Wiring and Lighting E-Book

Chris Kitcher

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 248

Veröffentlichungsjahr: 2020

Beschreibung

Wiring and Lighting provides a comprehensive guide to DIY wiring around the home. It sets out the regulations and legal requirements surrounding electrical installation work, giving clear guidelines that will enable the reader to understand what electrical work they are able to carry out, and what the testing and certification requirements are once the work is completed. Through step-by-step diagrams and photos, the book covers wiring for a wide range of tasks by examining the components of electrical systems and installations, including: different types of circuits; types of cables and cable installation under floors and through joists; isolating, earthing and bonding; accessory boxes and fixings; voltage bands; detailed advice on safety such as manual handling, working at height and electrical shock risk. Finally, schedules for inspection, testing and certification, and relevant sections of the Building Regulations are covered. Wiring and Lighting is fully updated in line with the 18th edition wiring regulations.

Leseprobe

Wiring and Lighting

CHRIS KITCHER

First published in 2012 by The Crowood Press Ltd Ramsbury, Marlborough Wiltshire SN8 2HR

[email protected]

www.crowood.com

New edition 2020

This e-book first published in 2020

© Chris Kitcher 2012 and 2020

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.

ISBN 978 1 78500 744 6

Disclaimer The author and the publisher do not accept any responsibility in any manner whatsoever for any error or omission, or any loss, damage, injury, adverse outcome, or liability of any kind incurred as a result of the use of any of the information contained in this book, or reliance upon it.

Unless otherwise stated, all photographs and drawings are by the author.

ABBREVIATIONS

CPC

Circuit Protective Conductor

CSA

Cross Sectional Area

DNO

District Network Operator

FELV

Functional Extra-Low Voltage

Isc

Short Circuit Current

LSF

Low Smoke Thermoplastic

MICC

Mineral Insulated Metal Clad Cable

PEFC

Prospective Earth Fault Current Test

PELV

Protected Extra-Low Voltage

PIR

Passive Infra-red Detector

PME

Protective Multiple Earthing

PSCC

Prospective Short Circuit Current Test

PV

Photovoltaic System

RCBO

Residual Current Device with Overload Protection

RCD

Residual Current Device

SELV

Separated Extra-Low Voltage

SWA

Steel Wired Armoured

Voc

Open Circuit Voltage

Contents

1 Important Information

2 Working Safely

3 Tools and Equipment

4 Voltage Bands

5 Dealing with Cables

6 Installation Methods

7 Planning an Electrical Job

8 Protective Earthing and Bonding, and Supply Systems

9 Wiring of Lighting Circuits

10 Power Circuits

11 Cable Selection

12 Photovoltaic Microgeneration Systems

13 Inspection, Testing and Certification

Index

CHAPTER 1

Important Information

INTRODUCTION

Before commencing any type of work on or around an electrical installation, it is very important to know and understand the legal requirements to which all of us must comply. These requirements apply to all who are involved in electrical work, whether it is a very large electrical contracting company working on commercial or industrial installations, or a DIY enthusiast carrying out very small electrical jobs at home.

Electricity can be very dangerous if it is not dealt with in the correct manner and this is why we have rules and regulations, which we must be aware of before picking up our tools to start work.

LEGAL REQUIREMENTS

The Health and Safety at Work Act 1979 (HASAWA) is a statutory document to which we must all comply; failure to comply with a statutory document is a criminal offence. HASAWA can be considered to be the umbrella, under which all of the other documents sit. The Electricity at Work Regulations 1989 (EAWR) is in place to provide the requirements for the safety of electrical installations and is also a statutory document.

This book is intended to provide information to anyone who is carrying out work on a domestic installation. Since 2005, electrical work carried out in domestic dwellings has been included in the building regulations and is known as building regulation part P. It is a legal requirement to comply with building regulations and failure to do so may result in a fine or even imprisonment.

Clearly, anyone who simply wants to carry out a small electrical job on their own property does not want to get wrapped up in too many rules and regulations, but it would be silly for us to ignore them. Imagine what the implications would be if we were to carry out electrical work that did not comply with the requirements and somebody got electrocuted or a building was damaged, possibly due to fire caused by a poor electrical installation. I am sure that house insurers would not be keen on paying out to repair any damage that was caused by poor workmanship; they would also not pay out for any damage caused by work that was carried out illegally. To ensure that this does not happen we must have a basic understanding of the rules to which we must work.

It is not a requirement to be qualified to carry out electrical work but we must be competent. The definition of a competent person is:

A person who possesses sufficient technical knowledge, relevant practical skills and experience for the nature of the electrical work undertaken and is able at all times to prevent danger and, where appropriate, injury to him/herself and others.

You will be the best person to decide if you fit that definition or not!

The important things to be aware of are:

All electrical work carried out must be in compliance with the current British Standard, which is BS 7671 Requirements for Electrical Installation. At the time of writing this book, the current standard is the 18th edition 2019. Compliance with this requires that all installed equipment and materials used are also to a British or suitable European standard. Of course there will be occasions where we need to install a piece of equipment that does not have a BS standard. An example of this could be if you have had a lamp made by a local blacksmith that you want to install as an outside light – the lamp will not have a British standard. In these situations you will need to make a judgement as to whether the lamp would be likely to meet the requirements of the British standard; in other words, will it be safe? As long as you are satisfied that it is safe and suitable for the use to which it is being put, it can be fitted; the only requirement is that the item is recorded as not being to a British standard on whatever certificate you need to complete for the particular job. The use of certificates will be covered in detail later in this book.

BUILDING REGULATIONS

Electrical installations must also comply with all of the relevant building regulations; this is a legal requirement. Building regulations are identified by the use of letters and they run from parts A through to P (though there is no part O). Of course, none of these building regulations are more important than any other; however, part P will have to be complied with along with all other requirements when considering carrying out electrical work in dwellings.

BUILDING REGULATION PART P

Because electrical installations in domestic dwellings are covered by building regulation part P, we have to be aware of what the requirements are.

First, regardless of what we are permitted to do, all parts of any electrical work that we carry out have to be in compliance with the latest edition of BS 7671 Electrical Wiring Regulations.

In most cases, part P requires us to notify building control of any electrical work that is being carried out. However, we are permitted, without notifying our local building control department, to add to an existing circuit; for example, this could be an additional lighting point or an additional socket outlet. We are also allowed to replace a damaged circuit, providing that the cable that we use is the same size and follows the same route as the original circuit. We would not, however, be permitted to change the rating or the type of protective device for any circuit. All work that is carried out must be inspected and tested correctly and the appropriate certification provided. The use and completion of different types of certification will be explained in detail late in this book.

NEW CIRCUITS

All new circuits, other than a single replacement, will be need to be notified to the local building control department, which will require the completion of a building notice and the payment of a fee. The building control officer will usually want to come out and inspect the work at each stage. Certainly he will want to inspect any parts of the installation that will not be visible to him once the work has been completed. Although the building inspector will inspect the various stages of the installation, it is the responsibility of the person carrying out the installation to provide the correct certification on completion of the work. As previously stated, it is not a requirement to be qualified to carry out any type of electrical work; however, it may be that the building control officer will need to be satisfied that you are competent enough to carry out and certificate on completion the work that you intend to carry out.

Certification of Electrical Work

It is a requirement of part P that all work carried out in a domestic dwelling is certificated, and, of course, it is very important that the correct type of certification is completed.

For alterations to an existing circuit, where the protective device remains unchanged, the correct certificate to be used is a Minor Electrical Installation Works Certificate. commonly known as a Minor Works Certificate.

All work carried out in a bathroom or a kitchen must be notified to building control; this is regardless of whether it is an addition or alteration to an existing circuit or whether it is a new circuit. Circuits installed to provide electricity to sheds and remote buildings are also notifiable.

Most electricians who are involved in domestic electrical installations will join a self-certification scheme and become a part P registered domestic installer, this would allow them to carry out work and certify it without completing a building notice for each job carried out. To become a registered installer you would need to contact your chosen scheme provider, who will send you details of their registration requirements. All registration bodies will require a fee. Once it is paid they will arrange to visit you, inspect your quality-management system and also look at some of your work.

ELECTRICAL INSTALLATION CERTIFICATE

An electrical installation certificate needs to be completed for all new installations, additions to existing installations and alterations to an existing installation. This certificate should not be issued unless the installation meets all of the requirements of BS7671.

A new installation would be a new electrical system installed into a new building or it could be a rewire of an existing installation. An addition of a new installation would be when a new circuit has been installed to an existing installation; this would also require the completion of an electrical installation certificate for the work carried out. A single installation that has been added to over a period of time, may have several electrical installation certificates. It is not permissible to add details to an existing certificate.

Alterations would be where, perhaps, the consumer’s unit has been changed along with the type of protective devices, or where circuit breakers have been replaced with RCBOs. In these instances, the electrical installation certificate is used to describe these alterations, and to indicate that the altered areas of the electrical system are compliant with the latest edition of the wiring regulations BS7671.

Electrical installation certificate.

Schedule of Inspections; the full Schedule can be seen on pp.146–147.

Schedule of test results.

Wherever an electrical installation certificate is used, it must be accompanied by a schedule of test results and a schedule of inspections. Again these documents must give information on the work that has just been carried out, not information on existing circuits. This, of course, will in some cases result in some installations having several of these documents, which have been provided over a period of time.

Before undertaking any work on an existing installation, it must first be ascertained that the installation is safe to add to. In some instances this will require the completion of an electrical installation condition report.

ELECTRICAL INSTALLATION CONDITION REPORT

An electrical installation condition report is a document that is completed to provide information on the condition of an electrical installation.

All domestic installations should be subjected to a condition report at intervals not exceeding 10 years. It is not a certificate, it is a report, which should be used to identify any faults or potential faults within an installation that may have developed over a period of time. Where faults or potential faults are found, they must be recorded as observations; these observations are classified at three levels:

Classification C1 indicates that the observation found was dangerous and should be dealt with immediately, as there is a risk of injury present.Classification C2 would be given where there was a potentially dangerous situation, which should be dealt with urgently. C2 could also be used where further investigation is required; in these instances, the investigation should be carried out as quickly as possible.Classification C3 is for observations that are not unsafe but improvements are recommended and should be considered.

Typical examples of classifications are:

C1 would be where a live conductor or live part could be touched, perhaps where a protective device is missing and the space has not been covered with a blanking device.C2 would be where an incorrect rating of protective device has been installed. Further investigation required could be where there is no evidence of protective bonding. C3 is used where the installation does not comply with the latest edition of BS7671; for example, a domestic installation pre 2019 does not have rcd protection on lighting circuits, socket outlets or circuits used in a bathroom.

Where a classification of C1 or C2 has been issued, the installation must be given an overall assessment of unsatisfactory; classification of C3 would be given an assessment of satisfactory.

Where an electrical installation condition report has been issued, it must be accompanied by a schedule of inspections and a schedule of test results.

It is very important to note that an electrical installation condition report should only be undertaken by persons who are experienced in the type of installation being inspected. Inspecting and testing of existing installations is a very skilled job and requires a great deal of knowledge and understanding. For this reason, detailed explanation on this type of work is not included in this book.

Electrical installation condition report.

ELECTRIC SHOCK

As stated right at the beginning of this book, electricity can be very dangerous if it is not treated with respect. Accidents can, and sometimes do, result in serious injury and even death.

Even the smallest electric shock can be fatal. Although it may not be a shock large enough to burn you, it may be large enough to cause a reflex action, which in turn could result in you falling from a pair of steps or a ladder. As an example: 1mA, which is 0.001 (1/1000) of an amp, is the current produced by an insulation resistance tester, which is regarded as the level that most people can feel as an electric shock. I suggest that if you have not already done so by accident, that you hold the probes of your insulation resistance test leads one in each hand and push the test button just to experience a shock of 1mA.

If the shock current rises to 10mA, most people will suffer muscular contraction and find it difficult, if not impossible, to let go of anything that is in their hand.

At 18mA, if the shock is across the chest, it will be impossible for most healthy people to breath and there is a strong possibility of burns

A shock current of between 50mA and 80mA will almost certainly result in ventricular fibrillation; in this situation CPR (cardiopulmonary resuscitation) is required to prevent death. Of course, all humans are different and the effects may change slightly for the given values. However, it is clear just how dangerous electricity can be and why we always need to take great care to ensure the safety of ourselves and others.

CHAPTER 2

Working Safely

SAFE ISOLATION

While it is true that some of the tests that we carry out on electrical installations are live tests, these tests are carried out using the correct equipment. Procedures are in place that must be followed to ensure that the person carrying out the testing, and any other persons, remain safe. We must never attempt to work on electrical equipment while it is still live.

The Electricity at Work Regulations

These state that:

No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless:

It is unreasonable in all the circumstances for it to be dead; andIt is reasonable in all the circumstances for him to be at work on or near it while it is live; andSuitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury.

As the EAWR 1989 is a statutory document, this means that anyone working on an electrical installation who is not complying with the requirements of it may be breaking the law.

To be safe we must take all of the precautions possible because, as we know, you cannot see electricity and usually, unless something is going wrong, you cannot smell or hear it. The best way to ensure safety when carrying out electrical work is to isolate the installation or the circuit that is being worked on. There is a well-documented procedure in place for this, which, believe it or not, is called the Safe Isolation Procedure and, providing we carry it out properly every time we need to isolate a circuit, we will be safe. When working on electrical systems, unless you are very sure it is safe to do so, never take short-cuts and never rush safe isolation.

Voltage indicator, padlock and notice.

The equipment we need is an approved voltage isolator or test lamp, a padlock and a notice.

Safe Isolation Procedure

Ensure that the circuit that is to be isolated is live, do not take a chance and assume it is live. We need to make sure that we are the ones who are isolating it; if we do not prove it is live to start with, it could be that we isolate the wrong circuit, and that the one we are working on gets switched on and becomes live while we are working on it. This can be done by just turning on the circuit and seeing if it works, or an approved test lamp or voltage indicator can be used. Do not use any piece of test equipment that has a switch on it, as if it is on the wrong setting or switched off, it may indicate that it is not live when in fact it is.Trace the point of isolation, which could be a type of switch, a circuit breaker or a fuse.Turn off the switch or circuit breaker and use a locking off device to ensure that it cannot be turned back on until you want it to be.Attach a notice at the point of isolation to indicate to others that the circuit has been isolated for a reason.Check that the circuit to be worked on is dead, using your approved voltage indicator.If the circuit looks like it is dead, check that the voltage indicator is working by testing it on a known supply or by using a proving unit.Recheck the circuit to be worked on.If it is dead, then it is safe to start work.

Isolator, fuse and circuit breaker.

Safe Isolation Flowchart

Check that the circuit is live.

Identify the point of isolation.

Isolate and lock off.

Fix notice by the point of isolation.

Use a voltage indicator/test lamp to check that the circuit is dead.

Prove that the voltage indicator/test lamp is functioning correctly by checking it on a known supply or proving unit.

Recheck that the circuit is dead and if it is, then it is safe to commence work.

MANUAL HANDLING

Of all injuries that last over 3 days and are reported to the Health and Safety Executive, 38 per cent are caused by manual handling.

Wherever possible it is best to avoid lifting/moving heavy loads, but of course it is not always possible, as even trying to gain access to lift a floorboard may require the moving of a piece of heavy furniture. If something needs to be moved or lifted, it is wise to take a few moments to assess the situation and perhaps decide on recruiting some help or even, in some cases, a mechanical lifting aid.

On the occasions when lifting is unavoidable, there are a few simple precautions that can be taken to reduce the risk of injury:

Think before lifting, and plan the lift.Can handling aids be used?Where is the load going to be placed?Will help be required with the load?Ensure that, if possible, you are facing in the direction that you will move having lifted the object.Make sure that all obstructions have been moved.Consider stopping and resting the load on a surface at intervals along the route as this will enable you to change your grip. Ensure that you are able to put the object down onto a suitable level surface on completion of the lift.

Correct lifting position.

When lifting:

Adopt a stable position before attempting to lift.Make sure that you can get a good hold on the object before attempting to lift it.Keep the load close to the body.Lift keeping your back straight, if possible.Avoid twisting or flexing your back.Move smoothly and keep your head up when handling.If your grip feels uncomfortable, put the load down and start again.

WORKING AT HEIGHT

Most of us at some point will need to work on, or install, equipment which is too high to reach from the ground without using some form of access equipment. On these occasions it is important that we work safely. In 2008/2009 over 4,000 major injuries were caused from falls at height.

It is important when working that we use the correct type of tools, including access equipment. Of course, there are many types of equipment that we can use if we are working at height. These can range from a simple hop-up for lower levels, right through to a full scaffold for major work at heights.

Providing we follow a few simple rules and use equipment that is suitable for the job, we will remain safe.

Step-Ladders

When working off step-ladders, always ensure that you are working from a level surface. We can, of course, ensure that the ladder is upright by using packing under the step-ladder feet; if we do, we must always make sure that the packing is secure and that the feet of the ladder cannot slip off.

Before use, always check them for safety; this includes looking at the feet.Ensure that they are fully open before attempting to climb them.Ensure that any locking devices are used.Never work off the top two steps.Never overreach.Avoid working side-on; always try and face the item you are working on.Try not to work from steps for more than 30 minutes without a break.Do not use steps if working with loads greater than 10kg.Never ever work on anything if you feel unsafe – always trust your instincts; if it feels unsafe, it is unsafe.

Step-ladder correctly positioned.

Ladders

When it comes to working from ladders, always ensure that the ground is firm and level.

Before use, always check the ladder for damage/wear and tear.Make sure that you have a good resting point for the top of the ladder; never rest it against the guttering or down pipes.Never work from a ladder for more than 30 minutes without a break.When setting the ladder, it should be at an angle of 75 degrees; this works out at a ratio of 1:4 (the foot of the ladder must be 1 unit out for every 4 units up).Wherever possible, get somebody to foot the ladder (stand on the bottom).When climbing the ladder. always make sure that both hands are free to hold onto the ladder stiles.Never hold on to the ladder rungs when climbing the ladder.Never work off the top three steps.Never overreach.Always secure the ladder before working from it.Never lean back off a ladder; use a piece of equipment called an easy reach to lift the ladder from the wall.

Ladder correctly positioned.

Remember! If it feels unsafe, it is unsafe.

Tower Scaffold

Whenever you are working from a tower, always make sure that it is erected to comply with the manufacturers’ instructions. The feet, braces, and outriggers are there for a purpose and should always be used.

Tower scaffold.

Make sure that the area where the tower is to be erected is level and firm.Never climb up the outside of a tower scaffold.Never use steps or a ladder off a tower scaffold.Never overreach.

Some electrical jobs will require the erection of a free-standing scaffold. This type of scaffold should always be erected by a professional scaffolder, and on completion must have a label fixed to it to show that it has been erected correctly and is safe. This is know as a ‘scaff tag’. The scaffold should be checked and the tag updated at regular intervals – often this will be weekly.

Scaffold safety tag.

CHAPTER 3

Tools and Equipment

To carry out electrical work safely and correctly you almost have to be a general builder. Very often the connection of the cables and electrical accessories is the easiest part of the job. Finding a route for, and installing, the cables is often the most difficult.

Having the correct tools for a job and knowing how to use them correctly can save a lot of time and make the job so much easier.

A basic electrician’s kit must consist of:

A claw hammer for fixing cable clips, helping to lift floorboards and various other tasks.A club hammer for heavy work, such as chasing walls.A pair of electrician’s pliers to use for preparing the cable conductors for termination.A pair of side-cutters to cut cable with.Cable insulation stripper to strip off the cable insulation, as required.Gland nut pliers, also called pump pliers.Small, terminal screwdriver.Medium and large, flat-end screwdriver.Small, medium and large Phillips (cross-head) screwdriver.Tape measure.A set of wood drill bits.A set of metal drill bits.Selection of masonry drills.A wood brace.A hand drill (wheel brace).Wood saw.Junior hacksaw.A hacksaw.Pad saw for cutting holes in plasterboard.A brick bolster for using to chase brick and plaster walls.A floor bolster to help lift floorboards (very often an electrician will use this as a brick bolster as well).A selection of cold chisels.A knife for stripping cables.A knife with a retractable blade for cutting plasterboard and other materials. (This type of knife is not particularly suitable for stripping cables, although some electricians use them.)A small spirit-level for use when fitting accessories.A large spirit-level when setting out.A set of wood chisels.Small trowel.

Tools to Make Life Easier

An electric power drill, either a battery or a low-voltage drill. A battery drill is preferable in many instances, as it eliminates the need to have the power switched on. It is advisable to keep a spare battery, which is fully charged, as you will find that the battery always runs flat at the most inconvenient time. You will need to ensure that the drill is powerful enough to carry out the work expected of it. If it is to be used for drilling holes in walls for screw fixings, you will need a percussion drill. It is also very important to remember that, if you overload your drill, it will burn out. Always try to keep pressure on the drill bit – it will last longer.

Most modern battery drills have a variable speed; it is very convenient to adapt this type of drill for use as an electric screwdriver, although it is advisable not to use it when fixing to a surface accessories such as Bakelite boxes or ceiling roses. This is because it is too easy for you to accidentally over-tighten the fixing screws and break the accessory; it can prove to be an expensive lesson.

SDS drill and chuck.

It is important also to ensure that the type of drill bits you buy are suitable for use with the type of drill you have. Most modern drills come with an SDS (special direct system) chuck and the drill bits simply push in and are held secure by a mechanism inside the drill. This type of chuck eliminates the use of a key to tighten the chuck onto the drill bit.

Head torch.

Another useful point is that a key chuck can be used as they are available with an SDS-type fitting, which fits into the end of the drill just as a drill bit would. This, of course, makes an SDS drill very versatile and resolves the problem of trying to find the chuck key, which you have put down somewhere but cannot remember where; also, the drill bit always remains tight in the chuck.

Flexible fishing tool.

Other useful tools include: