wiring matters- iet 2009 winter publication

ELECTRICAL PANELSTYPES OF ELECTRICAL PANELS, STANDARDS AND FORMS OF SEPARATION

WIRINGMATTERSWIRINGMATTERSWIRINGMATTERSThe Institution of Engineering and Technology

WINTER 09 ISSUE 33

Future developments in Standardisation

Supplies to electric vehicles

Energy effi cient lighting in domestic premises

How to meet the requirements of the Building Regulations

The use of “Arctic” cable

Cable for use at low-temperature

Types of person and the requirements of the Regulations

Examining skills andcompetencies

www.theiet.org/wiring

IET Wiring Matters | Winter 09

The IEE Wiring Regulations(BS 7671:2008) are based onEuropean Standards, which inturn are usually based oninternational standards. TheUK participates in bothEuropean and internationalstandards work.One new area of possible

development withininternational standards is anew section 7 providingrequirements for the suppliesto electric vehicles. Thisproposed new section 7 wouldonly apply to circuits intendedto supply electrical vehicles forcharging purposes and wouldcover the part of the electricalinstallation providing theconnection with an electricalvehicle to the fixed installation.

However, this is only a newwork item at this stage and it isimportant to point out that thismay not become aninternational standard. Thisarticle is based on draftproposals and, therefore, theactual requirements (if itbecame an internationalstandard) would probably bedifferent. Systems for thedistribution of electricity to the

public are outside the scope ofIEC 60364 low voltageelectrical installations (andalso outside the scope of BS 7671) therefore it isassumed that this new workitem applies to private suppliessuch as dwellings and privatecommercial and industrialestablishments.

The draft proposals mayinclude requirements for thetype and current rating ofsocket outlets, RCD protection,surge protection, measures ofprotection against electricshock, IP rating of equipment,impact protection againstmechanical damage, isolationand switching and fixingarrangements, etc.

Protection against electric shockIt is expected that theprotective measures ofobstacles, placing out of reach,non-conducting location andprotection by earth-free localequipotential bonding wouldnot be permitted.These measures are

contained in Sections 417 and418 of BS 7671:2008 and arenot for general application. The

Futuredevelopments in InternationalStandards for electricalinstallationsby Geoff Cronshaw

International Standards | 1


2 | International Standards

Wiring Matters is produced by IET Services Limited, a subsidiary of The Institution of Engineering and Technology (IET), for the IET.Michael Faraday House, Six Hills Way, Stevenage, Herts, SG1 2AY, United Kingdom Tel: +44 (0)1438 313311 Fax: +44 (0)1438 313465

Advertising Sales D Smith +44 (0)1438 767224 [email protected] | Editor G D Cronshaw +44 (0)1438 767384 [email protected] |Contributing Editors M Coles, J Elliott, P Bicheno| Design Sable Media SolutionsIEE Wiring Matters is a quarterly publication from the Institution of Engineering and Technology (IET). The IET is not as a body responsible for the opinions expressed.

©2009: The Institution of Engineering and Technology. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any formor by any means without the permission in writing of the publisher. Copying of articles is not permitted except for personal and internal use. Multiple copying of the content ofthis publication without permission is always illegal. Web-offset printing by Wyndeham Heron, The Bentall Complex, Colchester Road, Heybridge, Maldon, Essex, UK

*Postage/Handling: Postage within the UK is £3.50 for any number of titles. Outside UK (Europe) add £5.00 for first title and £2.00 for each additional book. Rest of World add £7.50 for the first book and £2.00 for each additional book. Books will be sent via airmail. Courier rates are available on request, please call +44 (0) 1438 767328 or email [email protected] for rates.

Co-operating Organisations The Institution of Engineering & Technology acknowledges the contribution made by the following organisations in the preparation of this publication: British Electrotechnical & Allied Manufacturers Association Ltd – P D Galbraith, M H Mullins | Department for Communities and Local Government – I Drummond | Electrical Contractors Association – D Locke, S Burchell | City & Guilds of London Institute – H R Lovegrove | Electrical Contractors Association of ScotlandSELECT – D Millar, N McGuiness | Health & Safety Executive – K Morton | Electrical Safety Council | ERA Technology Limited – M Coates, A Finney | Consultant - M Al-Rufaie | Dept of Health - C Holme | British Cables Association – C Reed | Scottish Building Standards Agency | Department for Business, Enterpriseand Regulatory Reform | GAMBICA – M Hadley, A. Sedhev | Lighting Association – L Barling | ISSN 1749-978-X

Thank you to Schneider Electric for the image used on the Front Cover and page 16

protective measures of section417 provide basic protection onlyand are for application ininstallations controlled orsupervised by skilled or instructedpersons. The fault protectiveprovisions of Section 418 arespecial and, again, subject tocontrol and effective supervisionby skilled or instructed persons.

External influencesPresence of water (AD)Any wiring system or equipmentselected and installed must besuitable for its location and able to operate satisfactorily withoutdeterioration during its workinglife. The presence of water canoccur in several ways, e.g. rain,splashing, steam/humidity,condensation and at eachlocation where it is expected to bepresent its effects must beconsidered. Suitable protectionmust be provided, both duringconstruction and for thecompleted installation.For example, draft proposals for

a connection point installedoutdoors requires IPX4 in order toprotect against water splashes(AD4).The IP classification code,

BS EN 60529:2004, describes asystem for classifying the degreesof protection provided by theenclosures of electrical equipment.The degree of protection providedby an enclosure is indicated by twonumerals. The first numeral

Table 1 showing IPcharacteristic numerals

PWRRFP94


4 | International Standards

indicates protection of personsagainst access to hazardousparts inside enclosures orprotection of equipment againstingress of solid foreign objects.The second numeral indicatesprotection of equipment againstingress of water (see table 1).More information on the IPclassification code is given inIEE Guidance Note 1 -Selection and Erection.

External influencesImpact (AG)The effect of environmentalconditions and generalcharacteristics around aninstallation should always beassessed to enable suitableelectrical equipment to bespecified. All electricalequipment selected must besuitable for its location, use

and method of installation.Therefore, for equipment

installed in a car park site forexample, draft requirementsmay require IK07 or evenhigher such as IK10 if installedin a more vulnerable location.The IK classification

standard BS EN 62262describes a system forclassifying the degrees ofprotection provided byenclosures for electricalequipment against externalmechanical impacts. Theletters IK are followed by twonumerals which identify aspecific impact energy.BS EN 62262:2002

specifies a system forclassifying the degrees ofprotection provided byenclosures against mechanicalimpact (IK code).

The Standard describes onlythe general requirements anddesignations for the system.The application of the

system to a specific enclosuretype will be covered by theBritish Standard applicable tothat equipment or enclosure.An enclosure is defined as apart providing protection ofequipment against certainexternal influences andprotection against contact.This may be considered toinclude conduit, trunking, etc.In general, the degree of

protection will apply to acomplete enclosure. If parts ofan enclosure have differentdegrees of protection, theymust be separately identified.The coding is separate fromthe IP rating and will bemarked separately as shown in table 2.

Switchgear and controlgear.BS 7671:2008 (IEE WiringRegulations) recognises fourdistinct types of isolation andswitching operation:(i) isolation(ii) switching off for

mechanical maintenance(iii) emergency switching(iv) functional switching.

Draft proposals for supplies toelectric vehicles includerequirements for emergencyswitching. It is worth notingthat BS 7671:2008 states that

a plug and socket outlet orsimilar device shall not beselected as a device foremergency switching.

Socket-outletsDraft requirements for socketoutlets may include similarrequirements to caravan sites.For example, industrial type16A 200 V – 250 V sockets toIEC 60309-2, with an IP ratingof IP44, one socket outlet percar park space, 30 mA RCDprotection, and requirementsfor mounting heights, etc.Other requirements may

include visual indication ofmains supply, means ofisolation/emergency switching,interlock to prevent theplugging/unplugging of thesocket-outlet unless the socket-outlet has been isolated fromthe supply and precautions toprevent the electrical vehicle tosupply the fixed installation.

ConclusionMore and more electricalvehicles are on the market. Asa result this new work item hasbeen introduced in order todevelop the basicrequirements for theconnection of the electricalvehicle to the fixed installation.This article is only intended asa brief overview of a possiblenew work item which may ormay not be developed into aninternational standard. n

When higher impact energy is required the value of 50 joules is recommended

Table 2: IK characterisitics of BS EN 62262:2002

DON’TMISS

SEE AND TRY OUT ALL THE LATEST ELECTRICALPRODUCTS FROM LEADING MANUFACTURERSAND SUPPLIERS

HUNDREDS OF SHOW DISCOUNTS

FREE SEMINARS ON KEY INDUSTRY ISSUES

FREE PROFESSIONAL ELECTRICIAN T-SHIRT

FREE BACON ROLL

To register for FREE entry, visit or call

01923 237799www.elexshow.info

ELEX2009Professional Electrician

TThhee EElleeccttrriicciiaannss’’ EExxhhiibbiittiioonn

Sponsored by

Sandown Park, Esher, SurreyTuesday 1st & Wednesday 2nd December 2009

10.00am - 4.00pm

6 | Energy Efficient Lighting

An article in the previousedition of Wiring Matters(Autumn 09 Issue 32) lookedat ‘energy efficiency ofluminaires’ which highlightedthe energy efficiencies ofvarious types of lamps andprovided specific informationfor the phasing out ofincandescent type lamps. Thisarticle looks at somerequirements for energyefficient lighting in domesticpremises and includesguidance on some typicalscenarios that can beencountered when working ona lighting system.

Building Regulations 2000energy efficiency requirementsThis article will look at therequirements of the BuildingRegulations 2000 asapplicable in England andWales. Energy efficiency isdealt with by requirements ofRegulations 4A, 17C and 17Dand Part L of Schedule 1 of theBuilding Regulations.Regulation 4A relates tothermal elements and sowould not be applicable tolighting. Regulation 17C refersto new buildings and 17Drefers to consequentialimprovements to the energy

performance of building workto an existing building (with atotal useful floor area over1000 m2). Part L of Schedule1 has requirements forconservation of fuel and powerand is reproduced in Figure 1.Fixed internal or externallighting systems are includedwithin the scope of a ‘fixedbuilding service’ as referred toin L1b and L1c of Schedule 1.The type of building workwhere energy efficient lightingrequirements would apply isthe provision of a newdwelling, an extension to anexisting dwelling or material

change of use of a building toa dwelling and thereplacement of a lightingsystem as part of rewiringworks. For domestic premisesthere are two approveddocuments that provideguidance on complying withPart L, L1A Conservation offuel and power in newdwellings and L1BConservation of fuel and powerin existing dwellings. Includedare specifications for theprovision of energy efficiencyfixed internal and externallighting and is summarized inFigure 2.

Energy efficient lightingin domestic premisesby Paul Bicheno


When looking to comply withL1c. the occupier of thepremises should be givendetails on the types of lamps toobtain as replacements,including the style, rating andconnection so as to continuethe benefits of energyefficiency. This is important ifthe premises have a mixture ofdedicated energy efficient lightfittings and their associatedlamps and retrofit energyefficient lamps.

What is an energy efficientlight fitting?An energy efficient light fittingas specified in the ApprovedDocuments L1A and L1B(Figure 2) is one thatcomprises the lamp, controlgear, housing, reflector, shadeor diffuser. This specifies thatthe fitting will only be capableof accepting lamps that have aluminous efficacy greater than40 lumens per circuit-watt,where ‘circuit-watts’ is thepower that the light fittingcontrol gear and lampconsumes. The lamps wouldtypically be of the compactfluorescent type with pin-based connections and sowould not accept lamps of thetraditional Edison Screw (SC)or Bayonet Cap (BC)connection types. In thecontext of energy efficientlighting the whole fitting wouldtypically be referred to as a‘dedicated fitting’ and there area number of traditional fittingdesigns available.In addition to a dedicated

energy efficient light fitting,compact fluorescent lamps are

available that that haveintegrated control gear with thetraditional SC and BCconnections types that alsohave a luminous efficacygreater than 40 lumens percircuit-watt. A number of lampdesigns have been developedto enable the replacement oftraditional lamp designs (e.g.traditional GLS, candle, miniglobe, reflector)

used in existing light fittings.Table 1 provides someinformation on the equivalentenergy efficient lamp for aparticular traditional lamp. Thetraditional tungsten filament andtungsten halogen type lamps donot meet the 40 lumens percircuit-watt requirement and soare not regarded as energyefficient lamps. Energy saving GU10 type


Energy Efficient Lighting | 7

L1. Conservation of Fuel and PowerReasonable provision shall be made for the conservation of fuel and power in buildings by:

a) limiting heat gains and losses:i.Through thermal elements and other parts of the building fabric;ii.From pipes, ducts and vessels used for space heating, space cooling and hot water services;

b) providing fixed building services that:i. Are energy efficient;ii. Have effective controls; andiii. Are commissioned by testing and adjusting as necessary to ensure they use nomore fuel and power than is reasonable in the circumstances; and

c) providing to the owner sufficient information about the building, the fixed buildingservices and their maintenance requirements so that the building can be operated insuch a manner as to use no more fuel and power than is reasonable in thecircumstances.

Note: bold text highlights requirements related to lighting.

Fixed internal lightingProvide light fittings (including the lamp, control gear, housing, reflector, shade or diffuser)that can only takes lamps having a luminous efficacy greater than 40 lumens per circuit-watt.

Provide fixed energy efficient light fittings (as above) that number no fewer than the greater of:a. one per 25 m2 of dwelling floor area (excluding garages), orb. one per four fixed lighting fittings.

Fixed external lightingFixed external lighting should enable the effective control and/or the use of efficient lampssuch that:

a. Either, the lamp capacity does not exceed 150 Watts per light fitting and the lightingautomatically switches off;i. When there is enough daylight; andii. When it is not required at night; or

b. The light fittings have sockets that can only be used with lamps having an efficacygreater than 40 lumens per circuit-watt.

Figure 1: Schedule 1 Part L1 (Conservation of fuel and power)

Figure 2: Provision of energy efficient fixed internal and external lighting

Traditional Energy efficient

100W 20-23W

75W 15-19W

60W 11-14W

40W 8-9W

25W 5-7W

Table 1: Equivalent energy efficient lamp for a particular traditional lamp


8 | Energy Efficient Lighting

halogen lamps are availablethat consume less power thanstandard halogen lamps,typically up to 30%, that canbe used to retrofit into existingGU10 type fittings. LightEmitting Diode (LED) arraylamps are now available thatconsume a small amount ofpower and have a longer lifethan the compact fluorescenttypes. These can be used toreplace halogen lamps inexisting light fittings or can beinstalled as part of a new LEDfitting or arrangement. Thereare also LED lamps availablefor the replacement oftraditional incandescentlamps, typically up to 40W.

Replacing an existing light fittingFor this scenario thereplacement of a light fitting indomestic premises would needto consider when the premiseswas built or created from amaterial change of use. If it ispost 6th April 2006 then thepremises is likely to alreadyinclude some dedicated lowenergy light fittings as the

building works would havelooked to comply with therequirements given inApproved Document L1A. Thededicated low energy lightfittings are likely to in be inareas such as the lounge,dining room, kitchen andhallways as these normallyhave lights switched on for themost hours in a day, so anyreplacement of these fittingswould need to be of thededicated low energy type soas to retain the energy efficientstatus. Replacement of a lightfitting that is not an energyefficient type could be carriedout but it should be recognisedthat the continual maintenancewith regards to replacement oflamps may not be possible duethe phasing out programme ofincandescent lamps.

For older domestic premisesthat did not need to meet theprovision of energy efficientlight fittings, the BuildingRegulations does notspecifically state that thereplacement of a light fittinghas to be with an energyefficient type as the

requirements relate toextensions to a dwelling, wherea dwelling is created from amaterial change of use or anexisting lighting system isbeing replaced as part ofrewiring works. Replacing alight fitting is not replacing alighting system and it isunlikely that the occupierwould be in a worse positionwith regards to their energyusage. However, the occupiershould be encouraged to havean energy efficient light fitting.

Rewiring a lighting circuitFor this scenario the rewiring ofa lighting circuit in a dwellingwould need to comply with theconservation of energy andpower requirements related to afixed building service asdetailed in Approved DocumentL1B (Figure 2). The appropriatenumber of fixed internal energyefficient dedicated type lightfittings should be installed inthe main living areas wherelighting is on for the mostnumber of hours. Any fixedexternal lighting that forms partof the rewiring work as supplied

by the fixed electricalinstallation should also complywith the requirements forexternal lighting.

Installing lighting as part ofbuilding works for an extensionto domestic premisesFor this scenario theinstallation of additional fixedinternal and/or external lightingin a dwelling due to buildingwork, such as an extensionwould need to comply with theconservation of energy andpower requirements related toa fixed building service asdetailed in ApprovedDocument L1B (Figure 2). Fora newer dwelling that includesa number of energy efficientlight fittings, reasonableprovision of energy efficientlighting is expected in theextension so that the occupiercontinues to obtain thebenefits. For an older dwellingthat does not have any energyefficient light fittings then therewill be an obvious benefit ofinstalling energy efficient lightfittings as part of the buildingwork. The guidance does

Imag

e co

urte

sy o

f Phi

lips


recognise flexibility, so it couldbe reasonable to install energyefficient fittings in main livingareas that did not previouslyhave any rather than theextension to fulfil therequirements. However asalready highlighted there are anumber of energy efficientlighting solutions available ,therefore energy efficientsolutions should be agreedwith the occupier, especially ifthe phasing out of traditionallamps is highlighted as part ofthe selection process.

Code for sustainable homesThe technical guidance for theprovision of energy efficientlighting in approved documentL1A for new dwellings is theminimum standard. In April2007 the Governmentintroduced the ‘Code forSustainable Homes’ which is anational standard for thedesign and construction ofsustainable new homes. TheCode sets minimum standardsfor energy and water use forhomes within England. From1st May 2008 it wasmandatory for a new home tohave a rating against the code.The Code supports thegovernment target that all newhomes will be zero carbonfrom 2016. The associatedtechnical guidance documentincludes requirements for theprovision of energy efficientlight fittings that exceed thecurrent requirements ofBuilding Regulations.

Additional informationThe energy saving trust is an independent organisationthat promotes action on energy saving issues(www.energysavingtrust.org.uk).The following publicationsrelating to energy efficientlighting are available;n Energy efficient lighting –guidance for installers and specifiers (CE61)n Low energy domestic

lighting (GIL20)n Cost benefit of lighting(CE56)n Energy saving lampsshould be marked with theenergy saving recommendedcertification mark. This meansthey have been independentlytested to verify their overallquality and energy efficiencyclaims.

n A guide to energy savinglight bulbs is available from theLighting Association website(http://www.lightingassociation.com/pdf/EST_lighting_English_Final09.pdf)n Aurora has a useful tool forshowing the benefits of usingenergy efficient lamps alongwith a range of energy efficientlighting solutions.www.aurora.eu.com/EnergyCalculator.aspxwww.aurora.eu.com/lowenergy

n Information on the Codefor Sustainable Homes isavailable from theCommunities and LocalGovernment website(http://www.communities.gov.uk/planningandbuilding/buildingregulations/legislation/codesustainable/)

n Building Regulationsapproved documents alongwith the government proposalsfor the development of Part Lare available from thegovernment planning portal(www.planningportal.gov.uk).

n Local Authority BuildingControl (www.labc.uk.com)

£59.99 EX VATFROM ONLYPRICES START

ROTATE PRINTFOR CABLE ANDPIPE LABELS

FUNCTION PERFECT

PT-7600VPIncludes carry case and mains adaptor

How many times have you been let down by previous labelling?A Brother P-touch label printer comes pre-loaded with electrical symbols, a back-lit display and produces durable labels, which leave a lasting impression of the true professional you really are. Ideal for all jobs from cable agging and pipe identi cation to identifying electrical components.

Contact your usual electrical wholesaler or visit www.brother.co.uk/electricianAll Brother label printers come with a 3 year warranty upon registration.


10 | Types of person and the requirements

BS 7671 containsrequirements for the designand construction of electricalinstallations with the intentionof producing an installationwhich is both safe to use andwhich is capable of beingemployed for its intended

purpose (120.1 refers). Thescope of installation typescovered by BS 7671 is verybroad. Indeed, the everincreasing complexity ofinstallations and the continuingdevelopment and subsequentrecognition of technical

innovations and productsnecessitates the inclusion ofadditional requirements. Toillustrate this, the scope of BS 7671 has been expandedin the 17th Edition to includerequirements relating toinstallations in Marinas,

Exhibitions, Shows and Stands,Solar Photovoltaic supplysystems and Mobile andTransportable units and,indeed, will expand still furtherwhen amendment one isreleased mid 2011. It is not uncommon for the

design, construction and initialverification of a smalldomestic, industrial orcommercial installation oradditions or alterations onsuch installations to be carriedout by one and the sameperson. However, the design ofmore complex or specialistinstallations will typically becarried out by a number ofindividuals given specificduties or areas of responsibilityor by design consultancies.The actual installation processwill then often be performed bya specialist electricalcontractor as will the requiredinspection, testing andcertification. It is also notuncommon for a separatebody to be taken on tocommission the installationprior to handover. Increasingly,different aspects of the overallproject such as the installationof fire protection and fire alarmsystems, lightning protectionand, indeed, items of complexor specialist productionequipment will be dealt with byseparate contractors.BS 7671 also contains

requirements for theinspection, testing andcertification of the installationboth during the initialverification process andperiodically throughout the lifeof the installation. Asmentioned above, the personor company carrying out initialinstallation work must also becapable of inspecting, testingand certificating the work thatthey have carried out. Howeverpersons or companies carryingout periodic inspections andproducing reports on thecondition of an existinginstallation, whether or not

Types of person and therequirements of the Wiring Regulationsby Jon Elliott


Types of person and the requirements | 11

originally installed by them,need to look at the installationin a different way. They are ineffect commenting upon thecontinuing suitability for use ofthe installation based upontheir observations and theresults of a range of testswhich they have performed.However unlike whenperforming initial verification,they need to bear in mindwhen the installation was firstinstalled and hence whatrequirements were in force atthat time. They also need toapply judgement as virtually allinstallations will, with thepassing of time, show somesigns of damage, deteriorationand general wear-and-tearwhich may or may not havediminished the safety of theinstallation.The issue of maintainability

of an installation is alsoaddressed within BS 7671albeit briefly. Personsmaintaining an installation mayrequire either basic or in-depthknowledge of the installation orthe equipment thereindependent upon the dutiesthey are required to performand their level of responsibility.In larger, more complexinstallations a person orpersons will be required to haveoversight of and responsibilityfor the work activities carriedout by the maintenance staff intheir employ.Upon completion the

installation has to performproperly the tasks for which itis designed. However, personsmaking use of, or operating theinstallation will require differentcapabilities depending uponthe nature and complexity ofthe premises and its intendedpurpose. In domesticpremises, a user should beable to operate the switchgearto control lighting and otherfinal circuits within theinstallation, periodically pressthe integral test button onresidual current devices, reset

overcurrent protective devicesand possibly replace fuses. Ina factory environment amachine operator should besufficiently knowledgeable touse those pieces of equipmentto which they have beenassigned such that they aresafe and productive. This willrequire guidance of both whatshould be done and whatshould not. A deep knowledgeor understanding of theworkings of the machinery may not be necessary.However, the operator willneed to be aware of theirlimitations and as such when itwill be necessary to call onpersons with greater expertisefor assistance.BS 7671 also contains a

number of limitations as towhat class of person mayperform particular activitiescovered by the requirementstherein. These limitations areput in place either on accountof particular hazards whichmight only be avoided by aperson possessing a requisitelevel of knowledge, such as forexample the use of protectivemeasures where obstacles orplacing out of reach is to beused to provide basicprotection (417.1 refers) orwhere continued monitoring ofthe effectiveness of the supplyand earthing arrangements isnecessary to ensure safe use(717.411.4 refers).

It can be seen therefore that • there are many differenttypes of installation covered bythe scope of BS 7671 • electrical installations aredesigned, constructed,inspected, tested, certificated,used and maintained by adiverse range of people• these people will needdifferent skills sets dependingupon how they are involvedwith the construction, use orupkeep of the installation.

BS 7671 recognises three

types of person which aredefined in Part 2:

Ordinary person. A person whois neither a skilled person noran instructed person.

Instructed person. A personadequately advised orsupervised by skilled persons to enable him/her to avoiddangers which electricity maycreate.

Skilled person. A person withtechnical knowledge orsufficient experience to enablehim/her to avoid dangerswhich electricity may create.

Some clarification of what ismeant by these definitions isgiven in Appendix 5 whichclassifies external influencesand is expanded upon below.

Ordinary personBeing neither electricallyskilled nor instructed, ordinarypersons do not have sufficientknowledge, experience orsupervision to avoid thedangers which electricity maycreate. Residents of domesticpremises and the users ofcaravans, boats and leisurecraft are typical examples asare employees within theworkplace unless specificallyidentified as being skilled orinstructed in connection withtheir work activities. It shouldbe noted at this point that alldomestic premises should bedesigned to be suitable for useby ordinary persons. As such,it is neither here nor therewhether the current orprospective occupier is otherthan an ordinary person.

Instructed personBoth persons with someelectrical knowledge and thosewith none may be classified asinstructed persons.This would include for

example operators of machineryin an industrial environment and

some grades of maintenancestaff employed to carry outspecific duties for which theyhave received specific andsufficient instruction. It wouldalso by necessity includetrainees and apprentices whohave to be given increasingopportunities, albeit whilstsuitably supervised, in order toallow them to become skilledthemselves in time.At the other extreme it is

necessary from time to time forelectrical plant rooms to becleaned or redecorated. Atsuch times the decoratorsshould be informed ofparticular hazards which may exist in the particularlocations in which they areworking. Neverthelesssupervision by a suitablyskilled person may still benecessary in somecircumstances even whenbasic instruction has beengiven. Clearly in such cases itwill fall upon someone to carryout a risk assessment...

Skilled personPersons become skilled as aresult of a number of factorsincluding guided learningachieved from completion ofappropriate education andtraining within a further or higher educationestablishment and supervisedwork experience within thework environment in whichthey wish to become skilled.Generally speaking, becomingskilled takes a considerableperiod of time during which atransferable skills andunderpinning knowledge baseis developed which can thenapplied to differing situationsas the trainee is given evermore practical experience. Oncompletion of a number ofpredefined objectives, whichtypically include both practicaland theoretical tests, a personis judged to be skilled at aparticular level such aselectrician, approved


12 | Types of person and the requirements

electrician, electrical fitter,technician or the like.However it should always be

borne in mind that there aremany aspects in whichpersons may be skilled withina particular occupation and assuch when a person considerstheir suitability or that of theirstaff to perform particular tasksthey should be consideringwhether the required skills arepossessed in order to completethe task in hand properly andsafely. An electrician forexample who since their initialtraining has always worked indomestic premises and is fullyconversant with the range ofactivities typical to suchpremises may be completelyout of their depth if placed inan industrial or commercialinstallation. Similarly althoughmany of the skills picked up byan electrician during theirtraining and day-to-day workexperience will be transferableto new situations it may onoccasion be necessary foradditional skills to be learnedto enable particular specialisedequipment to be installed

and/or maintained; or to attendsubject updating activities inorder to refresh or update theirknowledge. This brings us tothe issue of competency.

CompetencyThe publication of the 17thEdition saw the introduction of adefinition of competent person:

Competent person. A personwho possesses sufficienttechnical knowledge, relevantpractical skills and experiencefor the nature of the electricalwork undertaken and is able atall times to prevent dangerand, where appropriate, injuryto him/herself and others.

The wording of this definition isvery closely based upon thecontent of Regulation 16 of theElectricity at Work Regulations1989 and the guidanceprovided on this regulation bythe Health and Safety Executivein their publication HSR25Memorandum of guidance onthe Electricity at WorkRegulations 1989. It is verysimilar to the definition of skilled

person. Regulation 16 of EWR1989 is reproduced below:

No person shall be engaged inany work activity wheretechnical knowledge orexperience is necessary toprevent danger or, whereappropriate, injury, unless hepossesses such knowledge orexperience, or is under suchdegree of supervision as maybe appropriate having regardto the nature of the work.

Looking at this it can be seenthat Regulation 16 recognisesthat competency may beachieved from an individualhaving sufficient knowledge andexperience to avoid danger orinjury, or from their beingsupervised to some extent bysomeone having suchknowledge and experience. Assuch it can be seen that either askilled or an instructed personand indeed even an ordinaryperson may, in somecircumstances, be consideredto be competent.However an extremely

important aspect of

competency, too frequentlyoverlooked, is the need forpersons to know the limits oftheir ability and technicalknowledge. This failure isclearly demonstrated by theunacceptably high number ofdeaths and injuries that occurto persons employed to work onor near electrical installationsand persons under their controlor indeed to persons usinginstallations designed orinstalled by someone purportedto be competent. It is inevitablethat a person will experiencenew situations, products andworking practices in the courseof their career, however theymust always work within theirlimits and where necessaryeither complete the necessarysubject updating or engage theservices of a specialistpossessing the requiredcompetencies to carry out thework on their behalf.In the next edition of Wiring

Matters we will look atparticular requirements withinBS 7671 where the type ofperson involved is of somesignificance. n

Capability of persons

BA1 Ordinary Uninstructed persons

BA2 Children Children in locations intended for their occupation Nurseries Requirement for inaccessibility ofNOTE - This class does not necessarily electrical equipment. Limitation of apply to family dwellings temperature of accessible surfaces

BA3 Handicapped Persons not in command of their Hospitals Requirement for inaccessibility ofphysical and/or intellectual abilities electrical equipment. Limitation of (sick person, old persons) temperature of accessible surfaces

BA4 Instructed Persons adequately advised or supervised Electrical operating areasby skilled persons to enable them to avoiddangers which electricity may create (operating and maintenance staff)

BA5 Skilled Persons with technical knowledge Closed electrical operating areasknowledge or sufficient experienceto enable them to avoid dangers which electricity may create (engineers and technicians)

Extract from Appendix 5 of BS 7671 (Concise list of external influences)

Switch on and save with the latest electrical courses from the IET

New for 2010

Don’t delay!

To discuss your training requirements with one of our short course experts, please call 01438 767289 or email [email protected]

www.theiet.org/courses-wm

Download the new brochure at:

P A R T P F O R B R I G H T S P A R K S

Simple, straightforward and hassle-free, it’s no wonder more electricians are joining ELECSA than any other Part P scheme. Maybe it’s because our application process is just ridiculously easy and once registered we keep the paperwork down to an absolute minimum. Or the fact that we’ve introduced a flexible direct debit payment process that allows you to spread the cost of your assessment fee. Perhaps its our assessors, all of which are time-served electricians who offer a fair and objective service. Whatever the reasons are, be a bright spark and ease the process of Part P with ELECSA.

Contact the ELECSA Registration Team on

0845 634 9043or email [email protected]

www.elecsa.co.uk

No Worrie


<#> | Strap line14 | The use of Arctic cable

In Wiring Matters Summer2009, Issue 31, an article waspublished entitled Cables fortemporary installations andincluded a sub-section headedThe use of "Arctic" cable. TheIET's technical helpline took anumber of calls with acommon theme - i.e. can blue-sheathed cable, made to BS 6500, be used for 230 Va.c. single-phase supplies toequipment in temporary use?The answer is yes but not attemperatures lower than +5°C.The following is intended toclarify.

IntroductionIt is common to see blue-sheathed flexible cables,sometimes referred to as"Arctic" cable, used ontemporary low-voltageinstallations, such asconstruction sites, fairgroundsand musical events. Inaddition to blue, this type ofcable is available in manydifferent colours, such asyellow and orange and somecables even have the wordARCTIC embossed throughoutthe length. Not all cables aresuitable for all applications. It

is, therefore, important toestablish the suitability of thecable in question prior toselection by referencing thestandard to which the cable ismanufactured. Two standardsfor flexible cable will beconsidered here - BS 7919and BS 6500.

Cables to BS 7919Electric cables — Flexiblecables rated up to 450/750 V,for use with appliances andequipment intended forindustrial and similarenvironments

Ordinary duty low temperaturePVC insulated and sheath300/500 V flexible cable,manufactured to BS 7919 Table44 (not harmonised),commonly referred to as 3183A(Arctic Grade Flex), wasspecifically designed and,hence, included in the BritishStandard, for use at 110 V a.c.from centre tappedtransformers (55 V - 0 - 55 V).The cable is suitable forinstallation and handling downto a temperature of -25°C, e.g.suitable for construction siteinstallations and is often seen in

The use of “Arctic’ cable by Mark Coles

Cable Type Standard reference Recommendations for use CommentsBS 7919:2000

Ordinary duty low Table 44 The cables are suitable for Usage on UK building sites, withtemperature PVC – use on ELV systems (110V centre ELV (110 V centre tapped) may sheathed cord circular tapped) on building sites in the UK; include hand-held tools.

– use with temporary traffic light systemswhen suitably protected.The cables are not suitable for:– outdoor use at standard voltages– in industrial* or agricultural buildings

Table 7B: Cables conforming to BS 7919 – Guide to use


The use of Arctic cable | 15

use on temporary road works forsupplies to traffic lights; Table7B from BS 7450, refers.Note that cables to BS 7919Table 44 have not beenharmonised to European HDs.This is because the use of 110 Va.c. supplies from centre tappedtransformers (55 V - 0 - 55 V) isa UK only practice and is notrecognised or practisedelsewhere.

BS 6500Electric cables - Flexible cordsrated up to 300/500 V, for usewith appliances and equipmentintended for domestic, officeand similar environmentsOrdinary duty PVC insulatedand sheath 300/500 V flexiblecable to BS 6500, commonlyreferred to as 3183Y(harmonised number H05VV-F), is suitable for use at 230 Va.c. The cable is suitable forinstallation and handling downto a temperature of +5°C.

Neither BS 6500 nor BS 7919requires the cable to be markedwith the word Arctic. Should anycable be marked as Arctic, it issolely the responsibility of themanufacture to justify any suchclaim. The only PVC flexiblecable that could be classified asbeing suitable for lowtemperature use is a cable toBS 7919 Table 44 as it can beinstalled and handled down to atemperature of -25°C; it wouldseem logical that only this cablewould/should have the term‘ARCTIC’ marked on it.

SummaryThe table shown abovesummarises this article.

Further readingn BS 6500:2000 - Electriccables - Flexible cords ratedup to 300/500 V, for use with appliances andequipment intended fordomestic, office and similarenvironmentsn BS 7540-3:2005 Electriccables - Guide to use forcables with a rated voltage notexceeding 450/750 V - Part 3:National standard cables notincluded in HD 21 and HD 22n BS 7919:2001 Electriccables - Flexible cables ratedup to 450/750 V, for use withappliances and equipmentintended for industrial andsimilar environments n

Cable standard Suitable voltage Lowest temperature for installation and handling

BS 7919 Table 44 110 V a.c. (55 V - 0 - 55 V) -25°C

BS 6500 up to 300 V a.c. 1Ø or 500 V a.c. 3Ø +5°C

Specialist Electrical Training & Consultancy

High voltage accredited courses & competence assessment, including:

• HV safety training: land based & marine/offshore power systems

• HV ‘authorised person’ training courses

• Electrical protection & switchgear maintenance

• 17th Edition Wiring Regulations

• HV safety rules auditing and developing

• Electrical Testing

• Basic Electrical Safety

• Electrical Equipment in Hazardous Area

• Electrical for Non-electrical Personnel

Training centres in the UK & Cyprus

The Faraday Centre Tel: 01642 467236

www.faradaycentre.co.uk

MoD ELCAS

Approved

Training

Provider

Specialist Electrical Training &Consultancy

• HV safety training: land based & marine/offshorepower systems

• HV ‘authorised person’ training courses• LV ‘authorised person’ training• Electrical protection & switchgear maintenance• 17th Edition Wiring Regulations• HV safety rules auditing and developing• HV sanction for test• ROV HV safety operation• Electrical equipment in hazardous area• Electrical for non-electrical personnel• Live testing on AC & DC systems• Industrial electrical plant maintenance• Basic electrical safety training

Training centres in the UK & Cyprus

The Faraday CentreTel: 01642 467236


17th Edition IEE Wiring Regulations ExamsGain the City & Guilds 2382 Part 10Join our 3-day course and take theexam on the third day:• 18–20 January 2010• 15–17 March 2010• 17–19 May 2010

Already got the 16th Edition? Update your quali-cation!Gain the 17th Edition City & Guilds 2382 Part 20 with our 1-day course:• 21 January 2010• 18 March 2010• 20 May 2010

All inclusive cost£480 for the 3-day course or £210 for the 1-day course includes tuition,online exam entry, manuals, lunch and refreshments.

LocationWest Thames College, London Road, Isleworth,West London TW7 4HSTrain: IsleworthTube: Osterley or Hounslow East (Piccadilly Line)Bus: 237, 235, H37 and 117 stop at the college.We are located just

10 minutes’walk from Hounslow Bus StationParking: Limited

For more informationContact Penny O’Hare on 020 8326 2492email: [email protected]:www.west-thames.ac.uk

ExcellentPass Rates!


16 | Electrical Panels

Electrical Panels by Mark Coles

IntroductionAt many events in which theIET participate, such as theELEX and InterBuild shows,questions are asked aboutstandards to which hand-wiredelectrical control panels are tocomply. This article looks attypes and forms of electricalpanels, uses, competency andthe standards to which theyare to comply.

Electrical panels come inmany shapes and sizes (ofcourse) and have manyapplications. Consider a simpleempty box which is then firmlyfixed to the ground or buildingstructure, adapted to encloseelectrical equipment andterminations to perform aparticular function - the emptybox becomes an electricalpanel and issues relating toelectrical safety are to beconsidered.

Factory built panels and Formsof Electrical SeparationBS EN 60439-1:1999 givesguidance on the forms ofseparation applicable to

factory-built switchgear andcontrolgear assemblies(switchboards, motor controlcentres, distribution boards,busbar trunking systems, etc.),known as type-tested andpartially type-testedassemblies. These forms ofseparation provide protectionagainst contact with live parts ( known as basic protection)belonging to adjacent devicesand protection from theprobability of initiating arcingfaults and the passage offoreign bodies between units ofthe assembly. The Standardalso gives guidance on otherrequirements for protectionagainst electric shock.

Four forms of separation areindicated in the main text ofBS EN 60439-1:1999 butthere is no specific detail givenon how these forms are to beachieved. It is stated in theStandard that the form ofseparation should be agreedbetween manufacturer anddesigner/user. It shall beremembered that higher formsof separation specified will

increase costs but will givebetter operational flexibilityregarding safe working whenconnecting in additionalcircuits or carrying outmaintenance. This ‘trade-off’must be carefully assessed.

The four forms given havebasic definitions andapplications but Forms 2 to 4can be further subdivided intomore specific ‘Types’(applications) by discussion andagreement with manufacturers.

Form 1This form provides for anenclosure to provide protectionagainst direct contact with liveparts but does not provide anyinternal separation ofswitching, isolation or controlitems or terminations. Theseoverall assemblies are oftenknown as ‘wardrobe’ type withlarge front opening doors,usually with an integral door-interlocked isolator. Operatingthe isolator interrupts allfunctions but allows the doorto be opened to gain access tothe assembly for installation or

maintenance. Such assembliesnormally have lower faultwithstand and it may beinconvenient to shut down awhole plant or system for asimple maintenance or repairoperation.

Form 2The overall assemblyenclosure provides protectionagainst direct contact with liveparts; separation is providedbetween the busbar assemblyand switching, isolation,control items and terminations.There is very little advantage ofthis over Form 1 and the styleis similar. Form 2 can besubdivided into:

n Type 1 - in which thebusbars are separated byinsulation of the bars.n Type 2 - in which thebusbars are separated bymetallic or non-metallic rigidbarriers.

Form 3The enclosure providesprotection against direct

Imag

e co

urte

sy o

f Sch

neid

er E

lect

ric

PRODUCT SHOWCASE | 17

For details on how to feature your product contact Danielle Smith on 01438 767224


CREDIT CRUNCH TAKING EFFECT?For a limited period of time, NAPIT isoffering you the opportunity to transferyour electrical membership to NAPIT for *FREE and receive 18 months for the price of 12!*

This offer is only valid until 8th March 2010,so call NAPIT on: 0870 444 1392or alternatively email: [email protected]* Conditions apply

NAPIT4th Floor, Mill 3, Pleasley Vale Business ParkMansfield, Nottinghamshire. NG19 8RL

www.napit.org.uk

FREE Estimating Software & Catalogue DVDElectrika is supported by the UK’s leadingbrands to bring you: • 140,000 updated Trade Prices• 1000’s PDF Catalogues & Technical Docs• Professional quality Estimating package• Built-in Ordering & Job Costing• Add your own Specials • Create your own Local Databases• Regular price updatesVisit www.electrika.com to register for yourFree DVDElectrika LtdT: 0161 945 5124 E: [email protected]

www.electrika.com

In-Company electrical trainingThe IET runs in-company electricaltraining courses which are carefullytailored to best suit your company’srequirements. Reduce staff time awayfrom the workplace and eliminate traveland accommodation costs by havingcourses run on your premises. Contact us to discuss your requirements on 01438 767289 or email [email protected] IETT: 01438 767289 E: [email protected]

www.theiet.org/courses

Greenlee hole punching tools have launched a newhydraulic battery punch driver featuring Lithium Ionbattery technology making accurate punching ofholes effortless and with minimal noise or vibration: • More Power – 18V 3Ah Li-Ion batteries 20 min charge• More Ergonomics –totally balanced around the wrist, minimisingwork fatigue (RSI).

• Punches last longer – the tool automatically detects when the holehas been made, turning the tool off and preventing die damage.

• Punching Range – mild and stainless, up to 105 x 105mm sq or96mm round.

Visit www.klauke.com for more information and to request the new catalogue.E: [email protected] Tel. 01986 891519 www.klauke.com

On-Site GuideThe On-Site Guide is intended to enablethe competent electrician to deal withsmall installations (up to 100 A, 3-phase). It includes simple circuitcalculations and provides essentialinformation in a convenient, easy-to-useform, avoiding the need for detailedcalculations. Buy your copy atwww.theiet.org/osg

Institution of Engineering and TechnologyMichael Faraday HouseSix Hills Way, Stevenage. SG1 2AYT: +44 (0)1438 313311

www.theiet.org/osg

17TH EDITION TESTING & CERTIFICATIONSeaward has introduced an innovative newconcept in 17th edition fixed electricalinstallation testing and certification in the shapeof the new Power Plus 1557.

The new concept works by incorporating anelectronic copy of the inspection and testcertificate in a combined multi-function electricaltester and data logger.

The lightweight PowerPlus 1557multifunction tester has been designed for maximum portability andease-of-use. Unique onboard electronic certificate software enables testdata to be recorded directly by the tester using a replica of theinspection and test certificate, which is displayed on the instrument.

www.seaward.co.uk

www.brother.co.uk/labelling

ROVs High Voltage SafetyThe strong link between practical ‘hands-on’ training and work practices createsrelevant, enduring and transferableoutcome. The Faraday Centre providehands-on training to support theoreticallearning. Courses include high voltagesafety operation on land-basedswitchgear equipment, marine/offshoreand Remote Operated Vehicles (ROVs).

The Faraday Centre LtdUnit 3 Stephenson Court, Skippers Lane Industrial EstateMiddlesbrough. TS6 6UTTel: +44 (0) 1642 467236


Handheld Electronic Label PrinterBrother’s P-touch range of durable handheld electronic label printersare perfect for electrical installers who need to mark wiring and toolsclearly and effectively. Brother’s patented TZ tapes create durablelabels that are scuff, fade, water, temperature and chemical resistant.

The label printers are designed to withstandtough on-site conditions and their

compact design make them easy to store and transport.Brother T: 0844 499 9444

Call: +44 (0)1438 767328 Fax: +44 (0)1438 767375 www.theiet.org&

The On-Site Guide is intended to enable thecompetent electrician to deal with smallinstallations (up to 100 A, 3-phase). Itprovides essential information in aconvenient, easy-to-use form, avoiding theneed for detailed calculations.

Contents: Introduction. The service position.Protection. Earthing and bonding. Isolationand switching. Labelling. Final circuits.Locations containing a bath or shower.Inspection and testing. Guidance on initialtesting of installations. Operation of RCDs.

ON-SITE GUIDE BS 7671:2008

Updated to align with the 17th Edition of theIEE Wiring Regulations, it also includes a newchapter on requirements for Scotland.

Contents: Legislation. Design, selection anderection of electrical installations. Mainsposition. Circuit specifications. Specialinstallations, special locations and kitchens.Inspection and testing. Safe working.Maintenance. Three-phase supplies. OtherBuilding Regulations. Identification ofconductors. Scottish building standards.Appendices. Index.

STANDARDS AN

D CO

MPLIAN

CE

The Wiring Regulations are the nationalstandard to which all domesticand industrial wiring must conform.Substantial changes have beenincorporated in BS 7671:2008 to align withEuropean documents. Essential for allelectricians, electrical contractors and theirmanagers, installation designers, andstudents in further education andprofessional training.

Contents: Scope, Object and FundamentalPrinciples. Definitions. Assessment ofGeneral Characteristics. Protection for Safety.Selection and Erection of Equipment.Special Installations or Locations. Inspectionand Testing.

REQUIREMENTSFOR ELECTRICALINSTALLATIONSBS 7671:2008 (IEE Wiring Regulations,17th Edition)

• Paperback 389pp • 2008 • ISBN 978-0-86341-844-0 • Order book PWR1700B £75

ELECTRICIAN’SGUIDE TO THEBUILDINGREGULATIONSPart P, 2nd Edition

• Paperback 180pp • 2008 • ISBN 978-0-86341-854-9 • Order book PWGO170B £22

• Paperback 234pp • 2008 • ISBN 978-0-86341-862-4 • Order book PWGP170B £22

The Institution prepares regulations for the safety of electrical installations for buildings, the IEE Wiring Regulations (BS 7671),which has now become the standard for the UK and many other countries. It has also prepared the Code of Practice forInstallation of Electrical and Electronic Equipment In Ships (BS 8450) and recommends, internationally, the requirements forMobile and Fixed Offshore Installations. The Institution provides guidance on the application of BS 7671 through publicationsfocused on the various activities from design of the installation through to final test and certification with further guidance formaintenance. This includes a series of eight Guidance Notes, two Codes of Practice and model forms for use in wiringinstallations.

• Paperback 186pp • 2008 • ISBN 978-0-86341-550-0 • Order book PWR05030 £22

This book provides step-by-step guidanceon the design of electrical installations, fromdomestic installation final circuit design tofault level calculations for LV/large LVsystems.

Apprentices and trainees will find it veryhelpful in carrying out the calculationsnecessary for a basic installation. It has alsobeen prepared to provide a designsequence, calculations and data for acomplete design to be carried out. It isintended to include all necessary cable andequipment data to carry out the calculations.Consultants will be able to check thecalculations of their design packages.

It includes calculations and necessaryreference data not found in the designpackages, such as cable conductor andsheath temperatures and allowances forharmonics.

Contents: Design sequence. Simpleinstallations and final circuits. Maximumdemand and diversity. Selection of cablesfor current-carrying capacity. Voltage drop.Fault current. Shock protection. Protectiveconductors. Calculations associated withtesting. Impedance of copper andaluminium conductors. Harmonics.Protection against voltage disturbances.Busbar trunking. Appendices. Index.

ELECTRICALINSTALLATIONDESIGN GUIDECalculations forElectricians andDesigners

BEST SELLER BEST SELLER BEST SELLER

BEST SELLERNEW

ELECTRICIAN’SGUIDE TOEMERGENCYLIGHTING

P Cook

The Electrician’s Guide to EmergencyLighting is one of a number of publicationsprepared by the IET to provide guidance onelectrical installations in buildings. Thispublication is concerned with emergencylighting and in particular emergency escapelighting and must be read in conjunctionwith the legislation: Approved Document Band the British Standards, in particular BS5266.

• Paperback c88pp• 2009• ISBN 978-0-86341-551-7• Order book PWR05020 £22

NOWAVAILABLE

8

18 | Standards and Compliance

This Guidance Note enlarges upon andsimplifies relevant requirements of BS7671:2008. It includes detailed coverage ofexternal influences and factors affecting theinstallation of cables and equipment. Itdiscusses various types of protective devicesin easy-to-read text and includes illustrationsin full colour.

• Paperback 216pp • 2009 • ISBN 978-0-86341-855-6 • Order book PWG1170B

£30

This Guidance Note enlarges upon andsimplifies relevant requirements of BS 7671:2008. It includes detailed coverageof mechanical maintenance, emergencyswitching, functional switching in easy-to-read text. It also includes illustrations in fullcolour.

GUIDANCE NOTE 2:Isolation & Switching,

5th Edition


£25

Suitable for the City & Guilds 2391Certificate in Inspection, Testing andCertification, this Guidance Note isconcerned principally with Inspection andTesting. It has been updated to align withthe IEE Wiring Regulations 17th Edition (BS7671:2008). It includes detailed coverageof initial verification, periodic inspection andtest instruments.

GUIDANCE NOTE 3:Inspection & Testing,

5th Edition

ELECTRICAL CRAFTPRINCIPALS:Volume 1, 5th Edition

ELECTRICAL CRAFTPRINCIPALS:Volume 2, 5th Edition


£25

• Paperback 344pp • 2009 • ISBN 978-0-86341-932-4 • Order book PBNS0330

£25

• Paperback 432pp • 2009 • ISBN 978-0-86341-933-§ • Order book PBNS0340

£25

GUIDANCE NOTE 1:Selection & Erection of

Equipment, 5th Edition

This Guidance Note enlarges upon andsimplifies relevant requirements of BS7671:2008. It includes detailed coverage ofthermal effects, locations with increased risk,cable selection and safety service in easy-to-read text. It also includes full-colourillustrations.

• Paperback 104pp • 2009 • ISBN 978-0-86341-858-7• Order book PWG4170B

£25

GUIDANCE NOTE 4:Protection Against Fire,

5th Edition

This Guidance Note enlarges upon andsimplifies relevant requirements of BS7671:2008. It includes detailed coverage ofthe protective measures against electricshock. It also includes full-colour illustrations.


£25

GUIDANCE NOTE 5:Protection Against Electric

Shock, 5th Edition

This Guidance Note enlarges upon andsimplifies relevant requirements of BS7671:2008. It includes guidance onprotection of conductors in parallel againstovercurrent and includes an overview of thenew appendix 4 of BS 7671:2008.


£25

GUIDANCE NOTE 6:Protection Against

Overcurrent, 5th Edition

This Guidance Note enlarges upon andsimplifies relevant requirements of BS7671:2008. It includes detailed coverage ofnew special locations covered in the IEEWiring Regulations 17th Edition in easy-to-read text. It also includes full colourillustrations.

• Paperback 142pp• 2009 • ISBN 978-0-86341-861-7 • Order book PWG7170B

£25

GUIDANCE NOTE 7:Special Locations,

3rd Edition

This Guidance Note is principally concernedwith the electrical installation aspects ofearthing and bonding together withautomatic disconnection, which forms theprincipal protective measure against indirectcontact electric shock.

• Paperback 168pp• 2007 • ISBN 978-0-86341-616-3 • Order book PWRG0241

£25

GUIDANCE NOTE 8:Earthing & Bonding,

1st Edition

BEST SELLING WIRING REGULATIONS BOOK SERIES

NOWAVAILABLE

NOWAVAILABLE

NOWAVAILABLE

NOWAVAILABLE

NOWAVAILABLE

NOWAVAILABLE

NOWAVAILABLE

Standards and Compliance | 19



Electrical Panels | 21

contact with live parts and alsoseparation is provided betweenthe busbars and switching,isolation or control items andbetween all these items.Outgoing terminals are notseparated from each other, orperhaps from the busbars.Form 3 can be subdividedinto:

n Form 3a - in which outgoingterminals are not separatedfrom the busbars.

n Form 3b - in which outgoingterminals are separated fromthe busbars.

Form 3b can be furthersubdivided into:

− Type 1 - in which thebusbars are insulated forseparation.

− Type 2 - in which busbarseparation is by metallic ornon-metallic rigid barriers orpartitions.

Form 4The enclosure providesprotection against direct contactwith live parts and internalseparation of the busbars fromall switching, isolation andcontrol items and outgoingterminations and separation ofall items and outgoingterminations from each other.This allows for access to anysingle item, such as a switch-fuse or starter and its outgoingterminations, to enable work tobe carried out whilst theassembly remains operational.Protection is also providedagainst an arcing fault in onedevice affecting other items.This is the usual form specifiedfor commercial and industrialswitchgear and controlgearassemblies but the designer hasto consider whether, due to theextra cost, such requirementsare necessary or justified. Form4 can be subdivided into seventypes:

Type 1 - in which the busbarsare separated by insulation ffcoverings. Terminals forexternal conductors are in thesame compartment as theassociated item of switchgear,etc., but cables may beglanded elsewhere.

Type 2 - in which the busbarsare separated by metallic ornon-metallic rigid barriers orpartitions. Terminals orexternal conductors are in thesame compartment as theassociated item of switchgear,etc., but cables may beglanded elsewhere.

Type 3 - in which separationrequirements are by metallic ornon-metallic rigid barriers orpartitions. Terminals orexternal conductors are in thesame compartment as theassociated item of switchgear,etc. and each item has its ownintegral cable glanding facility.

Type 4 - in which the busbarsare separated by insulatedcoverings. Terminals forexternal conductors are not inthe same compartment as the

associated item of switchgear,etc., but in separate enclosedspaces. However, cables maybe glanded elsewhere.

Type 5 - in which busbars areseparated by metallic or non-metallic rigid barriers orpartitions. Terminals forexternal conductors are not inthe same compartment as theassociated item of switchgear,etc., but in separate enclosedspaces and terminals may beseparated by insulatedcoverings. Cables may beglanded in common cablingchambers.

Type 6 - in which all separationrequirements are by metallic ornon-metallic rigid barriers orpartitions. Terminals forexternal conductors are not inthe same compartment as theassociated item of switchgear,etc., but in separate enclosedspaces and cables are glandedin common cabling chambers.

Type 7 - in which all separationrequirements are by metallic ornon-metallic rigid barriers orpartitions. Terminals for

external conductors are not inthe same compartment as theassociated item of switchgear,etc., but in separate enclosedspaces and the termination foreach item has its own integralglanding facility (see Figure 2).Switchboard manufacturerstherefore cannot give all-embracing assurances for safeworking, according to the formof separation with parts of theassembly energized.Specifying a particular form ofseparation will not guaranteethis for any given formnumber.

GeneralAssemblies are to be designedand constructed so as to beable to withstand the thermaland dynamic stresses resultingfrom fault currents up to theirrated values.

The installation designermust specify the prospectivefault current conditions at thepoint of installation. Busbarsystems for switchgear andcontrolgear should beadequately rated for thenormal duty and maximumfault current level expected

Figure 1: Form 1 construction


22 | Electrical Panels

and should be well supportedand braced, as theelectromechanical stressesunder fault conditions can besevere.

Bespoke panelsMany electrical panels aremade for bespoke applicationswhich require much moreconsideration than selectingfactory built units from acatalogue. The environmentaland local conditions will havethe greatest influence on thechoice of panel. The followingissues will need to beconsidered when choosing thecorrect panel for theapplication:

n weather - if the panel is tobe located outdoors, a feeder-pillar or telecommunicationscabinet for example, theweather will be a factor indeciding the overall IP rating ofthe cabinet; see BS EN 50529

n material - the material ofmanufacture is an importantissue - metallic or a type ofplastic, for example. Plasticmaterials are usually muchlighter than metallic; metallicunits are often made from

aluminium, sometimesstainless steel

n mechanical impact - if thereis a mechanical impact issue,such as the risk of beingstruck by moving objects, BS EN 62262 providesinformation on the IK rating ofenclosures

n vandalism - if the panel issusceptible to unauthorisedentry or vandalism a lockingmechanism will need to beconsidered in addition tovandal-proof fixings

n hazardous locations - panelsinstalled in hazardouslocations will need to meet therequirements of BS EN 60079suite of standards, e.g. GroupI: electrical apparatus formines susceptible to firedamp;Group II: electrical apparatusfor places with an explosivegas atmosphere other thanmines susceptible to firedampwith sub-division IIA, IIB or IIC

n temperature - ambienttemperature expected and theamount of heat emitted byinternal components; externallow temperatures may mean

that internal heating would berequired; high externaltemperatures (solar gain) maycall for internal cooling

n electromagneticcompatibility and interferenceissues may need to beaddressed

A concise list of externalinfluences can be found inAppendix 5 of BS 7671:2008.

Electrical safetyWhen constructing a bespokeelectrical panel, therequirements of BS 7671 areto be considered. The methodof protection against electricshock will be establishedbased on the environment inwhich the panel is located andthe particular application.Regulation 410.3.3 requiresthat in each part of aninstallation, one or moreprotective measures are to beapplied, taking account of theconditions of externalinfluence. BS 7671 generallyrecognises the following fourmethods of protection againstelectric shock:

(i) Automatic disconnection of

supply (Section 411) (ii) Double or reinforced

insulation (Section 412) (iii) Electrical separation for the

supply to one item ofcurrent-using equipment(Section 413)

(iv) Extra-low voltage (SELVand PELV) (Section 414).

In electrical installations themost commonly usedprotective measure isautomatic disconnection ofsupply. Automaticdisconnection of supply is aprotective measure in which:

(i) basic protection is providedby basic insulation of liveparts or by barriers orenclosures, and

(ii) fault protection is providedby protective earthing,protective equipotentialbonding and automaticdisconnection in case of afault. Regulation 412.2.4.1 states

that the requirements for basicand fault protection can bemet if the rated voltage of thecable(s) is not less than thenominal voltage of the systemand at least 300/500 V andthat adequate mechanicalprotection of the basicinsulation is provided.Adequate implies the non-metallic sheath of the cable ornon-metallic trunking orducting complying with the BS EN 50085 series, or non-metallic conduit complyingwith the BS EN 61386 series. Note that the where a lid or

door in an insulating enclosurecan be opened without the useof a tool or key, all conductiveparts which are accessiblewhen the lid or door is openmust be behind an insulatingbarrier (providing a degree ofprotection not less than IPXXBor IP2X) preventing personsfrom coming unintentionallyinto contact with thoseconductive parts. Thisinsulating barrier shall beremovable only by the use of a

Figure 2: Form 4 construction


Electrical Panels | 23

tool or key; Regulation412.2.2.3 refers.Slotted trunking, Figure 3,

will not meet the IPXXB orIP2X requirement ofRegulation 412.2.2.3,therefore, if the panel remainsfully energised upon opening,only insulted and sheathedcables or wiring from SELV orPELV sources should beinstalled within the trunking. Ifnon-sheathed cables operatingat voltages in excess of theSELV and PELV requirementsof Regulation 414.1.1 areinstalled in slotted trunking, afurther barrier must beinstalled preventing access.It should also be realised

that Regulation 8 of theElectricity at Work Regulationsplaces an absoluterequirement (one that shall bemet regardless of cost or anyother consideration) onprotective conductorconnections to earth:

… a conductor shall beregarded as earthed when it isconnected to the general massof earth by conductors ofsufficient strength andcurrent-carrying capability todischarge electrical energy toearth.

It may be questionedwhether the termination ofsteel or aluminium wire armour(where used as a protectiveconductor) with glands intometal gland plates, whichthemselves may only be boltedto the switchgear orcontrolgear frame, is anadequate connection. Cablegland ‘earth tags’ andsupplementary connections tothe equipment earth terminalsmay be necessary. In any caseit should be ensured that anypaint or other surface finish onthe switchgear does notprevent effective electricalcontinuity between theadjacent parts. During siteinstallation andcommissioning, tests as

required by BS 7671 Part 6should be carried out on thecomplete assembly, plus anyother specific tests advised bythe manufacturer or requiredby the client, user or engineer.It is not usual to carry out arepeat of specialist tests, e.g. aflash test at site; however, inthe event of such arequirement or request, themanufacturer’s advice shouldbe sought.

CompetencyAs with all installations, workmust only be undertaken bycompetent persons. BS 7671is not a statutory documentand it is not a legalrequirement to follow thepractices referred to within.Primarily, the main piece oflegislation to consider is theElectricity at Work regulations1989 (EWR). The EWR statesthat all systems are to be safeso as to prevent danger andprevent the risk of injury. The designer and installer

must be aware of the statutoryrequirements under theElectricity at Work Regulationsand the Construction (Design& Management) Regulations2007 (CDM 2007), etc., for thesafe design, construction,operation and provision formaintenance of electricalequipment assemblies.Adequate access,

working space and lightingneed to be provided wherework is to be carried out on ornear equipment, in order thatpersons may work safely.The Memorandum to the

Electricity at work Regulations1989, HS(R)25, records thatthe IEE Wiring Regulations iswidely recognised andaccepted in the UK andcompliance with them is likelyto achieve compliance withrelevant aspects of the 1989Regulations in point 7 of theintroduction. n

References and furtherinformationn BS 7671:2008Requirements for ElectricalInstallations, IEE WiringRegulations, SeventeenthEdition n Electricity at Workregulations 1989 -www.opsi.gov.uk/si/si1989/Uksi_19890635_en_1.htmn Memorandum of guidanceon the Electricity at WorkRegulations 1989 (HSR25) -free download -www.hse.gov.uk/pubns/books/hsr25.htmn The Construction (Design & Management)Regulations 2007 -www.hse.gov.uk/construction/cdm.htm

n Guidance Note 1 - Selectionand Erection n BS EN 50529:1992 Degreesof protection provided byenclosures (IP code)n BS EN 62262:2002 Degreesof protection provided byenclosures for electricalequipment against mechanicalimpacts (IK code)n BS EN 60079 Electricalapparatus for explosive gasatmospheres suite ofstandardsn BS EN 60439-1:1999 Low-voltage switchgear andcontrolgear assemblies. Type-tested and partially type-testedassembliesn BS EN 50085-1:2005 Cabletrunking systems and cableducting systems for electricalinstallations. Generalrequirementsn BS EN 61386-1:2008Conduit systems for cablemanagement. Generalrequirementsn BEAMA Guide to verificationof low voltage powerswitchgear and control gear -www.beama.org.uk/UserFiles/file/publications/installation/BAVG.pdf

Figure 3: Slotted trunking

The IEE Wiring Regulations17th Edition (BS 7671:2008)includes additional sections onspecial locations that were notincluded in the previous edition;as follows: Marinas (Section709), Exhibitions, shows andstands (Section 711), Floor andceiling heating systems (Section753), Mobile and transportableunits (Section 717),Fairgrounds, amusement parksand circuses (Section 740), andPhotovoltaic power systems(Section 712). The speciallocations that were contained in

the previous edition of BS 7671have been revised to align withthe latest IEC and CENELECstandards.All those involved in

electrical installation workneed to be familiar with thesenew requirements.

Help is at hand, in the form of anew edition of IEE GuidanceNote 7 (Special Locations).

For example: Section 701locations containing a bath orshower. What’s new?

Changes to the zonal system,RCD protection on all bathroomcircuits, 230 V socket outletspermitted 3 m horizontally fromthe boundary of zone 1;supplementary equipotentialbonding may be omittedsubject to the Regulationsbeing met. Chapter 1 of IEEGuidance Note 7 gives detailedrequirements.

RCD ProtectionRegulation 701.411.3.3 nowrequires that additionalprotection shall be provided for

all circuits of the location by theuse of one or more RCDshaving the characteristicsspecified in Regulation 415.1.1.This is a significant change.Previously (601-09-02), onlyfixed current using equipment(other than electric showers)located in zone 1 required 30mA RCD protection and currentusing equipment (other thanfixed current using equipment –such as a washing machine, ifsuitable for use in a bathroom,connected through a fusedconnection unit) in zone 3required 30mA RCD protection.Regulation 701.411.3.3 meansthat all circuits, includinglighting, electric showers,heated towel rails, etc., requireRCD protection, not exceeding 30 mA.

230 volt socket-outlets Another significant change isintroduced by Regulation701.512.3. This now permits230 V socket-outlets to beinstalled in a room containinga bath or shower providingthey are installed 3 mhorizontally from the boundaryof zone 1. This changeresolves the ambiguity thatexisted between locationscontaining a bath or showerand a bedroom containing ashower.

How to order your copy of IEEGuidance Note 7 (availablefrom the 30th November 2009).By phone: +44(0)1438 767328By fax +44(0)1438 767375By email [email protected]. Over the web www.theiet.org/shop n


24 | IEE Guidance Note 7

ELECTRICAL PANELSTYPES OF ELECTRICAL PANELS, STANDARDS AND FORMS OF SEPARATION

WIRINGMATTERSWIRINGMATTERSThe Institution of Engineering and Technology

WINTER 09 ISSUE 33

Future developments in Standardisation

Supplies to electric vehicles

Energy effi cient lighting in domestic premises

How to meet the requirements of the Building Regulations

The use of “Arctic” cable

Cable for use at low-temperature

Types of person and the requirements of the Regulations

Examining skills andcompetencies

www.theiet.org/wiring

luminaireIPX4 luminaire

IPX4 extract fanpull-cord switch

shower

zone 1 zone 2

3 m (min)

socket-outlet

shaver unit

zone 0

switched flex outlet

2.25 m

0.6 m

outside zones

WIRING MATTERS Get your own copyWiring Matters is free. It is published quarterly and keeps you up to date with issues in electrical installations. To make sure you get your copy add or update your contact details via:

www.theiet.org/wm

New IEE Guidance Note 7 by Geoff Cronshaw

7

Guidance Note 7

SpecialLocations

IEE Wiring Regulations Seventeenth EditionBS 7671:2008 Requirements for Electrical Installations17th

The Institution of Engineering and Technology is registered as a Charity in England & Wales (no 211014) and Scotland (no SCO38698)

Essential tools of the trade New from the Institution of Engineering and Technology

For further information, or to order online, visit

www.theiet.org/wiringregs

Guidance Note 6:Protection Against OvercurrentPaperback, 113pp ISBN: 978-0-86341-860-0Product Code PWG6170B Price £25

This book enlarges upon and simplifies relevant requirements of BS 7671:2008. It includes guidance on protection of conductors in parallel against overcurrent and the effect of harmonic currents on balanced 3-phase systems.

Visit www.theiet.org/gn6wm

Guidance Note 7: Special LocationsPaperback, 142pp ISBN: 978-0-86341-861-7Product Code PWG7170B Price £25

The Guidance Note enlarges upon and simplifies relevant requirements of BS 7671:2008. It includes detailed coverage of new special locations covered in the IEE Wiring Regulations 17th Edition in easy-to-read text. It also includes full colour illustrations.

Visit www.theiet.org/gn7wm

ohm

Enlightened electricians choose NAPIT

Ω

Member benefits include:

NOEXTRACHARGE forelectrical commercial & industrialworks and periodic reports

FREEmembership to electricalTrade Association and onlineforum

WORKQUALITY guarantee onnotified workFREE legal and technical advicehelplinesSAVE up to £180 when joiningfrom another scheme provider

To speak to the industry gurus please call: 0800 954 0438

[email protected] www.napit.org.uk