DEFENCE ESTATES MINISTRY OF DEFENCE ________________________________________________________________ Edition 1 - 2004

Specification 034

Electrical Installations

Specification 034

Electrical Installations

Spec 034 -forme~yPSA Standard Specification (M&E) No I

DEFENCE ESTATESMINISTRY OF DEFENCE

Edition 1 - 2004

No Warranty is given as to the accuracy of this Specification or its fitness for purpose.

Ministry ofDefence CopyrightApplications forreproduction should be made to Defence Estates

@ crown copyright 2004Updated to include new references, current technology, materials and working practices.

Prepared by Defence Estates

Edition 1 - 2004

Specification 034

Contents

Page

CONTENTS

TABLES v

FOREWORD vi

ABBREVIATIONS vii

SECTION ONE - GENERAL REQUIREMENTS I1.1 EXTENT OF WORK 11.2 RELATED DOCUMENTS I1.3 DEFINITIONS 11.4 REGULATIONS 21.5 STANDARDS 21.6 APPROVAL 2

SECTION TWO - POWER DISTRIBUTION EQUIPMENT 32.1 ELECTRICALCHARACTERISTICS OF ASSEMBLIES 32.2 ENCLOSURES OF ASSEMBLIES 32.3 BUSBAR TRUNKING SYSTEMS 32.4 DISTRIBUTION BOARDS 42.5 AIR-BREAK SWITCHES 42.6 MOULDED-CASE CIRCUIT-BREAKERS 42.7 FUSES 42.8 MINIATURE CIRCUIT-BREAKERS 52.9 RESIDUAL CURRENT-OPERATED CIRCUIT-BREAKERS 52.10 CONTACTORS 52.11 FRAMEWORK 52.12 ERECTION 52.13 MARKING AND NOTICES 6

SECTION THREE - POWER DISTRIBUTION CABLES 73.1 CABLES 73.2 JOINTING AND TERMINATING CABLES 73.3 CONNECTING AND TERMINATING CONDUCTORS 83.4 SLEEVES, TAPES AND SEALING COMPOUNDS 83.5 JOINTING PAPER-INSULATED CABLES 83.6 TERMINATING PAPER-INSULATED CABLES 93.7 JOINTING AND TERMINATING THERMOSETTING

AND THERMOPLASTIC (PVC) INSULATED CABLES 93.8 JOINTING CNE CABLES 93.9 JOINTING DISSIMILAR CABLES 93.10 STOP ENDS 10

SECTION FOUR - ALARM, CONTROL, COMMUNICATION AND MONITORING CABLES 114.1 CABLES 114.2 JOINTS AND TERMINATIONS 114.3 JOINTING THERMOSETTING (POLYETHYLENE) -INSULATED CABLES 114.4 TERMINATING THERMOSETTING (POLYETHYLENE) INSULATED CABLES 114.5 JOINTING THERMOSETTING (POLYETHYLENE)-INSULATED CABLES TO PAPER-

INSULATED CABLES 114.6 SEGREGATION 12

Edition 1 -2004

Specification 0344.7 MARKING 12

SECTION FIVE - CABLE SUPPORTS 135.1 SELECTION OF CABLE SUPPORTS 135.2 PROTECTIVE FINISHES FOR FERROUS MATERIALS 135.3 CABLE TRAY 135.4 CABLE CLEATS 145.5 CABLE RACKS AND CABLE LADDERS 145.6 CABLE HANGERS 145.7 SUSPENSION AND FIXINGS 145.8 BONDING 14

SECTION SIX - CABLE INSTALLATION 176.1 ROUTES 176.2 SEGREGATION 176.3 SUPPORTS AND FIXINGS 176.4 TRENCHING 176.5 WARNING TAPES AND COVERS 186.6 DUCTS 186.7 LAYING OF DUCTS 196.8 HANDLING OF CABLES 196.9 SEALING DUCTS AND OPENINGS 206.10 CABLE GUARDS 206.11 MARKING OF CABLES 206.12 REDUNDANT CABLES 21

SECTION SEVEN - OVERHEAD LINES 237.1 OVERHEAD LINES 237.2 CONNECTIONS TO BUILDINGS 237.3 CATENARY WIRE SUPPORTS 23

SECTION EIGHT - WIRING SYSTEM: CABLES IN CONDUIT, TRUNKING AND DUCTING 258.1 CABLES 258.2 CONDUIT 258.3 STEEL CONDUIT AND FITTINGS 258.4 NON-METALLIC CONDUIT 258.5 TRUNKING AND DUCTING 258.6 STEEL TRUNKING 268.7 UNDERFLOOR DUCTING AND FLOOR TRUNKING 268.8 ROUTES AND SEGREGATION 268.9 SUPPORTS AND FIXINGS 268.10 INSTALLATION 278.11 PROTECTIVE CONDUCTOR 288.12 WIRING - 288.13 MITIGATION OF PLASTICISER FROM THERMOPLASTIC (PVC) MATERIALS 28SECTION NINE - WIRING SYSTEM: MULTI-CORE SHEATHED CABLES 309.1 CABLES 309.2 BOXES 309.3 ROUTES AND SEGREGATION 309.4 INSTALLATION 309.5 PREFABRICATED WIRING INSTALLATIONS 31

SECTION TEN - WIRING SYSTEM: MINERAL-INSULATED CABLES 3310.1 CABLES 3310.2 TERMINATION 3310.3 JOINTS 3410.4 ROUTES AND SEGREGATION 3410.5 SUPPORTS AND FIXINGS 3410.6 INSTALLATION 34

SECTION ELEVEN - EARTHING 3711.1 MATERIALS 3711.2 EARTH ELECTRODES 3711.3 CONDUCTORS 37

II Edition 1 -2004

Specification 03411.4 JOINTS AND CONNECTIONS 3711.5 INSPECTION PITS 3811.6 SUPPORTS AND FIXINGS 3811.7 INSTALLATION 3811.8 BONDING TO INCOMING SERVICES 38

SECTION TWELVE - WIRING ACCESSORIES AND SMALL EQUIPMENT 3912.1 ACCESSORIES-GENERAL 3912.2 SWITCHES 3912.3 DIMMERS 3912.4 SOCKET OUTLETS 4012.5 SOCKET OUTLETS FOR WET LOCATIONS 4012.6 PLUGS 4012.7 SHAVER SOCKET OUTLETS 4012.8 FUSED CONNECTION UNITS 4012.9 COOKER CONTROL UNITS 4012.10 TELEPHONE CORD-OUTLETS 4012.11 SAFETY ISOLATING TRANSFORMERS 4012.12 ROOM THERMOSTATS 4112.13 ELECTRICITY METERS 4112.14 TIME SWITCHES 4112.15 PHOTO-ELECTRIC CONTROL UNITS 4112.16 BELLS AND BUZZERS 4112.17 PUSHES 4112.18 INDICATORS 4112.19 TERMINAL BLOCKS 4112.20 MOUNTING HEIGHTS 41

SECTION THIRTEEN - CONNECTIONS TO APPLIANCES AND MOTORS 4513.1 GENERAL 4513.2 FLEXIBLE CORDS 4513.3 WATER HEATERS 4513.4 ROOM HEATERS 4513.5 TOWEL RAILS 4513.6 COOKERS 4513.7 WASTE DISPOSAL UNITS (DOMESTIC) 4513.8 SANITARY DISPOSAL UNITS 4613.9 EXTRACT FANS 4613.10 OTHER APPLIANCES 4613.11 PLANT, MACHINERY AND MOTORS 46

SECTION FOURTEEN - LUMINAIRES AND LAMPS 4914.1 LUMINAIRES 4914.2 STREET LIGHTING COLUMNS 4914.3 LAMPS 4914.4 LAMPHOLDERS 4914.5 CEILING ROSES 4914.6 PENDANTSAND CHAIN SUSPENSIONS 5014.7 SUPPORTS AND FIXINGS 5014.8 WIRING CONNECTIONS 50

SECTION FIFTEEN - EMERGENCY LIGHTING 5315.1 GENERAL 5315.2 CENTRAL BATTERIES 5315.3 CENTRAL BATTERY CONTROL EQUIPMENT 5315.4 WIRING 53

SECTION SIXTEEN - POTENTIALLY EXPLOSIVE ATMOSPHERES 5516.1 STANDARDSAND CODES OF PRACTICE 5516.2 MINISTRY OF DEFENCE MILITARY EXPLOSIVES AREAS 55

SECTION SEVENTEEN - LIGHTNING PROTECTION OF BUILDINGS 5717.1 GENERAL 5717.2 AIR TERMINATIONS 57

Edition I - 2004 III

Specification 03417.3 DOWN CONDUCTORS 5717.4 JOINTS 5717.5 EARTH ELECTRODES 5817.6 FIXINGS 58

SECTION EIGHTEEN - CATHODIC PROTECTION 5918.1 GENERAL 5918.2 GROUNDBEDS 5918.3 SOURCE OF POWER 5918.4 CABLING 5918.5 TEST POINTS AND BONDING 6018.6 MARKING 60

SECTION NINETEEN - INSPECTION AND TESTING 6119.1 GENERAL 6119,2 INFORMATION 6119.3 TESTING METHODS 6119.4 POWER CABLES 6119.5 ALARM, CONTROL, COMMUNICATION AND MONITORING CABLES 6119.6 CONDUIT AND TRUNKING 6119.7 EARTH ELECTRODES 6119.8 LIGHTNING PROTECTION 6219.9 EARTH FAULT LOOP IMPEDANCES 6219.10 EMERGENCY LIGHTING SYSTEMS 6219.11 POTENTIALLY EXPLOSIVE ATMOSPHERES 6219.12 CATHODIC PROTECTION 6219.13 RECORDS AND CERTIFICATES 62

SECTION TWENTY - DRAWINGS AND DOCUMENTS BY CONTRACTOR 6320.1 EXTENT OF PROVISION 6320.2 INSTALLATION DRAWINGS AND DOCUMENTS 6320.3 BUILDERS WORK DRAWINGS 6320.4 AS-INSTALLED DRAWINGS 6320.5 MAINTENANCE AND OPERATING INSTRUCTIONS 64

APPENDIX ONE - LIST OF STANDARDS 67

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Specification 034

Tables

TABLE 5A FIXING FOR CABLE SUPPORTS 15

TABLE 6A MINIMUM SPACING OF CABLES 22

TABLE 6B MINIMUM COVER FOR CABLES 22

TABLE 8A CONDUIT AND TRUNKING FIXINGS 29

TABLE 8B PLASTERCISER MITIGATION 29

TABLE I OA MINERAL-INSULATED CABLE SHEATH COLOURS 35

TABLE lOB MINERAL-INSULATED CABLE FIXINGS 35

TABLE 12A MOUNTING HEIGHTS (FOR ACCESSORIES AND EQUIPMENT) 43TABLE 13A CONNECTIONS TO APPLIANCES 47

TABLE 14A LAMPHOLDERS 51

TABLE 17A CONDUCTOR FIXINGS (LIGHTNING PROTECTION) 58

Edition 1 -2004 V

Specification 034

Foreword

This Specification is one of a series prepared by Defence Estates (DE) anagency ofthe Ministryof Defence (MOD) primarily for use in its contracts formechanical and electrical engineering works. The Specification coverselectrical installations for buildingsother thandwellings. It is a revision of theformer Property Sevices Agency (PSA) Standard Specification (M&E) No.1,dated 1985.

2. When this Specification is used in connection with a defence contract then it isto be read in conjunction with such further documents setting out contractualrequirements particular to the contract. Where the words as indicated,where indicated or unless otherwise indicated are included in the text, it isthe designer/specifiers responsibility to ensure that the information referred to isincluded in the documentation package. (See clause 1.3.3).

3. Whilst this Specification was written by DE foruse on MOD contracts, it isacknowledged that it could be usefully applied to other contracts. DEcommends its use to other Government Departments. Itmay, therefore, be usedoutside the MOD Estate. However, no warranty is given as to the accuracy ofthis Specification or its fitness for anypurpose.

4. This update includes modifications taking account of the 16th Edition of theWiring Regulations, nowBritish Standard (BS) 7671:2001 Amendment No. 1,2002 (AMD 13628) andthe lEE Guidance Notes issued alongside. Theopportunity hasbeen taken to update various references to other standards. It isrecognised that electrical engineering standards are rapidly changing, with manyBS EN series standards replacing older BS standards. Standards current at thetime of contract should be assumed to be appropriate. Other updates have takenaccount of new materials and equipment coming into use since the last issue,and minor corrections have beenmade. (A major review of the scope andcontent has not been attempted at this time.)

5. It should be noted that this document nowexcludes fire alarm and detectionsystems and Aviation Ground Lighting installations.

6. Compliance with the contents of this document will not in itself conferimmunity from legal obligations.

7. These specifications havebeen devised for the useof the Crown and itscontractors in the execution of contracts for the Crown. The Crown herebyexcludes all liability (other than liability for death or personal injury)whatsoever and howeverarising (including, but without limitation, negligenceon the part of the Crown, its servants or agents) forany loss or damage howevercaused where the Standard is used for anyother purpose.

8. Compliance with a DE functional standard does not of itself confer immunityfrom legal obligations.

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Specification 034

Abbreviations

The following abbreviations are used in this specification:

ac alternating currentBSRIA Building Services Research and Information AssociationBS British StandardBS EN British Standard Euro NormCNE Combined Neutral and EarthCOSHH Control of Substances Hazardous to HealthCPC Circuit Protective Conductordc direct currentDE Defence EstatesELV Extra low voltageEPR Ethylene propylenerubberESI Electricity Supply IndustryGLS General lighting serviceGRP Glass Reinforced PlasticHOFR Heat and oil resistant and flame retardantHV High VoltageICEL Industry Committee forEmergency LightingIDMT Inverse Defmite Minimum TimelEE Institution of Electrical EngineersIP Ingress Protection as defined in BS EN 60529LDU Link disconnecting unitLSF Low smoke and fumeLV Low VoltageMCB Miniature circuit-breakerMOD Ministry ofDefencePVC Polyvinyl chlorideRCCB Residual current operated circuit breaker without integrated

overcurrent protection -RCBO Residual current operated circuit breaker with integrated

overcurrent protectionXLPE Cross-linked polyethylene

Edition 1 -2004 VII

Specification 034

Section One - General Requirements

1.1 EXTENT OF WORK

1.1.1 This Specification states the requirementsfor the supplying, assembling, fixing in position,connecting, inspecting, testing and leaving inworking order, new, modified or additionalelectrical installations.

1.1.2 The work shall comprise the whole ofthelabour and, unless otherwiseindicated, all thematerials necessary to form acomplete installation,includingsuch tests, adjustments andcommissioning as are prescribed in subsequentclauses and as may otherwisebe required to give aneffective working installation to the satisfaction ofthe Project Manager.1.1.3 The words complete installation inclauses 1.1.2 and 1.5.1 shall mean not only the itemsof electrical equipment conveyed by thisSpecification,but all the incidental sundrycomponents necessary for the complete execution ofthe works and for the properoperation of theinstallation, whether or not these sundry componentsare mentioned in detail in the tender documentsissued in connection with the contract.

1.1.4 Items listed in the contract documents orotherwiseindicated will be supplied to theContractor.

1.1.5 Unless otherwise indicated, work externalto buildings shall include the supply and installationof: sand for cable bedding and cover cable warning covers, cable warning tapes and

cable markers poles/posts.

1.1.6 Unless otherwise indicated, the followingwill be carried out by others: trenching, hole digging and backfihling duct laying and construction of cable drawpits builders work.

1.1.7 Drawings and documents shall beprovided by the Contractor in accordance withSection 20.

1.1.8 Adequate protection ofequipment duringtransit shall be provided by Manufacturers and theContractor shall ensure adequate protection on site.The Contractor shall advise the Project Manager ofanydamage that occurs to equipment includingfinishes and shall carry out repairs as directed by theProject Manager.

1.2 RELATED DOCUMENTS

1.2.1 Related documents will be enumerated inthe invitation to tender or in an appendix to theparticular clauses. They will include theconditions of contract, particular clauses and anysupplementary specifications, schedules anddrawings that relate to the contract.

1.2.2 If anydiscrepancy is found between thisSpecification and the relateddocuments, regulationsor standards, the appropriate Officer shall beinformed. During the tender stage and prior to acontract being placed the Officer shall be as listed inthe documents; thereafter the Project Manager shallbe consulted.

1.3 DEFINITIONS

1.3.1 The defmitions in BS 767 1:2001 applythroughout this Specification.

1.3.2 Where work is undertakenas aSubcontract, Contractor shall meanSubcontractor.

1.3.3 The words as indicated, whereindicated, unless otherwise indicated, refer toitems or requirements indicated elsewhere in thetender documents issued in connection with thecontract, for example on a drawing, in asupplementary specification or schedule.

1.3.4 Project Manager shall mean an officialof the MOD or commercial representativeresponsible for the purpose ofmanagement andadministration of the works covered within thisSpecification.

Edition 1 -2004

Specification 034 Section One - General Requirements

1.3.5 The Project Manager shall, whererequired, consult with competentpersons to ensurethat deviations from specification are satisfactory.Alternatives may be used with the specific writtenapproval of the Project Manager.

1.4 REGULATIONS

1.4.1 Each installation shall comply with allrelevant statutory instruments andregulationsincluding, but not limited to, the following: Electricityat Work Regulations 1989 Electricity Supply Regulations 1988 Health and Safety at Work etc. Act 1974 Construction (Design and Management)

Regulations 1994 BS 7671:2001 Requirements forElectrical

Installations requirements of the local electricity,

telecommunications, gas and water Suppliers; COSHH Regulations 2002 Construction (WorkingPlaces) Regulations

1966 Dangerous Substances and Explosive

Atmospheres Regulations 2002 (DSEAR) Electrical safety quality and continuity

regulations 2002.

EUDirectives implemented into British regulations.

In addition the guidance publishedin the InstitutionofElectrical Engineers (lEE) Guidance Notes shallbe followed.

1.4.2 The Contractor shall fulfil the relevantduties under the Construction (DesignandManagement) Regulations as Principal Contractor orshall co-ordinate with the Principal Contractor asappropriate.

1.5 STANDARDS

1.5.1 The complete installation shall complywith all relevant British Standards and, whereindicated, with other Standards and Specifications,and all amendments thereto. The relevant issuesshall be those current threemonths before the datefor return of tender, unless alternative dates areindicated.

1.5.2 Where practicable, each item ofequipment shall be clearly and indelibly marked toindicate the standard with which it complies.Alternatively a Certificate of Compliance shall beprovided for the Project Manager, to be included inthe handover documentation.

1.5.3 Where equipment or services areindicated to be manufactured or provided under aparticular certification, licensing or qualityassurance scheme, the Manufacturer or Suppliershall be a current participant in the relevant scheme.A Certificate of Compliance shall be provided forthe Project Manager, to be included in the handoverdocumentation

1.5.4 Equipment supplied shall be of a standardthat ensures its compliance with all appropriateBritish Standards and EU requirements.

1.6 APPROVAL

1.6.1 The Project Managers approval shall notrelieve the Contractor ofhis contractualresponsibilities and obligations. The Contractorshall be responsible for discrepancies, errors oromissions on drawings or other documentationsupplied by him, whether they havebeen approvedby the Project Manager or not, provided suchdiscrepancies, errors or omissions are not duetoincorrect information given in writing by the ProjectManager. The Contractor shall be responsible forensuring that equipment complies with the specifiedrequirements.

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Specification 034

Section Two Power Distribution Equipment

2.1 ELECTRICAL CHARACTERISTICS OFASSEMBLIES

2.1.1 The electrical characteristics ofcomponent parts of assemblies shall apply when thecomponents are mounted in their enclosures,appropriate derating factors having beenallowed forthe effect of the enclosures, other components andinterconnections.

2.1.2 Site built assemblies shall not be allowedexcept with the express written approval of theProject Manager.

2.2 ENCLOSURES OF ASSEMBLIES

2.2.1 Doors shall have fastenings with provisionfor locking in the closed position, or shall require aspecial tool for opening.

2.2.2 Fixing holes forequipment insidebuildingsmay be inside or outside the enclosure.Equipment to be located outside buildings shall havefixing lugs external to the enclosure.

2.2.3 Earthing terminals shall be appropriatelyfitted to each enclosure, suitable for internal andexternal connection, to enable the exposedconductive parts of the factory built assembly to beconnected to a protective conductor. Where theenclosure has a painted finish, provision shallbemadefor the earthing terminal to be electricallyconnected to the enclosure without the needtoremove any paint from ferrous metal.

2.2.4 Adequate spacing shall be allowed forspreading of cable tails to avoid stress on theinsulation or terminals; if necessary, proprietaryextension boxes shall be fitted to standardenclosures.

2.2.5 Glandplates shall be provided asappropriate for the type of cable to be connected.For single-core cables, non-ferrous gland plates shallbe provided, and there shall be a clearance of notless than 25mm between cable glands and ferrousmetal.

2.2.6 Ferrous parts of enclosures located outsidebuildings or atother locations, as indicated, shall beprotected against corrosion by a hot-dip galvanisedcoating to BS EN ISO 1461 or by a zinc sprayedcoating to BS EN 22063 with the Manufacturersstandard finish or as indicated.

2.2.7 The resins and dyes used in themanufacture of Glass Reinforced Plastic (GRP)enclosures shall be able to withstandcontinuously atemperature of 50C.

2.2.8 The minimum acceptable degree ofingress protection (IP) from all directions oftheinstalled assembly shall be as indicated.

2.3 BUSBAR TRUNKING SYSTEMS

2.3.1 Busbar trunking systems shall complywith BS EN 60439-2 and clauses 2.1 and2.2. Theyshall have a fault withstandcurrent as indicated.

2.3.2 Busbar trunking systems shall be suitableformechanical loads as defined in BS EN 60439-2,and they shall not be used to support otherequipment.

2.3.3 A means of isolation shall be provided;the number of poles shaltbe as indicated.

2.3.4 The phase sequence shall be maintainedalong the entire length of each busbar trunkingsystem and shallbe identical in all systems in theinstallation. Phase colour shall be clearly andpermanently marked in each trunking unit.

2.3.5 Conductors shallbe supported by highgrade non-hygroscopic and non-tracking insulatingmaterial. They shall be anchored in at least oneposition and a means of taking up expansion andcontraction incorporated.

2.3.6 Tap-offpoints, where indicated, shall beprovided with covers or shutters to screen entry tolive conductors when the position is not occupiedwith a tap-offunit. Tap-off units shall be providedas indicated.

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Specification 34 Section Two Power Distribution Equipment

2.3.7 Where the enclosure is of metal it shall becontinuously connected andbonded as an exposedconductive part. An earth continuity conductor shallbe provided and bonded to an earthing terminalfitted to each trunking unit forming the system andto the protective conductor of the incoming cable atthe feeder unit.

2.3.8 The length ofbusbar trunking systemsshall be determined from drawings for tenderpurposes,but all measurements shall be checked onsite prior to manufacture or installation.

2.4 DISTRIBUTION BOARDS

2.4.1 Fuseboards andminiature circuit-breakerboards shall comply with BS EN 60439-3 andclauses 2.1 and 2.2. Fuses andminiature circuitbreakers shall comply with clauses 2.7 and 2.8 andshall be as indicated.

2.4.2 Fuseboards shall be shielded or shroudedto meet at least IP2X standard.

2.4.3 In distribution boards neutral busbars andearth bars shall have at least one outgoing terminalfor each outgoing circuit. Consideration of therequirements forhigh leakage current installationsshall be given.

2.4.4 A multi-terminal bar for the circuitprotective conductors shall be provided forbothinsulated andmetal cased distributionboards. Itshall be directly connected to the earthing terminalwithout dependence on the exposed conductive partsofthe enclosure.

2.4.5 Identification ofeach fuseway andMiniature Circuit Breaker (MCB) way shall be bypermanent numbering. Identification on the neutralbusbar andprotective conductor bar shall clearlyrelate each terminal to its respective fuseway orMCB way.

2.4.6 - 10% spare fuseways or MCB ways shallbe provided unless otherwise indicated. Wherespecific ratings are indicated, fuses or MCBs shallbe incorporated, otherwisethe ways shall beprovided with proprietarycovers suitable for futureadditions.

2.4.7 Each distribution board shall be fittedwith a means of isolation.

2.5 AIR-BREAK SWITCHES

2.5.1 Air-breakswitches shall comply with BSEN 60947-3 and clause 2.1 and have a utilisationcategoryof AC-22 or AC-23 as indicated. Othercharacteristics of the equipment shall be asindicated.

2.5.2 All switches including fuse combinationunits shall meet the requirements for switch-disconnectors.

2.5.3 Switches used as motor starters shall be toAppendix A of BS EN 60947-3.

2.5.4 Operatingmechanisms shall beindependent manual or as indicated.

2.5.5 Where indicated auxiliary contacts shallbe incorporated in switches.

2.5.6 Each switch shall have a facility forpadlocking in the OFF position.2.5.7 Fuse combination units shall be fitted withfuses complying with clause 2.7.3.

2.5.8 Enclosures shall comply with clause 2.2.

2.6 MOULDED-CASE CIRCUIT-BREAKERS

2.6.1 Moulded-case circuit breakers shallcomply with BS EN 60947-2 and clause 2.1. Theyshall have the voltage and current ratings, rated dutyand rated short-circuit breaking capacity asindicated. The rated short-time withstandtime shallbe one second unless otherwiseindicated.

2.6.2 MCCBs shall be of the independentmanual closing air-break type, rated for anuninterrupted duty, unless otherwise indicated.

2.6.3 Auxiliary facilities, including powerclosing andundervoltage releases, shall be providedonly as indicated.

2.6.4 Each MCCB shall have afacility forpadlocking in the OFF position.

2.6.5 Enclosures shall comply with clause 2.2.

2.7 FUSES

2.7.1 The type andcurrent rating of fuses shallbe as indicated.

2.7.2 Cartridge fuse links complying with BS1361 shall be Type I. Fuse carriers, bases andassociated parts shall also comply with BS 1361.

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Specification 034 Section Two - Power Distribution Equipment

2.7.3 Cartridge fuse links complying with BS88/BS EN 60269 shall be Class gG (or Class gM inmotor circuits) unless otherwise indicated. Motorcircuit fuse links shall be used only where indicated.Fuse carriers, bases and associated parts shall alsocomply with BS 88.

2.8 MINIATURE CIRCUIT-BREAKERS(MCBs)

2.8.1 MCBs shall comply with BS EN 60898and clause 2.1. They shall have the voltage andcurrent ratings andthe category ofduty, and be ofthe type, as indicated.

2.9 RESIDUAL CURRENT-OPERATEDCIRCUIT-BREAKERS (RCBO)

2.9.1 RCBOs shall comply with BS EN 61008(RCCBs) or BS EN 61009 (RCBOs) asappropriate. The ratedvoltage, ratedcurrent, ratedtripping current andrated breaking capacity shall beas indicated.

2.9.2 Where indicated RCCB/RCBOs shallhaveelectronically amplified sensors. They shall beofthe instantaneous, inverse defmite minimum time(IDMT) or fixed time delaytype as indicated.

2.10 CONTACTORS

2.10.1 Contactors shall comply with BS EN60947-4-1 and clause 2.1. They shall be air-breaktype andhave the voltage and current ratings, typeofduty, utilisation category and electrical enduranceas indicated.

2.10.2 Contactors shall be electromagnetic,suitable for the control arrangement as indicated.Operating coils shall be suitable for alternatingcurrent (ac) unless otherwiseindicated, and shall beprotected by cartridge fuses. Latch-in contactorsshall be provided only where indicated.

2.10.3 Enclosures shall comply with clause 2.2.Inbuilt isolating switches complying with clause 2.5and selector/test switches shall be fitted, asindicated.

2.11 FRAMEWORK

2.11.1 Frameworks for supporting electricalequipment shall be constructed from mild steel plateand strip, cold andhot rolled steel sections or slottedangles, complying with BS EN 10162, 10111, BS

4345 andBS EN 10025, 10113, 10130, 10131 or10149 as appropriate. Metal-arc welding shallcomply with BS EN 1011.

2.11.2 Frameworksmounted within abuildingshall have a galvanised finish with a coatingequivalent to, andnot less than, type Z275 to BS EN10147, but Manufacturers standard finishes will beaccepted for slotted angles. All metal exposedduring fabrication shall be given acoat of zinc-richpaint, brushed on, and fmished matching theManufacturers finish.

2.11.3 Frameworksmounted outside a buildingor at other locations as indicated shall be hot-dipgalvanised to BS EN ISO 1461 or sheradize coatedto BS 4921. Metal exposed during fabrication shallbe cleaned with awire brush andgiven a coat ofzinc-rich paint, brushed on.

2.11.4 Bolts, nuts, washers and screws shall benon-corrosive and compatible with the environmentin which theyare installed.

2.12 ERECTION

2.12.1 Equipment, including associatedaccessories, shallbe fixed independently ofthewiring system. All fixing bolts, nuts, washers andscrews shall be non-corrosive and suitable for theenvironment in which they are installed.

2.12.2 Equipment shall be located so that a clearworking space for operation, inspection andmaintenance is provided. Minimum dimensionsshall be in accordance with the recommendationscontained in Defence Works Functional StandardDesign and Maintenance Guide 08: Spacerequirements for plant access, operation andmaintenance. In the caseof cupboards which are tooshallow to meet the requirement with the doorsclosed, equipment shall be located in the elevationarea of the clear door opening.

2.12.3 Single items of equipment shall bemounted 1450mm above finished floor level to thecentre ofthe equipment, unless otherwise indicated.Groups of equipment, other than floor standing,factory-built assemblies, shallbe arranged so that nopart of the equipment requiring access for operationor maintenance shall be less than 500mm or morethan 2000mm above finished floor level, unlessotherwise indicated.

2.12.4 The suitability of equipment to fit into theavailable space shall be checked before it is ordered.Where the requirements of clauses 2.12.2 or 2.12.3

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Specification 34 Section Two Power Distribution Equipment

are unable to be met, the Project Manager shall beconsulted.

2.13 MARKINGAND NOTICES

2.13.1 All diagrams, charts, tables and thewording for labels and notices shall be submitted forthe approval of the Project Manager before theyareinstalled.

2.13.2 Identification labels shall be fixed to theoutside of equipment enclosures. Label format andmaterials shall be appropriate to the installation and

shall be fixed by non-corrosive materials appropriateto the intended application and location.

2.13.3 Characters for labels fixed on the meansof isolation at the origin of each installation shall beat least 10mm high and 1.5mm thick. On all otherlabels characters shall be at least 4mm high and0.5mm thick.

2.13.4 Where thereare two or more incomingsupplies this shall be clearly indicated at each pointof isolation. Labels on single-phase equipmentsupplied from a three-phase supply shall indicate thephase to which it is connected.

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Specification 34

Section Three Power Distribution Cables

3.1 CABLES

3.1.1 The type, size and conductormaterial ofpower cables shall be as indicated.

3.1.2 Paper-insulated cables up to, andincluding, 11kV shall comply with BS 6480; theyshall be mass-impregnated, non-draining, beltedtype. Sheaths shall be of lead for armoured cablesand lead alloy forunarmoured cables.

3.1.3 Paper-insulated aluminium sheath cablesup to, and including, 11kV shall comply with BS6480 as far as it is applicable.

3.1.4 Combined neutral/earth (CNE) cables upto andincluding, 1kV shall comply with ElectricityAssociation Technical Standard 09-9 forWaveconalcable. They shall be used in TN-C-S systems only.

3.1.5 Thermosetting (XLPE or EPR) insulatedcables above 6.6kV andup to, and including, 33kVshall comply with IEC Standard 60 502 or BS 6622.

3.1.6 Thermosetting (XLPE) insulated cablesup to, andincluding, 3.3kV shall comply with BS5467, BS 7889 or BS 6724 as appropriate.

3.1.7 Thermoplastic (PVC) insulated cable upto, and including, 3.3kV, and armoured with wire oraluminium strip, shall comply with BS 6346.

3.1.8 Cables complying with Sections 8 and 10may also be indicated forpower distribution.

3.1.9 - Reduced neutral conductors shall not beused unless indicated.

3.1.10 An oversheath or serving, of theManufacturers standard colour for LV cables andred for HV cables, shall be provided unlessotherwiseindicated.

3.1.11 Installation of cables shall comply withSection 6.

3.2 JOINTING AND TERMINATINGCABLES

3.2.1 Joints and terminations shall comply withclauses 3.2.2 to 3.2.12 inclusive, and with clauses3.3 to 3.9 inclusive as appropriate to the type ofcable. All joint andtermination equipment shall beused to the Manufacturers recommendations. TheProject Manager shall be consulted where it isproposed to install joints that are not indicated.3.2.2 The Project Manager shall be givenevidence that the joint or tennination Manufacturerhas stated that the materials to be employed aresuitable for the type of cable to be jointed orterminated.

3.2.3 A cable shall not be cut until the jointingor terminating commences and the work shallproceed continuously until it is completed. Allnecessaryprecautions shallbe taken to preventdamage and ingress of moisture and impurities.Cable ends shall be free from moisture beforejointing commences and a sample ofpaper frompaper-insulated cables shall be tested formoisture.Where circumstances prevent completion the cableends shall be sealed. This shall be by plumbing oflead sheathed cables anciby hermetically sealingaluminium sheathed cables. For polymeric cableswith polymeric oversheaths appropriate heatshrinkor cold applied end caps shall be used.

3.2.4 The Contractor shall employ staff who arefullyqualified andcompetent for the types ofjointsand terminations to be made. Jointers employed forboth LV and HV work must produce evidence oftraining by the Manufacturer or an appropriatetraining authority in the completion of LVor HVjoints andterminations as appropriate.3.2.5 Core identification shall be matched ateach joint without twisting or crossing ofthe cores.Where numbered cores are jointed to colouredcores, the system adopted shallbe consistentthroughout all cable runs and, on sites with existinginstallations, consistent with the system already inuse. The location of the joint shall be recorded andincluded in the handover documentation.

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Specification 34 Section Three Power Distribution Cables

3.2.6 At the last joint in an HVrun or in anappropriately sized end box where phasing-out is tobe done, the joint or fmal connection shall not bemade until the Project Manager or his competentrepresentative has witnessed, and approved, thephasing-out.

3.2.7 Joints selected for usewith armouredcables shall not reduce the fault current withstandcapacity nor increase the impedanceof the circuitprotective conductor (CPC) and shall be of atypeapprovedby the Project Manager.3.2.8 Armouring andmetal sheaths shall beconnected by abonding conductor directly to theexternal earthing terminal of the equipment at allterminations. The cross sectional area of bondingconductors forLV cables shall be calculated or sizedin accordance with Table 54Gof BS 7671: and HVcables it shall be to BS 7197. Metal sheaths ofsingle core cables shall be bonded and earthed at onepoint only, unless indicated otherwise, and insulatedglands shall be used at the open-circuit end or ends.

3.2.9 Cable tails at terminations shall be formedby separating andbringing out the cores. Each tailshall be long enough to connect to the terminals ofthe equipment.

3.2.10 At the terminations of single core cables,gland plates shall comply with clause 2.2.5. Forthree phase circuits the phase conductors shall bearranged, where practical, in trefoil formation wherethey pass through enclosures of equipment.

3.2.11 Core identification at LV terminationsshall be by coloured or numberedplastic stretch orshrink ferrules on the cores. For HV and LVterminations coloured or numbered discs shallbeprovided on the outside ofsealing boxes to indicatethe disposition of the phases and neutral conductorsinside. Insulating tape shall not be used for markingcables insidejoints or terminations.3.2.12 Continuity of spare cores shall bemaintained atjoints, and at terminations the coresshall be connected to earth at the supply end and in aspare terminal at the load end.

3.3 CONNECTINGAND TERMINATINGCONDUCTORS

3.3.1 All connections and terminations shallnormally be by means of compression fittings.Solder maybe used only for connecting orterminating paper-insulated cables. Mechanicalconnectors may only be used where theManufacturer ofthe joint or termination hasconfirmed, in writing, the suitability ofthe chosen

connector for use with their product.

3.3.2 Cable soldering sockets shall be of correctsize for the conductorwithout excessive clearance.

3.3.3 Compression connectors and associateddies for the compression tool shall be the correcttype and size. The tool shall be so designed that thecorrect compression must be applied before it can bereleased.

3.4 SLEEVES, TAPES AND SEALINGCOMPOUNDS

3.4.1 Sleeves shall be of the shrink type,applied to the Manufacturers recommendations.They shallprovide sufficient thickness ofinsulationto suit the particular application.

3.4.2 Insulating tapes used in joints andterminations shallbe compatible with, and have atemperature ratingand insulating property not lessthan, the cable insulation. They shall comply withBS 3924, but crepe paper tapes may be used forjointing paper-insulated cables.

3.4.3selvedge.

Impregnated cotton tapes shall be double

3.4.4 All tapes shall be stored in sealedcontainers until required.

3.4.5 Resin fillings should, as far as isreasonably practicable, be safe and without risk tohealth. Each pack shall include COSHHRegulations warnings about any hazards in its use,eg. dermatitic or toxic properties, with details of theprecautions that the user must take to minimisethese.

3.4.6 Hot-pouring sealing compound shall behard setting. Selection of the compound shall takeaccount of the ambient temperature oftheinstallation as well as the characteristics of the joint.Voids shall not be allowed in the compound.

3.5 JOINTING PAPER-INSULATED CABLES

3.5.1 Joints shall comply with clauses 3.2, 3.3,3.4 and the following.

3.5.2 For lead sheath cables, joints shall bemade within an assemblycomprising plumbed leador coppersleeves enclosed in casting moulds forcoldpouring resins.

3.5.3 For HVjoints above 3.3kV, purpose-madepaper tubeor crepe paper tape insulation is preferred

8 Edition 1 2004

Specification 34 Section Three Power Distribution Cables

with impregnated paper separators used with three-phase cables. Where these are not used, and forjoints up to and including 3.3kV, the radial thicknessofinsulation over connectors shall be twice theradial thickness ofthe cable coreinsulation. Theradial thickness ofthe belt insulation shall be equalto the radial thickness ofthe cable coreinsulation.

3.5.4 The outer protection boxes for leadsheathed cables shall be cast-iron, split type. Theminimum thickness of compound between the innerjoint sleeves andthe box shall be 12mm. Mouldboxes for cast resin joints need not haveadditionalouter protection.

3.5.5 For screened cable, continuity ofscreening shall be maintainedacross the joint.

3.6 TERMINATING PAPER-INSULATEDCABLES

3.6.1 Terminations shall comply with clauses3.2, 3.3, 3.4 and the following.

3.6.2 A barrier against the ingress ofmoistureinto the cable cores shall be formed belowcompound or shrink sleeve level. For copperconductors up to andincluding 70mm, the coresshall be sweated solid, and for the larger sizes andfor aluminium conductors a ferrule shall be sweatedonto each core. The tails shall be lapped with tapecomplying with clause 3.4, or covered with shrinktype sleeves.

3.6.3 Shrink type sleeves maybe used wherethe cable termination is within an equipmentenclosure, unless otherwiseindicated. At the entryto the enclosure the cable shallbe supported by abolt-onwiping gland at which the armouring shallterminate. The cable shall be securely supportedwithin the enclosure.

3.6.4 End dividing boxes shall be one of thefollowingtypes, as indicated:

1. Coiapound filled, split type, cast-iron boxeswith filling holes sealed by screwed plugs orcaps, and with brass wiping glands and armourclamps. Topplates shall be tapped, orprovided with porcelain bushings or insulatorsas required. Tapped top outlets shall have aminimum of 10mm ofthread.

2. Cast iron or fabricated steel cable boxes fittedto switchgear or transformers.

3.6.5 Pole mounted boxes forLV cables shallbe cast-iron of the tier type, but shrink type sleevesmay be used subject to the approval of the Project

Manager. Fixing ofpole-mounted boxes shall notrequire any cuttingof the pole.

3.7 JOINTING AND TERMINATINGTHERMOSETTING AND THERMOPLASTIC(PVC) INSULATED CABLES

3.7.1 Joints and terminations forThermosetting(XLPE/EPR) andThermoplastic (PVC) insulatedcables shall comply with clauses 3.2, 3.3 and 3.4,the appropriate Part ofBS 4579, BS 7888 or BS6910 and the following.

3.7.2 Joints shall be of the cast resin or shrinktype or combination of cast resin and shrinkmaterial.

3.7.3 Armour Termination shall be by means ofmechanical cable glands complying with BS 6121.For armoured cables the glands shall have an earthbond attachment. For cables with conductors largerthan 35mm the earth termination shall be integralwith the body ofthe gland. Glands used withaluminiumarmoured cables shall be of aluminium,but for all other situations theyshall be of brass,unless otherwise indicated.

3.7.4 Shrink type or pre-moulded products maybe used where an HV cable termination is within anequipment enclosure, unless otherwiseindicated. Atthe entry to the enclosure the cable shall besupported by a mechanical cable gland complyingwith clause 3.7.3. The cable shall be securelysupported within the enclosure.

Note: - Manufactures advice shallbe sought whenreplacing a compound filled termination with aheatshrink type termination to ensure compatibilitybetween the tennination type and the enclosure.

3.7.5 Shrink type or pre-moulded products maybe used where a termination is pole-mounted,subject to the approval of the Project Manager.Additionally, HV cables shall be fitted with shrouds.

3.8 JOINTING CNE CABLES

3.8.1 Jointing shall comply with the clauses ofthis Section relevant to the type of cable. Theprotective conductor shall not be broken under anycircumstances when making a service tee-joint.

3.9 JOINTING DISSIMILAR CABLES

3.9.1 Dissimilar cables shall be jointed onlywhere indicated or with the approval ofthe ProjectManager.

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Specification 34 Section Three Power Distribution Cables

3.9.2 Jointing shall comply with clauses 3.2,3.3, 3.4 and shall be suitable for the two types ofcable concerned.

3.10 STOP ENDS

3.10.1 The term STOP END means theprovision of a permanent seal in which all cores areinsulated and protectedso that the cable can beenergised safely.

10 Edition 1 2004

Specification 34

Section Four Alarm, Control, Communication andMonitoring Cables

4.1 CABLES

4.1.1 The type and size of cables shall be asindicated. Section 4 specifies those, which will bemost commonly used.

4.1.2 Thermosetting andThermoplasticinsulated and sheathed cables, with or withoutscreening and armouring, shall comply with BS3573.

4.1.3 Cables shall be installed in accordancewith this Section, Section 6, and Sections 3, 8, 9 or10, as appropriate.

4.2 JOINTS AND TERMINATIONS

4.2.1 Joints and terminations shall comply withclause 4.2.2, and appropriate parts of Sections 3 and10. For coaxial cables and other special cables,joints and terminations shall comply with theManufacturers requirements.

4.2.2 Joints shall be located above groundunless otherwise indicated. Joint boxes shall besupported securely on short posts or other approvedstructures. Where joints are buried, the joint boxshall be positioned a short distance from, and atright angles to, the line of the route and at the samedepth as the cable.

4.3 JOINTING THERMOSETTINGPOLYETHYLENE-INSULATED CABLES

4.3.1the following.

Joints shall comply with clause 4.2 and

4.3.2 Joints in two-core cables shall be made inadaptable boxes complying with clause 8.3. Cablesshall be terminated at the boxes with compressionglands and armourclamping cones. Joints inconductors shall be madeusing insulated terminalblocks complying with the requirements of clause12.19. Boxes shallbe filled with an inert,permanentlyplastic compound havinga highinsulation value, and shall be completelywrapped inThermoplastic (PVC) self-adhesive tape or similar.

4.3.3 Joints in multi-pair cables with 20 orfewer pairs, including tee-joints having a branchcable of not more than four cores, shall be madeinsingle ended bell-type boxes with expandingplugassemblies. The complete cable, including thearmouring and outer sheath, shall be clamped in aneoprene expander plug.

4.3.4 Joints in cables havingmore than 20pairs, including tee-joints having a branchcable ofnot more than four cores, shallbe made as indicated.Approved sleeve type boxes complying with thecable Manufacturers recommendations shall beused.

4.3.5 Link disconnecting units located aboveground shall be used where tee-joints having abranch cable of more than four cores are to be made.

4.4 TERMINATING THERMOPLASTIC(POLYETHYLENE) INSULATED CABLES

4.4.1 Terminations shall comply with clause 4.2and the following.

4.4.2 Cables shall be terminated at linkdisconnecting units (LDU), which shallbe suppliedcomplete with terminal strips and compressionglands.

4.4.3 The armouring of all cables entering theLDU shall be bonded together, unless otherwiseindicated. The conductivity ofthe bondingconductor shall be not less than the conductivity ofthe armouring ofthe largest cable.

4.5 JOINTING TIIERMOSETTING(POLYETHYLENE) INSULATED CABLES TOPAPER-INSULATED CABLES

4.5.1 Joints shall comply with clauses 4.2 andshall be madeusing single ended bell-type boxeswith expanding plug assemblies.

4.5.2 The finished joints shall be filled with aninert, permanentlyplastic compound havinga highinsulation value.

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Specification 34 Section Four Alarm, Control, Communication and Monitoring Cables

4.6 SEGREGATION

4.6.1 Segregation of cables from those of othersystems and from equipment, pipework andductwork shall comply with clause 6.2 and with anyadditional requirements that are othewise indicated.Any requirements that are indicated for segregatingcircuits of particular systems shall be observed.

4.6.2 Band 2 cables shall not be installed in thesame conduits, trunking compartments or cableducting compartments as Band 1 cables, unlessotherwise indicated, and any requirements that areindicated for segregating circuits of particularsystems shall be observed.

4.7 MARKING

4.7.1 Marking of cables and the termination ofconductors shall comply with clause 6.11, 8.1.5,9.1.2 and 10.6.9 as appropriate, to the type of cable.

4.7.2 A label indicating the system concernedshall identify all joint boxes. Labels shall be inaccordance with clause 2.13.

4.7.3 A diagram showing the allocation ofterminals for each incoming cable shall bepermanently fixed inside each joint box cover. Thediagram shall be afforded protection suitable for theenvironment in which it is located.

12 Edition 1 2004

Section Five Cable Supports

5.1 SELECTION OF CABLE SUPPORTS

5.1.1 The type and sizes of cable supportsystems shall be selected by the Contractor to suitthe circumstances of the installation, unlessotherwise indicated. They shall also comply withclauses 5.2 to 5.8 inclusive, and the followingpreferences shall be taken into account:

for horizontal runs - cable tray or cablerack

for vertical runs - cable cleats or cabletray or cable rack.

Where marshallingof cables occurs (eg. atswitchboards) - cable racks.

5.1.2 The selection, sizing and installation ofcable supports shall take account of the requirementsof Section 6.

5.2 PROTECTIVE FINISHES FOR FERROUSMATERIALS

5.2.1 All ferrous metal for cable tray, cableracks, cable ladder, cable hangers and their fixingsand suspensions shall have a galvanised finish.

5.2.2 Galvanised finishes shall be hot dipped toBS EN ISO 1461, except that support steelwork indryindoor unpolluted areas shall be galvanised toZ275ofBSEN 10147.

5.2.3 In offshore, coastal and polluted areaswhere ferrous materials are used, consideration shallbe given to the use of stainless steel or silicon steelwith l2OO g/m2 coating to BS EN ISO 1461.

5.3 CABLE TRAY

5.3.1 Cable tray shall be metal, plastic or GRP,as indicated. Metal cable tray shall comply withclauses 5.2 and 5.3.2 to 5.3.8. Steel mesh baskettrays may be used only for data, communications,alarm and similar wiring systems, unless otherwiseindicated.

5.3.2 Cable trays shall be perforated. Metalcable trays shall be formed from carbon steel plate

complying with BS EN 10130, 10131 or 10149 asappropriate. Trays and supports shall be selected toprovide adequate support without sagging more than1/360 of the support span, or as indicated.

5.3.3 Bends, tees, risers, reducers and four-waycrosspieces shall be factory made wherever possible,and shall be of the same construction, material,thickness and finish as the cable tray. All tees andcrosspieces shall have a 45gusset on each sidefrom the point of intersection.

5.3.4 Cable trays shall be cut along a line ofunperforated material. Holes cut in cable trays forthe passage of cables shall be fitted with grommets,bushes or other lining. Cutting of cable trays shallbe kept to a minimum.

5.3.5 Each length of a cable tray shall besecurely bolted to an adjacent length with factorymade couplings of adequate dimensions to preventsagging or twisting in accordance with theManufacturers recommendations. Where required,bolts and nuts shall be appropriately dimensionedmushroom-head steel roofing type complying withBS 1494. Ends of coupling bolts shall not come intocontact with the cables. No welding shall be used inthe joining of cable trays.

5.3.6 Where cables are laid on the cable traythey shall be secured by ties, each tie securing thecables of only one circuit~The ties shall be of aproprietary type low in halogen, self extinguishingand ultra-violet resistant. The use of wire or similarmaterial is not permitted. Ties shall be used at lessthan 600mm intervals along each cable, and within100mm of each bend or set.

5.3.7 Cables shall be supported by cable cleatswhere cable trays are vertical. Mineral-insulatedcables on vertical trays shall be supported by saddlesor clips.

5.3.8 Cable trays shall be fixed atregularintervals in accordance with Manufacturersrecommendations but not exceeding 1200mm and at225mm from bends andintersections. A minimumclear space of 25mm shall be left behind all cabletrays.

5.3.9 Cable trays shall be installed with a 20mmgap at building or structural expansion joints. Cable

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Specification 34 Section Five Cable Supports

tray supports shall be installed within 150mm oneither side of the joint.

5.4 CABLE CLEATS

5.4.1 Cable cleats shall be made from materialsthat are resistant to corrosion without the need fortreatment or special finish. Plastic materials shall benon-brittle down to 20C.Non-metallic cleats usedfor low smoke fume (LSF) cables shall be of LSFmaterial.

5.4.2 Cable cleats shall be of a size such thatthey can be tightened down to grip the cableswithout exerting undue pressure or strain on them.For vertical cables two-bolt cable cleats shall beused which shall grip the cables firmly enough toprevent them slipping.

5.4.3 The spacing of cable cleats shall complywith the lEE Guidance Notes to BS 7671. Cleatsshall be located immediately on each side of bendsin the cable.

5.4.4 Single core cables shall be cleated withtrefoil cleats, where appropriate.

5.5 CABLE RACKS AND CABLELADDERS

5.5.1 Cable racks shall comply with clause 5.2and shall be constructed from proprietary systemsusing channel sections with return lips andcompatible fixing accessories.

5.5.2 Ladder rack shall be factory made fromsteel complying with clause 5.2.

5.5.3 Racks and supports shall be selected toprovide adequate support without racks saggingmore than 1/360 of the support span, or as indicated.

5.5.4 Cable racks and ladders shall be installedwith a 20mm gap at building or structural expansionjoints. Supports shall be installed within 150mm oneither sids of the joint.

5.5.5 Cables shall be fixed to racks and laddersby cable cleats.

5.6 CABLE HANGERS

5.6.1 Cable hangers shall be used only whereindicated. They shall be made from mild steel flatbar complying with clause 5.2.

5.7 SUSPENSION AND FIXINGS

5.7.1 Proprietary suspension systemscomprising channel sections with return lips andcompatible fixing accessories or slotted anglescomplying with BS 6946 shall be used. Fixings maybe fabricated from mild steel flat bar wherenecessary. Metal arc welding shall comply with BSEN 1011.

5.7.2 Fixing to the building fabric shall complywith Table 5A, unless otherwise indicated.

5.7.3 No shot firing shall be used and nodrilling or welding of structural steelwork shall bedone without the approval of the Project Manager.

5.7.4 Suspensions and fixings shall comply withclause 5.2.

5.7.5 Bolts, nuts, washers and screws shall benon-corrosive and compatible with the environmentin which they are installed.

5.8 BONDING

5.8.1 Metallic cable trays, racks and laddersshall be electrically andmechanically continuousthroughout and bonded to the earth system.

5.8.2 Supplementary bonding shall be installedwherever necessary, between component parts ofcable trays, racks or ladders where the method ofmechanical connection does not provide permanentand reliable metal-to-metal joints of negligibleimpedance. An earth bonding strip having aminimum cross section of 6mm2 shall be installedacross the gap at building or structural expansionjoints.

14 Edition 1 - 2004

TABLE 5A FIXING FOR CABLE SUPPORTS

Building Fabric Type of Fixing

Structural steelwork Purpose made clamps, the type to be approved by the Project Manager.

Non-structural steelwork As for structural steelwork, or bolts, washers and nuts

Concrete, brick or building blocks Expanding anchors, or screws and plugs, to be approved by the ProjectManager.

Timber Coach Bolts

Edition 1 - 2004 15

Specification 34

16 Edition 1 - 2004

Specification 34

Section Six - Cable Installation

6.1 ROUTES

6.1.1 Unless the routes of cables are indicatedon the drawings they shall be determined by theContractor and approved by the Project Managerbefore work is started.

6.1.2 Cables installed on the surface shall beparallel with the lines of the building constructionand properly aligned.

6.1.3 Cables buried below ground shall, as faras practicable, follow the features of the site such asroadways and building lines. Ducts at road and railcrossings shall normallybe at right angles to the lineof the road.

6.2 SEGREGATION

6.2.1 A minimum clearance in accordance withTable 6A shall be allowed from anyequipment,pipework or ductwork. The distance shall bemeasured from the external surface of any lagging.In the event of difficulty in achieving theserequirements the Project Manager shall beconsulted.

6.2.2 Spacing between cables shall comply withTable 6A andbe arranged so that the grouping factorused in the cable calculations shall not be affected.In the event of difficulty in achieving theserequirements the Project Manager shall beconsulted.

6.2.3 Where indicated, space shall be allowedalong cable routes for future additions, and cablesupports shall be of adequate size for the ultimateload.

6.2.4 Adequate space shall be left betweencable runs and the building fabric and other servicesto allow for the future removal or installation ofcables.

6.3 SUPPORTS AND FIXINGS

6.3.1 Cables shall be adequately supported, byone ofthe methods specified in Section 5,throughout their length except where they runthrough cable ducts or are buried direct in the

ground. Fixing direct to the building fabric by cablecleats may be adopted for single runs subject to theapproval of the Project Manager, and whereindicated.

6.3.2 Where cables are not continuouslysupported, the supports shall be spaced to the cableManufacturers recommendations.

6.3.3 Cables shall be supported within 300mmof their termination at equipment. The weightof acable shall not be carried by a terminal box or gland.The distance maybe increased to suit therequirements of clause 13.11.

6.3.4 Where cables cross expansion andsettlement joints in the building structure they shallbe fixed 300mm each side ofthe joint and sufficientslack left between to allow for movement. Wherethe cables are buried in the building fabric, suitableprovision shall be made to allow for movement ofthe structure. The Contractor shall submit hisproposals for the approval of the Project Manager.

6.4 TRENCHING

6.4.1 No work shall conmience until theContractor has taken all reasonable steps to ensurethat the area is free of all cables, drains and otherservices, or that the location has been determined ofthose services known to exist. Health and SafetyExecutive publication HS(G) 47 gives guidance foravoiding underground services.

6.4.2 Unless otherwise indicated, excavationswithin 600mm of existing services shall be by handdigging. All services uncovered, whether expectedor not, shall be reported immediately to the ProjectManager, and they shall be supported by slings orother suitablemeans and protected. Any damage toservices, however minor, shallbe reportedimmediately to the Project Manager. No repairs orreplacement shall be done unless the ProjectManager gives approval.

6.4.3 When cable trenches are opened, allnecessary safety precautions shall be taken toprevent accidents anddamage occurring. Cablesshall be laid expediently with regard to projectrequirements. The Project Managers approval shallbe obtained before a trench is backfilled. Ideally

Edition 1 -2004 17

Specification 34 Section Six Cable Installation

backfilling shall be commenced within 24 hours ofcable laying and the work completed speedily.

6.4.4 Cables shall be buried at a sufficient depthto avoid being damaged by any disturbance of theground reasonably likely to occur. Trenches shall beexcavated to such depth but not less than specifiedin Table 6B.

6.4.5 Turf and topsoil shall be removedcarefully andpreserved for reinstatement in theiroriginal positions. Spoil from the trench intended forre use as reinstatement material shall be removedfrom the lip of the trench by at least 150 mm.

6.4.6 Excavations shall be carried out inaccordance with BS 6031, BS 8000 Part 1 and shallcomply with the Construction (Working Places)Regulations, 1966 and all other relevant statutoryrequirements. Excavations shall be kept free ofwater and protected against damage or collapse.The safety of persons and the protection ofstructures, buildings, roads, sewers and servicesfrom damage shall be ensured. All necessarysheeting, timbering, strutting and shoring shall besupplied, erected and subsequently removed.

6.4.7 Before cables are laid, the bottom of thetrench shall be graded evenly, cleared of loosestones and then covered for the full width of thetrench with a 75mm layer of compacted sieved sand.Where the level ofthe trench bottom has to changethe slope shall not be greater than 1 in 12.

6.4.8 After cables havebeen laid a further layerof sieved sand shall be added over the full width ofthe trench, and tamped to provide finally not lessthan 50mm cover over the cables.

6.4.9 Trenches shall be backfihled in layers andeach layer shall be rammed. The first two layersshall be 100mm deep and rammed by hand; theremaining layers shall be not less than 200mm deepand power ramming may be used. Warning tapesand covers shall be included as specified in clause6.5. Where applicable, topsoil and turfshall bereplaced~ndthe final level shall be level with, ornot more than, 25mm above, the adjacent groundlevel. A higher degree of consolidation is requiredfor excavations within shoulders and over-runs andadjacent to paved areas used by aircraft. At theselocations the final layer of reinstatement shall becompacted by power ramming until maximumpossible compaction is achieved.

6.5 WARNING TAPES AND COVERS

6.5.1 A warning tape shall be placed above eachcable that is laid direct in the ground and above eachcable duct. The tape shall be laid at a depth of

Edition I -2004

300mm below the finished surface level exceptwhere the depth of roadway or paved area baseexceeds 300mm in which case the tape shall be laidimmediately below the base.

6.5.2 Warning tapes shall be of polythene notless than 150mm wide and 0.1mm thick. They shallbe yellow in colour and bear the continuouslyrepeated legend CAUTION ELECTRIC CABLEBELOW, or similar, in black letters not less than30mm high.

6.5.3 Interlocking cable warning covers shall beprovided for HV cables and for mineral-insulatedcables. For other cables they shall be provided onlywhere indicated. They shall be of proprietarymanufacture and shall be laid directly on the tampedsand that covers the cables.

6.6 DUCTS

6.6.1 Cables shall be installed in cable ductswhere they pass under, or within, Sm ofrailwaytracks, where they pass under roadways or otherareas with vehicular access, where theyaresupported on bridges, where they enter buildings,and additionally where indicated.

6.6.2 Cables shall be protected by steel tubes onbridges. All other cable ducts shall be selected bythe Contractor from the alternatives listed in clauses6.6.4 to 6.6.6 to suit the circumstances of theinstallation, unless otherwise indicated.

6.6.3 Ducts shall be of a size suitable for thecables to be drawn-in andwithdrawn withoutdamage. The minimum size ofbore shall be 100mm.The bore shall be smooth and entirely free fromrough spots, sharp edges) imperfections andprotuberances.

6.6.4 Cable ducts of vitrified clay shall complywith BS 65 and shall be extra strength class. Theyshall be joined with plastic flexible sleeves toprovide self-alignment of the bore.

6.6.5 Thermoplastic (PVC) ducts shall beunpiasticized Thermoplastic (PVC) pipe complyingeither with BS 4660 or BS 5481 as appropriate, orwith BS 3506 classes B, C, D or E. They shall haverubber sealing rings complying with BS EN 681.Thermoplastic (PVC) ducts shall not be used wherethe depth of cover exceeds 1 m.

6.6.6 Steel tubes shall comply with BS 1387and shall have screwed socket joints and end bushes.Tubes shall be protected against corrosion with acoat of bitumastic paint before they are installed.Tubes of 100mm bore shall be of light thickness;above this size they shall be medium thickness.

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Specification 34 Section Six Cable Installation

6.7 LAYING OF DUCTS

6.7.1 Unless otherwise indicated, cable ductsshall be laid at depths which comply with therequirements of Table 6B.

6.7.2 The bottom of trenches shall be rammedto provide a flat firm bedding. Where rock ispresent a layer of loose soil shall be spread over thebottom and also rammed. In water-logged orunstable soil a 75mm thickness of grade 10 concrete,as defined in BS 8110, with 20mm aggregate shallbe laid as a foundation and soil placed around andabove to a depth of 75mm above the top of the duct.

6.7.3 Where cable ducts pass under, or within,Sm ofrailway tracks or under roadways, the bottomof trenches shall be rammed and the ducts laid on,and surrounded by concrete, providing a minimumcover of 150mm all around. The concrete shall begrade 20, as defined in BS 8110, with 20mmaggregate. At each joint in the ducts, flexibilityshall be maintained by forming ajoint in theconcrete by a 25mm thick compressible foam filler.

6.7.4 Cable ducts shall extend not less than imbeyond the limit of roadways andpaved areas. Theyshall be at least 150mm away from gas and waterpipes, drains, sewers and electrical plant. Whereservices cross, the clearance shall be not less than50mm. If difficulty arises in achieving theseminimum clearances the Project Manager shall beconsulted.

6.7.5 Deflection from a straight line andvariation in depth shall not exceed 1 in 30horizontally nor 1 in 60 vertically and the cable ductshall pass the alignment tests.

6.7.6 Draw-pits shall be constructed at eachchange of direction and, for straight runs, at intervalsnot exceeding 25m unless otherwise indicated.Draw-pits shall be of adequate size to enable cablesto be drawn-in without damage or undue stress dueto bending. The construction of draw-pits and theircovers shall be as indicated.

6.7.7 Concrete shall comply with BS 8110 andshall be of a class suitable for the sulphate content ofthe soil in accordance with Table 6.1 of the Code ofPractice.

6.7.8 Alignment shall be proved by drawing amandrel through each duct. The diameter ofmandrel shall be 7mm less than the bore diameter.Mandrels shall be of wood, 250mm long.

6.7.9 While cable ducts are being laid nylon,polypropylene or similar draw-lines shall bethreaded through each length of duct. The draw-lines shall have a breaking strength of not less than

550N and shall be at least 4m longer than the ductrun.

6.7.10 Immediately after laying, and beforebackfilling the trench, the ends of the cable ductsshall be sealed temporarily with proprietary plugs.Draw-lines shall be secured outside the plugs.

6.7.11 Backfilling shall be in accordance withclause 6.4.9. Where a cable duct is not usedimmediately, temporary marker posts shall beinstalled to locate the ends of the duct andshall beretained in position until cables are drawn in.Markers shall be white painted wooden posts 75mmx 75mm, standing not less than 600mm out of theground.

6.7.12 Ducts shall be cleared with a mandrel150mm long and having a diameter 12mm less thanthe bore diameter immediately before cables aredrawn-in. The mandrel shallbe followed by acircularwire brush with a diameter 12mm more thanthe bore diameter.

6.8 HANDLING OF CABLES

6.8.1 Installation of cables shall be carried outonly when the ambient temperature is above 0Cunless a written statement from the CableManufacturer confirms that no damage to the cablewill result, and the approval ofthe Project Manageris given. The temperature of the cable shall havebeen above 0C,or above the minimum temperaturerecommended by the Manufacturer, for at least 24hours immediately prior to installation. Any specialmeasures to achieve this shall be subject to approvalby the Project Manager.

6.8.2 Cables shall be handled with care andevery effort made to avoid damage to the cables, toother services and to the building fabric.Recommendations or instructions available from thecable Manufacturer concerning the installation ofcables shall be taken into account. Any damageshall be reported immediately to the ProjectManager.

6.8.3 Cable drums shall be unloaded carefullyby means of either a crane or ramp and impact withthe ground shall be avoided. They shall besupported on axles or axle stands while the cable isbeing pulled. Twisting and abrasion of the cableserving or oversheath shallbe avoided.

6.8.4 Cables shall be pulled over cable rollersadequately spacedto prevent the cable beingdragged over ground or other surface. Cablestockings shall be used forhauling cables pulled intothrust borings or cable ducts, and for all cablesexceeding 1Om length. Precautions shall be taken to

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Specification 34 Section Six Cable Installation

ensure that strain is taken on the cable cores as wellas the sheath and excessive strain shall be avoided.Under no circumstances shall vehicles be used topull cables in, appropriate cable winches or handpulling only shall be used.

6.8.5 Cables laid in trenches shall cross othercables only at junctions. Clearances between thecables shall be maintained at crossovers. Cablesshall not be laid one above the other except whereindicated.

6.8.6 Only one cable shall be pulled into eachduct except for the following, which may bebunched subject to the requirements of Table 6A anda maximum space factor of 20%.

Single-core cables forming one circuit;

Mineral-insulated cables;

Alarm, control, and monitoringcables;

Pilotcables associated with another powercable in the duct.

Cables that are to be installed in the sameduct shall be bunched together and pulled inone operation. Additional cables shall notbe drawn-in subsequently.

6.8.7 The ends of all cables shall be sealedduring installation by an appropriateheatshrink orcold applied end cap, unless jointing or terminationis carried out immediately. The sealed ends ofpower cables shall be marked with the letter A orZ to indicate the core sequence: A at the endwhere the sequence is clockwise and Z where it isanti-clockwise.

6.8.8 At no time shall cables be bent to a radiusless thanthe Manufacturers recommendedminimum.

6.9 SEALING DUCTS AND OPENINGS

6.9.1 - The ends of all ducts and service conduits(including spare ways) shall be sealed after cableshavebeen installed.

6.9.2 Where ducts and service conduits enterbuildings, proprietary seals shall be used to form abarrier against gas, water, oil, fire and attack byvermin. Spare ducts and service conduits shall besimilarly sealed with removable material. Themethod of sealing shall be submitted for the ProjectManagers approval before work commences.

6.9.3 Fire barriers at fire-resistant structuralelements, such as floors andwalls, shall satisfy the

requirements of BS 476 Parts 20 and 22 forinsulation, stability and integrity for the period oftime indicated. The method shall be submitted forthe Project Managers approval before workcommences.

6.10 CABLE GUARDS

6.10.1 Cable guards shall be fitted where cablesare mounted at low level on walls, poles, towers orother locations as indicated.

6.10.2 Cable guards shall be constructed from1.6mm thick galvanised steel sheet complying withclause 2.11 and formedinto a casing with externalflanges for fixing to the fabric.

6.10.3 Guards shall extend to a height of 3.5mabove ground or floor level for HV cables and 1 .Smfor LV cables. In external locations the guards shallextend 300mm below finished ground level and theyshall be protectedinside and out with bitumasticpaint extending from the bottom up to 150mm abovefinished ground level.

6.11 MARKING OF CABLES

6.11.1 Marker posts or slabs shall permanentlyidentify the location of buried cables. The wordingon the markers shall be HV CABLE or LVCABLE as appropriate; in addition the wordJOINT shall be added where appropriate. Postsshall only be used where they do not causeobstruction or danger.

6.11.2 Cable marker slabs shall be installed, asrequired, flush with the finished ground level, on theprecise line of the cable.

6.11.3 Cable markers shall be located at everypoint where a cable enters a building, sub-station,plinth or distribution pillar, at each joint, change ofdirection, road andpathway crossing, and along theroute of the cable at intervals not exceeding 45m.

6.11.4 Cables shallbe colour coded inaccordance with BS 1710 except where cables areburied, located in switchrooms, in ducts and spacesdesignated solely for electrical services, or haveorange oversheaths. Colour coding, where used,shall be conspicuous bands, not less than 100mmlong, located at least once within each separatecompartment through which the cables pass andatintervals not exceeding 1 2m.

6.11 5 Trunkingor ducting shall be permanentlyand conspicuously identified. The method ofidentification shall be as indicated or approved bythe Project Manager

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Specification 34 Section Six Cable Installation

6.11.6 Cables shall be permanently andconspicuously identified. The method ofidentification shall be as indicated or approved bythe Project Manager.6.11.7 Cable identification shall be locatedwithin 500mm of terminations and joints, at leastonce within each separate compartment throughwhich the cables pass, at intervals not exceeding24m, and shall coincide with the colour bands,where used. Consideration shall also be given toidentifying cables at entry or exit points and whereburied cables emerge from the ground.

6.11.8 Every cable end shall be provided with ameans of identification showing the designation,number and cross-sectional area of cores and ratedvoltage of the cable.

6.12 REDUNDANT CABLES

6.12.1 Where indicated, redundant cables shallbe removed or stop-ended in a manner complyingwith clause 3.10 and clearly marked.

6.12.2 Removed cables shall be disposed ofin amanner approved by the Project Manager.

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Specification 34

TABLE 6A

Section Six Cable Installation

MINIMUM SPACING OF CABLES

Location Cable

mm

HV

mm

LV

mm

Telephone

mm

Co-axial

mm

EquipmentPipeworkDuctwork

mmBuried:

HVLVTelephoneCo-axialFibre Optic

50300300300300

30025

150150150

30030050

15050

30015050

15050

300300200200200

In Air:HVLVTelephoneCo-axial

50300300300

300(see note 2)

150150

30015000

30015000

300150100100

NOTES:1. The minimum spacing apply unless otherwise indicated.2. LV cables in air may be bunched subject to any requirements regarding segregation and installation methods set out in the BS 7671:

Requirements for Electrical Installations, Guidance Note No.1, and as stated in 6,2.3. When cables are in steel pipes the minimum spacings need not be maintained, but a minimum space of 25mm shall be left between the

pipes.

TABLE 6B MINIMUM COVER FOR CABLES

Type ofcable

Location and DEpth of Cover

In open ground and underpavements

mm

Underroadways

mm

Under oralongsiderailways

mm

In othersituations

mm

HV 800 10001800 As indicated

LVTelephone

Co-axialFibre Optic

500600

(light traffic)800

(heavy traffic)

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Specification 34

Section Seven Overhead Lines

7.1 OVERHEAD LINES

7.1.1 HV overhead lines shall comply withElectricity Association Technical Standard 43-40.

7.1.2 LV overhead lines shall comply with thelatest issue of ElectricityAssociation TechnicalStandard 43-30.

7.2 CONNECTIONS TO BUILDINGS

7.2.1 Service lines shall be Thermoplastic(PVC) insulated cables with copper or aluminiumconductors as indicated, complying with BS 6485,type 8 or 16 as appropriate for the nominal voltageof the system andBS 7884, BS 215 or BS EN 50183as appropriate.

7.2.2 Cables from the service line terminationinto the building shall be single core Thermoplastic(PVC) insulated with a sheath, complying with BS6004. Core identification colours shall extendthroughout the length of the cables.

7.2.3 The Contractor shall include, for thesupply and fixing of all insulators, brackets ortimber posts necessary for terminating service linesat buildings, unless otherwise indicated. Bracketsand fixings shall comply with Section 5.

7.3 CATENARY WIRE SUPPORTS

7.3.1 Short span overhead links betweenbuildings shall be Thermoplastic (PVC) insulatedcables complying with BS 6004, with copper oraluminium conductors as indicated. The cables shallbe supported by a catenary wire which shallbepreferably integral with the cable.

7.3.2 Catenary supported cables shall beinstalled in accordance with the BS 7671 and thelEE GuidanceNotes.

7.3.3 Details ofthe type of catenary system andfixing to be used shall be submitted to the ProjectManager, whose written approval shall be obtainedbefore work proceeds.

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Specification 34

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Specification 34

Section Eight - Wiring System: Cables in Conduit,Trunking and Ducting

8.1 CABLES

8.1.1 The type and size of cables shall be asindicated. Clauses 8.1.2 to 8.1.4 specify thosewhich will be used most commonly.

8.1.2 Thermoplastic (PVC) insulated sheathedand non-sheathed cables shall comply with BS 6004.They shall have copper conductors unless otherwiseindicated.

8.1.3 LSF cables shall comply with BS 7211and shall have copperconductors unless otherwiseindicated.

8.1.4 Thermosetting (Rubber) insulated non-sheathed cables shall comply with BS 6007.

8.1.5 Core identification colours shall extendthroughout the length of Thermoplastic (PVC)insulated cables. Where appropriate the coloursshall be as indicated. The additional identificationrequirements of clause 8.12.6 shall also be met.

8.1.6 Cables shall be protected throughout theirlength by trunking, ducting, conduit and equipmentenclosures. Framework or partitions mayonly beused as protection with sheathed wiring systems.

8.2 CONDUIT

8.2.1 Conduit, including flexible and pliableconduits, shall be either steel or non-metallic asindicated, and comply with the appropriate BritishStandards.

8.3 STEEL CONDUIT AND FITTINGS

8.3.1 Steel conduits and fittings shall bescrewed classification unless otherwise indicated orapproved by the Project Manager.

8.3.2 The protection against corrosion ofconduits and conduit fittings for general use insidebuildings shall be Class 2. For use outside buildings,in plant rooms, floor trenches, other locations asindicated and in floor screeds, the protection shallbeClass 4.

8.3.3 When located outside buildings, adaptableconduit boxes and covers shallbe as indicated.

8.3.4 When conduit boxes are installed flushwith the building fabric, overlapping covers shall befitted.

8.3.5 Flexible steel conduit for general useinside buildings shall beType A with protectionagainst corrosion equivalent to Class 2. For use inplant rooms and other locations as indicated theprotection shall be Class 4. Adaptors shall be of thesolid type.

8.3.6 Prewired pliable conduit systems mayonly be used where indicated.

8.4 NON-METALLIC CONDUIT

8.4.1 Non-metallic conduit shall be rigid heavyduty Thermoplastic (PVC) unless otherwiseindicated. Joints shall be made using solventapprovedby the conduit Manufacturer.

8.4.2 Pliable conduits shall be heavy duty,reinforced, unless otherwise indicated. Pliableconduit shall not be used where the ambienttemperature may exceed 60Cor where mineral oilsor petrol are present.

8.4.3 Flexible conduits shall be used forconnections to moving or vibrating equipment.

8.5 TRUNKING AND DUCTING

8.5.1 Trunking and ducting shall be of steel orinsulating material as indicated, and shall complywith BS 4678 andclauses 8.6 or 8.7 whereappropriate.

8.5.2 Trunking shall provide a minimum degreeof protection of 141 when used inside buildings andshall not normally be used in wetor outdoor areas.Trunking used outside buildings, or at otherlocations indicated, shall provide a minimum degreeof protection of IP44.

8.5.3 Partitions shall be of the same material asthe trunking or ducting. The gap between partitions

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Specification 34 Section Eight Wiring System: Cables in Conduit, Trunking and Ducting

and trunking covers shall be a minimum to ensurethat segregation of circuits is maintained.

8.5.4 Manufacturers proprietary fittings shallbe used. Site fabricated fittings may only be usedwith specific written approval of the ProjectManager and only where these are inadequate willsite fabricated fittings be accepted. Fittingsfabricated on site shall be comparable inconstruction with the rest of the trunking or ductingsystem.

8.5.5 Ends ofruns shall be fitted withremovable covers to permit future extension.

8.5.6as indicated.

The size oftrunking and ducting shallbe

8.5.7 Trunking with the cover on the side orbottom shall be fitted with removable cable retainingstraps at intervals not exceeding lm. Cables shall besupported at intervals not exceeding 3m wheretrunking runs vertically. The method of supportshall allow for future easy removal of, or additionto, the cables and shall be submitted for the approvalof the Project Manager.

8.6 STEEL TRUNKING

8.6.1 Unless otherwise indicated, the protectionagainst corrosion for general use inside the buildingsshall be Class 2; for use outside buildings, in plantrooms, floor trenches and other locations asindicated, the protection shall be Class 3.

8.6.2 Bonding links shall be provided at eachjoint and secured by screws, nuts andshakeproofwashers. The bonding links shall make contact withthe metal of the trunking or fitting, and continuityshall not depend on contact through the screws, noron removal on site of paint finish from ferrousmetal.

8.6.3joints.

Factory made connectors shall be used at

8.7 UNDERFLOOR DUCTINGAND FLOORTRUNKING

8.7.1 Protection against corrosion shallbe Class3.

8.7.2 Service outlet boxes andjunction boxesshall be constructed from sheet steel of the samefinish as the ducting, with top frames adjustable forheight at each corner. The frames shall be castaluminium unless otherwise indicated. Segregationof the compartments of the ducting shall be

maintained through the boxes.

8.7.3 Each service outletbox shall have outletunits as indicated. The complete assembly shallcomply with the requirements of BS 6701.

8.7.4 Lids of service outlet boxes and of floortrunking shall be of cast aluminiumunless otherwiseindicated. The lids shall be arranged toaccommodate the floor finish, as indicated.

8.8 ROUTES AND SEGREGATION

8.8.1 The routes of conduit, trunking andducting shall be as indicated. Where there is adiscrepancy or omission, the route shall bedetermined by the Contractor and approvedby theProject Manager before work is started. Thisrequirement shall apply where the conduit, trunkingor duct is concealed within the building fabric aswell as where they are on the surface.

8.8.2 Conduit, trunking andducting shall beparallel with the lines of the building constructionandproperly aligned, except where conduit ispermitted in floor screeds. Conduit buried in wallfinishes shall run verticallyonly, unless the ProjectManager gives approval to deviate from thisrequirement.

8.8.3 A minimum clearance of 150mm shall beallowed from anyequipment, pipeworkor ductwork;the distance being measured from the externalsurface of any lagging. In the event of difficulty inachieving this requirement the Project Manager shallbe consulted.

8.8.4 Trunking shall be positioned so thatadequate clearance is provided for access to thewiring. It is preferred that the covers shall be on thetop or sides of the trunking, but where this isimpracticable covers may be on the bottom, subjectto the approval of the Project Manager. Cablesupport shall be as clause 8.5.7.

8.9 SUPPORTS AND FIXINGS

8.9.1 Where conduit and trunking are not fixeddirectly to the building fabric theyshall besuspended in accordance with clause 5.7.

8.9.2 A support shall be positioned within300mm of each bend and conduit box. Conduitboxes shall be fixed to the fabric of the buildingindependently of the conduit. Where the conduitboxes have aminimum degree of protection of 1P44the fixings shall not reduce the protection.

8.9.3 Conduit and trunking shall be fixed in

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Specification 34 Section Eight Wiring System: Cables in Conduit, Trunking and Ducting

accordance with Table 8A. No shot firing shall beused andno drilling or welding of structuralsteelwork shall be done without the approval of theProject Manager.

8.9.4 Screws andnuts shall be non-corrosiveand compatible with the environment in which theyare installed.

8.10 INSTALLATION

8.10.1 If the protective finish of any materialshas been damaged, those materials shall either notbe used or any remedial work shall be approvedbythe Project Manager before use. Conduits shall beclean and free from oil.

8.10.2 Holes in trunking shall be drilled, punchedor cut by ring-saw. Trunking shall be free fromsharp edges andburrs.

8.10.3 Connections between trunking andequipment shall be by screwed couplers andbushes,flanged couplings or specially fabricated connectors.Direct attachment of steel trunking to equipmentwill be permitted only if cable entries are providedwith bushes or grommets or other lining methodsapprovedby the Project Manager. Cutting andbending the material of trunking to form flanges forconnection to equipment will not be permitted.

8.10.4 Steel conduit shall be connected by meansof a coupler and an externally screwed bush atequipment not provided with screwed entries and attrunking. Bushes shall be tightenedby spanners;pliers and toothed wrenches shall not be used.

8.10.5 Cable entries from trunking to distributionboards shall be adequate for cabling from all waysincluding spares.

8.10.6 Where a terminal block is to beaccommodated in a circular box, an extension ringof sufficient depth to ensure adequate space for theterminal block and cables shall be fitted to the box.

8.10.7 - The length of thread on the ends of steelconduit shall match that in the conduit fittings orequipment. Exposed thread is not permitted.Running couplings with backnuts may be used withconduit having Class 2 protection, but where theprotection is Class 4 only manufactured runningjoints will be accepted. Exposed thread on runningcouplings shall be given a coat of zinc-rich plant.

8.10.8 Joints between Thermoplastic (PVC)conduit and fittings shall be made with a suitableadhesive, but expansion couplers shall be included.

8.10.9 Conduit shall be cold bent on site with asuitable bending tool, without deforming its crosssection.

8.10.10 The interval between draw-in boxes inconduit systems shall not exceed therecommendations contained in BS 7671 and the lEEGuidance Notes.

8.10.11 Unless otherwise indicated, conduit buriedin concrete shall have at least 30mm depth of coverand shall be securely fixed to prevent movementduring pouring and vibrating of the concrete.Conduit buried in plaster shall have at least 5mmdepth of cover.

8.10.12 Where conduits, trunking or ducting, crossexpansion and settlement joints in the buildingstructure, suitable provision shall be made to allowfor movement of the structure. Purpose madeexpansion couplings shall be used in trunking. TheContractor shall submit his proposals for theapproval of the Project Manager.8.10.13 Where conduit passes through an externalwall the conduit shallbe plastic and a conduit boxshall be fitted on the outer side of the wall. Thisshall be filled with an inert, permanentlyplasticcompound havinga high insulation value.

8.10.14 Conduit, trunking and ducting shall beinstalled in screeds only where indicated, or afterreceipt of the Project Managers approval. Conduitboxes in floors, other than for agreed outlets, are notpermitted.

8.10.15 Flush floor trunking andunderfloorducting shallbe straight, level and adjusted in heightto relate to the finished floor level.

8.10.16 Open ends of conduit and ducts shall betemporarily plugged immediately they are installedto prevent ingress of water and solid material. Flushfloor trunking and the boxes of underfloor ductingshall be fitted with temporary lids immediately theyare installed, andthey shall be maintained aseffective protection against ingress of water andsolid material until the permanent lids are fitted afterscreeding is complete.

8.10.17 The method to be used forforming firebarriers at fire-resistant structural elements such asfloors and walls shall be submitted for the ProjectManagers approval.

8.10.18 Installed conduits and ducts shall becleaned internally with a swab before cables aredrawn-in.

8.10.19 If the protective finish ofconduit,trunking or ducting is damaged after fixing, the

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Specification 34 Section Eight Wiring System: Cables in Conduit, Trunking and Ductingdamage shall be made good in a manner approved

by the Project Manager.8.11 PROTECTIVE CONDUCTOR

8.11.1 A protective conductor shall be drawnthrough all conduit and trunking systems andconnected to earthing terminals. Each section oftrunking shall be bonded to the protective conductor.Notwithstanding the provision of a separateprotective conductor the continuity of the conduit,trunking and ducting shall be to the same standard asthough they were the sole protective conductors.

8.11.2 Where live conductors terminate at, orloop into, terminals adjacent to an appliance oraccessorythe protective conductor shall be similarlyterminated.

8.11.3 The earthing terminal of a socket outlet orother accessory mounted on the lid of steel trunkingshall be connected by aseparate protectiveconductor to an earthing terminal incorporated in thefixed part of the trunking.

8.12 WIRING

8.12.1 No wiring shall be carried out until theappropriate tests required in clause 19.6.2 have beendone and the Project Manager has given hisclearance forwiring to commence.

8.12.2 A loop-in form of wiring shall be used asfar as practicable or unless otherwise indicated.Joints in conductors shall be made using insulatedterminal blocks complying with the requirements ofclause 12.19.

8.12.3 Adequate slack shallbe left in cables atexpansion joints.

8.12.4 A draw-wire shall be installed, afterswabbing,