article in each section and scan

3. Enter your name and email address.

4. Download your certificate for use as part of your annual CPD record

All certificates are valid for one year from the issue date If you’re having any issues with downloading your certificate or using the system, please email us at: pe@hamerville.co.uk

THE CODEBREAKERS

Unfor tunately, we see these used quite frequently these days. They ’re of ten used instead of Henley blocks or similar termination points to split meter tails for numerous reasons Correc tly named ‘I nsulation Piercing Connec tors’ or ‘Line Taps’, they ’re designed to be used where they ’re at height and out of reach.

Although there are many different manufac turers of this type of connec tor, this manufac turer states clearly that they ’re to be used for specific overhead LV cables and should also be used in conjunc tion with cable suppor t equipment to reduce mechanical stress. The requirements and protec tive measures that can be used on overhead lines and tak ing advantage of out- of-reach caveats differ greatly from those that can be used where terminations can be readily accessed Placed out of reach is a protec tive measure that sk illed persons must control or super vise

understand that its improper fitting has lef t access to live par ts, which is an immediate danger. Anyone in contac t with this – the client or future engineers –could receive a fatal shock

Before we consider that this equipment is not being used as its manufac turer envisaged, we need to

Secondly, we need to look at the need for any terminations in a cable to be suppor ted and taken into an adequate

enclosure Understandably tak ing into an adequate enclosure may not be where this equipment was designed for, as this may not be possible when dealing with overhead lines, however. I n this case, they ’re not being used as the manufac turer designed them for, and so must be taken into an adequate enclosure

Need help with cracking those all-impor tant EICR codes? Ever y month the technical team at NAPIT will be studying your latest ‘Caught on Camera’ photos and offering advice on the next steps, should you find a similar installation. If you want the team at NAPIT to help crack your codes then send your pic tures through to us at:

This is a prime example of why we must ensure that EICRs are carried out and that any elec trical work is under taken by adequately qualified, sk illed and registered persons

M ixing different manufac turers' equipment in one manufac turer ’s enclosure without the main manufac turer ’s consent has long been unacceptable – and for a good reason Different manufac turers design their equipment to operate and discharge gasses etc , in different direc tions When we mix different manufac turers' equipment, there is a danger that those gasses can be discharged onto conduc tive par ts where they aren' t designed, or type tested, to be and can cause a fire or other damage

I n this case, the two manufac turers (Eaton and MEM) merged and are now one entity, or ac t as subsidiaries.

3-phase Eaton MCB fit.

Not only is it now unlikely to be adequately terminated to the busbar, but the MCB’s off/on switch direc tion is also different from the rest of the devices in the DB This could cause confusion in the event of required emergenc y isolation

There are single -phase Eaton devices in the board that appear to be a replacement for possibly unavailable MEM devices and look to fit as they should

Although some manufac turers will allow retrofitting of newer devices in older boards, some do not, and some different ranges of manufac turers' equipment may not be compatible. I f in doubt, always consult the manufac turer to ascer tain if the devices fitted are acceptable

Although they are, in effec t, the same manufac turer, the original MEM DB is clearly older than the newer Eaton MCBs that have been fitted This means that the original DB has been butchered to make a

“Mixing different manufacturers’ equipment in one manufacturer’s enclosure without the main manufacturer’s consent has long been unacceptable – and for a good reason.”

GUIDA NCE ON EQ UIP MENT IN METER BOXES

The experts at NICEIC provide more detail on the installation of equipment in meter boxes.

Electrical equipment associated with the consumer’s electrical installation is increasingly being found within the meter cabinet of domestic and similar premises The space within such cabinets is limited and typically allocated for specific usages by the distributor and energy supplier and therefore, should not be used to house other equipment

If this guidance is ignored and inappropriate equipment is installed within an enclosure, restricting the activities of the distributor or supplier, customers may incur financial penalties to have such equipment relocated This is likely to lead to customer complaints against the contractor originally responsible for the installation and result in reputational damage for the installer

Introduction

Industry

guidance on meter enclosure provision

The Energy Networks Association (ENA) is the body representing energy networks in the UK and Ireland. The ENA provide guidance within Appendix B (Spatial requirements for whole current metering) of its publication Energy Recommendation G87

When an electrical supply is laid on to a domestic or similar premises, the host Distribution Licence Holder will require the provision of a suitable enclosure at the service position to house the intake and metering equipment Although this enclosure is provided with the property, the distributor will specify that only equipment belonging to the distributor and meter operator (MOP) should be installed therein.

Issue 2: 2015 – Guidelines for the Provision of Low Voltage Connections to Multiple Occupancy Buildings (EREC G87) on the minimum provision of space in meter enclosures This is summarised in Fig 1 It should be noted that the arrangement of equipment as laid out in EREC G87 and as shown in Fig 1 is for illustrative purposes only The ENA recognises in its guidance that a “best use of space” approach may be adopted based on particular circumstances and equipment required to be installed

Nevertheless, the guidance also highlights that these minimum space requirements do not allow for the inclusion of any other additional customer equipment

Individual Distribution Network Operators (DNOs) will issue their own guidelines on

the provision of space in meter enclosures as a condition in their “Connection Offer” to customers This guidance, although based on the information given in EREC G87, may vary Typically, the space is divided into four, as shown in Fig 2 However, the guidance on additional customer equipment does not differ from that of EREC G87, as can be seen in Fig 2.

This advice has increased significance because of the smart meter rollout program, as some modern meters and associated equipment can take up more space than the meters they replace Additionally, it is becoming increasingly common for domestic or similar premises to be provided with three-phase intakes to facilitate future developments in the supply of electricity, such as “prosuming” and the introduction of networks operated by Distribution System Operators (DSO) This will inevitably result in more demand for space for equipment at the intake position.

Fig 1 ENA EREC G87 guidance on the installation of whole current metering equipment at the ser vice position

Fig 2 Typical DNO recommendation for space allocation within a meter box enclosure

Installation of electrical equipment in the meter enclosure

Increasingly, contractors are installing equipment other than that directly associated with the supply and metering arrangements in meter enclosures at the service position. Evidence shows (see Fig 3) that installers of electric vehicle charging equipment find external meter enclosures to be a convenient location to install equipment such as joint boxes/connections in the meter tails, isolating switches, and small consumer units

In some cases, carrying out the work in this way may have been encouraged by the property owner or occupant, as it avoids the need to install often aesthetically unpleasing electrical enclosures on the exterior of the property

Implications for the customer

If the DNO or MOP need to attend a domestic or similar premises and encounter equipment other than that used for supply or metering purposes within an approved meter enclosure, this may prevent work activities such as:

● the replacement of lifetime-expired equipment;

● the installation of smart metering equipment;

● the installation of new cut-outs to provide enhanced supply capacity to allow for:

● an extension to the property;

● the connection of embedded generation; or

● the provision of electric vehicle charging equipment or other equipment which increases the maximum demand at the premises.

In such cases, where there is insufficient space within the meter enclosure, the planned replacement or upgrading work cannot proceed until sufficient space is made available therein.

The ENA have issued the following statement:

“While the meter cabinet is the customer’s, it is a space designed for the use of electricity industry apparatus only and no allowance is made for additional equipment. For safety reasons, we would

not recommend that any internal wiring, including a consumer unit, is installed within the cabinet ” Energy Networks Association

Furthermore, this is supported by guidance from the Department for Business, Energy & Industrial Strategy in Section 2.9 of its publication Smart Meter Guidance for Domestic New Builds – Guidance for Developers and Architects, and relevant to all those involved in the specification of metering locations in new-build premises, which is reproduced below:

“External meter boxes/cupboards should only contain equipment required to enable an electricity (or gas) supply to be provided to the premises safely, as defined by relevant regulations.

● Items permitted to be installed within electricity meter boxes/cupboards include: the local isolating device (e.g. main cut-out fuse), the electricity meter and communications hub, and may include a single- or double pole-isolation device (installed between the electricity meter and consumer unit).”

Therefore, where the guidance of the organisations discussed in this article is ignored, preventing any future upgrade work, the customer will be instructed by the DNO/MOP to employ a suitably competent person to remove and relocate

the inappropriate equipment – all at the customer’s expense and potentially incurring reputational damage for the previous installer

Summary

A meter enclosure may be provided at the service position of a premises to allow for the installation of the intake and metering equipment

The space allocation for this enclosure allows for the replacement of lifetime-expired equipment, installation of Smart Meter equipment and for some degree of future supply capacity upgrade

Only intake and metering equipment should be installed in the meter enclosure, as there is no allowance of space for housing additional equipment not associated with those functions

If a DNO or MOP attends the premises to carry out work on their equipment and insufficient space is available within the meter enclosure, work will not be able to proceed The customer will need to organise (at their expense) the removal of unrelated equipment to create the space needed for the work to be carried out

NICEIC strongly recommends that electrical contractors do not install any other equipment within meter enclosures.

Fig 3 Equipment associated with provision of electric vehicle charging points installed within external meter enclosures

EAW R AND B S 7671: C A N O N EHELPT HE OT HER?

In this article, the late Paul Skyrme looks at the relationship between the Electricity at Work Regulations and BS 7671.

This article intends to explain the inter-relationship between standards and legislation, using BS 7671 and the Electricity at Work Regulations as the reference point Firstly, it should remembered that standards are not compulsory They may be considered best or good practice, or even the bare minimum (BS 7671, I’m looking at you), but they’re not mandatory for compliance with the law.

For work being undertaken by electricians in the UK, one of the most important pieces of law is the Electricity At Work Regulations 1989 (as amended), referred to from here forward as EAWR

EAWR applies to all electricians or anyone undertaking electrical works, regardless of where those works are being undertaken – a private home, a shop, a hospital, a railway, or the Houses of Parliament.

If we look at EAWR in a little more detail, we’ll see that some of the requirements will fall under the the designer of the installation, under the remit of the installer, under the remit of the person u the inspection and testing

Even with this quick glance, see that the legislation is far-re hopefully, if we follow BS 7671, meet the requirements of EAWR is this so?

We have the legal requireme EAWR (Legislation), and our me to comply with this when at wo in whatever capacity we work with the installation in BS 7671 (Non-mandatory standard)

BS 7671 even has an introductory note written by His Majesty’s Health and Safety Executive (HSE) suggesting and endorsing the use of BS 7671 to meet the requirements of EAWR

In a nutshell, this gives us a piece of legislation – EAWR – and the means to meet it – BS 7671

If we now consider BS 7671, we will find Appendices in there labelled ‘Normative’ and ‘Informative’. Only one Normative Appendix – Appendix 1 – lists the standards referenced in BS7671

Why are they in there and why is this important?

They are there to illustrate that these standards relate to the products we purchase to complete our electrical installations under BS 7671 This ensures that the products are safe to use and that a product made to these standards

should be safe to use anywhere in the European Economic Area – not just the EU, but slightly further afield.

What does Normative mean?

In this situation, applied to this Appendix, Normative means that the Appendix itself forms part of the requirements for BS 7; that is, to comply with BS 7671, one must comply with the requirements of Appendix 1

Much of what is listed in Appendix 1 are product standards, so the designer, constructor, inspector and tester have little or no control over them. Is that important? Perhaps, perhaps not

If the designer is also specifying equipment, then to comply with BS 7671, the equipment specified must meet the requirements of the product standard listed in Appendix 1

Before you ask, this doesn’t mean the designer needs to start by buying the product standard and then getting their hands dirty to check that the selected product meets the requirements The electing the product to be used nstead satisfy themselves that the s compliant by using the tools in the legislation which facilitate is often known as ‘undertaking ence’

ols are available and how do we m?

s are the CE/UKCA (I will use CE is point forward to mean both CE KCA) marking and the eclarations of Conformity (DoC) Electrical products must be safe to be placed on the market or otherwise made available in the marketplace

This requirement extends not only to items for sale to paying clients but also to any equipment made internally to meet the needs of the business. So, a test adaptor made internally within the company should be CE-marked.

For now, we’ll ignore internally designed and manufactured products and will only consider products selected and purchased on the open market to construct an electrical installation, such as isolators, light fittings, switches etc

How would we check these?

Firstly, we need to get hold of the DoC for the product The structure and content of the DoC are defined in the law This law is the Low Voltage Directive (LVD), as amended, and is transcribed into UK law, mirroring the safety requirements of the LVD, as the Electrical Equipment Safety Regulations (EESR) On the DoC, a requirement is to list the standards used for compliance with the legislation

So, in this case the due diligence called for would be to verify that the product standards listed on the DoC meet those required by the legislation and that this standard is also listed in BS 7671

The product manufacturer is responsible for compliance, following the product standard and completing the DoC. There is, therefore, the possibility of the information being incorrect or misleading on the DoC or that the product will not meet the requirements of the product standard

There’s nothing that the specifier can do concerning this except, perhaps, selecting products from reputable and reliable manufacturers with a good reputation in the supply chain and procuring these items from reliable and reputable sources

In conclusion

The aim of this article has been to provide a brief overview of how a standard (BS 7671) can be used to meet a piece of legislation (EAWR), what a Normative reference in the standard is, and how this Normative reference can be used to assist in ensuring that products selected for use under BS 7671 meet the relevant product legislation (EER) and assist in compliance with the EAWR

Further information and background on this subject can be found at the following links:

● Health and Safety at Work etc. Act 1974 (legislation gov uk)

● The Electricity at Work Regulations 1989 (legislation.gov.uk)

● The Electrical Equipment (Safety) Regulations 2016 (legislation gov uk)

● Directive 2014/35/EU of the European Parliament and of the Council on the harmonisation of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits (europa eu)

● The Electricity at Work Regulations 1989. Guidance on Regulations (hse gov uk)

WHAT IS LS 0H CABL E?

QI find myself working with LS0H cable on a more regular basis these days. Is this going to become the norm, and if so, how shall I tackle it? I find it very difficult to work with.

Use of LS0H (low smoke zero hydrogen) cable is indeed on the rise in the UK. While it isn’t a new product, a heightened awareness of fire safety, coupled with its growing prevalence in the USA, Ireland, and Europe, has seen the fire-safe material come into more common usage in the UK recently

Made from thermoplastic material, LS0H was first developed in 1979 It is an incredibly tough cable jacketing that’s resistant to fire and fumes, and – critically – doesn’t produce smoke when it burns This has a dramatic impact on how it reacts to fire and high temperatures While PVC may be cheaper, it produces a thick, acrid, highly toxic, and corrosive smoke This smoke kills We know that smoke inhalation is a bigger cause of death than fire itself in fire-related emergencies

The Kings Cross Fire in 1987, for example, claimed the lives of 31 people and injured 100 more The fire took hold for several varied reasons It began with a lit match on an escalator, but thick black smoke filling the ticket hall claimed the lives of almost everyone present. In response, cables containing halogen ceased to be used on the London Underground, and awareness and usage of LS0H cables grew

Now, with the legacy of the Grenfell Tower tragedy looming large, we’re seeing a further rise in LS0H cable jacketing In any area where smoke and toxic fumes could pose a risk to life, LS0H should be used. In public buildings and high-density housing in particular, use of LS0H is critical Should a fire take hold, fumes from LS0H cabling will emit less than 0 5% HCL gas, dramatically cutting toxicity What’s more,

a lack of smoke will result in enhanced visibility, enabling easier evacuation

It's also important to distinguish between LS0H and LSF (low smoke and fume) cable LSF is made from a modified PVC compound and emits 15 – 22% HCL gas upon burning. That’s 8 – 13% less than standard PVC. However, toxic fumes and thick black smoke will still pose significant danger to life While is marginally safer than PVC, SF should not be confused with S0H which emits 0 5% HCL gas and therefore does not produce toxic fumes or black smoke Nor does it pose a danger to life.

Cost-cutting measures –such as specifying PVC or LSF cable when LS0H is safer and more appropriate – are rightfully falling out of practise New regulations around the use of LS0H are anticipated But LS0H is more

Brinley Buckley-Roberts, Brand Manager at Carl Kammerling International, answers a common contractor query related to the use of LS0H cable.

Use of LS0H cable in rail applications has increased in recent times

“Critically, LS0H doesn’t produce any smoke when it burns.”

difficult to work with than PVC cable The material is stronger and less flexible than its PVC or LSF counterparts Many electricians have reported challenges in stripping the LS0H, as standard cable strippers fail to meet the strength of the thermoplastic material.

Working with LS0H cable may be more challenging and time-consuming, but choosing this cable over PVC or LSF could save lives Armed with the right tools and equipment, and knowledge of its excellent fire safe credentials, tackling LS0H can and can be straightforward and worthwhile process

WHAT EQUIPMENT IS RECOMMENDED FOR USE WITH LS0H CABLE?

Specialist strippers, made from toughened materials and with multiple blades, should be used when working with LS0H cable Using the correct bracket size for the width of the cable, LS0H cable strippers peel the cable along its length, like a banana skin, allowing for simple stripping.

Due to its tougher nature, LS0H can also be less flexible This can lead to cracking during installation To prevent this, specialist lubricant is recommended to reduce friction Of course, it’s important to also choose non-toxic, non-flammable, and non-corrosive lubricant

CK Tools’ LS0H cable stripper includes two titanium nitrade coated blades and four cable brackets to tackle any size of LS0H cable

GET MORE DETAILS ON C.K’S LS0H CABLE STRIPPER AT: WWW.RDR.LINK/EAT014

A SURGE IN C O MP L E X I TY

What is a complex installation?

When we talk about complex installations, we generally mean those that aren’t simple domestic dwellings or basic commercial installs.

That doesn’t mean that all domestic installations are simple installations, nor does it mean all commercial and industrial installations are complex When an installation becomes more complex, it may have the following:

● Multiple sub-boards

● Sensitive equipment (general)

● Sensitive equipment rooms or Zones (specialist)

● High-value equipment (individual electric vehicle charging)

● High-value equipment (multiple electric vehicle charging systems)

● Data collection and holding systems

● Life safety and support systems

● Emergency egress systems

● Surveillance systems (security)

● Surveillance systems (critical safety)

● Security entrance and exit systems

● Multiple surge inlet threat areas (anything that can import a surge or overvoltage threat to an installation)

● TV aerials and satellite coax

● Overhead telephone lines

● Solar PV array (roof-mounted)

● SolarPVarray(ground-installedPV farm)

● CCTV equipment (generally taken to be those on purpose-built columns, etc )

● Outside lights (generally taken to be lamp posts, etc )

● Electric gates.

This list isn’t exhaustive by any means, but we can see the type of installation that can easily slide from simple to complex, with the emphasis now placed on SMART integration

It’s possible that many future installations could easily fall within the

remit of being classified as complex, especially where SMART applications can have a lower voltage withstand (Uw), with more Category 1 equipment present

Why do we need to look carefully at these installations?

If we take the standard requirement of BS 7671 Regulation 443 4 1 and its three bullet points aside, which are in place for indirect stokes on the incoming supply, we are left with Regulation 443 1 1 This requests that we take into account switching overvoltages where atmospheric protection is not installed

As well as Regulation 443, Regulation 534 4 1 6 requires that we consider not only switching loads but also where overvoltages can be introduced from other services feeding into secondary buildings on a site, or from them if they represent areas of multiple inlet threats

Where atmospheric protection is omitted, it’s prudent to look at protecting against switching damage We need to do this because the magnitude of switching surges tends to be less than those of an atmospheric nature, but they can be just as costly

While atmospheric protection will generally afford switching protection as a side effect, there are issues with this in both complex larger installations and those with multiple surge inlet threat areas.

What are the threats?

It stands to reason that we need to look at switching overvoltages more as an industry. From a magnitude of occurrences perspective, the most damage to sensitive equipment comes from switching overvoltages, not atmospheric These overvoltage switching threats can come from any number of different sources, both internal and external

Examples of internal switching overvoltages are:

● Large motors

● Lifts

● Air Handling Units (AHUs)

● Air conditioners

● Pumps

● Process and/or manufacturing equipment

● Production line evolution operations

● Welding equipment

● Large lighting banks

● Commercial or industrial ovens

● Multiple EV charger systems

● CNC machines

● Autoclaves

● Alternative sources of supply

Again, this list isn’t exhaustive, and the sensitivity of the equipment that needs to be protected may be affected by much smaller overvoltages

External to the installation, where National Grid operations may switch or changeover equipment, this can also affect sensitive equipment within an installation

External switching is harder to predict, pinpoint or prove, so there is a feeling that it could be best practice to look at the consequences at the design stage and discuss with the client what their expectations or risk to their business could be and design accordingly

If a client risk assessment highlights a high cost to their business model from lost

NAPIT’s technical experts look at the importance of surge protection in complex installations.

production, lost data, or damage to equipment, there may well be a need to include switching overvoltage protection within the installation design criteria

What to think about at the design stage

As with all designs, there are a few things we need to consider when specifying surge devices. Firstly, each manufacturer’s device is tuned or manufactured to specific attenuation values

This means we can’t mix and match between manufacturers, as the device protection trail-off zone from one manufacturer may not favour the activation zone of the downstream device of a different manufacturer I mention downstream because, in physically larger installations, the protection afforded by a single device starts to lapse at about 10 metres, in most scenarios, due to resonation or oscillation, causing the overvoltage surge to pick up in magnitude

This reduction in effectiveness means that the designer may need to incorporate multiple devices along a circuit, especially where very sensitive or essential equipment needs to be protected

Where this is impractical due to the length of the circuit, SPDs placed at the load end of the circuit to protect particular equipment types may be prudent and more budget friendly

Although any increase in the magnitude of an overvoltage 10 metres after a surge protective device due to resonance is often associated with high-energy lightning stroke events, they can still be caused by manmade/switching loads, albeit with lesser degrees of magnitude

A lesser degree of magnitude can still cause significant damage to sensitive

electronics and equipment, and the designer needs to understand that manmade/switching overloads are more frequent than atmospheric overvoltages

The accumulation of damage and degradation to both equipment and SPDs over time by manmade or switching overvoltages mustn’t be overlooked or underestimated by the designer.

We also need to reduce overvoltages from multiple surge inlet threat areas Although the supply cable may be protected, surge inlet threat areas can still introduce an atmospheric event that can cause significant damage. For this reason, careful thought also needs to be given to the input and output signal lines of control cabinets or controls to roof mounted plant

Overvoltage protection devices will stop downstream surges from an atmospheric stroke (lightning), but they can’t protect the upstream equipment. This is because the sheer destructive force of an atmospheric stroke, even with lightning protection, will cause some damage What we are looking to do here is reduce the devastation within the installation

We can see this by looking at Fig 1, which shows a more complex installation.

If, for example, there were a lightning stroke on the CCTV equipment, the resultant energy would be directed into the installation and cause massive damage If there were appropriate surge protection here, the rest of the installation would be saved if the overvoltage devices were specified correctly; the CCTV camera, however, would be destroyed

There is no absolute protection from lightning; any Lightning Protection System (LPS) or associated Surge Protective Devices (SPDs) will only mitigate or reduce

the effect of an atmospheric event, which is why the CCTV mentioned earlier would become sacrificed

However, overvoltage devices or SPDs will protect totally against switching overvoltages, as the magnitude is significantly reduced

The only trade-off that the designer needs to understand is that each time a surge device operates, its effectiveness is reduced to the extent that it will need to be replaced when it reaches a pre-designed level This can be via the modular devices often found within consumer units or complete replacement where compact Type 3 devices are used in back boxes for fire alarm panels, etc

What’s available to help with the possible threats?

There are many different types of SPDs on the market, not just for inclusion into the mains voltage side of an installation They are available for coax, data and everything else in between

If in doubt, speak to the manufacturer you are looking to specify before confirming your design or ask them to be involved –they’re more than willing to help.

How to keep up to speed

If you feel that you need more guidance or would like to gain a more in-depth level of design knowledge, NAPIT Training can provide both electrical installation design and surge protection courses. Either would greatly enhance your understanding of two very complex subjects

B S 7671:2018 The cor rigend um explained

Following the announcement from the IET and BSI, that a corrigendum to BS 7671:2018+A2:2022 would come into effect, Jake Green, Head of Technical Engagement at Scolmore Group, provides some more detail on the changes.

Under the auspices of the IET/BSI, JPEL64, the committee responsible for BS 7671, have issued a corrigendum to address issues raised after the publication of Amendment 2 of BS 7671: 2018 These issues fall into three specific areas:

● Protected escape routes – amendment to Regulation 422.2 to clarify the scope of the provision in general installations, and a new provision for medical locations (710 422 2)

● Birthing pools – amendment to Regulation 701 1 removing the reference to birthing pools

● Provision of protection against overvoltage for safety services

Protected escape routes

Regulation 422.2 has been amended to provide clarification on its application The regulation now states:

‘Cables or other electrical equipment shall not be installed in a firefighting lobby, shaft or staircase of a protected escape route ’

The text in bold italics is the amended detail This change enables designers to better understand the scope of application of this requirement. Note 2 to Regulations 422.2 has been similarly amended, however, there are no changes to the guidance given in Appendix 13

Further to this change to Regulation 422 2, a new regulation (710 422 2 201) has been added to Section 710 covering medical locations This new text takes account of the specific concerns of the

health sector and points towards the guidance issued under HTMs (England), SHTMs (Scotland) and WHTMs (Wales)

Birthing pools

Regulation 701 1 in Section 701 (Locations containing a bath or shower) has been amended to remove the reference to birthing pools This change supports the work of designers in the health sector

Protection against transient overvoltages of atmospheric origin

Regulation 443 4 1 now limits the requirement for transient overvoltage protection to two conditions, (serious injury to, or loss of human life, and significant financial or data loss) by removing the reference to ‘safety services’

However, the rest of the regulation remains the same, and protection against transient overvoltages (typically using SPD) should still ‘ … be provided unless the owner of the installation declares it is not required due to any loss or damage being tolerable ’

As a consequence of this change, Table 443 2 has been amended by deleting the references to alarm panels, computers and home electronics

Furthermore, the note attached to Regulation 534.4.1.1 has been amended to remove the example of ‘fire/security alarm systems’

All of these changes became ‘live’ on May 15th 2023

Dr. Zzeus

IN THIS REGULAR COLUMN, ‘DR. ZZEUS’ TOM BROOKES, md of zzeus training and CHAIRMAN OF THE FSA, WILL ANSWER YOUR QUESTIONS RELATED TO FIRE SAFETY COMPLIANCE. THIS COLUMN COVERS INSPECTION PERIODS AND PROCESSES...

We’ve just changed fire alarm service companies to save money in the current climate. When I questioned why the new company was not testing voltages, batteries, and some other checks at the six-monthly service that the old company did, they said the old company were doing too much testing and that what they were currently doing met the standard. Is there a checklist of what should be done?

It sounds very much like the new service provider either does not know the standard or is trying to get away with not completing a service correctly BS 5839-1:2017 Clause 45 3 covers the six-monthly inspections, and 45 4 covers the yearly inspection I have listed the minimum checks that should be carried out at the six-month visit; your provider can do more than this, but not less Changing suppliers entirely based on price can be a wrong move; for a fire alarm company, the most expensive part is the employees’ wages, so cutting the price down often involves the engineer doing less, cutting corners or missing parts of the service

Review the system logbook for recorded faults and ensure appropriate action has been taken.

Visually inspect for any structural or occupancy changes affecting compliance with the standards:

a. Check unobstructed and visible manual call points and any new fire exits that have been created have a manual call point adjacent to exits that

lead to a place of “Ultimate safety”

b. Assess any new partitions or ones that may have been moved within 500 mm of automatic fire detectors

c Ensure no storage encroaches within 300 mm of ceilings

d. Check clear space (500 mm) below automatic fire detectors

e. Evaluate the suitability of existing detectors for changed areas

f. Check additional fire detection and alarm equipment that may be needed for alterations or extensions.

Check false alarm records, note the rate in the past 12 months, and take appropriate action

Measure battery voltage with mains power on, ensuring it aligns with manufacturer recommendations before other tests (without additional load)

Disconnect the standby battery, activate alarms, and verify the power supply output voltage close to the nominal value Simulate full load if necessary (minimum 95% nominal voltage)

Inspect batteries and connections and load test without mains power

Test fire alarm functions of the Control and Indicating Equipment (CIE) using at least one detector or manual call point per circuit Record devices used in the logbook

Confirm the fire alarm signal upon at least one manual call point or fire detector operation

Verify proper operation of CIE controls and visual indicators

Check the automatic transmission facility for alarm signals to an Alarm Receiving Centre, ensuring the correct transmission of each signal type.

Test all ancillary functions of the CIE

Where feasible, check fault indicators and circuits through simulated fault conditions

Test printers for functionality and legibility and ensure sufficient consumables until the next service visit.

Service all radio systems as per the manufacturer's recommendations

Perform additional checks and tests recommended by the manufacturer for the CIE and other system components

Report any remaining defects to premises management, complete the system logbook, and issue an inspection and servicing certificate

DO YOU HAVE A QUESTION YOU'D LIKE ANSWERED?

EMAIL YOUR QUERIES TO: TOM@ZZEUS.ORG.UK

OV ERVOLTA GE PROTEC T ION: THE LATES T UPDATE

Electrium provides a brief overview of one specific update in the Corrigendum: overvoltage protection.

it’s now well documented that the IET has updated certain requirements in Section 443 of BS 7671 Amendment 2 Those requirements relate to providing protection against transient overvoltages of an atmospheric origin or due to switching

The revised requirements of Regulation 443.4.1 are as follows:

Protection against transient over-voltages shall be provided where the consequence caused by the overvoltage could result in:

● Serious injury to, or loss of, human life

● Significant financial or data loss

● And in all other cases protection against transient over-voltages shall be provided unless the owner of the installation declares it’s not required.

Previous references to overvoltages causing the failure of a safety service, as defined in Part 2 has been removed by the revised wording to Regulation 443 4 1

All other cases

Ironically the clearest part of Regulation 443 4 1 is item 3 which says that overvoltage protection is required in all other cases This catch all scenario requires the installer and the installation owner to have a conversation on the basis that overvoltage protection is automatically included in the design, and if after that conversation an owner says “no thanks” then the contractor should record that decision on a departure note and the completion certificate

Owner responsibilities

While Regulation 443 4 1 takes account of circumstances where the owner of the installation could choose to declare that overvoltage protection is not required (which may be because any loss or damage is considered tolerable and the owner is willing to accept all risks of damage to equipment and any consequential losses) the benefits of protection in any modern installation with its plethora of sensitive electronic equipment will far outweigh any up-front SPD costs

“This scenario requires the installer and the installation owner to have a conversation on the basis that overvoltage protection is automatically included in the design...”

Specific situations

Although Regulation 443 4 1 refers to some specific situations it does not provide any guidance as to which types of premises are considered as ones where overvoltage can cause “serious injury to, or loss of, human life”. Nor does it advise which types of installation are susceptible to “significant financial or data loss” from an overvoltage fault Designers and installers must use their own judgement

However, the types of premises that come to mind – hospitals, care homes, banks and financial institutions may well already have the subject covered in their electrical installation specifications

SECTION 1

ENDS!

SCAN THE QR CODE TO CLAIM

YOUR CPD CREDIT FOR THIS SECTION OR VISIT: WWW.RDR.LINK/EAT017

The Wylex single module SPD is fully rated at 100 A and does not need MCB protection It connects directly onto the busbar ( just like an MCB) in way number one It uses fewer cable links than some alternative products and

WYLEX SINGLE MODULE SPD

T HE USE OF INSULAT ION PIERCING CONNECTORS ON MET ER TAILS

It has come to the attention of the NICEIC that some contractors installing EVCPs are using insulation piercing connectors (IPC) in order to provide a branch from the meter tails to supply an EVCP. This article looks into the use of such types of connectors for this purpose and strongly recommends that they’re not used.

When an electrical supply is laid on to domestic or similar premises, the host Distribution License Holder (DLH) will require the provision of a suitable meter cabinet at the service position to house the intake and metering equipment.

Although this meter cabinet is provided with the property, the distributor will specify that only equipment belonging to the distributor and meter operator (MOP) should be installed therein

The space within such cabinets is limited and therefore allocated for specific

usages by the distributor and energy supplier, and therefore should not be used to house other equipment relating to the consumers installation

IPCs are not designed for use on insulated and sheathed meter tails If encountered by Distribution Network Operators (DNOs) or MOPs when attending to carry out work, some will, with the customer’s permission, remove the IPC and remake the connection with a more suitable method In the event that the customer will not allow this replacement work to be carried out, the DNO or MOP may refuse to carry out their planned updating or improvement works.

Concerns relating to the use of insulation piercing connectors in meter cabinets

IPCs are a type of connector in which electrical contact with the conductor is made by metallic protrusions which pierce the insulation of an aerial bundled cable core. The relevant product standard for such connectors is BS EN 50483-4:2009

Test requirements for low voltage aerial bundled cable accessories - Part 4: Connectors

The scope of BS EN 50483-4 states that the standard applies to connectors used for the electrical connection of aerial bundled cables (ABC) only.

A number of concerns have been raised in respect of the use of IPCs to provide a connection to types of cable other than ABC, and in particular meter tails

Effectiveness of connections

When an IPC of the type seen being used in meter cabinets is tightened down onto an XLPE insulated conductor of an ABC, the core behaves like a solid conductor However, when installed on a typical double insulated copper meter tail the individual circular shaped strands of the conductor spread under compression, reducing the effective contact area of the connection while increasing the termination resistance

Where installed in the meter cabinet neither the meter tails nor the IPCs are fixed, which may allow movement in the connection. This could result in heat build-up, which may lead to joint failure

Further, if the IPC is not correctly aligned with the conductor when installed, the IPC will not clamp down as intended, which may also contribute to a poor connection

These factors raise concerns as to whether the requirements of BS 7671 for effectiveness of joints and connections have been met (134 1 4, 134 1 5, 522 8 5 and Section 526)

The combined thickness of the insulation and sheath of a meter tail is noticeably thicker than the insulation on an ABC conductor As a result, it is unlikely that the ‘teeth’ of the connector will engage fully The IPCs are being employed outside of the scope of their product standard, but electrical contractors are not in a position to determine which IPCs might be suitable

for use to provide a connection that is no less safe than using other recognised means of connecting into meter tails, as required by BS 7671 (See regulations 120 3, 133 1 3 and 511 2)

The possibility of poor connections is a particular concern, given the high currents that may be drawn by an EV during certain periods of its charging cycle.

Protection against electric shock

BS 7671 states that a protective measure shall consist of:

● An appropriate combination of a provision for basic protection and an independent provision for fault protection, or

● An enhanced protective provision which provides both basic and fault protection (410 3 2)

Typically, the protective measure employed is automatic disconnection of supply (ADS), in which basic protection is provided by basic insulation, barriers or enclosures and fault protection is provided by protective earthing, protective equipotential bonding and automatic disconnection in the event of a fault (411 1)

However, this protective measure is not typically applied to the meter tails situated before the first fault protective device of the electrical installation (434 3)

More typically, the protective measure of double or reinforced insulation is used for the meter tails, and other equipment between the service fuse and the first protective device of the installation Double or reinforced insulation is a protective measure in which:

● Basic protection is provided by basic insulation and fault protection is provided by supplementary insulation, or

● Basic and fault protection are both provided by reinforced insulation between live parts and accessible parts

Although the meter tails are insulated and

sheathed, so meeting the requirements of regulation 412 2 for basic and fault protection for double insulation (412 2 4 1), the IPC is not When IPCs are used in an aerial application the danger of inadvertent contact is minimal given the mounting height above ground effectively placing them out of reach

However, where IPCs are installed within a meter cabinet they are in a readily accessible enclosure to which it is not possible to prevent unauthorised access As a result, the conditions for protection by double insulation are not met.

Summary

Currently, there are no IPCs designed specifically for use on double insulated meter tails As it is not possible for a contractor to confirm that the use of IPCs in this manner is no less safe than using a recognised means of connecting to the meter tails, such use is a non-compliance with the requirements of BS 7671

Attitudes of Distribution Network Operators (DNOs) or Meter Operators (MOPs) on encountering IPCs used to connect to meter tails may vary

Some will advise the customer of their concerns regarding the use of this means of connection and, with the customer’s permission may remove the IPC and remake the connection using a means recognised as suitable for such use.

In the event that the customer refuses to allow this replacement work to be carried out, the DNO or MOP may issue an Electricity Deficiency Notice and decline to carry out their planned updating or improvement works

In either case, the customer may raise complaints in respect of the original use of IPCs on the meter tails, causing reputational damage for the contractor who installed them initially

As a result, NICEIC strongly recommends that electrical contractors do not use IPCs to provide a branch connection in meter tails.

Fig 1 Constructional differences between typical ABC and meter tail cables

The requirement for emergency lighting in non-domestic premises is laid out in legislation throughout the UK. Here Matt Tighe, Technical Service Manager with ESP, briefly considers the requirements of legislation and the British Standards and Codes of Practice that apply to the design, installation, commissioning and maintenance of emergency lighting systems.

EMERGENCY LIGHT ING IN NON-DOMESTIC P REMISES

Legislation

The Regulatory Reform (Fire Safety) Order 2005 (FSO) in England and Wales, Fire (Scotland) Act 2005, Fire Safety (Scotland) Regulations 2006, Fire and Re s c u e S

O r d e r 2006 and the Fire Safety Regulations (Northern Ireland) 2010 detail a series of legislative requirements for persons having responsibility for occupants of a building

The FSO uses the term ‘responsible person’ and ‘nominated person’ is used in Scotland and Northern Ireland

Under the FSO, the responsible person must take such general fire precautions as will ensure the safety of his employees and those persons who are not employees but who are using his premises (clause 8 FSO)

Amongst other things, clause 14 of the FSO requires that:

● Emergency routes and exits must be indicated by signs

● Emergency routes and exits requiring illumination must be provided with emergency lighting of adequate intensity in the case of failure of their normal lighting

u i r e s t h a t t h e b u i l d i n g i s d e s i g n e d t o i n c l u d e, ‘ a p p r o p r i a t e m e a n s o f e s c a p e i n c a s e o f f i r e ’ S i m i l a r r e q u i r e m e n t s e x i s t i n S c h e d u l e 5 , c l a u s e

2 1 0 o f t h e B u i l d i n g ( S c o t l a n d ) Re g u l a t i o n s Le g i s l a t i o n d e t a i l s t h e r e q u i r e m e n t s f o r e m e r g e n c y e s c a p e l i g h t i n g ; h o w e v e r, i t i s t h e v a r i o u s B r i t i s h St a n d a r d s a n d c o d e s o f p r a c t i c e t h a t p r o v i d e t h e n e c e s s a r y g u i d a n c e o n h o w e m e r g e n c y e s c a p e l i g h t i n g s y s t e m s s h o u l d b e d e s i g n e d a n d i n s t a l l e d

G u i d a n c e

T h e g u i d a n c e a v a i l a b l e f o r t h o s e d e s i g n i n g , i n s t a l l i n g a n d m a i n t a i n i n g e m e r g e n c y l i g h t i n g s y s t e m s i s v a r i e d H o w e v e r, t h e p r i m a r y g u i d a n c e i s f o u n d i n t h r e e r e l a t e d B r i t i s h St a n d a r d s :

● B S 5 2 6 6 - 1 : 2 0 1 6 E m e r g e n c y l i g h t i n g –

Pa r t 1 : C o d e o f p r a c t i c e f o r t h e e m e r g e n c y l i g h t i n g o f p r e m i s e s

● B S E N 5 0 1 7 2 : 2 0 0 4

● Health Technical Memorandum 05-02: Firecode (HTM 05-02)

● Health Technical Memorandum 06-01 –Electrical services: supply and distribution

● LG2: Lighting for healthcare premises (2019) – CIBSE

● LG12: Emergency lighting (2022) – CIBSE

BS 5266-1 – pre-design

BS 5266-1 is the principal code of practice for emergency lighting systems. The scope of BS 5266-1 is threefold:

● To assist occupants to leave a building during an emergency – Escape route lighting

● To help protect occupants if they stay in a building during an emergency –Emergency safety lighting

● To help occupants to continue normal operations in the event of failure of the supply to normal lighting – Standby lighting

Figure 1 in BS 5266-1 highlights the types of emergency lighting systems and the associated activity(ies) It is important that the designer is aware of the specific nature of the emergency lighting system

There are, for example, differences in lighting levels and times associated with each of the arrangements detailed in the table (pictured, right)

Clause 4 of BS 5266-1 makes it clear about the need for consultation between the responsible person, the owner/developer (occupier), the architect, the lighting engineer, the installation contractor, the enforcing authorities, the electricity supplier/distributor, and any other relevant persons at an early stage

The purpose of the consultation stage is to define the way in which the system is intended to operate

Clause 4 of BS 5266-1 further recommends that plans of the premises are available early in the process to assist with the consultation stage Clause 5 1 of BS EN 50172 details the plans should include, escape routes, open areas, high risk task areas, safety equipment (e g fire safety equipment etc ), and details of normal lighting and its control systems

Records of the emergency lighting system must be kept, including the location and type of system components, including luminaires, test devices, and any control power units (clause 4 3 BS 5266-1 and clause 6.1 BS EN 50172).

Conclusion

Legislation requires emergency lighting systems in non-domestic premises The responsibility for such systems falls to the ‘responsible person’.

The guidance issued under British Standards, HTMs and CIBSE give designers, installers, commissioning engineers and maintenance personnel help in ensuring that a suitable and sufficient system can be selected, erected and maintained

ESP provides a design service for emergency lighting systems However, it is important that any designers are part of the early consultation process to align

with the recommendations of BS 5266-1 and other associated standards

ESP can offer a team of dedicated design engineers who are trained and qualified in all relevant British Standards, including BS 5266. They can provide an in-depth solution to any challenges a building offers, through a combination of site visits and the study of site drawings

GET MORE DETAILS ABOUT THE EMERGENCY LIGHTING

SYSTEM DESIGN SERVICE

AVAILABLE FROM ESP BY VISITING: WWW.RDR.LINK/EAU016

THE CODEBREAKERS

Well, what can I say? This is absolutely horrendous and in a special location as well This is exactly the reason the Client should always use a competent and registered electrician.

I can’t pass comment on why the fan doesn’t work; it may be damaged and need replacing, or it may have a circuit fault which has meant there is no longer a live feed to it Both of these things are easy fixes for a competent electrician

I can only guess that the circuit has developed a fault, and the person called to repair it either couldn’t carr y out fault finding or didn’t k now how to I’m going to take the route that they didn’t k now how to on this occasion.

I could say the cable is at risk from premature collapse, but it seems to have beaten me to it! There is some merit, however, for suggesting this could be an entanglement issue for fire safety ser vices entering the building in the event of a fire

By rigging a power feed from a light fitting, using an unsuppor ted cable is ver y dangerous I t won’t take much for the twin and ear th cable to become detached from a terminal securing a conductor, potentially initiating a shock risk scenario. There is a potential for an IP infringement, but we can’t determine that from this photo.

This is a ver y dangerous and foolhardy repair/modification that is only going one way from a coding perspective

Need help with cracking those all-impor tant EICR codes? Ever y month the technical team at NAPIT will be studying your latest ‘Caught on Camera’ photos and offering advice on the next steps, should you find a similar installation. If you want the team at NAPIT to help crack your codes then send your pic tures through to us at: pe@hamer ville.co.uk

STEVE BRENNAN: OVER RECENT MONTHS I’M FINDING MORE AND MORE ‘BANJOS’ BEING EARTHED USING SELF-TAPPERS. I WAS WONDERING IF THIS IS ACCEPTABLE OR IS THERE A PROHIBITIVE REGULATION?

We often consider it wrong when we see something we aren’t used to seeing. Sometimes it is, sometimes it isn’t, and sometimes it ’s a subjective take on a new practice This could well be one of those occasions

The BS 7671 take on this is that connections should be of sound mechanical strength and electrical conductance; Regulation 134 1 4 is the one to look at The use of nut and bolt fixings on SWA ear thing tabs, or ‘banjos’, has long been the go -to method. That said, the type of self-taper used in metal enclosures probably wasn’t around or too prevalent when SWA cables were first used.

This doesn’t make them unusable, but there are some questions you need to ask yourself :

1. Does it afford the same mechanical and conductance proper ties?

2 Does it present a damage risk to other cables?

3 Is it really any less effective?

4. What does the SWA gland manufacturer say?

The first one can be checked by measuring for continuity and possibly an IR test. After that, if we look at the possible damage to other circuits, the cable is distanced quite well from the self-tapper, and to be completely fair, there are just as many sharp edges on some nut and bolt screw threads, so I don’t see that as an issue in this case. Additionally, we can see that the enclosure manufacturer has used something similar to fix the top access panel in place.

Something to consider also is that the self-tapper will dig into the bare metal of the enclosure and may have more effective contact and continuity proper ties, as opposed to the nut and bolt, although both should have some of the enclosure paint removed to ensure good electrical contact.

After all of those things are looked at, we need to see what the SWA gland manufacturer says This can be tricky as there are many, and pinpointing the actual one could prove fruitless

For me, this is an inspector ’s engineering judgement call as to whether this is coded at all, and if it is, it may only be a C3 rising to something more if there is visible damage to a cable, which there doesn’t seem to be here. So, in this case, I wouldn’t code this at all, but I may note on the obser vations that it should be monitored at its next EICR to confirm that the contact sur face is adequate

The A2:2022 18th Edition Codebreakers publication is priced at £22.00 (members) and £24.00 (non-members). It is available in both hard copy and digital versions

* Price is VAT exempt and excludes postage and packaging.

ORDER YOUR COPY OF NAPIT CODEBREAKERS BY VISITING: WWW.RDR.LINK/EAU014

I T ’s ‘OPEN’ SE ASON!

The Open Charge Point Protocol (OCPP) is an application protocol that enables communication between electric vehicle (EV) charge points and a smart back-office management system

Originally invented by Joury de Reuver and Franc Buve, the protocol has since been promoted globally by the Open Charge Alliance and become an industry-wide standard that allows seamless interoperability between the hardware, software, and electrified vehicles In addition to that, it means you can change the charging network without ever having to change the original infrastructure.

Why is OCPP important to the EV industry?

Since the number of drivers making the switch has dramatically increased over the last few years, it is crucial the

charging infrastructure is always accessible and available. Having an OCPP-compliant EV charge point will allow for future advancements and requirements in the industry to ensure an accessible charging experience

As technology evolves and new features or capabilities emerge, the network will be able to complete over-the-air updates and create those changes This ensures scalability and futureproofing of the charging infrastructure, minimising the need for costly replacements or upgrades

What are the overall benefits of OCPP to EV drivers and CPOs?

There are several benefits that both EV drivers and charge point operators can take advantage of due to the standardisation of OCPP Drivers will gain access to a wider charging network and be able to use EV charge points from different manufacturers and service providers This means they will not be tied down to just one manufacturer or service provider and can even choose a preference when it comes to charging at home or in public Communication between the charge point and vehicle

will also ensure drivers benefit from a smooth and reliable charging experience.

Charge point operators will also benefit from the freedom to choose from a range of hardware and software providers Again, this will be futureproofed due to the open protocol having the ability to update as/when new features or regulations are introduced which will maximise the initial investment.

The standardised communication provided by OCPP simplifies the management and control of EV charge points, meaning CPOs can benefit from remotely monitoring every charging activity which will reduce maintenance costs and improve the overall operational efficiency.

What are the benefits of OCPP to installers?

Installers aren’t limited to a certain brand or supplier thanks to OCPPs compatibility This means they can offer customers a wider range of EV charging solutions, increasing profits and customer satisfaction Benefits for installers also include scalability, remote management capabilities, data access and future-proofing These benefits contribute to more efficient installation processes and the ability to build and manage charging infrastructure networks effectively

The team at Sevadis provide more detail on the Open Charge Point Protocol (OCPP), its standardisation and what this means for EV charge point installations.

IT’S A MATERIAL CHOICE

Before you install a cable management system you need to understand where you will install it and make sure that you select the right material to avoid corrosion. In this article Paul Nolan, Projects Director for the Hudson Group, takes a closer look at what factors you should consider.

We’ve all seen rusty or corroded cable management and containment systems due to someone selecting the wrong material But equally there is little point in choosing a more expensive corrosion resistant material if you’re installing the system in an office

And there are a lot of materials and treatments to choose from. So, when would you choose pregalvanised and what about powder coated, stainless steel or GRP? There are dozens of choices that you can make

Clearly the first step is to understand where you will be installing it Thankfully there is guidance and we can refer to EN ISO 12944-2 which classifies corrosion and gives examples of where you may find it (see the table in Fig 1).

The right material for the job

Looking at the table in Fig 1, let’s go through what materials you might use

Where there is a very low corrosivity, or C1, you will most likely be indoors in an office, school, hotel or perhaps a shop Here you would typically choose electro zinc plated or pregalvanised steel

Raising the stakes higher to a low to moderate, or C2 environment, you will be installing product in places such as industrial

premises, sports halls, warehouses or partially covered outdoor areas. Here we would suggest you install a pregalvanised

Fig. 1

steel cable management system

For C3 and moderate corrosivity, think outdoors or in a light industrial area, then you need to go beyond a pregalvanised solution. For these applications you would use hot dip galvanised, CPC or powder coated steel or PVC systems

For seriously corrosive applications where there is a high humidity or significant pollution, such as in chemical plants, dockyards or swimming pools, you will need hot dip galvanised, powder coated steel, stainless steel, PVC or GRP systems This is a C4 environment from the table in Fig 1.

And when the going gets really tough, where there is almost constant condensation and/or high pollution such as you might see in chemical or water treatment plants, heavy industry and dockyards, then you need to install a material that will stand the test of time

Known as a C5I classification you should consider stainless steel, deep galvanised steel or GRP cable management systems for these jobs.

And finally, there are marine environments where high moisture salinity, or salt, will add to the corrosion Here you really do need to use 316L stainless or a GRP system.

Some additional pointers

Corrosion is only one factor to consider when selecting your cable management material We’ve already talked about balancing corrosion resistance against price, but there are some other things that you should think about

In projects where there are a lot of electronics, perhaps in a data centre or where there are lots of computers, you need to know about zinc whiskers. These are very thin zinc strands that form on the underside of galvanised products They grow over time and will eventually break off, causing problems for electronics

Also, not all galvanised products are the same Pregalvanised steel will typically have a coating of between 8 - 20 microns while hot dip galvanised will give a standard coating of between 45 - 65 microns, but this is an average and the product will not be coated equally

For greater protection manufacturers can provide deep galvanised solutions where different carbon steels attract more zinc when dipped to provide an even thicker coating of greater than 160 microns But if you hear the term “double dipping” then take no notice because someone is trying to fool you. Dipping steel a second time will make no difference to the thickness of the coating

Equally not all stainless steels are the same – 316L is more corrosion resistant than 304L The ‘L’ means that it is a low carbon version of the standard stainless so it is more easily weldable, but 316L, which is known as “marine grade”, has more Molybdenum which makes it more

corrosion resistant to chlorides and therefore salty environments

New materials and treatments

Remember also that material science does not stand still – new and better materials and treatments are constantly being developed A good example is a new finish called Magnelis This offers better corrosive resistance than galvanised options, it is self-healing for cut edge protection and is more cost-effective It’s certainly something you should consider in the future

And for really extreme environments many turn to GRP, or glass reinforced polymer, as a go-to material. Even here you need to be aware of what you’re installing since the mechanical properties of this material can vary

Delving deeper there are four main resin types of GRP cable management products which will suit different specific atmospheric environments, but that is a whole new subject

Getting the material right for your next cable management or containment installation is vital if you want to provide a long lasting and cost-effective solution for your customer

There is a huge range of materials available to choose from Remember that if you are in doubt, you can always phone the manufacturer to ask for advice, especially if they offer a wide range of different materials

This article is based on a CPD seminar run by the Hudson Group – ‘Selecting the Correct Environmental Material’

GET MORE DETAILS ON THE RANGE OF CABLE MANAGEMENT SOLUTIONS

AVAILABLE FROM HUDSON GROUP AT: WWW.RDR.LINK/EAU017

PART ING THE FOG

2023 Corrigendum.

On 9th May 2023, IET and BSI announced the release of a Corrigendum to BS 7671:2018+A2:2022 The Corrigendum was published on 15th May 2023 and makes changes to six areas of BS 7671 that came into effect immediately

There is often a Corrigendum issued after BS 7671: Requirements for Electrical Installations, is published in a new edition or amendment.

What is a Corrigendum?

The word is derived from the Latin word corrigere, which means to correct

In this case, with regard to BS 7671, it refers to text or information that should be removed and/or alternative wording that should be added within the next release of the printed or electronic version of BS 7671 This will be the second Corrigendum since the publication of BS 7671:2018 in July 2018 The first Corrigendum was published in December 2018

The Corrigendum is available on the IET website and is free to download, but you’re not permitted to create further electronic copies without permission The reason for this is that the IET is the joint publisher of BS 7671 with BSI BSI is the

National Standards Body for the UK and is the copyright holder of standards emanating from IEC and CENELEC, where BS 7671 has its origins

What are the changes and additions?

The Corrigendum contains corrections to BS 7671:2018+A2:2022, and where appropriate, includes the new text in red Where text has been deleted, strikethroughs are included in red The Corrigendum changes have been brought together in Table 1, which lists each change and addition item and the page number in the current BS 7671 where it occurs A brief description of the content follows the regulation number

When do we have to use the Corrigendum?

It is intended for immediate implementation as of 15th May, and these changes will apply to any new installations designed after this date If you had an installation designed and in progress prior to 15th May, you can continue and certify to that design. However, if you wish to implement any changes, you must comply with BS 7671 and the Corrigendum in order to meet the initial certification requirements

Precautions where a particular risk of fire exists

Regulation 422 2 Protected escape routes (as shown in Fig 1), has the following addition to the wording:

Cables or other electrical equipment shall not be installed in a firefighting lobby, shaft or staircase of a protected escape route unless part of:

(i) An essential fire safety or related safety system

(ii) General needs lighting

(iii) Socket-outlets provided for cleaning or maintenance

NOTE 1: Guidance is provided in Appendix 13

NOTE 2: Generally, this means cables in a firefighting lobby, shaft or staircase of a protected escape route should be limited to lighting and associated accessories, emergency lighting and fire detection and alarm systems, although cables for other safety systems may be necessary

Hospitals may have special requirements as detailed in Section 710

This addition has been introduced to provide clarity where cables are installed, cross or otherwise impact a protected

Frank Bertie, Chief Technical Officer at NAPIT, examines the May

Fig 1: Restrictions to electrical equipment and cables installed inside firefighting lobbies, elevator shafts and stairwells has been introduced in the May 2023 Corrigendum

escape route It will require designers to leave clear areas where cables or equipment have to be excluded unless part of the three bullet points

Protection against transient overvoltages of atmospheric origin or due to switching

Regulation 443 4 1 Transient overvoltages due to the effects of indirect lightning strokes, has the following deletion to the text, not the bullet point, as to do so would impact indents (i) and (ii) which may be referenced elsewhere in BS 7671:

Protection against transient overvoltages shall be provided where the consequence caused by the overvoltage could result in:

(i) Serious injury to, or loss of, human life

(ii) Failure of a safety service, as defined in Part 2 Deleted by BS

7671:2018+A2:2022 Corrigendum (May 2023)

(iii) Significant financial or data loss

For all other cases, protection against transient overvoltages shall be provided unless the owner of the installation declares it is not required due to any loss or damage being tolerable and they accept the risk of damage to equipment and any consequential loss

The reason for the deletion was an unintended consequence, which may have prevented the upgrade of fire detection systems to LD2 specifications in accordance with surge protective device requirements

Although this wording has been removed, bullet (i) can be interpreted as indicating that a failure of a fire detection system to warn those present of a fire can lead to injury or loss of life

Notwithstanding bullet (i) a declaration will be required for all other installations should the owner accept the risk of damage The only area where this will create ambiguity is when the owner, such as a landlord, declares that they accept the risk the tenant would not have any means to be included in this declaration

The removal of examples in Table 443.2 and in Regulation 534.4.1.1 note are mostly

B

186422.2Regulation 422.2 has been amended to clarify the scope of the provision.

2107443.4.1

Indent (ii) of Regulation 443.4.1 has been removed. The term safety service, formerly included in Regulation 443.4.1 (ii), encompassed a wide range of systems. The provision, therefore, had unintended consequences for improvements to fire safety systems within installations.

3108443.6.2Table 443.2 has been amended to remove examples of equipment.

4164534.4.1.1

Note to Regulation 534.4.1.1 has been amended to remove examples of equipment.

5242701.1Regulation 701.1 has been amended to remove the reference to birthing pools.

6279710.422.2.201

A new Regulation, 710.422.2.201, to be inserted after 710.421.1.7, has been included in order to modify requirements in Regulation group 422.2 for protected escape routes in healthcare facilities.

7671

a housekeeping exercise in line with the removal of the wording in bullet (ii)

Locations containing a bath or a shower Regulation 701 1 scope has the following deletion:

The particular requirements of this section apply to the electrical installations in locations containing a fixed bath (bath tub, birthing pool) or shower and to the surrounding zones as described in these regulations This section does not apply to emergency facilities, such as emergency showers, used in industrial areas or laboratories

This has been carried out to alleviate an issue within medical environments where equipment is required to monitor mother and child throughout the birthing process This medical equipment requires socket-outlets, which were installed out of the 3m and subsequently, the 2 5m zone, and extension leads were used to supply power to it

Medical locations

The Corrigendum has introduced a new Regulation 710 422 2 201, which has the following wording:

Within a healthcare facility, cables or other electrical equipment may be installed in a protected escape route, where:

(i) The healthcare facility complies with Health Technical Memoranda (HTM) and healthcare fire safety guidance

(ii) The particulars of the electrical installation within the protected escape route are documented as part of a fire strategy

NOTE: Specific guidance on fire safety for healthcare premises can be found in relevant Health Technical Memoranda as published by the Department of Health/NHS England. There are equivalent guidance documents in other devolved administrations, e g Scotland (SHTM) and Wales (WHTM)

It is intended to provide assistance to healthcare facilities where they have particular difficulties with protected escape routes or moving patients between different departments in an emergency

Conclusion

When a Corrigendum is introduced, it is not a light decision, and is taken after much discussion, debate, and a thorough consideration of the effects such a change will have on the electrical industry

With any printed material, and especially with such a technical document of over 600 pages, there are occasions when minor corrections are required. It is important that any corrections to BS 7671 should be provided to the industry in order to maintain the safety requirements for electrical installations

Table 1: Individually listed Corrigendum changes and locations within BS

VOLTAGE IMBALANCE ON 3-PHASE SUPPLIES

Chauvin-Arnoux UK’s Julian Grant discusses the implications of voltage imbalance on the electrical supply of an installation, why it could be of critical importance, and how to avoid it.

Athree-phase power system is said to be balanced when the phase voltages have the same amplitude and are separated by a phase angle of 120˚ Accordingly, voltage imbalance describes a variation in a power system in which the voltage magnitudes, or the phase angle differences between them, or both, are not equal

Voltage imbalances are caused by big single-phase loads, such as induction furnaces, traction systems, and other large inductive machines, either drawing a current

between one phase and neutral that does not appear on the other two phases, or between two phases such that current is only drawn on two out of the three

Either way this causes the higher loaded phases to experience a greater voltage drop, reducing the voltage on those phases for all the other equipment connected to the same supply

The uneven distribution of lower power, more general, single-phase loads across a 3-phase system can also sometimes be bad enough to cause a slight voltage imbalance. This often occurs over time as an installation,

originally balanced during its construction, has additional circuits and equipment added to it

Getting the balance right

In rarer cases, voltage imbalance can be caused by the unequal degradation or failure of one or more PFC capacitor units in a bank, and temporary voltage imbalances can be produced by a fault on any one of the phases either within the facility or further back up the supply network

Having balanced phase voltages is arguably one of the most important requirements for an industrial installation,

particularly if it contains 3-phase motors Unbalanced voltages at motor terminals can cause a phase current imbalance of up to 10 times the percentage voltage imbalance for a fully loaded motor.

Accordingly, motors operating on imbalanced supplies need to be de-rated with significant reductions in available loading for relatively minor voltage imbalances Imbalances can also require the necessary de-rating of power cables due to increased I2R losses in the cable

According to the IEC, voltage unbalance is defined as the ratio of negative sequence voltage to the positive sequence voltage Basically, the 3-phase voltages can be mathematically expressed as a sum of positive, negative and zero sequence components

Positive sequence voltage creates flux in the direction that the motor is intended to rotate, and negative sequence voltages rotate in the opposite direction This creates flux in the opposite direction, however, since the positive sequence voltages are always much larger when the direction of motor rotation is not affected

The counter rotating negative sequence flux caused by negative sequence voltages creates additional heating in the motor windings that will eventually lead to insulation breakdown and premature motor failure A continuous operation at 10°C above the normal recommended operating temperature can reduce rotating machine

life by a factor of two

IEC 60034-1 imposes a 1% negative phase sequence voltage limit on the supply feeding machines. However, EN 50160 states that imbalances of up to 3% can be expected

Apart from the motors themselves, many solid-state motor controllers and inverters include components that are especially sensitive to voltage imbalances Some will protect themselves and the motor in the event of voltage imbalance and refuse to operate For less sophisticated devices reduced life of Variable Frequency Drive (VFD) front end diodes and bus capacitors are a common result of voltage imbalance

UPS, polyphase converters, and inverter supplies also perform with reduced efficiency in the face of voltage imbalances on the supply, creating unwanted ripple on their DC side and, in many cases, also creating increased harmonic currents on the supply

The case for energy logging

Fortunately, the measurement of voltage and load (current) balance, and therefore the identification of imbalance, is easily achieved using a power and energy logger (PEL) Connected at the incoming supply, the loading across the phases for the whole installation can be monitored over time to see how it might vary during the normal operating day or week

PELs can be quickly moved around the installation, non-intrusively connected, and utilised to measure individual equipment or circuit loads and voltages to achieve balance throughout the installation, and then reconnected to the incoming supply for ongoing monitoring

As well as voltage and load balance this will enable measurement and monitoring of other power quality parameters including power factor and harmonics

There are two obvious precautions or actions to reduce voltage imbalance and its effects

Firstly, use separate circuits for large single-phase loads and connect them as close to the point of the incoming supply as possible This will ensure that the load does not cause a voltage drop on any wiring utilised by other equipment that would subsequently then be subjected to that voltage drop

Secondly, ensure that all single-phase loads, large and small, are balanced evenly across all three phases These two simple steps could save a lot of headaches and expense

SECTION 2 ENDS!

DEMAND OR DIVERSITY?

Calculate or determine? That’s the question

Calculating the maximum demand of an installation’s capacity using diversity, along with taking account of equipment ratings, has always been a dark art There are numerous ways to calculate them; although the only real way is to use a data logger to determine what happens This is not ideal for the designer who is working with a clean sheet, and the installation currently doesn’t exist

As an industry, we’ve always used diversity factors, the most favoured being about 80 years old, so not ideal for today’s modern energy efficiency-driven industry It is, however, a starting point.

So, what is diversity?

Diversity is a factor that we allow in some installation designs, which takes account of the full design load of a circuit not being used all of the time, the sockets on a circuit not being loaded to maximum, or indeed some circuits hardly being used at all, such as a bell transformer for a doorbell

We refer to this holistic approach to determine how much load the installation will actually draw in reality as ‘diversity’

It allows for a much more accurate actual maximum demand than simply adding all of the possible different circuit load currents together, which could well be two to three times larger than the DNO supply cut-out, so not ideal and far from reality

The technical experts at NAPIT look at the problems facing designers who may be specifying heavy current using equipment connected to consumer units.

Calculate or determine maximum demand using diversity

The maximum demand of an installation is often difficult to determine; there is no single answer or way to achieve this

The On-site Solutions publication recommends taking the largest rated circuit and adding 40% of the total of the remaining circuits to give a maximum demand figure

However, this is entirely subjective and can be fine-tuned if the designer knows the likely load characteristics of the installation

Typical installations measured with a data logger, not incorporating EV chargers, can see very low load signatures, often below 25 A, which helps immensely when looking at using diversity to calculate or determine maximum demand

Fig 1: CU Requirement for Rated Diversity Factor

Assembly rating

On top of the maximum demand, we need to look at the rated current of the consumer unit and its assemblies This rated current has the symbol (InA)

InA the rated current of an assembly (consumer unit) is not necessarily the rating shown on the incoming device and is required to be provided on the consumer unit designation label It’s important to understand that when we add supplies to an installation, such as generators and solar systems, these extra incoming supplies need to be taken into account and incorporated into the rated current of the CU

In is the rated current or current setting of the incoming circuit overcurrent protective device, either incorporated within the low voltage switchgear and control gear assembly or upstream of it, and Ig(s) is the rated output current of the generating set or sets; then the rated current of the assembly InA must be equal to, or in excess of, the combined values of In and Ig(s), seen here in the following formula:

Formula: InA ≥ In + Ig(s)

We can see this requirement more clearly in Fig 1.

The total required rating for the CU InA needs to be 116 A In reality, this is likely to be 125 A as this would be the next rating size above 100 A

Rated diversity factor (RDF)

After all of that, we need to look at how we arrange those loads within the CU.

*

When manufacturers give ratings to assemblies, they take into account how much load could be placed on them and how the thermal effects of those loads could alter how those incorporated devices react. W h e r e t h e

charge points

The advice from NAPIT and manufacturers is to spread out high loads in a CU and put spaces or blanks between devices that operate at, or close to, their circuit design currents.

Where less used or lower load circuits are available, such as lighting, alarms, or external lighting, place these between, or next to, higher loaded circuits

This is done because when a device such as an MCB or RCBO runs at its design current, it will start to warm up; if the device next to it in the CU is also loaded to its maximum, the combined heat of the devices will start to affect each other internally

Without adequate cooling, the bi-metal strips, which form part of the overload current protection within the devices, will start to operate These bi-metal strips operate on the build-up of heat, usually from the device running in excess of its load current, but when that heat is added to by a device placed directly next to it, the strip can operate prematurely, as the extra heat causes it to operate as if there was a high current being drawn

This means that with a diversity factor of 0.5, a 32 A MCB/RCBO could only be rated to 16 amps if the devices surrounding it are heavily loaded and its ability to cool adequately is hindered This isn’t new and has been around for a while now; manufacturers put the rated diversity factor (RDF) in place to combat future perceived high continual loads, such as electric vehicle (EV)

Doing this will help mitigate the thermal effects of heat transfer between devices and help higher-loaded devices to cool down naturally by being away from high loads Although we don’t typically see these issues very often, as more EV charge points and other high loads are installed, we could start to see protective devices operating in an unwanted manner.

Conclusion

As both designers and installers, we must resist the temptation to install devices in a CU in a uniform manner We often install the larger ones altogether, followed by the next capacity down and so on; installers need to take account of the possible RDF de-rating of a CU and mix circuits to aid cooling and high load separation

Add to this the input from a solar array or other generators, plus any further complications from a heat pump and/or electric heating, and we can see how complex our domestic installations will become in the very near future

BS EN 61439-2 (typically Switchboards, Panel Boards and Motor Control Centres)

BS EN 61439-3 (typically Consumer Units and Distribution Boards)

Table 1: Values of Rated Diversity Factor (RDF) / assumed loading

INSTALLING EQUIPMENT

IN MEDICA L L OCAT IONS

In medical locations, it is necessary to ensure the safety of patients likely to be subjected to the application of medical electrical equipment. Here, Dale Fisher MIET MIHEEM MSOE, looks at the considerations that professionals need to make when installing equipment in such locations.

Introduction

It’s important to start this article by explaining some of the references that are made throughout:

EBB = Equipotential Bonding Busbar

SEBCP = Supplementary Equipotential Bonding Connection Point

Medical location = a location (area or room), where medical devices with applied parts are used, intended for purposes of diagnosis, treatment including cosmetic treatment, monitoring and care of patients

CPC = circuit protective conductor

Group classifications

Medical locations are divided into Group 0, Group 1, or Group 2.

In medical locations of Group 1 and Group 2, (this is referenced in the (IET and BSI, 2022) BS 7671 Table A710), the resistance of the protective conductors between the earth terminal of any socket-outlet (or fixed equipment) and any exposed-conductive-part and/or extraneous-conductive-part shall be such that the voltages of 25 V AC or 60 V DC are not exceeded, and the measured resistance between the earth terminal of any socket-outlet (or fixed equipment) and an extraneous-conductive-part shall not exceed 0.2 Ω.

What does this mean exactly?

Any point in the location, inclusive of conductive fittings, socket-outlet earth pins, SEVBCPs, all being connected to the EBB, shall have a maximum resistance of 0.2 Ω. Something to consider is that if you

could aim for closer to 0 1 Ω with your design, this will put you in a more comfortable position when commissioning

Also, just be mindful that whilst 0 2 Ω is conforming, readings that are closer to 0 2 Ω should really be looked at because, as mentioned previously, a reading closer to 0 1 Ω than 0 2 Ω is more suitable

Worked example

To provide a bit more clarity to all these figures and words, I will now detail a worked example using the figures given in the On-site Guide Table I1 Appendix I ‘resistance of copper and aluminium conductors’ (IET, 2022) (pictured above)

In my experience, I’ve found that it is better to work backwards when calculating the CPC size, because the limitation is at the end of the CPC circuit which is 0 1 Ω (0 1 being a better figure to design to than 0 2)

Therefore, if we can calculate the CPC from the furthest point to the EBB, then from the EBB to the earth bar (preferably a new dedicated earth bar within the electrical cupboard serving the medical location), then from the earth bar to the main existing earth bar (usually located within the main LV switchroom or electrical intake room), then we can justify our design proposals, and hopefully control the parameters of our earthing system for the medial location.

Consideration needs to be made when sizing the CPC to install between the EBB and the socket outlets for instance, because there is a maximum cable size that the terminals can take. There are many socket manufacturers where the maximum size their socket will take is 6 mm

So, we can use 6 0 mm cable as the first point of call for our cable selection

I calculated a maximum of 30 m from my EBB to my furthest socket outlet or equipotential bonding connection point (whichever is furthest away) The 30 m is mentioned in the starskstrom guide (Starkstrom, 2016) which suggests 30 m for 6 0 mm and 21 m for 4 0 mm earth cable)

It is also worth noting that the 30 m cable would be the installed cable length, and not the direct line of sight between the two points

When deciding which Ohm figure to choose from in table I1, we need to choose the ‘ –’ figure, as the other figures are for use when the ‘protective conductor’ is installed alongside the ‘line conductor’ (multi-core cable for instance)

Using my 6 0 mm figure, you can see that the figure is 3 08 milliohm per meter

I divided the figure in Table I1 by 1,000 (as this is detailed in milliohm, which is 1,000 Ω), as we want to calculate ohms in this instance, not milliohms. Therefore, 3 08 / 1,000 = 0 00308 Ω

I can then multiply this figure by my maximum length of cable (30 m because of the maximum terminal capacity)

0 00308 x 30 = 0.092 Ω

I then had a distance of 30 m from my new earth bar to my EBB.

The size of this cable is personal preference as a starting point (but always better to look at the other sizes) I chose to go with 16 mm Again, using the table I1, I use the figure of 1.15 Ω. 1.15 / 1,000 = 0 00115 Ω

0 00115 multiplied by my length of run (which is 30 m) is 0 00115 x 30 = 0.035 Ω

I then had a distance of 160 m from my main earth bar to my new earth bar within my scheme I chose to go with 35 mm Again, utilising the table I1, I use the figure of 0 524 Ω Therefore, 0 524 / 1,000 = 0 000524 Ω

0 000524 multiplied by my length of run (which is 160 m) is 0 000524 x 160 = 0.084 Ω

If we add all of these figures together, we then get the following result:

0 092 + 0 035 + 0 084 = 0 181 Ω

As you can see, I’ve designed the earthing system for my medical location to produce a reading below the 0.2 Ω.

As with everything I do, there is an element of engineering judgement, aligned with experience, industry legislation, and guidance If something doesn’t feel right, raise your voice and air your concerns

Key references:

* IET (2022) On-Site Guide Institution of Engineering and Technology

* IET and BSI (2022) Requirements for Electrical Installations Institution of Engineering and Technology

* Starkstrom (2016) Technical Guide - For Designers and Specifiers of Medical Facilities.

E ARTHING AND BONDING

It would appear that many people, including some whose work requires involvement with electrical installations, are not aware of the differences between earthing and bonding. This article outlines their different, but equally important, functions within an installation.

in general, virtually all electrical installations will require both earthing and bonding in order to meet the requirements of BS 7671

However, some installations, or parts thereof, may not require bonding where other protective measures have been put in place, and some of the less commonly used methods of protection will require the installation of bonding but not generally earthing As such, an understanding of the purpose of, and the differences between, earthing and bonding is essential

In order to explain the differences between earthing and bonding, it is first necessary to consider touch voltage

What is a touch voltage?

Touch voltage is the voltage present between simultaneously accessible conductive parts; that is, any combination of exposed-conductive-parts and/or extraneous-conductive-parts, or between accessible conductive parts and Earth, under Earth fault conditions

It should be noted that the value of actual (or effective) touch voltage may differ significantly from that of the

calculated (prospective) touch voltage as a result of the difference in impedance of the person, or even livestock, making the contact

In general, the touch voltage limit for installations is taken as 50 V AC or 120 V DC (415 2 2) It should be noted, however, that the touch voltage in medical locations of Group 1 and 2 should not exceed 25 V AC or 60 V DC (710 411 3 2 5 and 710 415 2 2) BS 7671 also contains requirements for measures to limit touch current in locations intended to be accessible to livestock (705.415.2.1 and 740.415.2.1).

Earthing

Earthing is a process that is intended to limit the duration of exposure to touch voltages Disconnection occurs when the relevant protective device, such as a circuit-breaker or fuse, operates under Earth fault conditions, disconnecting the supply to the circuit(s) in question within the time required by BS 7671

Such protective devices would not be able to operate within the required time without adequate earthing arrangements being in place.

Bonding

Bonding, on the other hand – or, more correctly, protective equipotential bonding (411 3 1 2) – is a process that is intended to keep the magnitude of a touch voltage (as described earlier) below the conventional touch voltage limit – that is, the touch voltage which is permitted to be present indefinitely without constituting a danger to persons or livestock

The danger of electric shock due to Earth fault conditions arises from the voltages, which may occur in an installation between:

● exposed-conductive-parts and other exposed-conductive-parts;

● extraneous-conductive-parts and other extraneous-conductive-parts;

● exposed-conductive-parts and extraneous-conductive-parts; and

● exposed-conductive-parts and Earth; or

● extraneous-conductive-parts and Earth

The presence of bonding, while primarily intended to limit the magnitude of touch voltage, will also typically help to reduce the time that such a touch voltage is present. This is because bonding provides

a number of parallel paths, reducing Earth fault loop impedance and hence increasing the fault current This in turn results in the more rapid operation of the relevant protective device.

There are two sub-sets of protective equipotential bonding:

● Main protective bonding; and

● Supplementary bonding

It should be noted that, while earthing and protective equipotential bonding are both constituent parts of fault protection, where the protective measure of automatic disconnection of supply is employed (411 1), supplementary bonding:

● is considered to be an addition that can be used to supplement fault protection; and

● may be applied to all, or part, of an electrical installation, or to a location, or to items of equipment (415 2)

Use of supplementary bonding where automatic disconnection is not feasible

Where it is not feasible for an overcurrent protective device to provide automatic disconnection in the event of a fault, or where the use of an RCD for this purpose is not appropriate, regulation 419 3 calls for the provision of supplementary protective equipotential bonding such that the voltage between simultaneously accessible exposed-conductive-parts and/or extraneous-conductive-parts shall not exceed 50 V AC or 120 V DC.

Earth-free local bonding

Where Earth-free local bonding is employed as a protective measure in an installation controlled by, or under the supervision of, an electrically skilled or instructed person, protective bonding conductors must be installed interconnecting all simultaneously accessible exposed-conductive-parts and extraneous-conductive-parts (418 2 2)

However, there must be no connection between the bonded exposed-conductive-parts and

extraneous-conductive-parts and Earth (418 2 3)

It is essential to the effectiveness of this protective measure that persons entering or leaving the location cannot be exposed to a dangerous potential difference, especially where a conductive floor isolated from Earth is connected to the earth-free bonding (418 2 4)

For this reason, although not called for specifically in BS 7671, measures such as the provision of electrical safety matting complying with an appropriate standard, (such as BS EN 61111: 2009 Live working – electrical insulating matting) are required outside the location.

Summary

Bonding is quite distinct from earthing in its purpose, its general arrangement and in many of the requirements of BS 7671 that it has to satisfy. Earthing is intended to limit the duration of touch voltages, while bonding is intended to limit the difference in potential between two accessible conductive parts (touch voltage)

A by-product of equipotential (main and supplementary) bonding is that, under Earth fault conditions, it may

reduce the duration (not just the magnitude) of the touch voltages in the installation. The reduction in touch voltage duration is related to the additional conductive paths that the bonding provides, which are in parallel with the earthing arrangement of the installation

The parallel paths allow a greater magnitude of Earth fault current to flow, which reduces the time taken for the relevant protective device to automatically disconnect the supply to the faulty circuit and consequently reduces the touch voltage duration

Where Earth-free local bonding is employed as a protective measure, the installation, or part thereof in which this protective measure is employed, must be controlled by, or under the supervision of, an electrically skilled or instructed person This is necessary to ensure that that no changes can be made that would impair the effectiveness of the protective measure

Fig 1 Touch voltage between an exposed-conductive-part and an extraneous-conductive-part

Dr. Zzeus

‘DR. ZZEUS’ TOM BROOKES, md of zzeus training and CHAIRMAN OF THE FSA, ANSWERS YOUR QUESTIONS RELATED TO FIRE SAFETY COMPLIANCE.

Q. We keep getting false alarms in hotel bedrooms, usually caused by steam or deodorants/hairsprays. The fire service is now threatening the hotel with being in special measures. What should we do?

Fire alarms are a crucial component of any building's safety infrastructure, providing early warnings in the event of a fire outbreak and saving lives

However, the issue of false alarms has been a persistent challenge in the UK and around the world

False alarms cause unnecessary panic and disruption and strain emergency services and resources

Recent estimates are that false alarms cost around £1 billion a year

The causes of false alarms can be diverse, ranging from cooking fumes and steam to dust particles and faulty sensors

Such incidents lead to a reduction in trust in fire alarm systems and an overall complacency in responding to alarms, which can have dire consequences when a real fire emergency occurs

How do we ensure that a hotel bedroom has suitable coverage while keeping false alarms to a minimum?

The standard smoke detector looks at smoke particles, but it will often mistake steam and dust as smoke and activate as a fire My first step is to check if the detector is sited suitably away from the bathroom door. Bad positioning regularly causes false alarms

A call-out engineer who is under pressure will often choose to install a heat detector that may cure the false alarm problem but will reduce the effectiveness of detecting a smouldering fire. If someone is sleeping very deeply,

they would most likely succumb to smoke inhalation before the temperature in the room is sufficient to activate a heat detector By installing a heat detector in a hotel bedroom you’re taking the risk that the occupant of the room of fire origin may not survive

In recent years, multi-sensor detectors have emerged as a promising solution to mitigate the problem of false alarms, enhancing the reliability and effectiveness of fire alarm systems

Unlike their single-sensor counterparts, multi-sensor detectors employ a combination of sensing technologies, such as heat, smoke, and Carbon Monoxide detection, to provide a more accurate analysis of the environment

How do multi-sensor detectors work?

These detectors use a multi-pronged approach to analyse the air for signs of fire They’re designed to differentiate between actual fire-related particles and common sources of false alarms like cooking fumes or dust. When a multi-sensor detector senses both an increase in heat and the presence of smoke particles, it’s more likely to trigger an alarm This dual confirmation

mechanism significantly reduces the chances of false alarms caused by non-fire sources

Some may recommend Carbon Monoxide detectors, which would cut down on false alarms from steam etc However, if it were a fast-flaming fire, a CO detector wouldn’t pick it up effectively

Over the last few years, ZZEUS

Training has spent time with Apollo Fire Detectors, understanding how multi-sensor detection works One of my favourites to help eliminate false alarms in hotel bedrooms is Apollo’s Discovery Carbon Monoxide (CO)/heat multi-sensor detector, which provides early warning of fire by detecting the presence of CO or heat, or a combination of both.

We’ve seen this detector in the Apollo test labs, and it effectively reduces false alarms whilst still providing a detection time of 20 seconds in multi-sensor mode

Multi-sensor CO and heat detectors provide a much safer option than a heat-only detector, and will offer early warning of carbon-based smouldering fires; good detection of flaming fires; ideal protection for small-volume sleeping risk areas; and resistance to false alarms caused by steam, dirt, and dust.

Special thanks to Jessica Mann for her help with this article

DO YOU HAVE A QUESTION YOU'D LIKE ANSWERED?

EMAIL YOUR QUERIES TO: TOM@ZZEUS.ORG.UK

Multi-sensor detector being tested in the Apollo test labs

ELEC T RICALEART HING: DO YOU KNOWTHE REQUIREMEN T S?

Jake Green, Head of Technical Engagement at Scolmore Group, takes a look at earth electrodes and the relevant code of practice associated with their application.

BS 7430: 2011+A1:2015 is a code of practice for protective earthing of electrical installations This standard is closely linked to the requirements of BS 7671, where relevant, and both should be considered when dealing with earthing requirements

BS 7430 provides recommendations on meeting the requirements for earthing of electrical installations The three areas include, protective earthing of low voltage installations, the interface between LV and HV substations (11 kV/400 V), and protective earthing and changeover switch arrangements for generators.

Earth electrodes

Earthing of a system (or equipment) requires a physical connection to the general mass of Earth The connection should have resistance such that any means of protection will operate as designed

There are many factors that will impinge upon the resistance of the connection to Earth. These will include the nature and properties of the soil within a location, rainfall, and the nature of the earth electrode For example, light clay soils will have a relatively low resistivity (c 5 Ωm), whilst granite has a resistivity in the region of 1,000 Ωm

The presence of low volumes of rainfall will also have a significant impact on soil resistivity For example, clay soil in

locations having a normal rainfall exceeding 500 mm/year has a typical resistivity in the region of 5 – 20 Ωm, whilst locations having a rainfall of less than 250 mm will have a resistivity range of 10 – 100 Ωm

An earthing system should be of high integrity and robust construction The use of an earthing system using earth electrodes relies on the resilience of the earth electrode(s) for the safe functioning of the protection system within an installation

The types of earth electrode can vary Regulation 542 2 2 of BS 7671 recognises seven permitted types of earth electrode, including earth rods or pipes, tapes or wires, earth plates and the like

The most commonly selected earth electrode is the rod

Application

Earth electrodes are to be (or may need to be) installed for: TT and IT earthing systems, earthed generator sets, to conform to Regulation 411 4 2, swimming pools having a PME earthing facility, agricultural premises, mobile or transportable units, EV charging installations, and prosuming installations

Where earth electrodes are installed, Regulation 542.2.1 requires that the earth electrode can withstand damage and take account of possible increases in resistance due to corrosion The means of connection must be electrically and mechanically sound (526 1) and be accessible for inspection, testing and maintenance (526 3)

Earth electrode resistance

Depending on the requirement of a particular regulation, the resistance of the earth electrode will have a maximum permitted value For example, for a TT earthing system, Regulation 411 5 3 details the conditions that must exist where an RCD is used for fault protection This regulation requires the disconnection time to be limited to:

i.

0.2 s for final circuits (411.3.2.2) or 1 s for distribution circuits (411 3 2 4), and ii RA x IΔn ≤ 50 V

Table 41 5 details the maximum earth fault loop impedances permitted for a range of values of RCDs

However, due to the risks associated with drying and freezing conditions, BS

7430 references a note under Table 41 5 of BS 7671 referencing a value in excess of 200 Ω not being stable

The earth electrode resistance is less a function of the diameter of the electrode and more to do with the depth that the electrode is driven, the ability of the rod to be driven into the ground without damage, and the number of electrodes connected in parallel Clause 9 5 3 in BS 7430 details how the resistance of rod electrodes may be calculated Where rod electrodes are to be paralleled to reduce

the resistance, rods will have to be separated by at least 6 m to gain the maximum benefit (Figure 14a BS 7430) The formulae to determine the resistance of a single electrode and parallel electrodes are detailed in clauses 9.5.3 and 9.5.4 of BS 7430. Clause 9 of BS 7430 details many more methods of connecting electrodes, and reference should be made to this standard

Conclusion

Earth electrodes are a necessary requirement for many parts of BS 7671 BS 7430 details the recommendations needed to ensure earth electrodes are correctly selected and installed.

Unicrimp supplies all the necessary elements for the safe installation of rod type earth electrodes

GET MORE DETAILS ABOUT THE FULL UNICRIMP

PRODUCT RANGE BY VISITING: WWW.RDR.LINK/EAV015

THE CODEBREAKERS

Inappropriate termination of armoured cables is something that seems to be happening more and more, and installers sometimes don' t understand the potential dangers associated with doing it.

Firstly, the use of BS 951 clamps is not acceptable for use on armoured cables in this manner This type of practice will put undue stress on the conductors, which may well damage them.

Secondly, the stripped-back conductors now only have basic insulation; the sheathing that surrounds them is a filler, designed to cushion the basic insulation from the armour strands This filler sheath does not possess the mechanical strength or proper ties required by the manufacturing standard for the cable.

So, in essence, we have two primar y infringements from a BS 7671 perspective, plus the obligator y failure to comply with manufacturers' requirements and installation using good work ing practices

On top of these basic faults, we also have a situation where the cable is unlikely to be suppor ted correctly, and so leading to a strain on the terminations

Need help with cracking those all-impor tant EICR codes? Ever y month the technical team at NAPIT will be studying your latest ‘Caught on Camera’ photos and offering advice on the next steps, should you find a similar installation. If you want the team at NAPIT to help crack your codes then send your pic tures through to us at: pe@hamer ville.co.uk

This is precisely why EICRs should be carried out regularly in domestic proper ties, especially when bought, sold, or rented out. There has been no regard for safe and correct wiring practices here; in fact, there are multiple potentials for serious injur y and/or fire.

BS 1363 socket outlets are designed for use with a back box; a direct fixture to the plasterboard isn’t acceptable.

The spur from the twin and ear th cable is only allowable if carried out correctly ; stripping the sheath back and twisting conductors onto it, as can be seen in one of the photos, is incredibly dangerous and carries a higher risk of fire due to the poor termination strength

How this individual thought bridging out the cpc with a strap wire would solve their circuit protection problems is a myster y Again, we have basic insulation not taken into an adequate enclosure

There are so many things wrong here, and it would warrant removing all of the other socket- outlets and accessories to check if they were in the same condition

The A2:2022 18th Edition Codebreakers publication is priced at £22.00 (members) and £24.00 (non-members). It is available in both hard copy and digital versions

ADDITIONALFIRE PROTECTION

Hager’s Technical Training Manager, Paul Chaffers, discusses the importance of providing additional fire protection, following the mandated use of Arc Fault Detection Devices (AFDD) in the latest Edition to the Wiring Regulations BS 7671:2018+A2:2022.

Way back in 2008 the 17th Edition of the Wiring Regulations was released and contained a new section “532 Devices for the protection against the risk of fire”.

Within that section, there was a mention of devices intended to provide protection from arc faults, but it was buried away in a “note” containing informative guidance Fast forward ten years to the 18th Edition 2018, where AFDDs became “recommended” and it is here that most designers started to really take notice

Recommendations

The issue with any recommendations provided in the Wiring Regulations is knowing when to follow them Some say they’re only informative and therefore can be ignored However, BS 7671 lists guidance on the language used within the Wiring Regulations and defines a recommendation as:

“Expression in the content of a document conveying that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others ”

Furthermore, it states that the implication of a recommendation means you should do it

So, you can see why designers struggle with omitting safety devices when they’re recommended

Mandatory requirement

BS 7671:2018+A2:2022 saw the mandating of AFDDs for the first time for a select amount of installation types The Regulation addresses buildings with a higher risk, concerning the level of difficulty for evacuation in an emergency, and considers the habits and capability of users

Regulation 421 1 7 requires AFDDs to conform to BS EN 62606 and be used on single-phase circuits supplying socket-outlets with a rated current not exceeding 32 A in:

● New builds,

● Rewires,

● Additions and alterations to socket-outlet circuits

● Higher Risk Residential Buildings (HRRB),

● Houses in Multiple Occupation (HMO),

● Purpose-built student accommodation,

● Care homes

For all other premises, AFDDs are recommended for single-phase circuits supplying socket-outlets with a rated current not exceeding 32 A

Installation requirements

Regulation 532.6 requires that where AFDDs are specified they shall be installed at the origin of the circuit This means installations with more than one socket-outlet circuit will require one AFDD per a circuit, as illustrated in Fig 1

It’s clear that AFDDs will be required for any work that involves the installation of new socket-outlets in one of the listed installation types, including:

It should also be noted that AFDDs will need to be specified for any of the four installation types requiring a consumer unit replacement Such additions and alterations are classified as new work and therefore must be designed, erected and verified in accordance with the latest version of BS 7671

Where socket-outlets need replacement for maintenance purposes and the client doesn’t wish to upgrade their circuit protection to include AFDDs, faulty or damaged accessories may be replaced without the addition of an AFDD This is permitted for safety reasons and is deemed acceptable because adding additional cost to maintenance may prevent it from being carried out This only concerns a like-for-like swap of damaged accessories and no other alterations

Fig 1 Example of AFDDs used at the origin of socket-outlet circuits

Increased protection

UK fire statistics report that electrical fires are still unacceptably high. Traditional protective devices that deal with overcurrent, residual current and overvoltage protection reduce the risk and consequence of electrical fire, but none of these can identify an arc fault

See Fig 2 to understand more about levels of protection

AFDDs use microprocessor technology to analyse the waveform of the electricity being used to detect any unusual signatures which would signify a dangerous arc on the circuit Numerous parameters are analysed – including the signature, duration and irregularity of the arc – enabling an algorithm to identify arc faults and to differentiate these from normally occurring arcs

This is essential because every day switching activities produce arcs For example, from switched and contractors, as well as arcs from equipment with motors, such as portable electrical tools, vacuum cleaners and washing machines

From this, we can see that AFDDs are intelligent devices capable of avoiding unwanted operation

Inspection and testing

Electricians encountering AFDDs for the first time will need to understand the inspection and testing requirements for both initial verification and periodic inspection

Fortunately, there are no additional tests to be conducted other than general compliance required by BS 7671 The product standard BS EN 62606 requires AFDDs to have manual or automatic test functions (or both)

The auto test function shall be performed at switch-on and at least every 24 hours Should a malfunction be detected the device shall trip and indicate failure The self-test rate will differ between manufacturers, for example Hager AFDDs self-test once every hour.

Functional testing

1 On the first installation of the device, push the test button

2. Once the test button has been pushed, the device should trip

Because AFDDs are available as standalone devices or AFDDs that incorporate integrated protective devices, particular care to follow manufacturer’s instructions is needed. There are no requirements for test buttons and fault indicators to be standardised

Hager’s RCBO/AFDD combined devices have a blue test button which doubles up as the RCD test button Regulation 514 12 2 requires this to be operated every six months

Insulation Resistance (IR) testing Internal components contain sensitive electronics which are connected to the load side of the device Therefore, caution is needed before applying the 500 V DC IR test, shown in Fig 3

For initial verification, Regulation 643 3 3 requires a 500 V DC test to be applied prior to the connection of any

sensitive equipment that is likely to influence the result of the test or be damaged Following connection of such equipment a further test at 250 V DC shall be applied

There is a “Note” that accompanies the Regulation advising the need to check individual manufacturer’s instructions

For circuits protected by Hager AFDDs they may remain connected to the AFDD during 500 V DC IR testing, providing the following is observed:

● AFDD switch must be in the OFF position,

● AFDD test button must not be pressed

Earth Fault Loop Impedance (Zs) testing If an earth fault loop impedance (Zs) measurement is carried out on a circuit containing an AFDD, it is recommended the low current (non-trip) setting is selected on the test equipment Carrying out this test using the high current method will most likely trip the device, especially for RCBO/AFDD combined devices (see Fig 4)

LEARN MORE ABOUT HAGER’S RANGE OF AFDDS WITH PRO TOOLS AT: WWW.RDR.LINK/EAV017

SECTION 3 ENDS! SCAN THE QR CODE TO CLAIM YOUR CPD CREDIT FOR THIS SECTION OR VISIT: WWW.RDR.LINK/EAV018

Fig 2 Levels of protection

Fig 3 Line to Neutral 500 V DC insulation resistance test

Fig 4 Earth Fault Loop Impedance (Zs) testing

STRIPPING BACK CABLE ENERGYWAS TAGE

Jake Hardcastle, Electrical Design Engineer at Thornley & Lumb Partnership, identifies some of the real hidden costs of inefficient cable calculations.

Designing an energy-efficient electrical installation involves thoughtful consideration of various factors in order to minimise energy consumption and maximise sustainability.

When designing electrical installations, designers should not only design a system that meets the clients’ needs, is cost-effective and is compliant with BS 7671, but also one that is energy efficient

This will commonly be considered through selected luminaires, lighting control, selection of energy efficient appliances etc However, one often overlooked source of energy wastage is inefficient cable sizing, and in a bid to reduce energy costs as much as practically possible, it is crucial to consider this.

While the idea of sizing a cable to reduce energy loss is nothing new, the continuous search for cost reductions, competitive tendering and the rising price of copper mean selecting a larger conductor size doesn’t seem economically attractive and many will often fail to notice the benefits.

Reconsidering cable size

In this article I want to delve into the impact of cable sizing on energy consumption and highlight the advantages gained from selecting a larger conductor size than what is strictly necessary – something that is often not given any consideration

By intentionally selecting a larger conductor size, we can effectively reduce wasted energy We will examine the potential savings and long-term benefits of using a larger cable size

Section 17.4 (Design Considerations) within Appendix 17 of BS 7671 states that: “consideration should be given to limiting the voltage drop within an installation to a level below of that required”

These values can be found in section 6.4 of Appendix 4. By reducing the voltage drop further than what is required, we can reduce the power wasted in the form of heat through a conductor

Selecting a cable size larger than what is the minimum required in order to satisfy BS 7671 can minimize energy wastage, providing a more energy efficient installation, and furthermore, can reduce

the client’s electricity costs

Increasing the cross-sectional area will reduce energy wastage but will increase initial installation costs The designer should determine whether the savings over a certain time period outweigh the initial higher cost

There are, of course, practical restrictions to this such as the size of terminations and the ability to be able to actually terminate the conductor within accessories

Additional recommendations on the energy efficiency of electrical installation design can be found in Appendix 17 of BS 7671:2018, Amendment 2:2022

Calculating energy wastage

To calculate the energy wastage in a cable, two things need to be known:

a) the current in the cable,

b) the resistance of that cable

The resistance values of cables can be found in the IET On-site Guide (Appendix I) and IET Guidance Note 3: Inspection and Testing.

Using an example of a 32 A EV charging point, supplied from a consumer unit 10m away, we can look at three different cable sizes and the comparisons on energy wastage

In order to calculate this, two of the basic principles of electrical engineering are to be used We can use the two following formulas to calculate the power wasted within a cable: V=IR (Ohm’s Law) and P=IV (Power Formula)

As resistance is directly proportional to voltage, i e , if resistance is increased, voltage will increase and therefore the higher the resistance of the cable, the greater the voltage drop will be.

As voltage and power are also directly proportional, the greater the voltage drop in the cable, the greater the power wasted will be As voltage drop increases, the voltage available for the connected appliance decreases, resulting in reduced efficiency and wasted energy Therefore, the voltage drop should be aimed to be as low as practically possible while striking a balance between energy savings and economic considerations

As the current of the circuit and resistance of the cable will be known, but not the voltage drop within the cable, we can substitute V in the formula P=IV for IxR in the Ohm’s law formula This leaves us with P=I2R This will give the power wasted within the conductor

The spreadsheet (pictured above) shows an example of three cable sizes used in this scenario Assuming the minimum conductor size permitted is 4mm2, in this example we can look at two additional larger conductors to be considered in this design

Looking at the spreadsheet it can be seen that 4mm2, 6mm2 and 10mm2 are

the three cable sizes considered Using a Steel Wire Armoured cable in this example and therefore the Circuit Protective Conductors being the same size as the Live conductors, the resistance values (mΩ/m) can then be selected from the On-Site Guide or GN3, as seen in column 2

Total cable resistance

In order to calculate the total cable resistance, this value must be multiplied by the length of the circuit and divided by 1,000 to convert from mΩ’s to Ohms Using the formula I2R, the current demand and resistance can be inputted to give the power wasted in the cable This figure can be divided by 1,000 and multiplied by the hours used per year to give Kwh per year This example is based on the usage of an EV charging point for 4 5 hours per day, five days per week over 50 weeks of the year

This figure can then be multiplied by the Kwh per unit charge which will vary depending on the energy provider and the time of day In this example a figure of 35p per Kwh is used

It can be seen from the table that using a 6mm2 cable opposed to a 4mm2 cable would give an annual saving of £12.34. Using pricing found at the time of writing this article, 3 core 4mm2 Steel Wire Armoured Cable can be purchased for £2 93 a meter and 6mm2 for £4 08, meaning 10m would cost £29 30 and £40.80 respectively. This means the payback period for using 6mm2 compared to 4mm2 would be a little under one year and you would see a saving in subsequent years

Using 10mm2 cable gives a further saving of £10 08 compared to 6mm2 cable and a total saving per year of £22.42 compared with 4mm2 cable. The cost of

10mm2 3 core Steel Wire Armoured is £6.52 per meter, totaling £66.20 for 10m, £25.40 more than 6mm2 or £36.90 more than 4mm2

The payback period for the 10mm2 cable compared to using 4mm2 cable would be approximately 1 64 years:

Payback Period = Initial Cost / Annual Savings = £36 90 / £22 42 = 1.64 years

It can be concluded that the payback period, even for the 10mm2 option, is relatively short considering how long something such as an EV charger will be in service for.

If the client was to have ownership of this installation for a long period of time it would be worth paying the additional installation costs for the savings that will follow each year, as well as the reduced power wasted and subsequent energy-efficient installation.

Never underestimate cable sizing

By selecting a larger cable with a lower resistance, energy efficiency can be significantly improved As well as increasing cost-effectiveness and reducing electricity bills, this contributes to a greener, more sustainable planet

In pursuit of the most energy-efficient electrical design, the importance of cable sizing should not be underestimated This example shows the impact of cable selection on energy consumption and while this shows the potential savings of only one circuit, consider very large homes with a hot tub, sauna, multiple EV chargers etc –the savings could be significant

If we then translate that to an industrial environment, the benefits could be even greater.

PROTEC TIVE EQUIP OTENTIA L BONDING

This article from the experts at NICEIC discusses the purpose of carrying out protective equipotential bonding in commercial and/or industrial type properties, and how to verify the electrical continuity of protective bonding conductors in such a location.

Introduction

The majority of electrical installations typically use Automatic Disconnection of Supply (ADS) as the protective measure for protection against electric shock In this article, the requirements of BS 7671 for protective equipotential bonding where ADS is used are considered ADS is a protective measure in which:

● basic protection is provided by basic insulation of live parts or by barriers or enclosures, in accordance with Section 416; and

● fault protection is provided by protective earthing, protective equipotential bonding and ADS in the event of a fault, in accordance with regulation Groups 411.3 to 411.6 (411.1 refers).

Where it is not feasible for an overcurrent protective device (OCPD) to provide the necessary disconnection time in accordance with regulation 411 3 2, or the

use of an RCD for such purpose is not appropriate, reference should be made to Section 419 (411 3 2 5)

Purpose of main protective bonding

In the event of an earth fault (a fault between a line conductor and an exposed-conductive-part or a protective conductor), a dangerous voltage – or more correctly, potential difference – can occur between simultaneously accessible exposed-conductive-parts and extraneous-conductive-parts in the installation, as shown in Fig 1

The primary purpose of main protective bonding is to limit the magnitude of any potentially hazardous touch voltages that may appear on exposed and/or extraneous-conductive metalwork within an equipotential zone with exposed-conductive-parts

Requirements for protective bonding

In each consumer’s installation within a building, main protective bonding

conductors complying with Chapter 54 of BS 7671 are required to connect any extraneous-conductive-parts, which are liable to introduce a dangerous potential difference, to the MET in accordance with regulation 411.3.1.2.

Extraneous-conductive-parts may be considered as conductive parts which do not form part of the electrical installation but may inherently introduce a potential, generally Earth potential Regulation 411 3 1 2 lists examples of items that can be extraneous-conductive-parts.

The note to 411 3 1 2 states that where non-metallic services, such as polyethylene gas or water pipes, enter a building and are then connected to metallic pipes within the building, as they are unlikely to be extraneous-conductiveparts there is no requirement to provide protective equipotential bonding

Regulation 411 3 1 2 also requires that the connection of a lightning protection system to the main bonding shall be in accordance with BS EN 62305 – Protection against

Fig 1 Potential touch voltage between motor starter and steelwork having no protective bonding

Fig 2 Structural steelwork ser ving as a protective bonding conductor

lightning The regulation further states that main bonding conductors shall be connected to the metallic sheath of any communications cable at the premises, provided that the consent of the owner or operator of the cable has been obtained Where consent is not granted, such details should be recorded on the appropriate electrical certification.

Commercial or industrial installations

As mentioned previously, it is a requirement for all extraneous-conductive-parts such as exposed structural steelwork, to be connected to the MET However, what designers and installers may not appreciate is that, in many cases, the structural steelwork can be utilised as a protective bonding conductor, as shown in Fig 2 (543 2 1 (vii))

Where the steel structural framework of a building is to be used as a protective conductor, regulation 543.2.6 requires the following conditions to be met:

(i) its electrical continuity can be assured for the life of the installation;

(ii) the cross-sectional area (csa) of the steelwork is not less than the minimum csa given by the application of regulation 543 1 1 whether:

● calculated in accordance with regulation 543 1 3; or

● selected in accordance with regulation 543 1 4;

(iii) unless compensatory measures are provided, precautions shall be taken against its removal; and

(iv) it has been considered for such a use and, if necessary, suitably adapted

Using the steelwork as a protective bonding conductor provides many benefits, not least that less cable is needed, particularly in larger installations, and that the steelwork provides a more convenient and efficient method of maintaining continuity as the steelwork is unlikely be removed

The connection from the accessory to the steelwork must be electrically and mechanically secure for the duration of the installation (526 1) Where a bonding connection is to be made, it is necessary to obtain prior permission before drilling holes arbitrarily An alternative method is to have a connection plate (as shown in Fig 3) welded to the structure. Other methods of making a secure connection are not precluded

Verification of electrical continuity

As with all protective bonding conductors, unless it is clearly visible throughout its full length and it can be assured the connections are electrically and mechanically secure, it will be necessary to perform continuity testing (643 2 1(i)) Such testing ensures that all protective bonding conductors, where fitted, are not only continuous but provide a sufficiently low ohmic value

Any extraneous-conductive-part without an effective connection to Earth will not provide an equipotential zone with any simultaneously accessible exposed-conductive-parts, which may lead to a risk of electric shock in the event of an earth fault

The test method typically used is the long lead (wandering lead) method, as shown in Fig 4

Before using a long lead, it should be

remembered to null the test leads or make a note of their resistance before carrying out the test

Having temporarily disconnected the main protective bonding conductor from the MET, the leads of the instrument should be attached, as shown in Fig 4 Note that where structural steelwork is used, it will be difficult to isolate any potential parallel paths

Where significant differences are observed in the resistance readings between simultaneously accessible extraneous-conductive-parts and exposed-conductive-parts, it may be necessary to install supplementary bonding – for example, as shown previously in Fig 1, between the metal cased motor starter and the structural steelwork

Note: It should be remembered to reconnect the main protective bonding conductor to the MET after completing the test

Summary

The primary purpose of main protective bonding is to minimise the magnitude of any touch voltages

Where the building structure consists of substantial steelwork, regulation 543.2.1 (vii) permits its use as a protective bonding conductor

As part of the verification process for ensuring continuity of any protective bonding conductor, there is no difference in the testing procedure where the structural steelwork has been used in preference to the use of individual copper cables

Fig 3 Means of connecting a protective bonding conductor to the structural steelwork

Fig 4 Verifying the electrical continuity of protective bonding conductors

THE CODEBREAKERS

CHARLOT TE ROBINSON: THIS WAS THE GLAND FOR THE PV SUPPLY IN AN INDUSTRIAL UNIT NOT ONLY DOES IT LOOK LIKE THE GLAND WAS MADE OFF WITH THE INSTALLER’S TEE TH, BUT THE BEDDING DOESN’ T EVEN MAKE IT TO THE GLAND AND WHAT ’S GOING ON WITH THE LOCK NUT?

With the advent of high fossil fuel prices and the demand for zero - emission elec tric vehicles, solar PV in conjunc tion with batter y storage will most likely star t to grow exponentially

The problem with that, as with EV and any other installation, is that it has to be done properly to be safe

As we can’t see what else is going on here, I’ll just confine the coding to the SWA gland.

First off, the armouring isn’t anchored adequately by the gland nut, some of the strands are ac tually inside, contac ting the single insulated conduc tors, and some are on the outside I t ’s likely that the armour isn’t adequately held and lacks mechanical strength

I can’t confirm if the armour is connec ted to the cpc, at the other end, by a banjo hidden from view or by contac t with the metal enclosure, so I won’t comment on it and assume it ’s taken care of What we can assume, though, is that there is an issue with the mechanical strength of the joint – the joint in this case being the SWA strands, meeting the SWA gland.

Single insulation must be taken inside an adequate enclosure; the surrounding armour strands are not considered to be an adequate enclosure Cutting the filler, or bedding material, too shor t shows a lack of experience or poor sk ills, which has now led to a potentially dangerous install

As for the lock nut, without seeing the install first hand, I’m confident the wrong size hole saw, or k nock out, has been used, and the gland didn’t sit properly I t ’s likely the lock nut is being used to bridge the gap made by the oversized hole saw I t ’s not ideal, but I think it would be unfair to code it unless there were signs it compromised the installation safety in some way

Although an excessive amount of the black PVC casing is stripped back , I’d hardly see that as a big problem

This is generally a poor excuse for an installation technique, as mak ing off SWA glands is bread and butter stuff Hopefully this will be an easy fix for someone carr ying out the remedial work

Need help with cracking those all-impor tant EICR codes? Ever y month the technical team at NAPIT will be studying your latest ‘Caught on Camera’ photos and offering advice on the next steps, should you find a similar installation. If you want the team at NAPIT to help crack your codes then send your pic tures through to us at: pe@hamer ville.co.uk

JMN ELECTRICAL: THIS WAS FOUND ON A RECENT EICR…!

Wow – what can I say about dealing with this one?

We often joke about using bell wire or accuse poorly trained or untrained people of such practices, but don' t actually see it ver y often

Not only has the installer wired an electric shower using a loudspeaker cable, they' ve also used a junction box to extend the supply from a piece of 3- core flex I can only guess at the size of the flex, which is likely to be 1 5 mm2 at best, at worst 0 75 mm2 To add a little more insult, there is no cpc as the speaker cable is 2- core, so the cpc is not extended past the junction box

The speaker cable is also single insulated; LV AC cables in excess of 50 V that are single insulated need to be in an enclosure or conduit Another question is the temperature range of the speaker cable insulation, which may not be acceptable

training I can only hope this was a home DIYer The thought that there was, or is, an individual at large carr ying out this k ind of installation quality is frightening I t just shows why we need to be more proactive as an industr y and drive EICRs on all proper ties more frequently

Although I can' t confirm it, I'm fairly confident that the conductors are undersized for the OCPD protecting them! I'm also assuming there is an OCPD, to be fair, but given the state of what we can see, I wouldn' t count on it

This is a foolhardy and unbelievably dangerous installation. The risk of fire due to conductor overheating and the potential for electric shock are incredibly high.

I don' t think that this was under taken by someone with even a minute amount of electrical

The A2:2022 18th Edition Codebreakers publication is priced at £22.00 (members) and £24.00 (non-members). It is available in both hard copy and digital versions * Price is VAT exempt and excludes postage and packaging.

A GUIDE TO FIRE RATED DOWNLIGHTS

This article, based on a seminar by ROBUS, looks at how fire rated downlights work and explains more about the legislation governing their use.

Also known as can lighting or recessed lighting, you’ve most likely received requests for downlights for a range of commercial and residential spaces due to their versatile, sleek design But if you need to install downlights in a ceiling, what are you going to have to do first? The answer is, you’ll have to create an opening in that ceiling! This is why fire rated downlights were invented

Why do you need fire rated downlights?

Imagine a plasterboard ceiling; perhaps there is one above your head right now. This ceiling helps slow the spread of fires because it works as a barrier In multi-storey buildings, where people reside on different levels, the ceiling below them must be fire protective in accordance with fire safety building regulations Once an opening is made in the ceiling, this barrier is compromised –

think of water running down your bathtub’s drain, but the water is actually fire! Fire rated downlights are designed to combat this issue with an intumescent seal.

The lifesaving intumescent seal

Intumescent material does not burn immediately on exposure to heat but usually expands in volume while decreasing in density Effectively, it fills the opening in the ceiling, restoring its fire resistance Intumescent seals can be made from a range of synthetic polymers and resin binders, such as silicone or epoxy.

Visually, there are only slight differences between these downlights; but these differences are crucial Once swollen, the intumescent seal blocks the spread of fire for a pre-determined period of time This delay gives the building users time to escape to safety while also protecting the property

D fire protection

Fire rated downlights are not a one-size-fits-all solution They receive ratings based on two factors: a) how long they can resist fires, and b) the specific type of ceiling they can be placed in To restore the integrity of the punctured ceiling, you must install a fire rated downlight that meets the fire protection requirements of that ceiling

Fire resistance is determined by the size of the dwelling

Downlights being installed on the top floor of a dwelling with no living space above technically do not require a fire rating However, to stop the spread of fire

This

through the attic space from one property to another, it is recommended that a fire rated product be installed

I-Joist rated downlights

The I-Joist offers an advanced structural alternative to the traditional solid timber approach; however, greater fire safety precautions are required compared to those for solid timber Even if a downlight conforms to the original fire endurance standards, this doesn't necessarily imply its adherence to I-Joist compatibility for your specific project.

Choosing your fire rated downlight

How do downlights earn their fire-rating?

Trial by fire is the answer! The process involves a ceiling subjected to fire that exceeds 600˚C (you may recall the TV show Brainiac: Science Abuse at this point) This test fails if the roof caves before the time period expected. If, during a 30-minute test, the ceiling collapses in 40 minutes, the fixture will pass the test If it crumbles in 20 minutes, it’s a failure

Always check the technical specifications to ensure it is designed to meet the fire protection required At ROBUS we describe a fire rated downlight as being “Designed and tested to retain the integrity of 30, 60 and

90-minute fire rated ceilings – compliant with Building Regulations Parts B, C and E” and that it is “Tested for use with I-Joists & Metal Web Joists”

Warning: never assume that a product labelled as 'fire rated' will meet the specific specifications you need. While a supplier might offer a test report to confirm the product's fire rating, it could be rated for only 30 minutes, for example

What are the building regulations for downlights?

When it comes to fire safety in buildings, Part B of the Building Regulations is the

go-to This covers a variety of topics such as installation rules, building code compliance, and regular inspection and care It is important to have qualified professionals (that’s you) install fire rated downlights in accordance with manufacturer guidelines and fire safety regulations

These regulations require specific flame-retardant standards, ranging from 30 to 120 minutes Always use approved models for your specific location Regular checks and upkeep are necessary to maintain fire safety However, it’s worth noting that changing lamps can be done as a DIY project, and surface-mounted downlights do not require a fire rating as they do not form part of the ceiling structure

Summary

Fire rated downlights gracefully bridge the gap between aesthetics and safety, catering to various ceiling types and fire resistance needs. While adhering to regulations is essential, they're more than just regulatory compliance; they're a testament to smart design meeting life-saving functionality

BROWSE THE LATEST ROBUS LIGHTING CATALOGUE AT: WWW.RDR.LINK/EAW021

Frank Bertie, Chief Technical Officer at NAPIT,

explains when to use an intended departure.

BREAKING THE RUL ES

When we look at a completed electrical installation or minor works electrical installation certificate, there are several areas where the information may be incorrectly recorded One of the most common errors is where the ‘departure’ fields have been completed and have details recorded

Even though the information regarding departures was updated with the introduction of BS 7671:2018 edition, and a minor change under Amendment 2, there still seems to be confusion as to what a departure from the requirements of BS 7671 is

For some reason, the term ‘departure’ is often regarded as either a ‘defect’, ‘omission’ or a ‘non-compliance’

Therefore, a ‘departure’ appears to have different meanings to those completing electrical documentation.

Previously, the lack of a definition in Part 2 of BS 7671 created a great deal of confusion as the term ‘departure’ is mentioned a number of times in BS 7671 Although departure is now included, as is non-compliance, ‘defect’ and ‘omission’ still remain undefined. The difficulty regarding departures is further compounded by the lack of published guidance

So, what is a ‘departure’?

The term, ‘departure’ is used within BS 7671 in Chapter 12 Regulation 120.3 where it is called an ‘intended departure’ and refers to ‘these parts’ Any ‘intended departure’ is the consideration of not following any of the technical requirements related to Chapter 13 Fundamental Principles and Parts 3-8, so it has to be a conscious decision taken after full and in-depth consideration

An intended departure from BS 7671 is where the designer of the electrical installation, after due care and attention, decides to use a method of installation which is not recognised in BS 7671.

The best example of this is where there is a new material or a new invention planning to be utilised as part of the electrical installation, ‘where the use of a new material or invention leads to departures from the Regulations’

Therefore, it is the designer’s responsibility to confirm that the ‘intended

departure’ results in the degree of safety of the installation which shall not be less than that obtained by compliance with the Regulations and shall be noted on the electrical installation certification specified in Part 6

What is the definition of a ‘departure’?

This definition was introduced in Part 2 of BS 7671:2018, where the wording states:

‘Deliberate decision not to comply fully with the requirements of BS 7671, for which the designer must declare that the resultant degree of safety is not less than that achievable by full compliance’

By clearly laying out the expectations of the departure, the designer should not be taking this lightly

To meet the full compliance of BS 7671, considerable details would need to be provided, so that those installing, inspecting and testing the electrical installation are also aware of the implications of such a decision.

Additionally, the client would have to be informed of such an undertaking prior to including it as a departure as they would be within their rights to reject such a process unless it can be confirmed that electrical safety is not less than fully compliant.

Incorrect recording of departures

Even though the definition provides a clear description of what this is, there’s still instances in which the items on electrical certification are incorrectly recorded.

These have been included when an addition or alteration has been carried out, and items that have been recorded under ‘Comments on existing installation’ in Electrical Installation Certificates (EIC) or Minor Electrical Installation Work Certificates (MEIWC) are sometimes recorded as ‘departures’ when they are not actually departures

Even when periodic inspection and testing is carried out, items are sometimes referred to as ‘departures’ when they are ‘observations’, which need to be noted in Section K, Observations of the Electrical Installation Condition Report (EICR) and given a Classification Code –C1, C2, FI or C3 The following are some examples of items incorrectly listed as departures where:

● Switch lines have not been identified as line conductors at the terminations

● Wiring colours have two versions of BS 7671

● BS 3871 circuit-breakers are installed

● Voltage operated ELCBs are in use within TT systems, which have been proven to operate correctly

● BS 3036 rewireable fuses are in use

Discussions on the appropriate code to assign to some of these observations on an EICR can be had, but we have to agree that none of them is an ‘intended departure’ as referred to in Regulation 120 3

Departures that may give rise to danger

It is possible that a designer, who has included a departure from BS 7671 into their design, may have incorrectly assumed that it is no less safe than would be achieved by compliance with BS 7671; it may even give rise to danger

As per the changes under BS 7671:2018, previous Regulation 621 2 (iv) listed departures that may give rise to danger was part of the reason for the changes and definitions for ‘departure’. Regulation 621.2 was replaced with Regulation 651 2, and bullet (vi) now refers to non-compliances which give rise to danger

The term ‘non-compliance’ was also reintroduced into the definitions to clarify the misunderstanding regarding departures.

Under installations designed by others, the installers have a duty to highlight to the designer any aspects of the design which they consider conflicting with BS 7671 and which they believe to be unsafe There is no legal defence against creating an unsafe installation based on poor and non-compliant instructions

When carrying out inspection and testing on an existing installation and recording the information on an EICR, there is no provision for recording ‘intended departures’ If any such departures have been recorded on the original EIC or MEIWC, the inspector should have this information to enable them to determine if these would be classed as a non-compliance which could give rise to danger, or be recorded for information in either Section K, Observations, or on a separate sheet appended to the EICR, or both

‘Intended departures’ must be recorded In accordance with Regulations 120.3, 133 1 3 and Regulation 133 5, details of any intended departures are required to be recorded on the Electrical Installation Certificate (EIC) (see Fig 1), or Minor Electrical Installation Works Certificate (MEIWC), as an example of where to list the intended departures.

In each of its three signature sections for design, construction and inspecting and testing, the EIC makes provision for recording departures for Regulations 120 3 and 133 5, with the designer solely responsible for specifying new materials under Regulation 133.1.3.

In larger installations, there may be mutual responsibility for the design

In domestic and similar installations, where an electrician often takes on all three responsibilities and a single signature EIC may be used, the electrician effectively becomes a designer

In the case of most installations where there are no departures, the word ‘None or N/A’ should be inserted, rather than leaving the spaces blank.

In the certification model forms prescribed by BS 7671, there is little room for including details of departures; therefore, it is usually necessary for departures from BS 7671 to be declared in other documents, such as specifications and/or operating manuals.

Such documents normally include a description of how the system is to operate and provide sufficient information to enable it to be used safely

Consequently, it would be appropriate to include reference to these intended departures in handover documentation.

Conclusion

A departure is not a ‘defect’, an ‘omission’, an ‘observation’ or a ‘non-compliance’ It is, however, an intended design decision taken after special consideration by the designer of the installation. Hopefully this has clarified some of the confusion over what a departure is and what it is not

Fig 1: Electrical Installation Certificate (EIC) highlighted sections for recording intended departures

INRUSH CURRENT S: THE TRUTH

Lights are flickering, protection devices are tripping for no apparent reason and IT equipment is randomly malfunctioning What’s going on? There can be many reasons for problems like these, but one that’s surprisingly common (yet often overlooked) is inrush currents

When we think about loads – motors, lights, IT equipment etc. – connected to an electrical installation, our primary concern is often with the current that the load draws from the installation: “that motor will draw about 30 A”, or “those lights will take about 2 A”, and so on

But these are steady-state currents and, important as they are, they don’t tell the whole story That’s because many types of load don’t draw their steady-state current from the moment they’re switched on. Before they settle into the steady-state condition, they draw a much larger current for a relatively short period of time This is the inrush current

An example

When a motor is energised using an ordinary electromagnetic starter, it can draw an inrush current that’s up to ten times its normal running current And, particularly if the motor is heavily loaded, it can take several seconds for the current to settle back to the steady-state value

Transformers draw even higher inrush currents at switch on – up to 25 times their normal rated current Even switch-mode power supplies, which these days are used in everything from computers to LED lighting systems, often draw surprisingly large inrush currents In

What exactly are inrush currents, why do they cause problems, and how can they be measured? Julian Grant of Chauvin Arnoux offers some answers.

other words, loads that draw inrush currents are everywhere!

Why does this matter?

Problems resulting from inrush currents can be divided into two categories The first involves circuit protection equipment, such as circuit breakers and fuses The purpose of these is to trip (or blow) if they’re subjected to a higher than normal current Unfortunately, an inrush current is

a higher than normal current, so it can often be difficult to select protection equipment such that it adequately protects the installation but doesn’t trip when a motor starts or a transformer is energised

The second category of problem involves voltage dips If you draw current from an electrical installation, the voltage supplied to the loads connected to that installation will inevitably fall This is

thanks to Ohm’s law, the impedance of the cables and other factors like the impedance of the transformer feeding the installation. It stands to reason, therefore, that if you draw a large inrush current, the voltage drop will be higher than in steady-state operating conditions

This sudden reduction in supply voltage may just make the lights flicker, which is annoying but not necessarily disruptive, or it may adversely affect the operation of computers and other electronic equipment, which is likely to be much more problematic.

There are two key takeaways from this particular discussion:

a) inrush currents are everywhere, and

b) they can be a source of trouble

What’s to be done?

Well, the first step, as always, is to gather reliable and accurate data about what’s really going on, and that means making measurements of the inrush currents in your installation But before you do this, there’s something you need to know: a number of instruments that claim to offer inrush measuring capabilities don’t always provide the full picture

The problem with these instruments is that they can only measure inrush from a

‘standing start’ – in other words, in a system that is initially powered off. This can be very inconvenient, and in most cases, it isn’t a true representation of what happens in real life, where a load that produces an inrush current is most likely to be connected to an installation that’s already live

True to form

To address this limitation, Chauvin Arnoux is now offering instruments with a True InRush function. As easy and convenient to use as ordinary clamp meters, these instruments can measure the initial inrush current when a specific load is connected to the installation, whether or not the installation was already powered, and can also measure subsequent inrush events caused by connecting further loads to the installation

To deliver this functionality the instruments use a novel measurement algorithm. First, this captures the steady-state current for the installation, which it filters to remove anticipated normal variations, producing an RMS reference current Then it carries out half-period monitoring, calculating the equivalent RMS current for every half cycle of the supply

If this exceeds a user-defined

threshold, which is an indication that an inrush event has occurred, the instrument starts making measurements every millisecond, and this continues for a total time of 100 ms. At the end of this time, the results are processed digitally to calculate the true inrush current for the period The graph (pictured, left) gives an overview of this procedure

The accurate and realistic inrush data provided puts you in a position to easily identify any problem areas of your installation, and also any problem loads Once these issues have been identified, remedial measures can be put in place.

These are outside the scope of this article, but could, for example, include installing a soft starter or a variable speed drive to control a motor rather than using a conventional electromagnetic starter, or upgrading protection devices so that they’re no longer prone to tripping by the inrush currents, but still provide a satisfactory protection function

When the appropriate remedial actions have been taken, the final step is to confirm that all is now well by repeating the inrush measurements In fact, it is advisable to routinely repeat the measurements, along with other key power quality measurements, at regular intervals to ensure that the performance of the installation is always optimised, and to provide warnings of any developing problems

As we’ve seen, determining the true value of inrush current in your installation is straightforward – providing that you use the right instrument

BROWSE THE FULL CHAUVIN ARNOUX RANGE OF CLAMP METERS WITH TRUE INRUSH MEASURING AT: WWW.RDR.LINK/EAW023

SECTION 4 ENDS! SCAN THE QR CODE TO CLAIM YOUR CPD CREDIT FOR THIS SECTION OR VISIT: WWW.RDR.LINK/EAW024

INSTALLING RCDS

Depending on the particular characteristics of the ‘electronic’ loads and controls connected to an electrical installation, an RCD could be exposed to a range of residual current waveforms and frequencies. Unless RCDs are selected that are compatible with the loads and other devices connected, the protection intended may be compromised, as the experts at NICEIC explain.

Introduction

Electronic components are to be found in most electrical products installed in modern electrical installations These include, for example:

● LED lights,

● Variable speed drives,

● UPS systems,

● Lighting and heating controllers,

● Appliances such as washing machines, induction hobs, dishwashers and fridges

Such ‘electronic’ products can, in normal operation, generate DC as well as residual current waveforms of high or mixed frequencies, as shown in Fig 1(a) Furthermore, in the event of a fault, the current flowing is likely, depending on where the fault occurs, to be complex in shape rather than the sinusoidal waveform as shown in Fig 1(b)

Therefore, an RCD exposed to such waveforms needs to be of a suitable type, otherwise a distorted waveform (or DC) could affect the time/current operation of an RCD and cause it to operate outside its correct operating characteristics – or, at worst, the RCD could fail to operate at all

It should be recognised that the term RCD covers a range of residual current devices While the selection of an RCD is primarily based on the residual current sensitivity required, other factors also need to be taken into account, including:

● the compatibility of the device with the type of loads connected,

● co-ordination between Types of RCDs, and

● selectivity between RCDs and other protective devices that may be connected in series

Classification of RCDs

The operating characteristics of a general purpose RCD (Type AC) is designed for sinusoidal waveforms of 50 Hz Exposure to high frequency waveforms or DC can saturate the core of the RCD, and may render the device unable to correctly detect residual currents, 1 and as such, fail to operate under fault conditions

Similarly, the correct operation of a Type A RCD cannot be assured where it is likely to be exposed to certain waveforms of mixed frequencies For these reasons, regulation 531.3.3 of BS 7671 requires that an appropriate ‘Type’ of RCD is

“It should be recognised that the term RCD covers a range of residual current devices. While the selection of an RCD is primarily based on the residual current sensitivity required, other factors also need to be taken into account...”

selected based on the frequencies and DC component likely to be present

When used to describe the operating characteristics of an RCD, the term ‘Type’ relates to the frequency and shape of current waveform for which operation is assured A summary of the Types of RCDs detailed in regulation 531 3 3 and the particular current waveforms for which they are designed is provided in Table 1.

In addition, the recommendations given in Figure A53 1 of Annex A53 of BS 7671, for protection against possible fault currents in systems with semiconductors should also be taken into account As such, regulation 531 3 3 details the different types of RCD that exist and may be selected for use

Note: An RCD intended for operation by ordinary persons should conform to the relevant product standard listed in regulation 531 3 4 1, whereas an RCD for use by skilled or instructed persons should conform to regulation 531.3.4.2.

Co-ordination between RCD Types

Where RCDs are connected in series within an installation, the selection of one Type of RCD should not impair the operation of another device Therefore, with reference to Table 1, RCDs should be co-ordinated such that:

● Type AC RCD should not be installed upstream of any other type of RCD,

● Type A RCD should not be installed upstream of a Type F or B RCDs, and

● Type B RCDs should not be installed downstream of any other type of RCD.

Selectivity between RCDs

Given the RCD Types are compatible, selectivity between RCDs connected in series based on the residual current is achieved where:

● the upstream RCD is of selective type (Type S2 or time-delayed type3 with appropriate time delay setting), and

● the ratio between the rated residual operating current (IΔn) of the upstream RCD and the downstream RCD is at least 3:1 (536 4 1 4)

A residual current protective device connected upstream of an RCD providing additional protection (rated residual current ≤ 30 mA), should be a Type S device, incorporating a time-delay for selectivity purposes

Note: A Type S RCD is not suitable for providing additional protection and where this device is installed it shall satisfy the disconnection requirements of Chapter 41 of BS 7671

Requirements for selectivity between overcurrent protective devices and RCDs are contained in regulation Group

536 4 1 5 It should be noted that a Residual Current Circuit Breaker (RCCB) is not designed to provide overload or short-circuit protection and so suitable devices providing such protection must be installed.

In the case of RCCBs housed within a typical consumer unit to BS EN 61439-3, short-circuit protection is provided by an upstream device, generally the supplier’s intake fuse, while overload protection is provided by the protective devices installed within the consumer unit

Therefore, the loads connected to a single RCCB must not cause the device to be subjected to a continuous overload exceeding its rating Additionally, the short-circuit withstand capability of the RCCB should have a rating higher than the highest prospective fault current that could occur at its point of installation (536 4 2 4)

Compatibility with SPDs

Regulation 534 4 7 requires an RCD installed upstream of a Surge Protective Device to be a transient resistant type having an immunity to surge currents (8/20) of up to 3 kA Both Type S RCCBs to BS EN 61008-1 and RCBOs to the BS EN 61009-1 satisfy this requirement

However, the installation of a Type 1 SPD downstream of an RCD is not recommended (534 4 7)

2 Type S RCDs are covered by the BS EN 61008 series (RCCBs) and BS EN 61009 (RCBOs)

3 Circuit-breakers

Table 1 Classification of RCDs

Fig 2 Correct co-ordination between upstream and downstream type RCDs

“An RCD intended for operation by ordinary persons should conform to the relevant product standard listed in regulation 531.3.4.1, whereas an RCD for use by skilled or instructed persons should conform to regulation 531.3.4.2”

Considerations for electrical testing

Irrespective of the function of an RCD, whether it is installed to provide fault protection, additional protection or protection against fire, its operation must be verified by testing (regulation Group 643 7)

In some circumstances, due to the compatibility of the RCD and the test instrument used, it may not be possible to obtain a measured value of earth fault loop impedance Historically, some earth fault loop impedance test instruments injected a DC current to saturate the core of the RCD prior to testing so that the actual test current is undetected by the RCD This technique of applying a DC bias effectively ‘blinded’ the RCD and prevented it tripping during the test Such a test was only suitable for certain devices such as Type AC and A RCDs

For other Types of RCD either a test instrument having a low current no trip facility or similar is required or the impedance value can be obtained by measuring the earth fault loop impedance on the supply side of the RCD and adding this to the value of the combined resistance (R1+R2) on the load side of the RCD

Alternatively, automatic disconnection of supply (ADS) may be confirmed by verifying the effectiveness of the RCD and confirmation of the continuity of protective conductors downstream of the RCD (643 7 1)

Summary

In addition to providing the correct level of residual current protection required, an RCD should be selected so that it is compatible with the operating characteristics of the loads it protects and other devices connected in series. As the nature of loads and their operating characteristics become more complex, then confirming the suitability of existing RCDs should not be overlooked

EV QUESTION T IME: PART1

In this first of a two-part article, Viktors Nikolajevs, CTEK’s Skillbase Manager in the UK, answers some of the key questions that installers are commonly raising around EV charge point installations.

Installers at our UK training sessions will ask a lot of questions when they’re learning how to best install EV charge points. But, there are certain topics that will crop up time and again at training events up and down the country

In my experience, installers are keen to find out all about EV charging, how the charging units work and the steps to effective installations They’re an

inquisitive lot and ask some very good questions at each session.

Here I’ll cover three of them, with further questions to come in the next issue:

QWhat RCD protection is there in EV charge points?

BS (IEC) EN 61851-1 Section 8 5 stipulates that all charging points must have RCD protection Where the EV supply equipment (EVSE) has only one connection point to the vehicle, or multiple connection points but only one can be active at any point, a single RCD can be used The RCD device can be integrated into the EVSE or external

If multiple connection points are available on a single piece of EVSE, then each connection point must have its own RCD protection incorporated into the EVSE

The RCD used must be compliant with either BS (IEC) EN 61008-1 (RCCBs), BS (IEC) EN 61009-1 (RCBOs), BS (IEC) EN 60947-2 (Modular RCD) or BS (IEC) EN 62423 (Type B RCCBs/RCBOs) standards

The RCD must have AC rating not exceeding 30mA Additionally, protection against smooth DC currents must be provided The standard states that a Type B device can be used or Type A if explicit protection against smooth DC greater than 6mA is integrated into the EVSE,

such as Residual Direct Current Detection Device (RDC-DD) as defined by BS (IEC) EN 62955:2018

QWhat is the minimum IK impact rating a charging unit must have?

According to BS 7671:2018+A2:2022

Section 722 512 2 203, charging points installed in public areas or car parks should have AG3 – impact of high severity rating

In practice that means that the charging points should be installed at heights and in positions where they’re least likely to be damaged in day-to-day use, adequate mechanical protection should be provided where there is risk of direct impact (such as bollards or barriers), and the charging equipment itself should have minimum IK08 rating

The IK rating indicates the degree of physical protection that applies to the complete enclosure of equipment In

simple terms, it indicates how hard the equipment can be hit before the enclosure can be expected to break

IK rating is described in BS (IEC) EN 62262:2002+A1:2021, where 12 ratings are defined – from IK00 having no protection to IK11 being able to withstand 50 Joules of force applied IK08 requires the equipment to be able to withstand five Joules of force

QIn what situations are AC chargers best and when are DC chargers more suitable?

DC chargers are great where the dwell time is shorter, such as motorway services and other roadside facilities on highways, where the driver only wants to pause their journey for half an hour or so

If the installation site host expects its visitors to stay for longer, such as shopping centres, car parks, workplaces or cinemas, AC destination charging is better as each

charge can be for more than a couple of hours You can also install several AC chargers for the price of one DC charger

Tap into training

The appetite for EV installation training is growing all the time as more installers want to expand their knowledge of what is a huge growth market

A City & Guilds survey of installers found that 45% of employers only recruit electricians who are already qualified or competent to install EV chargers Installers, therefore, are invited to our free online CTEK Skillbase training events to learn more about installing EV charging infrastructure

GET MORE DETAILS ABOUT CTEK’S TRAINING EVENTS AND SECURE A PLACE BY VISITING: WWW.RDR.LINK/EAX028

EART HING OR BONDING?

The technical experts at NAPIT examine the differences between Earthing and Bonding.

What’s in a name?

These two principles are often confused, either by name or purpose. Let’s be clear, they both have vital roles to play in an electrical installation, but they’re both very different in the way they achieve their requirements

The only real similarity they have is the green and yellow cable we use to denote them, which is where the confusion between the roles they fulfil is likely to stem from

Earthing conductors

Earth, or the greater mass of Earth, is where we consider the fault path for current to flow to in the event of a fault

That flow is channelled via earthing conductors Where the supply is a transformer, the earth point is usually the star point or neutral of the windings As earthing conductors carry fault current, they have to be designed to withstand enough current to initiate the operation of an overcurrent protective device

(OCPD) within the times stated in BS 7671, Table 41 1

Depending on the OCPD, the required fault current can be many times the magnitude of a device’s normal operating current

So, when we look at the circuit earthing conductor, or circuit protective conductor (cpc) as we refer to them, for a final circuit in a TN-C-S system, protected by a 32 A B curve MCB, it needs to be capable of handling 160 A for 0 4 seconds

In reality, a B curve MCB will operate almost instantaneously at 160 A

We can see from this requirement that we have to size our cpc or earthing conductor with the current flow they’re expected to see in the event of a fault There are a couple of ways we can do this: use Table 54 7 in BS 7671 or calculate the size we need

In order to calculate the size we need, we use the adiabatic equation given in Regulation 543.1.3 and shown in Fig 1.

Earthing conductor re-cap So, to put that all together, earthing conductors used for cpcs must meet the following criteria:

● They need to carry large currents for a short duration

● They can be sized in accordance with Table 54 7 in BS 7671 or

● They can be sized using the adiabatic equation in Regulation 543.1.3.

Using the adiabatic equation allows the use of smaller cross-sectional diameters of conductors than complying with Table 54 7 By doing this, the designer can use smaller, more cost-effective cable sizes Inspectors need to be aware of this when carrying out EICRs as an undersized

cpc may have been calculated using the adiabatic equation and therefore will be more than adequate.

Protective bonding conductors

Bonding conductors, or more accurately, protective bonding conductors, can be either:

● Main protective bonding conductors or

● Supplementary bonding conductors

They’re both similar in their principles, but as the name suggests, one is very much larger than the other

Main protective bonding conductors

Main protective bonding conductors are used to connect extraneous metallic parts to the main earth terminal (MET) We use the word ‘bonding’ because we’re bonding or connecting two parts together to create a zone of equal potential, or an equipotential zone – as it is known

Where extraneous metallic services or parts enter a building and are in contact with the general mass of Earth, it is possible that they can introduce a voltage

which can be different from that of the installation’s MET or, indeed, other extraneous metallic parts

When this happens, there is a potential for current to flow, dependent on the voltage magnitude and resistance of any conductor – we call this a potential difference If the potential difference has enough magnitude, it can cause a fatal electric shock

By bonding any extraneous metallic parts and the MET together, all of the different services and parts are at the same potential difference, and current cannot flow between them Main protective bonding conductors are sized in two ways depending on the earthing system being used.

All installations, except protective multiple earthing (PME), are sized in relation to the installation’s main earthing conductor (MEC), where the main

7671 Table 54 8

protective bonding conductors must be not less than half of the cross-sectional area of the MEC and no less than 6 mm2. Conductors sized in this way need not exceed 25 mm2 copper or its equivalent For PME earthing systems, the main protective bonding conductors must be sized in accordance with BS

This Table gives varying sizes a bonding conductor can be, based on the cross-sectional area of the incoming supply’s protective earthed neutral (PEN) conductor, but they can be no less than 10 mm2 and need not be bigger than 50 mm2 copper or its equivalent

Main protective bonding conductor re-cap

Quite different to earthing conductors, bonding conductors meet the following criteria:

● They’re not designed or required to carry large currents; they only balance the potential difference between extraneous parts,

● For PME installations, they must be sized in accordance with Table 54 8 in BS 7671,

● For non-PME installations, they can be no less than half the cross sectional area (csa) of the MEC and no less than 6 mm2

Main protective bonding conductors cannot be calculated using an adiabatic equation; they must be sized in accordance with Regulation 544 1 1 or Table 54 8

Supplementary bonding conductors

These carry out a similar role to main protective bonding but at a smaller scale, usually on an individual circuit, in an area that may benefit from a more localised equipotential zone

Areas currently requiring supplementary protective bonding are Part 7 special installations or locations:

● 701: Locations containing a bath or shower (this is usually relaxed where indents iv, v and vi of 701 415 2 have been met),

● 702: Swimming pools and other basins,

● 705: Agricultural and horticultural premises,

● 706: Conducting locations with restricted movement,

● 710: Medical locations,

● 740: Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses

Supplementary bonding conductors are generally much smaller in csa than main protective bonding conductors but must be no less than 2 5 mm2 for mechanically protected conductors and 4 mm2 for non-mechanically protected conductors

Conclusion

Earthing and bonding are two very different principles – one relies on carrying a high current to clear a fault, and the other relies on equalising any potential difference of voltage, so it isn’t likely to carry much current at all

CONTINUE YO UR P ROF E S SION A L DEVELOPMENT AT ELE X SHOW!

Taking place across two days, the ELEX 2024 tour is making six stops this year. And better still, we’ve got great news for those visitors that are serious about Continuing Professional Development!

Recent changes to The Electrotechnical Assessment Specification (EAS) which sets out the minimum requirements for a business to be recognised as technically competent by a Certification or Registration Body, includes a requirement for businesses to maintain appropriate records of qualifications, training (including Continuing Professional Development) and experience

To support this requirement, EVERY ELEX seminar is now CPD accredited, ensuring those individuals who make the time and effort to attend will receive a direct certificate of completion, which can

form a key part of your ongoing Continuing Professional Development record.

With industry regulation and legislation changing constantly, the extensive ELEX seminar programme will cover an array of topics, including the latest Amendment 2 to the 18th Edition and the changes this covers, along with best practice and technical advice for professionals to get stuck into Presentations will be delivered by experts in their field and the only cost to delegates is their time.

All seminars will take place in the IET Seminar Theatre located centrally in the exhibition hall and there’s no need for delegates to pre-book, just pre-register to attend the show

Whether you need some advice on the direction the sector is heading, want to chat with manufacturers about their latest solutions, view live demonstrations of the latest products or bag yourself a great

deal on tools and equipment from leading brands, your regional ELEX tradeshow has it all

will be visiting Alexandra Palace, Bolton Arena, Westpoint Exeter, YEC Harrogate, CBS Arena Coventry and Sandown Park this year – make sure

get along to your local event

INTEROPERABILITY LIGHTING

As the demand for smart lighting control solutions in the built environment continues to intensify, the need for educational buildings to run as safely and cost-effectively as possible is greater than ever

Building operators can now safely monitor and control energy, lighting, use of space, emergency system maintenance and much more However, for smart lighting to truly fulfil its potential, the most critical challenge to overcome is achieving interoperability.

How can you create an interoperable environment that delivers truly smart lighting to projects?

Smart lighting systems have delivered huge benefits to organisations since their creation and are, importantly, having a huge impact on the reduction of energy bills and carbon emissions across all sectors With budgets tightening and operating costs continuing to rise, making the move to smart lighting is something many businesses and organisations must consider in order to conserve funds and improve operational efficiencies

What benefits does smart lighting offer?

● Suitable for both internal and external lighting circuits, it can be used to control illumination in all spaces

● Responsive and adjustable, the automated technology ensures that lighting is used only where and when it is needed, reducing wasted energy use and its associated financial and environmental costs

● Lighting hues can be pre-set, providing a huge impact on safety and wellbeing

● Smart technology is measurable Recent advances in equipment mean that many smart lighting solutions now come with dashboard controls which can accurately measure lighting energy usage in real time, giving a clear view of lighting-based energy consumption data across one building or an entire portfolio This allows usage to be accurately evaluated and opportunities to reduce unnecessary use to be identified.

In this article, the experts at Ansell Lighting look at how interoperability lighting works and advise on how to create an interoperable environment.

To unlock these benefits you first need to achieve interoperability

What is interoperability?

It means creating an environment where systems and devices, produced by different manufacturers, use common communication protocols to work together seamlessly to deliver a truly smart lighting scheme.

What solutions are out there?

Zigbee: Widely used in smart home and building automation systems, Zigbee is a low-power wireless protocol that is designed to be interoperable across different devices and systems It operates on the 2 4 GHz frequency band and can support up to 65,000 devices on a single network.

Bluetooth mesh: Designed specifically for the Internet of Things (IoT), Bluetooth mesh operates on the same 2 4 GHz frequency band as Zigbee and can support up to 32,000 devices on a single network Bluetooth mesh is particularly well-suited for lighting applications, as it offers low latency and high reliability

Sensors: In addition to wireless protocols, smart lighting systems can also use sensors and triggers to achieve interoperability. Sensors can detect changes in the environment, such as occupancy or ambient light levels, and trigger actions such as turning lights on or off Triggers can be used to initiate actions based on specific events, such as a door opening, or a motion sensor being triggered

The Cloud: Using cloud-based services is another approach that can be considered to help manage and control different devices and systems. Cloud-based services can provide a central point of control for multiple devices and systems, making it easier to achieve interoperability

Is there any other advice for installers?

Whatever technology is selected, achieving interoperability in smart lighting requires a collaborative approach between all stakeholders involved in the design and use of the building. Specifying a truly interoperable system from the start will ensure that its benefits are harnessed for the long-term future

Dr. Zzeus

‘DR. ZZEUS’ TOM BROOKES, md of zzeus training and CHAIRMAN OF THE FSA, ANSWERS YOUR QUESTIONS RELATED TO FIRE SAFETY COMPLIANCE.

Here, I’m going to answer two questions relating to the skills of fire alarm and security installers:

1 How do you measure the resistance of a cable?

2 How do you calculate the resistance of a 1.5 mm standard fire alarm cable?

Continuity

BS 5839-1 clause 38 1 states that all installed cables with a manufacturer’s voltage rating suitable for mains use should be subject to insulation testing at 500 V d c Insulation resistance should be measured between each conductor and earth and achieve no less than 2 MΩ

It continues to say that on completion of the installation work,

where maximum circuit resistance for any circuit is specified by the manufacturer or supplier, measurement of the resistance of every such circuit must be documented At ZZEUS Training, this is standard day three practical electrical testing, but it may appear that some training providers are not doing this The standard is very clear: if you install a fire cable, you must test it Both should be done without devices attached

For this example, we are working out 85 m of 1 5 mm fire cable

Step 1) Calculate the ohms per metre –12 10/1,000 = 0.001210 ohms per metre

Step 2) Multiply the ohms per metre by the length of the cable – 85 m x 0.001210 = 0.1028 ohms expected.

Firstly, you need to know what the expected resistance of a cable is in set parameters; there are tables for the types of metal, and the temperature of the cable standard copper 1 5 mm fire cable at 20°C is 12 10 ohms per km

Next, you need to measure the cable's resistance physically For this step, you will need a calibrated multifunction tester or multi-meter to measure in ohms A word of caution: some multi-meters are inaccurate, so I prefer to use a multifunction tester

Zero or null the leads All good meters have this function; that way, you are taking a true reading from the cable only. Next, attach your positive lead to one end of the core and the negative to the other end, select ‘continuity’ and press ‘test’

You should get a reading close to the expected 0 1028 ohms; I would expect it to be within 5% on the new undamaged cable Ensure you attach the clips firmly, as loose clips can give a poor reading.

In the next column we’ll look at how you take an insulation reading on a fire cable

Resistance determines how difficult it is for current to flow and is measured in ohms (Ω)

DO YOU HAVE A QUESTION YOU'D LIKE ANSWERED?

EMAIL YOUR QUERIES TO: TOM@ZZEUS.ORG.UK

THE CODEBREAKERS

GARETH VICKERS: I FOUND THIS WHILE CARRYING OUT AN EICR CLEARLY THERE HAS BEEN CONTAC T ON THE EARTH BAR FROM THE LIVES, AND SOMEONE HAS ALSO REPLACED THE ORIGINAL SOCKE TS WITH THESE IT MUST HAVE BEEN A PLUMBER!

Ever y electrician will have come across this k ind of issue at some point – new faceplates where the existing conductors won’t reach the new terminals

To the competent, it ’s a simple fix: extend the conductors in a safe way that doesn’t compromise the current carr ying capacity of the circuit conductors or cause damage from improper termination. I t would appear the installer has failed on all counts here.

The Neutral conduc tor ex tension may not have an adequate current carr ying capacit y for the circuit, and too much of the un-insulated bare conduc tor is accessible Although long enough for the new terminal positions, the Line conduc tors haven’t been terminated adequately, and again too much un-insulated conduc tor is accessible

In this case, the un-insulated Line conductors are touching the socket- outlet ear thing bar when the accessor y is pushed back into position, causing arcing and a potential risk of fire.

G Current 131.3.1 134.1.1, 134.1.4, 421.1.7, 526, 651.2(ii) C2

FI GET THE BOOK AND CRACK THOSE CODES! Updated for BS 7671:2018+A2:2022, NAPIT ’s EICR Codebreakers publication is purpose -written to aid contractors, inspectors and clients, and now includes updates to align with Amendment 2 of the IE T 18th Edition Wiring Regulations The book is the per fect technical aid for electrical professionals and their customers 86 CPD Book PROFESSIONAL ELECTRICIAN

Need help with cracking those all-impor tant EICR codes? Ever y month the technical team at NAPIT will be studying your latest ‘Caught on Camera’ photos and offering advice on the next steps, should you find a similar installation. If you want the team at NAPIT to help crack your codes then send your pic tures through to us at: pe@hamer ville.co.uk

DANNY: THIS SOLAR INSTALLER TAPPED OFF THE POWER FROM THE MAIN SWITCH (80 A RCD RCCB 100 MILLIAMP) USING 2.5MM T WIN AND EARTH PVC CABLE STRAIGHT OFF THE MAIN 16MM TAILS!

Regardless of cost, it is never acceptable to connec t to a CU in this way, through lack of spare ways There should have been a CU upgrade, to ensure the PV array could be correc tly connec ted. Even though the PV circuit feeds into the outgoing side of a device, in a properly installed system, it is also considered a circuit and needs to be adequately protec ted against overcurrent and requires adequate isolation for maintenance.

O vercurrent protec tive devices are usually sized in accordance with the instruc tions provided by the inver ter manufac turer In this case, the PV array is connec ted to the incoming supply side of the ELCB isolator (see image 1) so there may not be any overcurrent, or fault protec tion, as the photos we have are limiting the information we can use

If used as an isolator (as the label suggests), the ELCB won’t isolate the PV array circuit The cables between the PV isolator (see image 2) and the ELCB incoming terminals, will be constantly Live with no way to isolate, or make safe for maintenance.

There is a potential for both shock and fire damage in this

installation as it stands and can only be coded one way. Without fur ther information on the complete install, its difficult to see just how poor this work manship is

That ’s the rub though, it ’s a poorly installed system, with a likely potential for danger, and needs to be remedied before it causes harm

FI

No apparent method of isolation for the PV circuit 132.15.201,

Incorrect and misleading labelling, with the potential to lead to harm (Fig 1)

Installation may not take account of inverter manufacturers instructions 134.1.1, 510.3

The A2:2022 18th Edition Codebreakers publication is priced at £22.00 (members) and £24.00 (non-members). It is available in both hard copy and digital versions

* Price is VAT exempt and excludes postage and packaging.

FI

C2

FI

T HE GUIDET O

LI-ION BESS SAFET Y

Paul Reeve, ECA Director of CSR, looks into the safety considerations installers should be aware of when dealing with Li-ion battery energy storage systems (BESSs).

In June 2023, the Construction Leadership Council launched an industry initiative to drastically reduce the use of diesel on construction sites Part of the initiative, headed by ECA, highlights safety considerations for the main alternatives to on-site diesel, including Li-ion battery energy storage systems Li-ion BESS does not routinely fail to danger but, as many social media viewers can confirm, when Li-ion goes into

‘thermal runaway’ the result can be dramatic, damaging and dangerous A new information note from CONIAC* on the safety issues surrounding on-site Li-ion BESS cites the main operational hazards as:

● Electrical failure or contact

● Mechanical damage

● Heat stress – ambient overheating

● Charging stress – overcharging/poor charging practice

Pent up electrical energy

Li-ion batteries, by their very nature, can hold significant electrical potential and if the terminals short-circuit (e.g. with an uninsulated object or due to mechanical damage) that electrical energy can be released rapidly

As a result, and in addition to all the general electrical safety precautions such as keeping unauthorized personnel away, on-site Li-ion batteries need:

● protection against electric shock that aligns with BS 7671/IET Electrical Energy Storage Systems CoP, including adequate fault protection and proper consideration of the risk of DC arc flash;

● a clearly communicated safe system of work for battery fault-finding, O&M, replacement, commissioning and decommissioning; and

● clear communication of the electrical isolation procedures to competent staff/contractors, including regard for any battery-reliant critical systems

Thermal runaway

In addition, faulty Li-ion batteries have become infamous for spectacular and dangerous thermal runaway This can produce profuse toxic and flammable gases, energetic flame and even explosion, and it can cascade quickly in adjacent battery cells.

To help prevent dangerous runaway, Li-ion batteries typically require electrical management systems to ensure operation within controlled parameters e g voltages, temperature and charge states (which adjusts as battery cells age) But if the cells are stressed or damaged, degradation leading to runaway can be fairly immediate or (perhaps worse) develop some weeks later. By the time a Li-ion battery produces detectable smoke, dangerous runaway may have already begun

However, earlier intervention after detecting initial ‘off gas’ as cell temperature and pressure rises can prevent dangerous runaway if there is a prompt shut down (even if it can’t prevent expensive battery damage) This makes effective BESS temperature monitoring a valuable precaution, whether by thermal imaging or thermometers or probes.

The hazards described here mean that only suitably trained and competent personnel should work with BESS or engage in BESS emergency measures In particular, anyone involved in testing, connection, isolation and/or charging/discharging, should know safe operational practice and be sufficiently

competent and trained (e g Level 3 Award in Design, Installation and Commissioning of Electrical Energy Storage Systems)

Planning for operational safety

In general, installing an on-site BESS needs a pre-site risk assessment (RA) which considers design and planning, transportation, installation and commissioning, operation and maintenance (O&M), emergency situations and end-of-service life. It will also need to consider additional measures for any BESS housed in a container

Quality equipment required

An additional root of operational Li-ion battery failure is poor BESS design and/or manufacture A BESS should be designed, manufactured and tested in line with UK-accepted product safety standards and component compatibility. Crucially, it should enable safe routine and emergency isolation A BESS should also be tested promptly when it arrives on-site – cycling (charging/discharging) the battery cells as prescribed by a reputable supplier

These and other safety measures highlighted in the CONIAC information note are essential when looking to bring BESS on-site, not just for safety and continuity reasons but, increasingly, to meet industry insurance requirements

In a panel

Emergency planning

An on-site emergency control plan for Li-ion BESS should include:

● a battery damage plan to include how to safely move batteries (which may include damaged batteries)

● a fire emergency plan to include:

■ equipment isolation/contained battery venting/personnel separation/evacuation – enabling a rapid call to the fire services (noting the risk of fire continuation or even escalation)

■ essential information for the fire services

■ initial cooling/flame fighting measures – avoiding/protecting against combustion products/fume inhalation

● a clear-up plan to include how electrolyte leakage will be safely cleared up and reported

The CONIAC information notes add that it “may take tens of thousands of litres of water, applied directly to a battery, to fully extinguish and cool down a sizable Li-ion battery fire” adding “BEWARE POSSIBLE RE-IGNITION ”

Sources of further information

The CONIAC* (HSE-supported Construction Industry Advisory Council) ‘Safety issues and alternatives to diesel’ group is chaired by ECA. Its current information notes are at: www.coniac.org.uk/working-groups/man aging-risk-well

Further reading

● IET Code of Practice for Electrical Energy Storage Systems

● Need to Know RE1 BESS: commercial Li-ion installations v1

● Need to Know RE2 Li-ion Battery Use and Storage v1

● National Operational Guidance at: www ukfrs com/guidance/search/rech argeable-batteries