Issue15 | Winter 2009 | ÂŁ5.00
Technical Manual online launched www.esc.org.uk
WELCOME Funding the Electrical Safety Council ’m sometimes asked how we manage to do so much, and that begs the question “Where do we get our funding from?”
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When told that we receive funds in the form of Gift Aid from our trading subsidiary, NICEIC, some of our industry partners question whether we can be truly independent, given that we rely on a major industry scheme operator for the majority of our funding. This may have been a reasonable point to make two or three years ago but, subsequent to the renaming (rebranding) of the Charity, a strategy has been developed that ensures clear blue water between the Electrical Safety Council and NICEIC across our respective activities. The funding arrangement is unique within the electrical contracting industry, as all of NICEIC’s surpluses from its trading activities are given to the Council, a registered charity, to enable us to raise consumer awareness of electrical safety issues. Through this funding, and with the support of other industry organisations that kindly contribute their technical expertise, we are also able to provide a wide range of technical information and guidance to the electrical industry through free-to-download publications such as the Best Practice Guides. We have ambitions to do a lot more to help develop awareness of electrical safety issues in the field of both electrical installations and electrical products, so we hope to encourage other stakeholders to provide financial support for other projects we want to undertake. We have already been successful in gaining support from the likes of ASDA for our Christmas lights initiative (page 14), and of
Electricfix for helping fund a series of seminars for electricians which we hope to roll out across the UK next year. ElectricFix is also supporting the dissemination of our Best Practice Guides by printing thousands of copies and then distributing them with their catalogues. (More details on page 4.) As we gain momentum in attracting further funding, we will not only be able to provide more support to users of electricity, but also to reaffirm our independence from our trading subsidiary, NICEIC.
But what about RCDs? My colleagues and I are often confronted with quizzical looks when we ask a caller on our helpline or a visitor to an exhibition if they have RCD protection at home. To be fair, ‘RCD’ is not a particularly consumerfriendly name so, in an effort to drive up awareness of this life saving device, I’m pleased to report that we will be embarking on an ambitious five year campaign to encourage greater use of RCDs. Details of the campaign can be found on page 20.
So remember - when you see a new guidance document produced by the Electrical Safety Council or become aware of a safety campaign that we’re running, it’s funded largely by electrical contractors and installers who have contributed either through services purchased from NICEIC, or through benefit in kind received from an industry body they are affiliated to. General News As you can see from the cover of this issue, we’re launching an exciting new subscription service for electrical contractors and installers, and others having a professional interest in electrical installation matters – The Essential Guide to the Wiring Regulations. Formerly known as ‘the Technical Manual’, the constantly developing and unique Guide, which has already been many years in the making, contains a wealth of up-to-date information and guidance on the requirements of BS 7671 (IEE Wiring Regulations). Check out the article on page 8 for more details. Smoke alarms are widely recognised as being a life saver and, thanks to a major TV and advertising campaign over the past five years or so, over 80% of UK households now have smoke alarms.
Walled Garden, Scotland
We’ve developed our presence in Scotland to the extent that we have now taken up residence at the Walled Garden, the office of SELECT, Scotland’s trade association for the electrical contracting industry. By taking an office in the recently completed extension, we’ve joined an industry hub made up of trade bodies and other organisations representing the M & E sector in Scotland. On a final note, I would like to belatedly wish you a happy and, hopefully, prosperous new year. As always, we would welcome feedback on Switched On, to help us improve the content. Email switchedon@esc.org.uk Phil Buckle Director General
ARE YOU GETTING SWITCHED ON REGULARLY? f you’ve been receiving printed copies of Switched On regularly with Professional Electrician, SELECT’s CableTalk or the NICEIC Connections magazines, you can expect to continue doing so for the foreseeable future.
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However, if you’ve received recent issues with the CIBSE Journal, Facilities Management Journal or IET Wiring Matters, you may wish to register on our website to be sure of continuing to be sent, free of charge, either the printed version or, alternatively, the electronic version (all issues
of which can be viewed on, or downloaded from, our website www.esc.org.uk).
If you wish to register to be sure of continuing to receive your free copy of Switched On, please go to www.esc.org.uk/switched-on
Selling dangerous goods... see page 20
issue 15 Winter ‘09
switchedon industry news
features
your insight into the electrical safety industry
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Welcome Also, Are you getting Switched On regularly?
14 ASDA funds festive light amnesty
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News in brief
15 Safety of portable appliances
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Have you ever been asked… Why did the identification colours used in the UK for fixed wiring change a few years ago?
Installation Forum – 16 Electrical th
Events for 2010 Also, Political Party Conferences, Readership survey
17 SkillElectric Final 2009
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Electrical installation work – who is the designer?
10 Access to service fuses 11 Plans underway for major safety
campaign Also, Guidance on the Electricity at Work Regulations now available free of charge
Also, Standard for earthing and bonding clamps revised
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Your Essential Guide to the Wiring Regulations – Available Now!
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Downlighters – can they be a fire hazard?
provided by landlords
17 Edition guidance Also, Household lamps to become more energy efficient
Also, Winner of UK SkillElectric 2008 strikes gold at WorldSkills
18 Adequacy of meter tails and
earthing conductors in existing domestic installations
20 National chain prosecuted for
selling dangerous lamps and kettles Also, Testing of supplies to street lighting
Published by: The Electrical Safety Council Unit 1.10, Canterbury Court, Kennington Park Business Centre, 1 - 3 Brixton Road, London SW9 6DE www.esc.org.uk www.eschub.org.uk www.switchedonkids.org.uk www.twothirtyvolts.org.uk Tel: 0870 040 0561 Fax: 0870 040 0560 email: switchedon@esc.org.uk SwitchedOn 3
NEWS IN BRIEF The Electrical Safety Council web link We often receive requests from external bodies to link to our website. However, whilst we encourage linking and are grateful for the support it demonstrates, web link we have previously been unable to provide our logo for display on external sites due to the risk of misuse.
Electrical Safety Council relocates Last October, the Electrical Safety Council moved its main London office from Victoria to Kennington, to enable the majority of our 25 staff to be co-located. The new address is: Unit 1.10 Canterbury Court Kennington Park Business Centre 1 - 3 Brixton Road London SW9 6DE
ElectricFix sponsors printing and distribution of Best Practice Guides We are very pleased to report that Electricfix, the major distributor of electrical products and accessories, has agreed to support our best practice agenda by printing our Best Practice Guides and distributing them to the 120,000 electrical contractors who regularly receive their catalogue.
We have therefore created a new ‘web link’ logo that can be freely used by bodies wishing to link to any of our websites. It can be downloaded from www.esc.org.uk/weblink
Electricity distributors emergency contact details
The office in Buckingham Gate is being retained as a meeting and technical resource centre.
Switched On goes far and wide! When we reported in the previous issue that we were temporarily boosting the distribution of Switched On, we had no idea that it would get as far as Nepal.
The Energy Networks Association (ENA) has published emergency contact details for all the electricity network operators in England, Wales and Scotland, which can be found at:
The photo shows our Chairman, Bill Wright, who took the autumn issue with him on a trek near the Annapurna foothills. His local guides evidently appreciated a good read too!
http://2009.energynetworks.org/ emergency-contacts/
The latest Guide (No 6) – Consumer unit replacement in domestic premises – is expected to be distributed in January, to be followed by other Guides in the series.
There’s also a map showing the areas covered by the various distributors at: http://2009.energynetworks.org/storage/ emergency-contact-nos_090624.pdf Why not save the relevant emergency number(s) on your mobile phone in case you need to contact the local electricity distributor in an emergency?
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HAVE YOU EVER BEEN ASKED ‌ Why did the identification colours used in the UK for fixed wiring change a few years ago? lthough the UK agreed 30 years ago to adopt the colour blue for neutral conductors, and has since used harmonised (brown/blue/green-andyellow) colours for the identification of the cores of flexible cables and flexible cords for electrical appliances etc, no similar move was made at the time towards harmonising the colours of non flexible cables used for fixed wiring.
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for the safety of electrical installations (BS 7671) established a Working Group to consider the position the UK should take with respect to the harmonisation of the colours of the cores of non flexible cables for fixed wiring. The Working Group concluded that the UK had no realistic option but to agree to use the colour blue for the neutral, and
Whilst the change in the UK to blue for the neutral and at least one black in multi phase circuits introduced the possibility of confusion with the black neutral and blue phase in existing three phase distribution circuits, the risk was generally considered to be manageable.
Cable colours across Europe in 1996
Courtesy of IET
We simply carried on using red, yellow and blue for the line (phase) conductors, black for the neutral, and green-and-yellow for the protective conductor. Unfortunately, whilst for decades the UK continued to ignore the need to consider harmonising its fixed wiring colours, much of the rest of Europe was standardising on blue for the neutral, with brown and/or black phases. The following chart shows the cable colour situation across Europe in 1996, with the UK clearly being very much out of step. When in 1999 it eventually became evident that, within a few years, a new European Standard (EN 60446) would legally require the use of the colour blue (rather than black) for the neutral conductors of fixed wiring throughout Europe, it became necessary for the UK to address the cable colour issue with some urgency. The Joint BSI/IEE committee responsible for the technical content of the UK standard
The Working Group's recommendations subsequently formed the basis of a UK proposal to which, much to the surprise of many, was accepted by the CENELEC countries almost unanimously. Europe now had the opportunity to fully harmonise the colour identification system not only for non flexible cables for fixed wiring, but also for flexible cables and cords, and distribution cables.
brown for the phase conductor of singlephase circuits. It also concluded that, due to the widespread adoption in the rest of Europe, the UK would also have to accept black for
Other European countries had made radical changes in their colour identification systems without undue safety problems, and the public in the UK were already familiar with a blue neutral and brown phase in the leads of their domestic appliances. After all, up until about 1994, UK consumers were expected to fit their own plug to almost every new appliance they bought! The colours of fixed wiring in the UK had also changed radically over the previous 90 years or so as can be seen from the following chart, apparently without serious safety problems.
Cable colour specified in past editions of the IEE Wiring Regulations
one of the other phases of a multi phase circuit. The Working Group also considered there was a need to be able to distinguish between the phases of a three phase circuit, and decided to propose the colour grey for one of the phases because, of the very few remaining pan European colour options, this seemed to have the least disadvantages.
So the new harmonised colours of brown, black and grey for the line conductors, blue for the neutral, and green-and-yellow for the protective conductor were introduced in Amendment No 2 to BS 7671: 2001 (IEE Wiring Regulations 16th Edition), and became a requirement for all new electrical installation work with effect from 1 April 2004 - All Fools Day, as some gleefully pointed out at the time!
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EVENTS FOR 2010 With the highly successful 2009 schedule of events now behind us, we look forward to a packed 2010. e will be participating in this year’s Elex and Sparks trade shows throughout the UK, which give us great opportunities to meet with apprentices, electricians and tutors, to distribute our best practice guidance, and to discuss face-to-face issues affecting the industry.
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We will continue to host the industry forums at Elex. These proved hugely popular last year, bringing together experts to discuss topical matters of interest or concern. With our increasing focus on improving the condition of the electrical installations in the UK’s rented housing stock, we will be attending even more events aimed at
landlords and specifiers to put across our electrical safety messages. We will again be attending the Homebuilding & Renovating Shows to talk to those engaged in building and renovation projects about their electrical installation work, and to encourage them and others planning to buy or sell properties to get their electrics installed or checked by a registered installer. Additionally, our active liaison with industry bodies will see us attending the Trading Standards Conference, the Citizens Advice Annual Conference, hosting two parliamentary receptions and again attending the conferences of the leading political parties later in the year. With our roadshow that was so successful in 2009 touring again throughout this year,
we look forward to meeting and working with a huge variety of people and groups to improve awareness of electrical safety issues.
Visit the events page on our website (www.esc.org.uk) for a full and up-todate programme of our activities.
POLITICAL PARTY CONFERENCES ast autumn, to further raise our profile in political circles, we again had an exhibition stand at the Labour, Conservative and Liberal Democrat conferences.
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The conference season began with the Liberal Democrats in Bournemouth. There, amongst others, we met with Baroness Tonge, one of our longstanding political supporters, who expressed continuing interest in our safety campaigns. After that it was a trip along the coast to Brighton for the Labour Party conference. One particularly constructive meeting was held with Kevin Barron MP, Chair of the Health Select Committee. Phil Buckle, our Director General, outlined the need for clear, accurate reporting of accident
data in the UK, to which Kevin was highly receptive. The re-establishment of a reliable accident data collection system in the UK is essential if we are to be able to effectively monitor and target threats to health from dangerous electrical installations and products. Finally, we headed north to Manchester for the Conservative conference. There we met with Stewart Jackson MP, Shadow Minister for Communities and Local Government, to discuss the safety of domestic electrical installations in rented properties. He was surprised to discover that, unlike for gas installations, there is no specific legal requirement for electrical installations in rented properties to be inspected tested for safety.
READERSHIP SURVEY e would like to thank all of you who completed the online readership survey we announced in the autumn issue.
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We are still analysing the feedback we’ve received, and will be reporting on it in the next issue. 6 SwitchedOn
Details of the lucky winners of the various prizes we offered to encourage readers to compete the survey can be found on our website, www.esc.org.uk.
Following an encouraging response, we hope to work with Mr Jackson in the future to help develop new requirements. Our stand carried a wide range of information about our current campaigns, including safer rented homes and the collection of accident and injury data through the NHS. A significant number of MPs and Councillors sought out the stand, having a specific interest in our work. In summary, it was a successful conference season for us, which should lead to some positive outcomes for the charity and the sector over coming months.
ELECTRICAL INSTALLATION WORK – WHO IS THE DESIGNER? ommon answers to this question range from ‘the architect’, ‘the specifier’ or ‘the consulting electrical engineer’ to ‘the builder’ or indeed ‘the customer’.
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In fact, with the possible exception of the consulting engineer, the others are specifiers. A specifier is primarily concerned with specifying the electrical equipment to be used and/or the positions of the points of utilisation such as socket-outlets and lighting points, in order to satisfy the customer’s functional requirements.
Designers on the other hand are concerned with translating the specification into an electrical design that satisfies customers’ functional requirements, is legal (for example compliant with Building Regulations) and, of paramount importance, safe, including ensuring that the completed installation will perform satisfactorily in the event of a fault, an overload or an emergency.
equipment and the provision of the appropriate precautions for special locations.
These aspects can only be achieved by an electrically competent person, such as an electrical contractor, who is working either to the national standard for the safety of electrical installations (BS 7671) or to standard electrical design criteria, such as those to be found in the IEE On Site Guide. In general, this requirement will exclude the architect, the builder and the intended user of the installation. Indeed, the electrical contractor is the designer in most situations, though may also be the specifier. The designer then is the person or organisation responsible for all aspects of the installation design. These include the selection of protective devices, the sizing and routing of cables, the installation methods used, the selection of suitable
standards (such as those for fire detection and alarm systems, and emergency lighting), and before completing the design calculations. If the designer chooses to use a standard circuit design, such as for a 32 A ring final circuit, it is that designer’s responsibility to ensure that the standard design selected is appropriate in all the circumstances for the intended purpose of that circuit.
The positioning of socket-outlets, lights etc is considered to be layout detail and not electrical design. However, the electrical designer will need to know the proposed positions of the equipment before determining whether or not such positions will allow compliance with the requirements of BS 7671 (Requirements for electrical installations) and other relevant
In cases where the electrical contractor is not the designer, the contractor would be well advised to obtain the designer’s certification on the electrical installation certificate before commencing the installation work, to help avoid any unforeseen liabilities later on.
lectrical contractors that usually undertake installation work in domestic and small commercial premises only may consider that they are not involved in electrical design. However, if no other person or organisation is specifically responsible for the installation design, then the contractor will inevitably assume the role and responsibilities of the designer.
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This applies even where the design work only involves the application of industry standard designs, such as for ring final circuits. In such cases, the contractor is responsible for the correct application of the industry standards and, consequently, for the design of the whole installation.
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“Fully updated to the ‘17th Edition’, The Essential Guide to the Wiring Regulations is a unique and authoritative source of reference on electrical installation safety matters”
Your Essential Guide to the G
reat news for the electrical installation industry and for those wishing to have a wealth of technical information at their fingertips – we’re making our definitive guide to complying with BS 7671 (IEE Wiring Regulations) and related standards available to all* - online!
Formerly known as ‘the Technical Manual’, the constantly developing Guide, which has already been many years in the making, currently comprises over 300 illustrated topics, each giving detailed information and guidance on how to comply with a particular aspect of BS 7671 or a related standard.
Fully updated to the ‘17th Edition’, the Essential Guide to the Wiring Regulations is a unique and authoritative source of reference on electrical installation safety matters, and a definitive guide to complying with the requirements of BS 7671 (IEE Wiring Regulations) and related standards, for the electrical contracting industry and other qualified practitioners.
In printed form, the topics would fill at least four large A4 binders. However, in this electronic age, all the topics are fully searchable on screen, and are hyperlinked where appropriate to related topics. All the published topics are kept under review, and are updated as and when necessary.
The Essential Guide comprises discrete articles, or ‘topics’, each of which concentrates on an electrical installation issue of interest to, amongst others, electrical installation contractors and installers, electrical engineers, electrical installation designers, college lecturers, electrical equipment manufacturers and the members of those committees responsible for the production of national and industry standards for electrical installations, equipment and products. The relevant requirements of BS 7671, other British Standard and Industry Codes of Practice are identified and amplified, and their implications explained. Many topics also incorporate data and other useful information on the subjects they cover.
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The Essential Guide is growing at the rate of about 40 new and significantly revised topics per year towards a target of 800 topics. But there’s no need to download updates – the latest version of the Guide is always the one online. However, for those who might prefer to keep some of the essential information at their fingertips on paper, each of the topics is printable in full colour as a PDF, which keeps the appearance and formatting perfect. The online version contains a range of interactive features, including: • Your popular searches • Your reading list • What’s new • Options for comments and feedback. • Dynamic search options and links
e Wiring Regulations – Available Now! Forthcoming topics will cover aspects of the following: • Building Regulations Approved Documents (England and Wales) • Earthing • Protective Multiple Earthing • Transformers In addition to the wide range of topics, subscribers to the online Essential Guide will gain access to additional technical material, including the BEAMA Guides. The Essential Guide is a valuable source of technical information and guidance for all those involved in electrical installation and allied work, including:
The intended users of the Essential Guide are persons trained to at least National Vocational Qualification (NVQ) Level 2 in electrical installation work, and having a good understanding of the requirements of BS 7671 and related standards. *By arrangement with our trading subsidiary NICEIC Group Ltd, the online version is already available (as ‘The Technical Manual) free of charge to NICEIC Approved Contractors, NICEIC Domestic Installers and, more recently, to NICEIC Partners. The NICEIC Partner scheme is an annual membership scheme which provides NICEIC clients, from a variety of organisations within the electrical contracting industry and related sectors, with a wide range of technical and business support services. (Email niceicpartner@niceic.com)
To trial the Essential Guide, and to subscribe, please visit our new Electrical Information Hub at www.eschub.org.uk
• electrical contractors and installers • electrical engineers • electrical installation designers • building services engineers • building services maintenance engineers • colleges and training bodies • electrical equipment manufacturers • housing associations • local authority building control and environmental services departments
A 12 month subscription to the online Essential Guide to the Wiring Regulations currently costs around £100 including VAT, which is exceptionally good value. But the price is under review, so don’t delay! To trial the Essential Guide, and to subscribe, please visit our new Electrical Information Hub at www.eschub.org.uk
• NHS Trusts • Facilities management companies SwitchedOn 9
ACCESS TO SERVICE FUSES
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here have been further developments since we reported on this subject in the autumn issue of Switched On. The following is an update report from the Distribution Connection and Use of System Agreement (DCUSA) Working Group, issued last October:
BACKGROUND The Distribution Connection and Use of System Agreement is a multi-party contract between electricity distributors and electricity suppliers/retailers. It governs the main relationship between people who sell electricity and the owners of the networks that transport it. Since 1990, the electricity supply market has been open to competition. As part of the arrangements, electricity suppliers are responsible for the energisation status of premises. Meter Operators (acting on behalf of an electricity supplier) change the energisation status of premises and work on the distributor’s termination equipment, that is, remove and replace service fuses. Distributors and Meter Operators have legal obligations under the 2002 Electricity Safety, Quality and Continuity Regulations (ESQCR) for their equipment on customer’s premises
WORKING GROUP FINDINGS Recognising that it is dangerous for work to be performed live and that it is unsatisfactory for seals to be broken by unauthorised persons, the parties to the DCUSA established a Working Group to seek to understand what practices are happening and why, and to recommended solutions for addressing the issue. The Working Group carried out a consultation in March last year and, as at the end of October, had met five times to consider the responses. Comments received indicated a clear desire from electricians to carry out de-energisation and re-energisation activity. However, few suppliers and Distribution Network Operators (DNOs) supported this activity.
but not under the control of the customer. The equipment must be designed, installed and maintained to ensure safety and continuity of supply. There are also obligations on suppliers, distributors and Meter Operators regarding revenue protection. When undertaking work at premises, electricians may require those premises to be de-energised. Electricians are not permitted by the distributor to undertake the de-energisation work themselves. In order to have premises de-energised, electricians must therefore identify who the electricity supplier is, contact them, and ask them to arrange for a Meter Operator agent to visit the premises to perform the work. There may be lead times associated with arranging for the work to be completed. Metering work is subject to the Electricity (Standards of Performance) Regulations 2005, which require the supplier to be able to agree a “timed appointment”within a two hour band. Where multi-premise projects such as
The Working Group has developed three potential solutions, set out as Options 1, 2 and 3 below, which it hopes could facilitate necessary work being done by authorised persons in a timely manner.
Option 1 – Approved accreditation scheme: This proposal would require the industry to develop a scheme whereby permission is granted by relevant parties to allow accredited electricians to de-energise sites to work on a customer’s equipment (typically the consumer unit). The scheme would need to be managed by an agreed body and provide a robust governance framework and possibly a training scheme. Any scheme developed would sit outside the DCUSA.
Option 2 – Fit double-pole isolators:
The Working Group has therefore considered the root causes of the issues and alternative solutions as a means of developing a solution.
This proposal would mandate the fitting of a double-pole isolator (DPI) on all new connections. In addition to this, suppliers
CONSULTATION The DCUSA Working Group report invited consultees to answer a series of questions relating to the three options.
consultation in March last year, in which we expressed a strong preference for what is now Option 1, the approved accreditation scheme for electrical contractors.
Our response to these questions was consistent with our response to the original
The short consultation period ended in early November, after which the Working Group
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rewiring of blocks of flats are involved, there may be more than one supplier involved and so the electrician could have to liaise with a number of parties. Suppliers may charge the customer for attending to perform a temporary deenergisation/re-energisation. Many suppliers also offer a service where their Meter Operators will attend to fit a double-pole isolator switch. The electrician can then use this to safely isolate the supply. Anecdotal evidence suggests that work may be being carried out while the electrical circuit is live, or de-energisations are carried out by unauthorised persons. In these cases the cut-out seals, which are designed to act as a deterrent to tampering, are broken. This impacts the distributor’s equipment, the customer’s installation connected to it, and the intermediate metering system, which could adversely affect the safety of the buildings and occupants.
would have to fit DPIs as part of any site visit to carry out metering works. Under this proposal, the customer would be deemed to have ownership of the DPI once fitted.
Option 3 – Improve existing supplier and agent processes: This proposal would require all parties to look at their in-house processes to make it easier for electricians to make appointments and ensure that they conform to the existing Electricity Standards of Performance Regulations. Under this proposal, the key processes around communication (identifying the right person and call handling) and timescales (speed of appointments) would need to be addressed. The governance of this proposal would also need to be determined – such as through a voluntary or mandatory Code of Practice. The proposal could be implemented either on its own or in conjunction with Options 1 or 2.
was expected to reconvene to consider all the responses before submitting a final recommendations report to the DCUSA Panel. We expect to be able to report the outcome of the DCUSA deliberations in the next issue of Switched On.
PLANS UNDERWAY FOR MAJOR SAFETY CAMPAIGN lectricity is an integral, but invisible, part of all our lives. So it’s easy to forget just how powerful and dangerous it can be. This is why, four years ago, the Electrical Safety Council was launched with the aim, amongst other things, of raising public awareness of electrical safety issues.
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For decades, there have been increasing requirements in the UK Wiring Rules (BS 7671, formerly the IEE Wiring Regulations) to introduce an important (but largely unknown to the public) electrical safety device - the residual current device or RCD - into buildings. And those in electrical installation industry have embraced the change because they know that RCD protection can help save lives and to some extent prevent electrical fires. Since mid-2008, there has been a requirement in the UK Wiring Rules to provide RCD protection for virtually every socket-outlet and circuit in homes as part of a new installation, major rewire or replacement of a consumer unit. But even the most optimistic estimates suggest that, as yet, only 25% of consumer units in the UK include an adequate level of RCD protection.
We want to dramatically increase ownership – and habitual use – of RCDs, in much the same way as has been done for smoke detectors. While the fundamental message of the campaign is simple, achieving our objective of increasing RCD protection in UK homes by 10% over the next 5 years will be a major challenge. Our primary target audience will be consumers who put themselves at greater risk of electrocution by using mainspowered equipment for improving their
homes and maintaining their gardens – without RCD protection. A campaign of this nature requires a range of approaches, from partnership marketing with retail outlets through to engaging national media and working closely with electrical contractors who support our aims. To register your support or to find out more about the RCD campaign, visit our website www.esc.org.uk or email enquiries@esc.org.uk
GUIDANCE ON THE ELECTRICITY AT WORK REGULATIONS NOW AVAILABLE FREE OF CHARGE s reported in the autumn issue of Switched On, many of the HSE’s priced publications that contain health and safety advice and guidance have been made freely available from the HSE's website in PDF format to view and print.
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One of these publications is the essential Memorandum of Guidance on the Electricity at Work Regulations 1989, which intended to assist duty holders in meeting the requirements of the Regulations. As all those involved in or with the electrical industry should know, the purpose of the Electricity at Work Regulations is to require precautions to be taken against the risk of death or personal injury from electricity in work activities.
The Regulations are made under the Health and Safety at Work etc Act 1974 (HSW Act), which imposes duties on employers, the self-employed and on employees, including certain classes of trainees. The Regulations impose duties on duty holders in respect of systems, electrical equipment and conductors, and in respect of work activities on or near electrical equipment. The duties are in addition to those imposed by the HSW Act. The Memorandum of Guidance sets out the Regulations and gives technical and legal guidance on them except as they apply to mines
or quarries. It should therefore be of interest and practical help to engineers and electricians (including those involved in the design, construction, operation or maintenance of electrical systems and equipment), technicians and their managers. As the introduction to the guidance makes clear, “Only those who have both the knowledge and the experience to make the right judgements and decisions and the necessary skill and ability to carry them into effect should undertake work subject to the Regulations. A little knowledge is often sufficient to make electrical equipment function but a much higher level of knowledge and experience is usually needed to ensure safety.”
Why not check out the guidance at
www.hse.gov.uk/pubns/books/hsr25.htm? SwitchedOn 11
DOWNLIGHTERS Of particular concern was the number of instances where important safety information marked on fittings (such as the rated wattage, ingress protection rating and suitability for mounting on combustible surfaces) was found to conflict with details given on product packaging and in the installation instructions. In one case, two labels had been attached to the fitting, each indicating a different rated wattage!
s reported in the Summer 2009 issue of Switched On, we have been working with the Surrey Fire and Rescue Service to investigate concerns that incorrectly selected, installed and/or maintained downlighters may have been the cause of a significant number of fires in homes.
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As part of the investigation, we commissioned an independent laboratory to carry out a limited safety assessment of, and thermal performance testing on, a selection of commercially-available downlighters. Eight downlighters were selected to include a broad range of lamp type, fitting design and price, and assessed against the requirements for safety and performance specified in product standards applicable to ‘recessed luminaires’.
Also, labels had been attached to the exterior surface of fittings and would therefore be hidden once installed and when lamps were being replaced. G
Endurance testing Endurance testing was performed by operating the downlighters for a period of 10 days mounted in a purpose-built enclosure, taking into account the installation instructions. After the test, to comply with the standard, the downlighters should not show any signs of deterioration or have caused damage to their surroundings.
In essence, the downlighters were first tested when installed in accordance with the manufacturers’ instructions, and then when covered over with two layers of 100 mm thick thermal insulation. For all but one of the downlighters, covering the luminaire was considered to be an ‘abnormal’ mode of operation which contravened the installation instructions. However, being covered in thermal insulation or other material is reportedly one of the main reasons for downlighters being the source of fires.
Four of the samples failed this endurance test. Subsequent inspection revealed discoloration of internal painted surfaces due to heat from lamps, and discoloration and peeling of labels making them unreadable. A typical example is shown here.
A detailed report giving a full description of the samples, the tests applied and findings of the assessment can be viewed on our website at: www.esc.org.uk
Summary of the findings All of the downlighters failed to meet one or more of the tests and inspections performed during the assessment. G
In two instances, overheating had caused scorching of wood surfaces around the fitting as shown here.
Markings and instructions Seven samples failed to provide appropriate markings, warnings and/or user instructions. G
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Thermal testing
Thermal testing was performed by operating the downlighters at their rated ambient temperature and when fitted with a lamp type specified by the manufacturer. The most widely available type of tungsten halogen lamp on the high street is the ‘cool beam’ or dichroic reflector lamp. A dichroic lamp has a reflector made of a material that reflects visible light forwards while allowing radiated heat to pass out of the back of the lamp, resulting in a beam of light that is ‘cooler’. The alternative type of lamp is made with an aluminium reflector that reflects both light and heat forwards and out of the front of the lamp. As the bases of the most common types of push-fit extra-low voltage dichroic and aluminium reflector lamps are identical, it is possible to fit either type in any extra-low voltage downlighter. However, most extra-low voltage downlighters are not designed to operate safely with both types of lamp. For example, aluminium reflector lamps are generally specified for downlighters having integral fire protection to ensure that heat radiated by the lamp is not directed back into the fire containment compartment of the luminaire. The interchangeability issue is a concern because, while preparing for the laboratory tests, we found it difficult to find the aluminium reflector type lamp in any of the normal retail sources over quite a wide area, or indeed in wholesalers. Therefore, even if consumers were aware of the need to select the correct lamp type for their particular downlighters, they might purchase the wrong type as a matter of necessity or expediency.
Can they be a FIRE HAZARD? Where appropriate, additional thermal testing was performed on downlighters with incorrect lamps types fitted to simulate an abnormal (but foreseeable) mode of operation.
Under these conditions, one of these five downlighters failed to operate for the required duration of ten days. An inspection after test revealed that the lampholder wiring had burnt out as shown below.
During the tests, no part of the downlighters should exceed the limiting temperatures specified in the product standard. Three of the samples failed the thermal test with specified lamps fitted, and a further two samples failed the abnormal thermal test with incorrect lamps fitted. In three cases, the temperature of the test recess mounting hole exceeded the specification limit of 90 oC. The highest recorded temperature was 115 oC.
For another sample, heavy scorching was observed around the recess through which the downlighter was mounted, as illustrated below.
In two cases, the insulated wiring at the lampholder exceeded the specified limit of 200 oC, the highest measured temperature being 219 oC.
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Endurance test: with covering of thermal insulation.
It would appear evident from the findings that the design of, the markings and instructions provided with, and the thermal performance of downlighters are significant factors that can increase the risk of fire where the minimum requirements of relevant product standards are not met. Following further discussions with the Surrey Fire & Rescue Service and the Department for Communities and Local Government (CLG), it is felt that enough evidence has been amassed from the laboratory testing and anecdotal evidence to support a UK-wide awareness campaign that would identify the main stakeholder groups (contractors, manufacturers, retailers, trade suppliers and consumers) to deliver key safety messages about the potential fire risks of downlighters - so watch this space! As with all product safety investigations undertaken, we are following up all the identified failures with the retailers and manufacturers concerned, and keeping the relevant authorities informed of our actions.
A recorded temperature of 171 oC immediately above one downlighter was almost twice the limit of 90 oC specified in the relevant product standard. Many other instances of temperatures exceeding specified limits were noted, both for the luminaires and associated parts such as transformer cases and supply cables, but were within the allowable tolerances and so not recorded as failures.
Conclusions
In a further case, significant scorching of the test recess above the downlighter was observed as shown in the photograph. During the test period,it was noted that the lamp failed, the most likely cause being excessive temperature rise.
Anyone who has reason to believe they have purchased an unsafe downlighter should contact their local authority trading standards office in the first instance. However, we would also like to hear from anyone regarding any general concerns about the safety of downlighters. Please send details to: productsafety@esc.org.uk
In addition to the four samples that failed the initial thermal endurance test, a further sample failed the additional endurance test when covered with thermal insulation.
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ASDA FUNDS FESTIVE LIGHTS AMNESTY ver the past few years, our festive messages have been centred around the safety of decorative lighting.
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We have been encouraging householders to consider the age and condition of their festive lights before reusing them and then, if they are in a satisfactory condition, to use them safely.
Our Christmas lighting leaflet has been widely distributed over the past three seasons, including through ASDA Living stores. The leaflet informs consumers about the various factors concerning decorative lighting they should take into account in order to minimise the risk of electric shock and fire.
We are delighted to say that ASDA has been very supportive of this aspect of our consumer safety campaigning. Indeed, last November, ASDA ran a ‘Christmas lights amnesty’ in partnership with us in their Living stores. The aim of the amnesty was to provide their customers with an opportunity to part-exchange old lighting sets that were either in poor condition or no longer had the packaging or safety information, for new, safer and more environmentallyfriendly sets. ASDA offered a trade-in deal which enabled their customers to purchase new LED lighting sets at a discount when bringing in their old sets for disposal. This resulted in tens of thousands of sets of lights being replaced during the amnesty weekend in late November. We are indebted to ASDA for their support with this initiative, and for their promotion of our electrical safety messages during the festive season and beyond. Their commitment to their customers’ safety and education are exemplary, and we hope that other major retailers will follow their lead.
STANDARD FOR EARTHING AND BONDING CLAMPS REVISED Electrical earthing – Clamps for earthing and bonding – Specification has been revised by the BSI Electrotechnical Committee GEL/600, upon which the Electrical Safety Council is represented. The amended standard supersedes BS 951: 1999, which is now withdrawn.
BS 951
current appropriate to the size of the connected conductor. When tested in accordance with the procedure given in Annex A of the standard, the temperature rise at the termination of the conductor and the interface of the clamp and test pipe is not to exceed 52 °C.
Test for short-circuit The amended standard does not introduce significant changes but, at the instigation of the Electrical Safety Council, does incorporate more performance-based requirements and new tests for temperature rise and short-circuit. Tests for checking impedance and torque are unchanged.
Test for temperature rise A temperature rise test is included to check the effectiveness of a clamp when carrying 14 SwitchedOn
A short-circuit test is included to check the robustness of a clamp under fault current conditions. When tested in accordance with the procedure given Annex B of the standard, no signs of damage which might impair further use must have occurred to any part of the clamp. An additional test is then carried out to check that the impedance between the protective conductor and the tube to which it is connected does not exceed 1 milliohm.
Courtesy of Tenby Industries Ltd
SAFETY OF PORTABLE APPLIANCES PROVIDED BY LANDLORDS his article summarises a part of our Landlords’ Guide to Electrical Safety* which gives safety recommendations relating to portable appliances.
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The majority of electric shock fatalities in homes are caused by faulty plugs, leads and appliances. Many of these fatalities can be avoided by landlords and tenants taking simple steps. It needs to be recognised that the safety of portable appliances relies to some extent on the condition of the fixed wiring in the premises. The incorrect use of any hand-held electrical appliance will increase the risk of electric shock to the user. For example, after using an appliance such as an iron, the user may wind the flexible cable around the appliance, and create a twist or kink in the cable. Repeating this process over time may lead to the cable being damaged, so increasing the risk of electric shock or fire. In order to minimize the risks, landlords and tenants need to take steps to help ensure that portable electrical equipment is safely used and stored, and checked for damage and deterioration at appropriate intervals.
mark are given preference. These marks indicate that the appliance has been assessed by an independent body as conforming to the relevant product standard, giving a greater assurance of electrical safety. It is also important to ensure that the electrical installation is suitable for the equipment provided and that the equipment is suitable for the conditions and location in which it is likely to be used. When providing new portable appliances to tenants, landlords should always ask the tenants to read and follow the manufacturers’ instructions. A copy of the instructions should be left in the property so that the tenants can refer to them as and when necessary. Landlords should also ensure that manufacturers’ instructions for existing electrical equipment in rented properties remain available for new tenants.
Inspecting portable appliances To ensure that portable appliances continue to be safe for use, basic visual safety checks should be carried out regularly. The checks that the landlord or the user of the appliance can safely carry out, with the appliance unplugged, include confirming that: G
We recommend that appliances with additional safety marks such as the British Standard Kitemark or the ‘BEAB Approved’
Where a portable appliance is likely to be used in the garden or driveway, it is strongly recommended that the socket-outlet supplying the appliance is protected by a Residual Current Device (RCD) with a rated residual operating current of 30 mA or less. An RCD is an electrical safety device that provides additional protection against electric shock if a person comes into contact with a live part, for example after having cut through a mower supply cable. We recommend that all socket-outlets that may reasonably expected to be used to supply electrical equipment for use outdoors are protected by a fixed RCD, that is one that is fitted in the consumer unit (fusebox) or built into the socket-outlets. Fixed RCDs should be tested by the user at quarterly intervals by pressing the test button marked ‘T’ or ‘Test’ as stated on the instructions that should be on or next to the consumer unit. (If none of the devices in the consumer unit have a test button, there is no central RCD protection.)
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there are no cuts or abrasions in the cable covering (sheath)
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the plug has no cracked casing or bent pins
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there are no loose parts or screws
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there are no signs of overheating or burning, particularly at the plug
Where there is no RCD in the consumer unit, we strongly recommend that a portable plug-in RCD is used between the plug of the appliance to be used outdoors and the socket-outlet. This plug-in type of RCD, which can cost less than £10, should be tested before each use in accordance with the manufacturer’s instructions.
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the outer covering of the cable is gripped by the cord grip in the plug top so that no coloured cable cores are visible from outside of the plug. (The function of the cord grip is to prevent the internal connections being pulled loose.)
Information relating to the testing of portable appliances can be found in Annex D of the Landlords’ Guide to Electrical Safety. This subject will be addressed in a subsequent issue of Switched On.
Supplying portable appliances Before supplying portable appliances to tenants, landlords should check that each appliance at least has the CE Mark, which is the manufacturer’s claim that the appliance meets all the relevant requirements of European legislation.
the fuse in the plug is correctly rated for the appliance
Portable appliances for use outdoors
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no part of the appliance is damaged (for example, cracked or dented) or missing (for example, a protective cover or screw).
The majority of dangerous defects in electrical appliances can be found by carrying out these basic visual checks.
* The Landlord’s Guide to Electrical Safety is available as a free download at www.esc.org.uk/business-andcommunity/guidance-for/landlords.html A limited number of printed copies may requested from enquiries@esc.org.uk SwitchedOn
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ELECTRICAL INSTALLATION FORUM 17th Edition guidance e are pleased to announce that City & Guilds has become the latest member of the Electrical Installation Forum, bringing the number of major industry bodies represented on the Forum up to 14.
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Where the earth fault loop impedance for a circuit exceeds the maximum Zs for the overcurrent device, is it permissible to use an RCD?
All boxes have to be completed with a tick or n/a. What then do you need to do with the boxes relating to cable routes in prescribed zones?
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In the model Schedule of Inspections in BS 7671, what has 'Presence of adequate arrangements for alternative sources' to do with automatic disconnection of supply?
For the industry-agreed answers to these and many other commonly-asked questions relating to the application of the 17th Edition, visit www.esc.org.uk/forum
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The model Schedule of Inspections in BS 7671 would be used as part of an Electrical installation certificate where a consumer unit was installed, but no circuit cables were replaced.
We recommend that those following the guidance provided by the Forum visit the site at least every couple of months to see what other additions and amendments have been made.
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The answers to several new commonlyasked questions have been added to the Forum’s website since the previous issue of Switched On was published, including: Is it acceptable to mount a cooker switch in a kitchen cupboard that is adjacent to the cooking appliance?
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HOUSEHOLD LAMPS TO BECOME MORE ENERGY EFFICIENT new set of energy efficiency requirements for lamps, set by the European Union (EU), started to come into effect last September,
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Traditional incandescent and halogen lamps will be gradually phased out from the market by the end of 2012. However, lamps that are banned will not be removed from the shops – retailers are allowed to sell their existing stocks. The requirements differentiate between lamps that are ‘clear’ (transparent) and non-clear.
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Non-clear lamps will need to reach the A-class according to the EU’s lamp energy label, which means energy savings of 75% or more as compared to traditional incandescent lamps. At present, only compact fluorescent lamps and LED lamps can achieve such high efficiency.
New requirements relating to the functionality of lamps (starting times, lifetimes etc) have also been introduced such that only quality lamps meeting users’ expectations will be allowed on the market. Additional product information will also be required on the packaging to help consumers make the right choice for the intended purpose.
Meanwhile, inefficient clear lamps will also be phased out gradually. As from last September, equivalents of clear incandescent lamps of 100 W or more must be made with more efficient technology, such as efficient halogens. This limit will be moved down to lower wattages gradually until 2012 (75 W in 2010, 60 W in 2011, 40 W and below in 2012).
According to the EU, the measure will save annually some 40 TWh of electrical energy by 2020, the equivalent of 11 million European household’s energy usage for the same period. It will also lead to a reduction of up to 15 million tons of CO2 emissions annually, contributing to the EU objective of cutting greenhouse gas emissions by 20% by 2020. Further measures are planned for reflector lamps such as those used in downlighters and spotlights. Perhaps these measures will reduce the risk of downlighters becoming the source of fires, which we’ve reported on in the article on page 12.
SKILLELECTRIC FINAL 2009 or the second successive year, we have been pleased to support the SkillElectric electrical installation skills competition as an official sponsor.
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Last October, the UK final took place live in front of thousands of onlookers at Interbuild, one of the biggest weeks in the industry’s calendar. Birmingham’s NEC once again played host as ten top UK finalists took part in two and a half days of practical skills tests based on real-life work situations, competing in purpose-built bays specially designed for the competition. The finalists were: G
Joseph McKinney (21), Electrical Services (County Antrim)
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Michael Cunnea (24), Glengaia Ltd (Fife)
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Ryan Anderson (20), James S Wilson Electrical Contractors (Perth)
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Matthew Derbyshire (28), Nottingham City Homes (Nottingham)
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Minesh Patel (18), Illumination UK (London)
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Sabrina Thomas (20), MR Electrical (Portsmouth)
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Chris Young (20), Rogers Restorations (Somerset)
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Alastair Harris (20), D&M Bathorpe (Boston, Lincolnshire)
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Nathan Willmott (20), NG Bailey & Co Ltd (Birmingham)
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Jamie Clement (21), Crown House Technology (Cardiff ).
In second place was Minesh Patel, employed by Illumination UK Ltd and trained by the College of North West London. Matthew Derbyshire, who came third, is employed by Nottingham City Homes and trained by Stephenson College.
To get to this stage, all contestants had completed a theory examination, and electrical installation work to a high standard at regional heats. First place was awarded to Chris Young of Rogers Restoration. Trained by Bridgwater College and accompanied by his employers, Chris said: “This has been a fantastic experience. The team spirit between everyone was amazing and it has been an honour to compete beside such talented people.” Chris (pictured right) received a cash prize and a selection of high-class industry equipment donated by the sponsors.
WINNER OF UK SKILLELECTRIC 2008 STRIKES GOLD AT WORLDSKILLS here is no doubt that getting involved in the UK skills competitions can lead to even greater things. Last year's SkillELECTRIC champion Richard Sagar has won the coveted Gold medal following a hard-fought international final at WorldSkills 2009, the world’s largest international skills competition.
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last September involving over 900 competitors from more than 50 countries. Overall, Team UK turned out an excellent performance, winning three golds, six bronzes and 14 Medallions of Excellence.
More information about the competition can be found at: www.skillmande.org.uk
Twenty-two year-old Richard from Langholm in Dumfriesshire, employed by Eden Electrics Ltd and trained by SECTT, competed against a quality line-up of top world-class contenders in the Electrotechnical Installations event in Calgary, Canada. He joined the 26-strong Team UK taking part in a huge range of skills competitions
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ADEQUACY OF METER TAILS AND EARTHING CONDUCTORS IN EXISTING DOMESTIC INSTALLATIONS Inspectors carrying out periodic inspections of installations in domestic premises occasionally find that the singlecore pvc/pvc copper meter tails have a cross sectional area of only 16 mm2 (current rating 87 A clipped direct), but the rated current of the distributor’s BS 1361 cut-out fuse is 100 A. The person compiling the Periodic Inspection Report is then faced with having to decide if the meter tails are suitable for continued service. The inspector may also find that the greenyellow pvc-insulated earthing conductor has a cross sectional area of only 10 mm2, rather than 16 mm2 as is usual for a new domestic installation. The question then arises as to whether the earthing conductor is suitable for continued service. These two issues are considered separately below. Meter tails 16 mm2 pvc/pvc copper meter tails can be suitable for continued service with a 100 A BS 1361 cut-out fuse if: a) the maximum demand of the installation, taking account of the load characteristics (diversity and load profile), does not exceed the current rating of the tails (Regulations 433.3.1(ii) and 523.1 refer), and b) the tails are protected against fault current in accordance with Section 434 of BS 7671.
As a practical tip, condition a) is likely to be met if the tails have been in service for several years and there is no sign of thermal damage at the terminations or to the cable sheath or insulation. However, where doubt exists that condition a) is met, an assessment should be made of the maximum demand (such as by suitable calculations or measurements) and this should be checked against the current rating of the meter tails. For condition b) to be met, the value of k2S2 for the meter tails must be greater than the value of let-through energy (I2t) of the fault current protective device (Regulation 434.5.2 refers). Compliance with condition b) has been checked graphically in Fig 1, on the basis of using the distributor’s 100 A BS 1361 fuse as the protective device for the tails. The figure includes the adiabatic line of the 16 mm2 pvc/pvc meter tails superimposed onto the time/current characteristic of a 100 A BS 1361 fuse plotted on double logarithmic graph paper, taken from Appendix 4 of BS 7671. The adiabatic line is drawn using a k value of 115 (taken from Table 43.1 of BS 7671 for 70 oC thermoplastic insulated copper live conductors) and an S of 16 mm2 (the conductor cross-sectional area). The simplest way to obtain the adiabatic line for a conductor of S mm2 cross-sectional area and a given value of k is to first plot along the horizontal line for 1 s the point corresponding to kS amperes (1840 A in the case of Fig 1). Then along the horizontal line
for 100 seconds plot the point corresponding to 0.1 kS amperes (184 A in the case of Fig 1). Join the two points by a straightedge and draw a straight line from the horizontal line corresponding to 5 s to the horizontal line corresponding to 0.1 s. It can be seen from Fig 1 that the adiabatic line lies wholly to the right of the fuse characteristic and does not intersect it. The absence of an intersection in these circumstances means that there is no minimum value of prospective fault current for which the tails will be protected against fault current by the 100 A fuse (the minimum value being the most onerous in the case of a fuse, as this leads to the highest value of let through energy (I2t)). Therefore condition (b) is met irrespective of the value of prospective fault current, within the rated breaking capacity of the fuse. Earthing conductor A 10 mm2 earthing conductor can be suitable for continued service with a 100 A BS 1361 cut-out fuse if the earthing conductor is protected against earth fault current in accordance with Regulation 543.1.3 (adiabatic equation). This will be the case if the value of k2S2 for the earthing conductor is greater than the value of let-through energy (I2t) of the fault current protective device. (This can be seen by re-arranging the adiabatic equation into the form k 2 S 2 >_ I 2 t.)
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Time/current characteristics of 100 A BS 1361 fuse
TIME, SECONDS
100
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Adiabatic line of 16mm2 meter tails (K = 115) 1
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0.01 1
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PROSPECTIVE CURRENT, rms AMPERES 18 SwitchedOn
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Fig 1 – Adiabatic line of 16 mm2 meter tails (line and neutral) plotted onto the time/current characteristic of a 100 A BS 1361 fuse. Note: The adiabatic line is plotted for disconnection times not less than 5 s, the longest time for which the adiabatic equation is valid.
Two cases need to be considered for protecting the earthing conductor against earth fault current:
Protection of the earthing conductor by an outgoing protective device of the consumer unit
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protection by the distributor’s 100 A BS 1361 fuse, and
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protection by an outgoing protective device of the consumer unit.
The possibility that the earthing conductor is protected by an outgoing device of the consumer unit need only be considered if the prospective earth fault current at the consumer unit is less than 800 A. For prospective earth fault currents higher than 800 A, protection is provided by the 100 A cut-out fuse as explained above.
The two cases are considered separately as follows. Protection of the earthing conductor by the distributor’s 100 A BS 1361 fuse Compliance with the adiabatic equation of Regulation 543.1.3 has been checked graphically in Fig 2, based on using the distributor’s 100 A BS 1361 fuse as the protective device for the earthing conductor. As in Fig 1, the adiabatic line is drawn using a k value of 115 (but this time taken from Table 54.3 of BS 7671 for a 70 oC thermoplastic insulated copper protective conductor bunched with the live conductors) and an S of 10 mm2 (the conductor cross sectional area). It can be seen from Fig 2 that the adiabatic line of the 10 mm2 earthing conductor intersects the time/current curve of the 100 A fuse at a point corresponding to a prospective earth fault current of 800 A. This means that the earthing conductor will be protected against earth fault current by the 100 A fuse, only if the prospective earth fault current at the consumer unit is 800 A or more (that is, Ze is less than 0.29 Ω, assuming a nominal voltage U0 of 230 V).
An outgoing protective device of the consumer unit can be expected to protect the earthing conductor if the following conditions 1), 2) and 3) below are met: 1) the meter tails meet the following conditions (i), (ii) and (iii) of Regulation 434.2.1, namely:
3) the value of let through energy (I2t) for the outgoing protective device under earth fault conditions is less than the value of k2S2 for the earthing conductor (that is, less than 1152 x 102 = 1,322,500 A2s). The relevant outgoing protective device to consider regarding condition 3) is the fuse or circuit-breaker having the highest rated current. Most, if not all, types and ratings of outgoing fuse and circuit-breaker normally fitted into consumer units in domestic premises will meet condition 3) where the prospective earth fault current is not more than 800 A. Two examples are: •
30 A semi-enclosed (rewireable) fuse to BS 3036: let-through energy (I 2 t) = 37,845 A2s (based on the most onerous condition of an earth fault current of 87 A and a disconnection time of 5 s, such as could be the case for a fault at the end of a final circuit)
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50 A Type B or C circuit-breaker to BS 3871 or BS EN 60898: let-through energy (I 2 t) = 64,000 A2s (based on the most onerous condition of an earth fault current of 800 A and an ‘instantaneous’ tripping time of 0.1 s).
(i) the length of run of the meter tails does not exceed 3 m, (ii) the conductors are installed in such a way as to reduce the risk of fault to a minimum, and (iii) the conductors are installed in such a way as to reduce to a minimum the risk of fire or danger to persons. Note: Conditions (i) and (iii) will generally be met if the single-core pvc/pvc meter tails (and the adjacent earthing conductor) are properly supported and are so located or mechanically protected that they are not vulnerable to mechanical damage, and the length of sheath removed at the terminations of the meter tails is kept to a minimum.
To summarise: provided conditions 1), 2) and 3) are met, an outgoing protective
2) the consumer unit is designed so that an earth fault is unlikely to occur in the consumer unit on the supply side of the outgoing protective devices (such as an allinsulated consumer unit complying with the relevant British Standard), and
device of the consumer unit can be expected to protect the earthing conductor against earth fault current.
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Time/current characteristics of 100 A BS 1361 fuse
Fig 2 – Adiabatic line of 10 mm2 earthing conductor plotted onto the time/current characteristic of a 100 A BS 1361 fuse. Note: The adiabatic line is plotted for disconnection times not less than 5 s, the longest time for which the adiabatic equation is valid.
TIME, SECONDS
100
10
Adiabatic line of 10 mm2 earthing conductor (K = 115) 1
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0.01 1
10
100
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PROSPECTIVE CURRENT, rms AMPERES SwitchedOn 19
NATIONAL CHAIN PROSECUTED FOR SELLING DANGEROUS LAMPS AND KETTLES national chain store has been prosecuted by Westminster City Council for selling electrically dangerous lamps and kettles.
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Zoostation Ltd, which runs trendy homeware and accessories store, Octopus, in Carnaby Street and the Trocadero as well as other stores across London and in Bath, York, Leeds and Manchester, pleaded guilty to three offences of selling dangerous electrical goods at City of Westminster magistrates' court in April last year. The company was prosecuted under the Consumer Protection Act 1987 and the Electrical Equipment (Safety) Regulations 1994. According to Westminster Trading Standards, the wiring of the 230 V metal lamps was so poorly insulated that it could turn the appliance live and deliver a potentially lethal electric shock. The kettles were also badly designed, such that water could run down into the base and affect the wiring - again turning the product live.
Westminster's trading standards officers sent sample lamps and kettles for testing by an expert electrical engineer, who confirmed the wiring was faulty and that the products were dangerous.
The company came to the attention of Trading Standards following a complaint in Manchester about a defective hairdryer. The case was referred to Westminster where the company's main office is based.
The officers then seized more than 2,700 lamps and kettles worth almost £80,000 from the chain's 12 stores nationwide with help from trading standards officers in other regions.
Zoostation Ltd was fined £7,000 and ordered to pay £12,000 in costs. Westminster City Council endeavoured to work with Zoostation to ensure all unsafe appliances were removed from the market. A formal product recall could only be issued with agreement and cooperation from Zoostation Ltd, otherwise the Council would have been be liable for all costs incurred in the process.
TESTING OF SUPPLIES TO STREET LIGHTING ollowing the electrocution of a dog that came into contact with a metallic street lighting column in Scotland last year, it came to light that the local authority’s street lighting department had not been testing the power supply external to the column.
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Although the department was fully inspecting and testing the parts of the
street lighting circuits they owned and operated, they believed, wrongly, that they were prohibited from measuring the external earth fault loop impedance on lighting circuits and columns supplied from the 5th core of the distributor’s cable. Subsequently, this mistaken belief was found to be common in many local authorities in Scotland. They have now
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been instructed by HSE to start fully testing lighting circuits supplied from 5th cores. HSE Electrical Specialists have been asked to inform local authorities in England and Wales of this issue, and of the need to include earth fault loop impedance tests on street lighting supplies. We are pleased to assist in spreading this message.
All the previous issues of Switched On are available to read or download from the ‘Business & Community’ section of our website.