WIRING MATTERS - Institution of Engineering and …...BS 5588-1 (a) New or materially altered dwelling complying with the recommendations of BS 5588-1 Existing dwelling where the structural

WIRINGMATTERS

Winter 2005 Issue 17

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FIRE ALARMS IN DWELLINGSReduce the risk ofdeath or injury from fire

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IN THE UK around 80% of all fire deaths andinjuries occur in dwellings, a total of 450 to 500 deaths and 14,000 injuries per annum, according to BS 5839-6: 2004.

The installation of a fire detection and alarmsystem can significantly reduce the risk of death orserious injury from fire. The fatality rate in fires indwellings is three times higher where there is nosmoke detector or where it is not working comparedto dwellings where a fully functioning smoke detectoris fitted. The installation of automatic smokedetectors is, effectively, required in new dwellings tosatisfy Building Regulations.

BUILDING REGULATIONSApproved Document B of the Building Regulations(2000), Fire Safety, deals with the followingRequirement from Part B of schedule 1 to theBuilding Regulations 2000.

Approved Document B states, in paragraph 1.2 thatin most houses the installation of smoke alarms orautomatic fire detection and alarm systems, cansignificantly increase the level of safety byautomatically giving an early warning of fire. Thedocument also states, in paragraph 1.3, that if housesare not protected by an automatic fire detection andalarm system in accordance with the relevantrecommendations of BS 5839: Part 1 Fire detection andalarm systems for buildings, Code of practice for

IEE Wiring Matters | Winter 2005 | www.iee.org

Means of warning and escape

B1. The building shall be designed and constructedso that there are appropriate provisions for the earlywarning of fire, and appropriate means of escape incase of fire from the building to a place of safetyoutside the building capable of being safely andeffectively used at all material times.

system design, installation and servicing to at least anL3 standard, or BS 5839: Part 6 Code of practice for thedesign and installation of fire detection and alarmsystems in dwellings to at least a Grade E type LD3standard, they should be provided with a suitablenumber of smoke alarms installed in accordance withthe guidance in paragraphs 1.4 to 1.22 of the ApprovedDocument.

Approved Document B can be downloaded free ofcharge from the Building Regulations section of thewebsite of the Office of the Deputy Prime Minister atwww.odpm.gov.uk

BS 5839-6: 2004 Electrical designers and contractors withresponsibilities for design, installation ormaintenance of fire alarm systems in dwellingsshould be aware of the recommendations given in BS5839-6: 2004 Fire detection and fire alarm systems forbuildings – Part 6: Code of practice for the design,installation, and maintenance of fire detection andfire alarm systems in dwellings and should obtain acopy of BS 5839-6 from BSI at 389 Chiswick High Road,London W4 4AL Tel: 0208 996 9000, www.bsi-global.com. The recommendations given in BS 5839-6applicable to houses, bungalows and flats arediscussed in this article.

Grades of systemThe Grades of system for fire alarm systems indwellings range from Grade A to Grade F. Grade Aand B systems are systems of a type described in BS 5839-1. In a Grade C system, the fire detectors aresupplied with a common power supply unit withcentral control equipment and this type of systemnormally incorporates a secondary rechargeablebattery. Fire alarm systems in dwellings are, in most cases, Grade D, E or F which do not employ a control panel.

FIRE ALARMS IN DWELLINGS By John Ware

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Published by IEE Publishing & Information Services Michael Faraday House, Six Hills Way, Stevenage, Herts, SG1 2AY, United KingdomTel: +44 (0)1438 313311 Fax: +44 (0)1438 313465

Sales and Project Coordinator L Hall +44 (0)1438 767351 [email protected] | Editor G D Cronshaw +44 (0)1438 [email protected] | Contributing Editors J Ware, M Coles, I Reeve | Chief Sub Editor Jim Hannah | Design SaBle Media SolutionsIEE Wiring Matters is a quarterly publication from the Institution of Electrical Engineers (IEE). The IEE is not as a body responsible for theopinions expressed.

©2005: The Institution of Electrical Engineers. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,or transmitted in any form or by any means without the permission in writing of the publisher. Copying of articles is not permitted except forpersonal and internal use. Multiple copying of the content of this publication without permission is always illegal. Web-offset printing byWyndeham Heron, The Bentall Complex, Colchester Road, Heybridge, Maldon, Essex, UK

Co-operating Organisations The Institution of Electrical Engineers acknowledges the contribution made by the followingorganisations in the preparation of this publication: British Electrotechnical & Allied Manufacturers Association Ltd – R Lewington,P D Galbraith, M H Mullins, P Sayer | Office of the Deputy Prime Minister – K Bromley, I Drummond | Electrical Contractors Association – D Locke, S Burchell | City & Guilds of London Institute – H R Lovegrove | Energy Networks Association –D J Start | Electrical ContractorsAssociation of Scotland SELECT – D Millar, N McGuiness | Health & Safety Executive – N Gove | National Inspection Council for ElectricalInstallation Contracting | ERA Technology Limited – M Coates | British Cables Association – C Reed

Grade Description and explanation

D A system of one or more mains-poweredsmoke alarms, each with an integral standbysupply. The system may, in addition, incorporateone or more mains-powered heat alarms, eachwith an integral standby supply.

One or more batteries or capacitors is providedto ensure protection is available under loss ofmains conditions.

E A system of one or more mains-powered smokealarms with no standby supply. The system may,in addition, incorporate one or more heatalarms, with or without standby supplies.

The system is potentially more reliable than aGrade F system, because it requires lessattention by the user. The cost of the systemis higher as a mains supply and interlinkingcables are required and the detectorsthemselves cost slightly more.

Loss of mains results in loss of protection.

F A system of one or more battery-poweredsmoke alarms. The system may, in addition,incorporate one or more battery-poweredheat alarms.

Grade F systems are the simplest form of firedetection and alarm system, are low cost andrelatively simple to install. Smoke alarms toBS 5446-1 and heat alarms to BS 5446-2 givea low battery warning.

A disadvantage of a Grade F system is thatremoval of the battery disables the protection.

Categories of systemFire alarm systems are usually installed in dwellings to protectlife (L) but may also be installed to protect property (P). Firealarm systems are divided into the following categories:

Grade Description and explanation

LD

Objective of categoryL systems is the protectionof life(D meansdwelling)

LD1 A system installed throughout the dwellingincorporating detectors in all circulation spaces that form part of the escape routesfrom the dwelling, and in all rooms and areas in which fire might start, other thantoilets, bathrooms and shower rooms

LD2 A system incorporating detectors in allcirculation spaces that form part of the escape routes from the dwelling, and in all rooms or areas that present a high firerisk to occupants

LD3 A system incorporating detectors in allcirculation spaces that form part of the escape routes from the dwelling

PD PD1 A system installed throughout the dwellingincorporating detectors in all areas in whichfire might start other than toilets, bath andshower rooms

PD2 A system incorporating detectors only indefined rooms or areas of the dwelling inwhich the risk of fire to property is judged to warrant their provision


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The Category of system needs to be defined in the specification and, except forCategory LD1 or PD1 systems, the details of the areas of the building to beprotected. Statutory requirements imposed by enforcing authorities and anyrequirements imposed by property insurers should state the Category ofsystem required.

The minimum Grade and Category of fire detection and alarm system forprotection of life in typical dwellings is given in the Table below (Part of Table1 of BS 5839-6. Refer to BS 5839 for full details)

Installation of fire alarm systemsPower suppliesSmoke and heat alarms that are to be

Minimum Grade and Category of system to be installed

Class ofdwelling

New or materiallyaltered dwellingcomplying with therecommendations ofBS 5588-1 (a)

New or materiallyaltered dwellingcomplying with therecommendations ofBS 5588-1 (a)

Existing dwellingwhere the structuralfire precautions are ofa lower standard than therecommendations ofBS 5588-1 (a)

Single family dwelling with no floor area greater than 200 m2 in area

Bungalow, flat,or owner-occupiedmaisonette or2-storey house

Grade Category Grade Category Grade Category

D LD2 F(b) LD3 D LD2

Rentedmaisonette or2-storeyhouse

D LD2 D LD3 D LD2

3-storeyhouse D LD2 D LD3 D LD2

4 or morestorey house B LD2 D LD2 B LD2

Single family dwelling with one or more floors greater than 200 m2 in area

Bungalow or flat D LD2 D LD3 D LD2

Maisonette or2-storeyhouse

B LD2 B LD2 B LD2

Three (or more)storey house

Grade A Category LD2. Refer to BS 5839-6 for full details

(a)Or guidance that supports national building regulations. For England and Wales see Approved Document B. BS 5588 is entitledFire precautions in the design, construction and use of buildings(b)A Grade E system should be fitted if there is any doubt as to whether the occupier will replace batteries. But a Grade D system should be fitted if the electricity supply might be disconnected because the occupier cannot pay for the supplyBatteries in smoke alarms in rented bungalows or flats should have a life of at least 5 years (with normal use) and removalshould necessitate a tool.

System Power supplyrecommendations

Grade D The mains supply to smoke andheat alarms should either be asingle independent circuit from thedwelling’s main distribution boardor a separately electrically-protected regularly used locallighting circuit.

Grade E The mains supply to smoke andheat alarms should be a singlededicated independent circuit fromthe dwelling’s main distributionboard.

Smoke and heat alarms should beinterconnected and, in this case,must be supplied from the samecircuit.

The circuit supplying the smokeand heat alarms should preferablynot be protected by an RCD unlessone is required for reasons ofelectrical safety, then either theRCD should serve only the circuitsupplying the smoke or heatalarms or the RCD protection of thefire alarm system should operateindependently of any RCDprotection for circuits supplyingsocket-outlets or portableequipment.

Grade F The batteries of smoke alarmsand any heat alarms should becapable of supplying the normalload, including the additionalload from routine weekly testingfor at least one year before thebattery fault warning is given.

At the point at which the batteryfault warning commences, thebatteries should have sufficientcapacity to give a fire alarmwarning signal for at least 4minutes or, in the absence of afire, a battery fault warning for atleast 30 days.


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interconnected by wiring should be connected on a single finalcircuit. Note that certain alarms are radio linked and such alarmsneed not be on the same final circuit

Wiring systemsAll cables should be selected and installed in accordance with therequirements of BS 7671 and the recommendations of BS 5839-6.Additional recommendations include:

InstallationFigs 2 to 4 (overleaf) illustrate the recommendationsgiven in BS 5839-6 for new houses, bungalows and flatswhere each floor area is not greater than 200 m2. Heatdetectors should be installed in every kitchen andprinciple habitable room. Alternatively, the detector inthe principle habitable room, but not the kitchen, maybe a smoke or carbon monoxide fire detector. Smokedetectors should be installed in halls and landings.

The installation of the fire alarm system shouldcomply with the requirements of BS 7671. Additionalrecommendations include:

� Sounders should be rigidly fixed to permanentconstruction. Wiring between detectors should beinstalled and routed so that mechanical damage is avoided.

� The installer should provide as-fitted drawings.

CommissioningThe system should be inspected.

Electrical tests made to the mains supply circuitshould include earth continuity, polarity, and earthfault loop impedance. Insulation tests should be madeof all installed cables as required by BS 7671.

Electronic equipment should be disconnected toavoid damage.

System Wiring system recommendations

Cables used for the mains supply to smoke alarms, any heatalarms and any interconnecting wiring may comprise anycable suitable for domestic mains wiring

Cables used for interconnecting smoke and heat alarmsshould be readily distinguishable from those supplyingpower, (for example by red colour coding). Such cables neednot be fire resistant.

Cables used for unmonitored circuits should be protectedagainst damage

Grade F Cables suitable for the voltage or current is suitable.

Cables used for unmonitored circuits should be protectedagainst damage

Grade DandGrade E

Fig 1: Supply to a Grade E system where theinstallation forms part of a TT system.

The 100 mA time-delayed RCD providesprotection for the fire alarm system (and othercircuits) and operates independently of the RCDprotection for the socket-outlets

main switch(100 mA time delayed RCD)S-type, double pole to BS EN 61008


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The entire system should be tested to ensure that itoperates satisfactorily and that, in particular,automatic fire detectors and any manual call pointsfunction correctly when tested. Smoke detectors shouldbe smoke tested with a simulated smoke aerosol thatwill not damage the detector. Heat detectors should betested by means of a suitable heat source unlessdetector damage would otherwise result. The heatsource should not have the ability to cause a fire. A liveflame should not be used.

It should be established that any interlinking worksand that sounders operate correctly.

Manufacturer’s tests should be carried out.

CertificationA certificate should have been issued to the user andthis should be available for inspection. For Grade Fsystems a certificate should be issued if installed by aprofessional installer.

User instructionsThe supplier of the fire alarm system should providethe user with operating instructions, which should besufficient to enable a lay person to understand,operate and maintain the system. Silencing anddisablement facilities should be explained but itshould be stressed that system readiness must not becompromised. Recommended action in the event of afire must stress the importance of all occupantsleaving the building as quickly as possible and thatthe fire service is summoned immediately regardlessof the size of the fire.

Routine testing and maintenanceInstructions to users must stress the importance ofroutine testing. The system should be tested weekly bypushing the test button. If the dwelling has beenunoccupied for a period during which the supply (ies)could have failed, the occupier should check that thesystem has not suffered total power failure and is stilloperable.

MaintenanceSmoke alarms in Grade D, E and F systems should becleaned periodically in accordance with themanufacturer’s instructions. Where experience showsthat undue deposits of dust and dirt are likely toaccumulate, so affecting the performance of the systembefore detectors are cleaned or changed, more frequentcleaning or changing should be carried out. �

Fig 4:New flat

Fig 3:New bungalow

Fig 2:New two-storey dwelling


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BackgroundThe requirements of BS 7671 have been harmonisedwith the technical intent of CENELEC Standard HD384.5.514: Identification, including 514.3: Identificationof conductors.

The cable standards have been harmonised withCENELEC Harmonisation Document HD 308 S2: 2001Identification of cores in cables and flexible cords.These standards specify the cable core markingincluding cable core colours to be implemented in theCENELEC countries.

British Standards for fixed and flexible cables havebeen harmonised with the colours in HD 308 S2. BS 7671 has been modified to align with these cablecolours, but also allows other suitable methods ofmarking connections by colours (tapes, sleeves ordiscs), or by alphanumerics (letters and/or numbers).

Electrical installation work that commenced onsite after the 31 March 2004 has been able to use thenew harmonised colours or use the old colours, butnot both. Work commencing on site after 31 March2006 will be required to comply with the harmonised

cable colours and must not use the old colours. For single phase installations the fixed installation

colours of red phase and black neutral have beenreplaced by brown phase and blue neutral, respectively.The protective conductor is still identified by thecolour combination green and yellow. For three phaseinstallations the fixed installation colours of red,yellow and blue for the phases and black neutral havebeen replaced by brown, black and grey for the phasesand blue neutral. The protective conductor is stillidentified by the colour combination green and yellow.Alternatively, all three of the phase conductor coresmay be coloured brown and marked L1, L2, and L3 atthe terminations.

Alteration or addition to an existing installationSingle-phaseAlterations or additions to a single phase installationdo not require marking at the interface between old andnew cabling providing they are correctly coloured. (Oldcabling coloured red for phase and black for neutral,and new cabling coloured brown for phase and blue for

Work commencing on site after 31 March 2006 will be requiredto comply with the harmonisedcable colours and must not use the old colours

NEW CABLECOLOURSDEADLINEAPPROACHESBy Geoff Cronshaw


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neutral.) A warning label must be provided atthe consumer unit or distribution board.

Two- or three-phase installationWhere an alteration or an addition is made toa two- or a three-phase installation wired inthe old core colours with cable to the newcore colours, unambiguous identification isrequired at the interface. Cores should bemarked as follows:

� Neutral conductors: old and new conductors: N

� Phase conductors: old and new conductors: L1, L2, And L3.

Further informationThis article is only intended as a briefoverview. For further information on theharmonised cable core colours such aslighting circuits and dc installations pleaserefer to BS 7671:2001 incorporatingAmendments No 1:2002 and No 2 2004. Alsoinformation on the harmonised cable corecolours is given in the IEE Electricians Guideto the Building Regulations. � Fig 2: Addition to a three-phase installation

Fig 1: Extension to a single-phase installation


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IEE WIRING REGULATIONS CD-ROMHINTS & TIPS By Ian Reeve

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WIRING MATTERS - Institution of Engineering and …...BS 5588-1 (a) New or materially altered dwelling complying with the recommendations of BS 5588-1 Existing dwelling where the structural