Electrical Installation Designs

Bill Atkinson, Roger Lovegrove, Gary Gundry

• Publisher: Wiley
• Year: 2012
• Print ISBN: 9781119992844
• eBook ISBN: 9781118477762
• Edition: 4
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

A practical and highly popular guide for electrical contractors of small installations, now fully revised in accordance with the latest wiring regulations

The book is a clearly written practical guide on how to design and complete a range of electrical installation projects in a competitive manner, while ensuring full compliance with the new Wiring Regulations (updated late 2008). The updated regulations introduced changes in terminology, such as 'basic' and 'fault protection', and also changed the regulation numbers. This new edition reflects these changes. It discusses new sections covering domestic, commercial, industrial and agricultural projects, including material on marinas, caravan sites, and small scale floodlighting. This book provides guidance on certification and test methods, with full attention given to electrical safety requirements.   Other brand new sections cover protective measures, additional protection by means of RCDs, the new cable guidelines for thin wall partitions and Part P of the Building Regulations. 

• Provides simple, practical guidance on how to design electrical installation projects, including worked examples and case studies
• Covers new cable guidelines and Part P of the Building Regulations (Electrical Installations) in line with 17^th edition of the Wiring Regulations BS 7671:2008
• New chapters on protective measures and additional protection by means of RCDs (residual current devices)
• Features new wiring projects such as marinas, caravan sites and small scale floodlighting and street lighting
• Fully illustrated, including illustrations new to the fourth edition 

1

Introduction

This book contains designs for electrical installations that have been prepared with reference to the Wiring Regulations and includes interpretations of particular technicalities.

This is not a do-it-yourself book for the amateur or untrained person. It is a guidance manual for competent electrical designers and students of installation practice.

As far as possible, all information accords with the requirements of BS 7671: 2008, incorporating Amendment 1, 2011 Requirements for Electrical Installations, the IET Wiring Regulations (17th edition), which is issued jointly by the British Standards Institution (BSI) and the Institution of Engineering and Technology (IET) as BS 7671. Relevant Regulation numbers and other references are shown in the margins. (Because of the space restrictions, the following abbreviations have been used: Ch. – Chapter; Sec. – Section; Defs – Definitions; App. – Appendix.) Reference is also made to various other British and European Standards and related Health and Safety documentation.

1.1 Layout of Chapters

Interspersed throughout the book are two types of chapters, giving information in different formats.

1. Project chapters: These may be compared with a selection of recipes for an experienced chef. The recipes give ideas for the design of typical electrical installations. Each project is dealt with on a stand-alone basis. Cross-references between these chapters are avoided, wherever possible, and similar information may be found for more than one scheme.

2. Topic chapters: These supplement the project chapters with in-depth discussion of generalised technicalities. They also provide study information on regulatory subjects. It may be necessary to refer to these details to finalise a design with particular problems.

1.2 Wiring Regulations

Throughout this book the terms Wiring Regulations (or Regulations) refer to BS 7671:2008 Requirements for Electrical Installations, the IET Wiring Regulations, issued jointly by the BSI and the IET. The Standard therefore represents a code of acceptable safety for electrical installations to protect:

131.1

• persons;
• property; and
• livestock.

against electrical hazards, which are described as:

• electric shock;
• fire;
• burns;
• ignition of a potentially explosive atmosphere;
• undervoltages, overvoltages and electromagnetic effects;
• injury from mechanical movement of electrically actuated machinery;
• power supply interruptions or interruptions of safety services; and
• arcing or burning, excessive pressure or toxic gases.

114.1

The Regulations are not a statutory document, but are quoted as a means of compliance with certain statutory instruments. Criminal charges could not be brought for failure to comply with the Wiring Regulations, and such non-compliance could be used in evidence if there were a charge for breach of the forthcoming Electrical Safety Quality and Continuity Regulations (ESQCR) or the Electricity at Work Regulations.

It would be most unwise to ignore any of the requirements of the Regulations. They must be considered in their entirety and are a pass or fail test. An installation cannot partially comply.

1.3 Terminology

In order to understand technicalities, the importance of correct terminology is stressed throughout this book. In general, however, the use of overcomplicated expressions and trade jargon has been avoided.

The Wiring Regulations contain a list of definitions for words and expressions, which may not accord with standard dictionary definitions. Wherever there is any doubt, the Wiring Regulations definition should be applied.

1.4 Competence and Responsibility

Any person involved with the installation of wiring in buildings takes on both legal and moral responsibilities for safety. A high level of technical and practical competence is essential. This can only be achieved with appropriate study.

There are always three components to an electrical installation project:

1. Design;

2. Installation;

3. Inspection and testing.

Often one person or company takes on all three responsibilities, especially for simple repetitive jobs such as house wiring. On larger schemes, specialist companies may be contractually involved for each aspect and in turn use a team of operators. As the work progresses from planning to completion, there must always be one or more supervising individuals, who will eventually certify that the three aspects of the contract have been carried out in accordance with the Wiring Regulations and any other statutory or specification requirements.

1.5 Procedures

1.5.1 Design

It is sometimes thought that the use of tried and tested methods removes the design aspect from a scheme. This is not the case. Every project involves electrotechnical design decisions, which should not to be confused with architectural or customer instructions for the physical location of electrical equipment. Thus, a self-employed electrical contractor, who makes a decision on the selection and connection of an electrical accessory, is a designer. The same applies to an electrician who makes a similar decision on behalf of an employer.

514.9

All technical design information must be recorded. This is a requirement of the Wiring Regulations. IET guidance stresses that it is essential to prepare a full specification prior to commencement or alteration of an electrical installation. The size and content of the specification will correspond with the complexity of the work. For simple installations, a schedule of circuit details and test results may suffice.

The designs shown in the following chapters are for guidance only and each one includes a suggestion for a suitable design specification. A person selecting this guidance makes a design decision and therefore becomes the person responsible.

632.3

Upon completion of a contract, the person or persons responsible for the design, construction, and inspection and testing of the installation must, as appropriate, provide the person who ordered the work with an Electrical Installation Certificate, stating the works that were carried out, together with schedules for inspection and for test results.

1.5.2 Installation

Where a technical design is drawn up by an electrical engineer or other competent person, it should not be the installer's job to check design details, unless this is one of the contract requirements. The installer is always under obligation to point out to the designer any obvious conflict with regulations or standards and the installer should always refuse to carry out substandard work. There would be no defence in law against creating an unsafe installation on the basis of inherently bad instructions.

The installer will use the designer's specification document as required by the Wiring Regulations. This may only cover performance requirements or may give full technical details for the selection and erection of equipment. Once again it must be emphasised that a non-technical instruction to take an electrical supply to a particular appliance or location does not constitute design information.

The installer has the responsibility to ensure that equipment is installed correctly and in accordance with the specification, supplemented by manufacturers' information. The installer is often delegated other tasks, such as that of negotiating with the electricity supply company and verifying local licensing requirements.

Upon completion of the project, the installer certifies that the installation work has been carried out in accordance with the Wiring Regulations.

1.6 Inspection and Test

610.1

No matter how simple or straightforward a job is, the work should always be inspected, both during the course of the work, and upon completion, and tested before the installation is put into service. This applies equally to work carried out by a self-employed operator. Self-certification is normally acceptable, provi...

Table of contents

• Cover
• Title Page
• Copyright
• About the Authors
• Preface to the Fourth Edition
• Acknowledgements
• Chapter 1: Introduction
• Chapter 2: Three Bedroom House
• Chapter 3: A Block of Retirement Flatlets
• Chapter 4: Overcurrent Protection
• Chapter 5: An Architect's Office
• Chapter 6: A High Street Shop
• Chapter 7: Earthing and Bonding
• Chapter 8: Car Service Workshop
• Chapter 9: Circuits
• Chapter 10: Farming and Horticulture
• Chapter 11: Isolation and Switching
• Chapter 12: A Village Sports Centre
• Chapter 13: An Indoor Swimming Pool
• Chapter 14: Cables and Wiring Systems
• Chapter 15: Inspection, Testing and Certification
• Chapter 16: A Caravan Park
• Chapter 17: Residual Current Devices
• Chapter 18: Flood Lighting (Outdoor Lighting) Project
• Chapter 19: Circuit Design Calculations
• Index