SPARKS Magazine Autumn 2023 issue

PROFESSIONAL PRESENTS:

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TOOL BAG

“If you’re an Electrician – here are some of my favourite tools that I’d recommend for your tool bag. Bosch Professional tools are quality made, robust and always get me through the toughest of tasks.”

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WANT TO BRING BOSCH PRO TO YOUR COLLEGE?

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EDITOR’S NOTE

Hanother awesome academic year. Whether you're new to the world of electrics or advancing in your apprenticeship, SPARKS has got your back every step of the way.

You can use our mag and on-line resources, your SPARKS course companions, to guide you towards an exceptional career.

And here's something you don't want to miss out on: Entries have just opened for the ‘SPARKS Learner of the Year 2024' and the 'SPARKS Female Skills 2024' competitions. Not only is this a great opportunity to showcase your skills and boost that confidence, but trust us – the prize line-up is . Connect with likeminded Sparky enthusiasts, have some fun and snag loads of amazing prizes. Don't get FOMO - chat with your lecturer to sign-up and don’t miss out!

Here's to a year of growth, and awesome achievements.

Celia Matthews

Managing Editor

MANAGING EDITOR: CELIA MATTHEWS celia.matthews@sng-publishing.co.uk

SENIOR GRAPHIC DESIGNER: LEE OWEN lee.owen@sng-publishing.co.uk

SENIOR DIGITAL CONTENT EXECUTIVE: PHOEBE MANSFIELD phoebe.mansfield@sng-publishing.co.uk

BUSINESS DEVELOPMENT MANAGER: PATRICK BLORE patrick.blore@sng-publishing.co.uk

BUSINESS DEVELOPMENT MANAGER: SARAH HERNE sarah.herne@sng-publishing.co.uk

EVENT MANAGER: SAMANTHA COLE samantha.cole@sng-publishing.co.uk

MANAGING DIRECTOR: ZOË TANNER zoe.tanner@sng-publishing.co.uk

TECHNICAL CONTRIBUTORS: Lewis Blakemore, Wigan & Leigh College

PRINTERS: Stephens & George, Wales

BUILD YOUR BRAND!

Check out these 3 top tips for building your brand.

1

SCHEDULE YOUR POSTS

Posting consistently on social media is key, but juggling it with college or work can be tough. You can save time by using a free social media scheduling tool to post ahead of time on various platforms. This frees up time for creating content, interacting with others, and growing your following.

Female Skills

2024

2024 OFLEARNER THE YEAR

For some social media inspo, check out what our SPARKS 2023 competitors are getting up to. Entering a competition like SPARKS LOY or SPARKS FSC is a great way to boost your confidence and help you to stand out from the crowd!

2

COLLABORATE WITH OTHERS

Creating content with other apprentices, tradespeople or local businesses can help expand your reach and introduce you to new audiences. Collaborative posts can be mutually beneficial and generate more engagement!

3

Sam Mackenzie –LOY23 Runner-up @sam_electrical_apprentice

Duncan Kinnaird –LOY23 Finalist @sparky_dunc

Caitlin-Rose Kerslake –FSC23 Finalist @caits.electrical

Remi Newman –LOY23 & FSC23 Competitor @thatgingersparky

BE AUTHENTIC

Show your personality, and let your passion for your trade shine through! This will help you to connect with your audience on a deeper level and make your profile stand out

SEARCH FOR SPARKS MAGAZINE

PHOEBE MANSFIELD SENIOR DIGITAL CONTENT EXECUTIVE

TAKES?

SPONSORS CONFIRMED SO FAR

“I T DOESN’T MATTER HOW MUCH OUT OF YOUR COMFORT ZONE YOU ARE, GO FOR IT!”

SCAN HERE TO DOWNLOAD LAST YEAR’S TEST

FANTASTIC PRIZES TO BE WON

SPARKS

Q&A: INSTALLATION TESTING

QWhy is it hard to get reliable results for loop impedance tests?

ALoop impedance tests can be tricky. Only very small test currents can be used on RCD-protected circuits to prevent tripping. But this, coupled with electrical noise on the circuit, can affect accuracy. Thankfully, the MFT-X1 tester from Megger with its smart TrueLoop™ technology and Confidence Meter, can solve this problem by indicating when the measurement is accurate and stable.

QWhy does automatic RCD testing take so long?

AWell, the reason is often due to the unnecessary tests included in fixed sequences. But with MFT-X1, you can program your own test sequence to include only the tests you actually need, saving you time.

Q Can I test EV charge points with a multifunction tester?

AIf it's a newer model, you're likely in luck! But remember to double-check with the manufacturer's datasheet. And don’t forget, you’ll still need an adapter to simulate a vehicle connection, which is necessary for carrying out the full range of tests.

DID YOU KNOW?

THE CONFIDENCE METER TRANSFORMS LOOP TESTING INTO A FASTER AND MORE RELIABLE PROCESS.

Understanding installation testing can be challenging. Fear not! Here, Peter Wade, an expert from Megger, answers some key questions.

BECOME AN AICO EXPERT INSTALLER

Aico’s free, award-winning Expert Installer training scheme is FIA CPD accredited and is designed to make sure installers have all the information they need to correctly install domestic home life safety systems, including Fire and Carbon Monoxide alarms and Environmental Sensors.

Once you become an Expert Installer, you will be invited to join the Aico Installer Community – a connected online platform built to support Expert Installers

Members of the community are eligible to participate in Aico’s free-of-charge City & Guilds Assured Training - Domestic Fire & CO Alarm Systems.

Visit

PRICING A JOB

As a new Sparky, getting your pricing on point is legit essential. Mess it up and you could be losing out on some serious cash.

Let's break this down with a rewiring job as our guide:

STEP 1

Begin by visiting the customer's place to assess the size of the project. During this initial meet, it's important to make sure you understand their goals and desires for the project.

STEP 2

Next up, you'll want to dive into the money side of things:

MATERIAL COSTS:

List out everything from cables, switches, circuit breakers, tool bits and other components. Total up what it's going to cost you.

LABOUR COSTS:

Estimate the hours you'll be on the job and set a fair hourly rate for your work.

ADDITIONAL EXPENSES:

Factor in things like your travel, skip costs, and the wear on your tools.

MARK-UP AND PROFIT MARGIN:

Remember to add a reasonable mark-up (typically around 10%-15%) on materials to keep your business thriving.

STEP 3

Use a tool like Excel or Google Sheets to keep track of these numbers and sum them up.

STEP 4

Once you've crunched the numbers, draft a clear quote for your client. If VAT is part of your pricing, be transparent about it in the final quote. They should know the total cost, inclusive of VAT.

[Your Company Name]

[Your Address]

[Your Contact Information]

Customer: [Customer's Name]

Customer Address: [Customer's Address]

Date: [Date]

Quotation for Full Electrical Rewire

SCOPE OF WORK:

Comprehensive electrical rewiring of the existing property, involving the replacement and upgrade of wiring, switches, sockets, and electrical fixtures throughout the premises.

QUOTATION:

Material Costs: £XXX

Labour Costs: £XXX

Additional Expenses: £XXX

Total Cost: £XXXX.XX

This quote is for your electrical rewiring project and may vary based on the final design and unforeseen complications. We will inform you of any additional charges before proceeding. Our aim is to complete the work efficiently and to the highest standards.

Payment Terms: A 25% deposit (£X,XXX.XX) is due upon quote acceptance. Another 25% is payable at the completion of the first fix, followed by 25% upon completion of the second fix, excluding the Distribution Board. The remaining 25% (£X,XXX.XX) should be paid upon project completion and your satisfaction. These amounts may be adjusted with prior agreement for any additional extras.

VALIDITY:

This quotation is valid for a period of 30 days from the date shown above. Thank you for considering [Your Company Name] for your rewiring needs. Should you have any questions or require further clarification, please do not hesitate to reach out to us.

Sincerely,

[Your Name]

[Your Company Name]

QUICK FACT QUOTE: A SET PRICE FOR A JOB ESTIMATE: A 'POSSIBLE' PRICE FOR A JOB, THAT COULD CHANGE

“A 10% -15% MARK-UP IS NORMAL”

THE SUPERHERO OF PLIERS!

The ultimate addition to your apprentice toolkit: New XP1000® VDE 4-in-1 Combination Cutters by Draper Tools.

THE RIGHT TOOLS

There are four tools to choose from – 160mm and 180mm plus their tethered options.

These great-looking pliers will soon become your best mate when tackling electrical tasks. That’s because they make quick work of:

ALWAYS USE PROTECTION

■ These tools are important because they are suitable for use on AC circuits up to 1,000V and DC circuits up to 1,500V

The range is VDE tested to 10,000V and is fully compliant with EN60900 standards

For extra peace of mind, all XP1000® tools come with a Lifetime Warranty.

SAFETY HAS NEVER LOOKED SO GOOD

Safety doesn’t need to be unappealing. The Combination Cutters’ horns look smart and prevent slippage on live conductors

The curvy handles are crafted with anti-slip TPE bi-material to ensure optimal grip, and they’re carefully shaped for comfort

The induction-hardened, premium steel jaws offer long term performance, to see you through your electrical career.

You don’t need to fill up your toolkit with lots of different tools, instead choose a plier that has multiple functions in one. Not only will you save money, but you’ll also save time on the job and space in your bag.

THE NEW XP1000® CUTTERS HAVE FOUR FUNCTIONS:

1) Side cutter

2) Pattress screw shear. (The 180mm pliers also shear 4mm conduit cover screws)

3) Wire bending anvil

4) 1.5 and 2.5mm wire strippers

MORE CHOICE WITH XP1000®

The extensive range of XP1000® VDE electrician’s tools also includes screwdrivers, slimline screwdrivers, pliers (with tethered options) and comprehensive sets of both to get the job done in your training centre or out on-site.

SCAN HERE

To find out more information

“ALL XP1000 TOOLS INCLUDE A LIFETIME WARRANTY”

®

SAFE ISOLATION

As you begin your journey, get to grips with safety. 'Safe Isolation' is the key to staying safe every day.

5 STEPS TO SAFETY

ISOLATION

TEST YOUR KNOWLEDGE SAFE

According to the IET Wiring Regulations, here are the five steps for safe isolation:

1 Identify the electrical circuit or equipment: Determine the specific circuit or equipment that needs to be isolated for the work to be carried out. This could include switches, sockets, lighting circuits, or appliances.

SAFE ISOLATION:

A set of steps that ensures any electrical equipment is properly switched off before you start working on it. You need to disconnect the power supply, make sure it can't be turned back on by accident, check that it really is off, and keep it that way until you've finished your work.

2

Switch off and lock out: Turn off the appropriate circuit breaker or switch in the consumer unit (main electrical panel) that controls the identified circuit or equipment. Once switched off, use a lockout device or a securely attached padlock to prevent the circuit from being inadvertently turned back on.

3

Verify isolation: Use a voltage tester or a suitable testing device to confirm that the circuit or equipment is no longer live and that electrical voltage is absent. Test at multiple points to ensure complete isolation.

4

Secure warning notices: Affix warning notices or tags at the consumer unit or switches to clearly indicate that work is being carried out and that the circuit or equipment should not be operated. These notices should include the name of the person carrying out the work and contact information.

Communicate and work safely: Inform other individuals present in the property, such as occupants or other workers, about the isolation and the ongoing work. Ensure that everyone is aware of the isolated circuit or equipment and understands not to attempt to use or operate it during the work period.

5

“KEEP IT SAFE WITH 'SAFE ISOLATION' PROCEDURES. IT'S THE DIFF BETWEEN A CHILL DAY AND A MAJOR YIKES”

QUICK QUIZ

A self-employed contractor sustained 415-volt electric shock injuries from the bare electrical wires supplying an overhead travelling crane, whilst installing computer cabling. The defendant company failed to follow procedures for safe isolation of the power supply to

The company was prosecuted under the Health and Safety at Work Act, and resulted in a hefty £15,000 fine! What three steps should the company have taken to avoid this from happening?

TOP TIPS FOR SAFE ISOLATION

Here are a few key tips to ensure you follow safe isolation procedures accurately:

1

2

3

4

5

Always plan ahead: Before you begin any electrical work, know which circuits and equipment will be involved, where the isolation points are, and what verification tests are needed.

Use the right tools: Ensure you have the correct equipment to carry out safe isolation, including approved voltage testers and locking-off devices.

Double-check everything: Don't just assume equipment is de-energised because it's switched off. Always check and then double-check using your testing equipment.

Lock and tag: After disconnecting, always lock the isolation point and use a warning tag. This prevents accidental reconnection by someone else.

Continuous verification: Regularly verify the isolation throughout your work. Conditions can change, and you need to be aware if they do.

SAFE ISOLATION = LESS ACCIDENTS + SAVES LIVES

2.

3.

QUIZ: SAFE ISOLATION

Test your knowledge by answering the following multiple-choice questions about Safe Isolation.

Q1 Which of the following is NOT a part of the Safe Isolation procedure? Ans.

A Verification of de-energisation

B Reconnecting the supply

C Disconnecting the supply

D Securing against accidental reconnection

Q4 Which tool is NOT essential during Safe Isolation procedures? Ans.

A Approved voltage tester

B Locking-off device

C Hammer

D Warning tag

Q2 The process of Safe Isolation is primarily performed to: Ans.

A Speed up the work process

B Ensure safety

C Save energy

D All of the above

Q3 What is the most common error made during Safe Isolation procedures? Ans.

A Forgetting to tag

B Incorrect verification tests

C Failing to secure against accidental reconnection

D Forgetting to disconnect

Q5 The approved document that gives guidance for electrical safety in dwellings is: Ans.

A Document P

B Document E

C Document S

D Document R

Q6 In the Safe Isolation procedure, the last step should be: Ans.

A Securing against accidental reconnection

B Verification of de-energisation

C Disconnecting the supply

D Attaching a warning tag

Q7

Which of the following should be used to confirm that equipment is de-energised during Safe Isolation? Ans.

A An approved voltage tester

B A regular voltmeter

C A multimeter

D An ohmmeter

Q8

According to the Electricity at Work Regulations 1989, who is responsible for Safe Isolation during electrical work? Ans.

A The person undertaking the work

B The site manager

C The homeowner

D The electrician's apprentice

Q9 After the Safe Isolation process, it is crucial to: Ans.

A Keep checking the isolation throughout the work

B Begin work immediately

C Reconnect the circuit to check for live wires

Q10

Which of the following is NOT a correct procedure for Safe Isolation? Ans.

A Using a locking-off device to secure the disconnecting switch in the off position

B Leaving the circuit breaker in the on position to check for remaining current

C Testing the circuit to confirm it is de-energised before starting work

D Attaching a warning tag to indicate ongoing work

Q11

What is the minimum number of steps recommended for safe isolation procedures when working in a domestic property according to the IET Wiring Regulations? Ans. A 3

Q12

As little as 50 volts can block the electrical signals between the brain and the muscles, causing various effects, such as: Ans.

A Stopping the heart beating properly

B Preventing the person from breathing

C Causing muscle spasms

D All of the above

APPLICATION

30 TH NOV

Female Skills 2024

SUPPORTING THE FUTURE OF THE INDUSTRY DESIGNED TO INDUSTRY STANDARDS

YOU GOT

HAVE WHAT IT

TAKES?

SPONSORS CONFIRMED SO FAR

“The prizes are absolutely amazing! I wasn't expecting to get all of that, and the money!

FANTASTIC PRIZES TO BE WON

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As co-publisher of the IET Wiring Regulations, now updated to BS 7671:2018+A2:2022, we have lots of information and guidance available to help you get into the electrical industry.

From informative articles on different ways into industry and the most relevant qualifications, to videos designed to help de-mystify certain areas of the IET Wiring Regulations, our website is full of useful resources for electrical students, including:

– Books for students, such as the Student’s Guide to the IET Wiring Regulations

– The Student’s Guide video series including topics such as Safe Isolation and Risk Assessment

– Wiring Matters magazine articles to help you with your studies

– A job profile bank detailing some of the many different career options available to you when you qualify

WORK FIT, STAY LIT

Want to stay safe, be comfy, while keeping it 100% profesh? Read on... #DressSmartStayLit

DURABLE MATERIAL

Ever heard of Cordura and 280gsm twill weave? This stuff's legit tough against rips and scratches, but still lets you move like you're in a TikTok dance challenge.

REINFORCED STRESS AREAS

Key stress areas, such as knees and seams, are triple-stitched for added resilience. Some have that EVA foam padding to give your knees that extra love during those tough jobs.

OUTER POCKETS

These pockets are the real MVP for your tools. Keep everything from those wire strippers to electrical tape handy. No more wasting time searching!

KNEE PAD POCKETS

Got knee pads? Slide them into these special pockets. Perfect for when you're working down low and want to avoid those "Ouch!" moments.

“PROTECT YOUR KNEES!”

BECOMING THE ELECTRICIAN OF TOMORROW

The demand for electricians is on the rise, and with it comes a variety of new work opportunities. Smart home technologies, sustainable retrofits, changing regulations, and the emergence of 'energy prosumers' emphasise the importance of staying ahead in the industry.

EVOLVING OPPORTUNITIES

The tech revolution brings exciting news: a plethora of opportunities have emerged! Government initiatives targeting budgetconscious smart energy consumers and green businesses are paving the way for the next generation of electricians. Staying proactive amidst these emerging opportunities is key.

Projects focusing on energy efficiency and the installation of smart technologies are increasingly popular. To navigate this evolving landscape, electricians are looking to industry experts for accessible tools and reading materials. This is where Schneider Electric steps in as a valuable resource.

Schneider Electric’s new e-book delves into different elements of running a successful business, ensuring that you are equipped for the future. Best of all, it’s free to download.

With the electrical industry rapidly evolving, there’s no better time to discover how to future-proof your career.

“UPSELLING ADDITIONAL PRODUCTS OR SERVICES CAN LEAD TO REPEAT BUSINESS AND POSITIVE REFERRALS”

KEY STEPS TO SUCCESS

STEP 1: ENHANCE YOUR SKILLS

Pursue professional accreditations and certifications to not only boost your credibility but also demonstrate your commitment to excellence. By effectively managing projects and adhering to industry standards, you can enhance your reputation, thus attracting more customers. With a new wave of technology supporting more sustainable energy solutions, there lies a great opportunity to differentiate yourself from the competition through enhanced training.

STEP 2: PROMOTE YOURSELF

A robust online presence is a powerful tool to engage potential clients. Success in marketing often rests on a well-optimised business website. Deploy keywords and local SEO strategies to improve your business's visibility in online searches. Utilise social media platforms to facilitate direct interaction with customers. You can showcase successful projects, answer questions, and receive valuable feedback. Further boost the credibility and appeal of your business by emphasising professionalism, featuring customer reviews, and providing userfriendly website navigation.

STEP 3: DARE TO ADAPT

Invest in new software tools to streamline project management, automate processes, and improve overall efficiency. Actively seeking out accreditations for low-carbon technologies like solar panels, heat pumps, and EV charging stations places you in a powerful position to meet the growing demand for sustainable solutions. Upselling additional products or services can demonstrate innovation, create value for customers, and lead to repeat business and positive referrals. By adopting these key strategies—taking advantage of new opportunities, enhancing skills, optimising your web presence, and embracing new technologies—you can secure a bright future in the rapidly evolving electrical industry.

TOP TIP

SCAN

To download the FREE 'Becoming the Electrician of Tomorrow' e-book here:

CUSTOMERS: TOP TEN RED FLAGS!

Stay sharp when dealing with customers. Here are ten signs to watch for:

1 BLAME GAME Watch for those blaming you for old issues. If they say "it was fine before you got here," but you know different, they might be trying to dodge responsibility.

2 EMPTY PROMISES

Be alert if a customer promises more jobs for a low rate but doesn't follow through.

3 SKETCHY DEALS

Big alert if they want secret deals, skipping required steps, or using cheap stuff to save money.

4 TOO MUCH BARGAINING Heads up with those always trying to get a lower price or wanting constant discounts. They might not see your worth.

7 NOT COOL VIBES Working with grumpy or aggressive customers can make things stressful.

5 MONEY DELAYS

If they're often late paying, don't like upfront costs, or are unclear about payment details, be cautious.

8 IGNORING YOUR KNOWHOW

Those who often ignore your advice might not trust your skills, which can lead to issues.

6 HIGH HOPES

Keep an eye on customers expecting too much for little money or wanting more than you agreed on.

9 TIME WASTERS

Changing plans, being late, or wanting more of your time than agreed can show a lack of respect.

10 UNCLEAR GOALS

If they can't be clear about their needs or keep changing their mind,

QUICK TIP

TRUST YOUR INSTINCTSIF SOMETHING FEELS OFF, PLAY IT SAFE!

ON TOP OF YOUR GAME

At the end of your apprenticeship you’ll need to complete the AM2 or AM2S Assessment before you can become fully qualified.

WHAT IS THIS?

It’s an in-depth assessment where you have to carry out specific tasks to show what you have learned during your apprenticeship.

BE PREPARED!

NET has a Self-Assessment Checklist so you can look at exactly what you need to do and make sure you have gained the right knowledge and practical experience. The AM2/AM2S is the pinnacle of everything you’ve learnt during your apprenticeship. So why not be proud of your skills and training and make it your mission to pass first time?

Ask your training provider about the AM2 or AM2S Checklist or find out more at www.netservices.org.uk/candidate-guidance

AM2 - THE LOWDOWN!

Calling all apprentices! Did you know that at the end of your apprenticeship you’ll need to take the AM2 assessment before you can become fully qualified?

WHAT DOES THIS MEAN?

Think of it as similar to a driving test – you spend weeks or months learning how to drive, then the driving test is where you put everything into practice and you are marked against strict criteria.

The AM2 is just like this - it’s an in-depth assessment where you have to carry out specific tasks to show what you have learned during your apprenticeship.

AM2S OR AM2D?

You’ll either take the AM2S or the AM2D assessment depending on whether you’re on the Installation & Maintenance Electrician apprenticeship, or the Domestic Electrician apprenticeship.

HOW IT WORKS

The whole test is split over three days, which are broken down into different sections such as safe isolation, installation, inspection, testing and certification, and fault finding.

Strict exam conditions are in place during the assessment, so this means that candidates are not allowed to use electronic devices or get help from anyone else. You’ll be monitored by an assessor who will be marking your work as the day progresses.

Once you pass the assessment, it’s one of the final steps in completing your apprenticeship and becoming a fully qualified electrician.

Even if it’s early days in your apprenticeship, why not take a look at what you’ll need to do during the assessment? The NET website gives you much more information on the assessments and each section in detail, including the checklists, how to best prepare and what happens during the assessment.

SCAN HERE

To find out more information

“THE NET WEBSITE HAS INFORMATION ON THE ASSESSMENTS AND EACH SECTION IN DETAIL”

TEST YOUR KNOWLEDGE

CABLE CALCULATIONS

REVISION GUIDE BY LEWIS BLAKEMORE QTLS

Agood understanding of cable calculations is crucial in order to ensure all circuitry cables are fit for purpose. A strict and scientific design process must be followed, thus confirming compliance with BS7671. So, here’s how it’s done…

SIMPLE STEPS TO FOLLOW

The following 11 steps will allow you to theoretically determine a circuit’s suitability in terms of protection, current carrying capacity, shock

STEP 1: Calculate design current (Ib)

STEP 2: Select type and rating of protective device (In)

STEP 3: Determine installation method

STEP 4: Determine necessary correction factors

STEP 5: Determine Iz

STEP 6: Determine It

STEP 7: Determine voltage drop

STEP 8: Determine Zs (Zs = Ze + (R1 +R2))

STEP 9: Determine Ipf

STEP 10: Determine disconnection time

STEP 11: Determine thermal constraints

■ Uo - nominal voltage

■ Ib - design current

■ In - rating of protective device

■ Iz - minimum current carrying capacity of cable

■ It - actual current carrying capacity

It

Getting the design and installation spot-on is crucial for a solid system. It's super important to size and calculate those cables correctly.

Electrical Lecturer at Wigan & Leigh College

STEP 1 -

You will have to calculate this. It is the normal resistive load current in the circuit. The following formulae apply to single and three phase supplies:

SINGLE PHASE SUPPLIES:

Ib = Power Uo

THREE PHASE SUPPLIES:

Ib = Power √3 x Uo

In a.c. circuits, the effects of either highly inductive or highly capacitive loads can produce a poor power factor (PF) You will have to allow for this. To find the design current, you may need to use the following equations:

SINGLE PHASE CIRCUITS:

Ib = Power Uo x PF

THREE PHASE CIRCUITS:

Ib = Power √3 × Uo × PF

STEP 2 - RATING OF THE PROTECTIVE DEVICE (In)

When you have worked out the design current of the circuit (Ib), you must next work out the current rating or setting (In) of the protective device. The IET Wiring Regulations says that current rating (In) must be no less than the design current (Ib) of the circuit. The reason for this is that the protective device must be able to pass enough current for the circuit to operate at full load, but without the protective device operating and disconnecting the circuit. Protective devices come in standard values and are found in BS7671 pages 67- 70.

CAPACITY & VOLTAGE DROP FOR CABLES

(BS7671: Appendix 4)

■ Ca - for ambient temperature (BS7671 Table 4B1- 4B2)

■ Cc – for circuits buried in the ground (BS7671 page 425 – x 0.9)

■ Cd – for depth of burial (BS7671 Table 4B4)

■ Cf – for semi enclosed fuse (x 0.725) (apply for circuits that may become overloaded)

■ Cg – for grouping (BS7671 Table 4C1- 4C6)

■ Ci – for thermal insulation (BS7671 page 423) (Not applicable for twin cables surrounded by thermal insulation)

■ Cs – for thermal resistivity of soil. (BS7671 Table 4B3)

It =

In

Ca x Cc x Cd x Cf x Cg x Ci x Cs

■ Go to the relevant table in Appendix 4 (BS 7671) that lists all the sizes, current carrying capacities and milli volts/ampere/metre of the various types of cable

■ From the correct table and column select the cable size that satisfies the calculated current carrying capacity

■ Note the correct column is determined by the installation method of the cable

■ Determine if the volt drop of the chosen cable satisfies BS 7671

■ The maximum permitted volt drop is 3% of the nominal voltage for lighting and 5% for power at the origin of the circuit

■ The actual volt drop can be calculated from the following formula:

Vd = Ib × l(m) × mv/A/m

■ The mv/A/m value is obtained from the relevant table in Appendix 4

■ Note the above equation has to be divided by 1000 or multiplied by 10-3

■ If the cable satisfies both the current carrying capacity and the volt drop values then it is the correct size to install.

STEPS 8 & 9 - Zs & PROSPECTIVE SHORT CIRCUIT CURRENT (PSCC)

BS7671 states that ‘protective devices shall be provided in a circuit to break any fault current flowing in conductors of that same circuit, before such current causes danger due to thermal or mechanical effects produced in those conductors or the associated connections’. This ‘prospective fault current’ must be taken into account when selecting the type of overcurrent device to be installed.

■ Uo = nominal supply voltage

■ Ze = loop impedance external to the installation

■ R1 = the resistance of the installation phase conductor to the fault point

■ R2 = the resistance of the installation return conductor to the fault point

■ Zs = total fault loop impedance

■ Zs = Ze + (R1 + R2).

You need to do a calculation to check that the circuit protective device will operate within the required time. You do this by checking that the actual Zs is lower than the maximum Zs given in the relevant table for the protective device you have chosen.

Maximum Zs can also be found from The IET Wiring Regulations or manufacturers’ data. Use the following formula to calculate the actual Zs:

R1+R2 =

WHERE:

mΩ/m value found in appendix I in the onsite guide X multiplier (mf) X Length 1000

Zs = Ze + (R1=R2)

■ Ze = the external impedance on the supply authority’s side of the earth fault loop. You can get this value from the supply authority. Typical maximum values are: TN-C-S (PME) system 0.35 ohms; TN-S (cable sheath) 0.8 ohms; TT system 200 ohms.

■ R1 + R2 = the resistance of the line conductor plus the cpc resistance. You can find values of resistance per metre for R1 + R2, for various combinations of line and cpc conductors up to and including 50mm in The IET On-Site Guide.

In order to apply thermal constraints, we first need to calculate the value of Ipf (fault current) from the following equation:

Ipf = Uo Zs

WHERE:

■ Uo = the nominal supply voltage

■ Zs = the total earth fault loop impedance

“GETTING DESIGN AND INSTALLATION JUST RIGHT IS THE HEART OF A SOLID AND SAFE SYSTEM”

STEPS 10 & 11 - DISCONNECTION TIME AND THERMAL CONSTRAINTS DISCONNECTION TIME

Using BS7671 and your calculated Ipf, you must now find out the time/current characteristics of the protective device. A selection of time/current characteristics for standard overcurrent protective devices is given in Appendix 3 of The IET Wiring Regulations. You can get the time (t) for disconnection to the corresponding earth fault current from these graphs.

ADIABATIC EQUATION

Now that you have chosen the type and size of cable to suit the conditions of the installation, you must look at thermal constraints. This is a check to make sure that the size of the cpc, ‘the earth conductor’, complies with the BS7671.

If there is a fault on the circuit, which could be a short circuit or earth fault, a fault current of hundreds or thousands of amperes could flow. Imagine that this is a 1mm2 or 2.5mm2 cable; We need to check that the cpc will be large enough to be able to carry this fault current for a short amount of time without causing any heat/fire damage. The formula that is used to check this situation is the adiabatic equation. The cpc will only need to carry the fault current for a short period of time, until the protective device operates.

THE EQUATION IS AS FOLLOWS: S = √Ipf2 × t k

WHERE:

■ S = the cross-sectional area of the cpc in mm2

■ I = the value of the earth fault current

■ t = the operating time of the disconnecting device in seconds

■ k = a factor depending on the conductor and its insulating material (BS7671 tables 54.2 - 54.7)

SCAN HERE

For an easy guide to cable sizing, check out this YouTube video from Sparky Help:

“WHEN STRIPPING STRANDED CABLE, BE CAREFUL NOT TO CUT THE COPPER. IT AFFECTS THE POWER FLOW”

QUIZ: CABLE CALCULATIONS

Let’s see how well you understand cable calculations. Test your knowledge by answering the following multiple choice questions.

Q1 The IET Wiring Regulations in relation to cable selection give tables on which of the following? Ans.

A Length

B Current carrying capacity

C Height

D Overheating capacity

Q2

If the voltage drop in an installation exceeds the permissible value it may be corrected by which of the following? Ans.

A Reducing the voltage

B Reducing the cable size

C ncreasing the cable size

D Increasing the voltage

Q3

If a ring main circuit has a 32A fuse 230V supply the maximum power available at any one time is which of the following: Ans.

A 73.36W

B 736W

C 7360W

D 73600W

Q4 The rating of a cable depends on its ability to lose heat produced in it by which of the following? Ans.

A Current it carries

B Voltage applied

C Density of the conductors

D Density of the insulation

Q5

An immersion type water heater is to be installed. If the water heater is rated at 3kW, 230V it should be installed as which of the following? Ans.

A A dedicated 10A radial circuit

B A dedicated 16A radial circuit

C A spur from a 32A appliance ring

D A spur from a 32A ring final circuit

CLASSROOM ACTIVITY

A three phase 9kW with a stated power factor of 0.95 motor is to be installed. The wiring system is to be single core cabling installed in an existing PVC trunking system. The trunking already contains two similar circuits. The supply is TNS, the voltage is 400/230V and the Ze is measured as 0.12 Ω. The ambient temperature in the area is 30ºC. Protection within the distribution board is afforded by BS 88 type fuses. The motor is to be situated 40m from the distribution board. Compliance with BS 7671 is compulsory. CALCULATE THE FOLLOWING: A Ib

TEST YOUR KNOWLEDGE

HEALTH & SAFETY

How well do you know your electrical health & safety? Have a go at these multiple choice questions to test your knowledge!

Q1 Which of the following is the best protective equipment for an electrician to wear when working live? Ans.

A Rubber gloves and safety glasses

B A cotton shirt and jeans

C A wool sweater and sneakers

D A polyester suit

Q2 If you come across an unfamiliar piece of electrical equipment, what should you do? Ans.

A Try to operate it

B Ignore it

C Refer to the manufacturer’s instructions

D Ask a colleague

Q3 What is a Residual Current Device (RCD) primarily used for? Ans.

A To increase the current flowing through a circuit

B To prevent electric shock

C To amplify the voltage in a circuit

D To reduce resistance

Q4 What should you do if you see a damaged electrical cable? Ans.

A Ignore it, it's not your responsibility

B Try to fix it yourself

C Report it to a supervisor

D Touch it to see if it's live

Q5 The Electricity at Work Regulations 1989 requires that: Ans.

A Only qualified persons can undertake electrical work

B Only employers are responsible for electrical safety

C Everyone in the workplace can undertake electrical work if supervised

D Electrical equipment does not need to be maintained

Q6 Which one of the following should not be done when working with electricity? Ans.

A Keep the working area dry

B Use tools with rubber or plastic handles

C Wear a metal watch or bracelet

D Double-check that power is off before working on a circuit

Q7

How often should portable electrical equipment be tested in a high-risk environment? Ans.

A Once a year

B Every six months

C Every five years

D It doesn't need to be tested

Q8 A properly worn safety hat can protect you from: Ans.

A Electric shock

B Falling objects

C Fire

D All of the above

Q9 Which is not a class of fire extinguisher suitable for electrical fires? Ans.

A CO2

B Dry powder

C Foam

D Water

Q10

When working with electrical systems, the first thing you should do is: Ans.

A Start working immediately

B Isolate the system and prove dead

C Work on the live system

D Ask a friend for advice

Q11 In the event of an electrical fire, what should you do first? Ans.

A Pour water on it

B Use a foam fire extinguisher

C Disconnect the electricity, if it's safe to do so

D Try to put out the fire with a blanket

Q12 Which of the following is NOT a risk associated with electricity? Ans.

A Fire

B Electrocution

C Hearing loss

D Electric shock

Q13 What does IP stand for in the context of electrical enclosures? Ans.

A Fire Internet Protocol

B Ingress Protection

C Internal Power

D Insulation Potential

Q14 According to the Health and Safety at Work Act 1974, who has a duty to prevent accidents in the workplace? Ans.

A Only the employer

B Only the employee

C Both the employer and the employee

D The government

HEALTH & SAFETY LEGISLATION

Let’s see how familiar you are with this legislation. Read through the list below and circle those that are non-statutory (hint: there are 3). Then, grab a piece of paper and write a brief description for each one, outlining what it covers and who is responsible.

DID YOU KNOW

STATUTORY LEGISLATION IS LAW FORMALLY ENACTED BY PARLIAMENT, BINDING AND ENFORCEABLE.

NON-STATUTORY LEGISLATION, WHILE NOT LEGALLY BINDING, PRESENTS INDUSTRY BEST PRACTICES AND GUIDELINES THAT CAN INFLUENCE LEGAL PROCEEDINGS.

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mIX & match

How well do you know your electrical terms? Have a go at the following mix & match quiz. Good luck! A

Devices used to protect against electric shock by quickly disconnecting the power when a leakage current is detected D

A protective tube or channel used to enclose and protect electrical wiring G

The process of generating an electromotive force in a circuit without direct electrical connection

TRANSFORMER

B

The measure of opposition to the flow of electric current in a circuit E

A device that transfers electrical energy between two or more circuits through electromagnetic induction H

Circuits used to control and operate electric motors

ELECTRICAL RESISTANCE

Devices that store electrical energy in an electric field and release it when needed

CAPACITORS

THREE-PHASE SYSTEMS

Systems that use three alternating currents with a 120-degree phase shift to provide power in industrial and commercial settings

ELECTRICAL INDUCTION

CONDUIT

The ratio of real power to apparent power, representing the efficiency of power usage

RCDS CURRENT(RESIDUALDEVICES)

POWER FACTOR

MOTOR CONTROL CIRCUIT

110MM KNOCK OUT!

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IF IT WORKS, IT WORKS!

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SPARKY 101: DECODING ELECTRICAL LINGO AWESOME

Know your electrical lingo? Check out these terms

AALTERNATING CURRENT (AC):

An electrical current that periodically reverses direction, commonly used to supply power to homes and businesses.

AMPERE (A):

A unit of measurement used to express the rate of electrical current flow.

ARMOURED CABLE:

An electrical cable that is protected by a metal or plastic covering, commonly used in outdoor or underground installations.

BBREAKER:

A device used to interrupt or break an electrical circuit when there is an overload or fault.

BUSBAR:

A metal bar used to distribute electrical power to different parts of a building or machine.

BALLAST:

An electrical component used to limit the current flowing through a light bulb, used to regulate its brightness.

CIRCUIT:

CA complete path through which electricity flows, typically consisting of a power source, wires, switches, and loads.

CONDUIT:

A pipe or tube used to protect electrical wires and cables, commonly made of metal or plastic.

CAPACITOR:

An electrical component that stores energy in an electric field, commonly used in electronic circuits to filter or smooth voltage fluctuations.

DDISTRIBUTION BOARD:

An electrical panel that contains circuit breakers or fuses used to control and distribute power to different parts of a building.

DIRECT CURRENT (DC):

An electrical current that flows in one direction only, commonly used in batteries and electronic devices.

DOUBLE-POLE SWITCH:

A switch that can control two separate circuits, commonly used to switch both live and neutral wires in a circuit.

EARTH:

EA connection to the ground used to protect against electrical shock and to provide a safe path for current to flow in case of a fault.

ELECTRICAL CURRENT:

The flow of electric charge through a conductor, typically measured in amperes.

ELECTROMAGNETIC INTERFERENCE (EMI):

The disturbance caused by electromagnetic signals that can interfere with the proper functioning of electrical or electronic equipment. EMI can be mitigated through shielding and filtering techniques.

that you'll likely run into during your studies.

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