24231881 Elsevier Portable Appliance Testing 2003 Edition

PAT: Portable Appliance Testing

By the same author

Electrical installation work

16th Edition Wiring Regulations: Inspection, Testingand Certification

16th Edition Wiring Regulations: Design andVerification of Electrical Installations

16th Edition Wiring Regulations: Explained andIllustrated

Wiring Systems and Fault Finding for InstallationElectricians

To Nicola

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PAT: PortableAppliance Testing

In-service inspection and testing ofelectrical equipment

Revised editionBrian Scaddan IEng, MIIE(elec)

Newnes

AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORDPARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO

NewnesAn imprint of ElsevierLinacre House, Jordan Hill, Oxford OX2 8DP200 Wheeler Road, Burlington MA 01803

First published 2000Revised edn 2003

Copyright © 2003, Brian Scaddan. All rights reserved

The right of Brian Scaddan to be identified as the author of this workhas been asserted in accordance with the Copyright, Designs andPatents Act 1988

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Contents

Preface ix

1. Legislation 12. Setting up 73. Equipment to be inspected and tested 134. Inspection 235. Combined inspection and testing 27

Appendix 1: Shock risk 37Appendix 2: Basic electrical theory revision 43Appendix 3: Sample 2377 questions: The

management of electrical equipmentmaintenance 49

Appendix 4: Sample 2377 questions: Inspectionand testing of electrical equipment 61

Appendix 5: Answers to test questions 69

Index 71

vii

The introduction of The Electricity at Work Regulations (EAWR)1989, prompted, among many other things, a rush to inspectand test portable appliances. The Regulations do not requiresuch inspecting and testing, nor do they specifically mentionportable appliances. They do, however, require any electricalsystem to be constructed, maintained and used in such a manneras to prevent danger, and in consequence inspection and testingof systems (portable appliances are systems) is needed in orderto determine if maintenance is required.

All electrical equipment connected to the fixed wiring of aninstallation will need attention, not just portable appliances. Ihave however left the title of this book as PAT: PortableAppliance Testing as such words are now indelibly imprintedon our minds, even though it should read ‘Inspection and Testingof In-service Electrical Equipment’.

The book is intended for those who need be involved in thisinspection and testing process, either as a business venture oras an ‘in-house’ procedure to conform with the EAWR. It isalso a useful reference document for anyone embarking on aCity & Guilds 2377 course.

Brian Scaddan

Preface

ix

1

1Legislation

There are four main sets of legislation that are applicable tothe inspection and testing of in-service electrical equipment:

• The Health & Safety at Work Act 1974 (H&SWA)• The Management of the Health & Safety at Work Act

Regulations 1999• The Provision & Use of Work Equipment Regulations

1998• The Electricity at Work Regulations 1989 (EAWR).

The Health & Safety at Work Act 1974

This applies to all persons – employers and employees – atwork, and places a duty of care on all to ensure the safety ofthemselves and others.

Regulation 16 of EAWR 1989 should be mentioned. ThisRegulation is absolute, this means no matter what the time orcost involved, it must be done. This Regulation deals with theperson being competent. The only way to prove to a court oflaw that you are a competent person is through regular training.Regular training? Every week or perhaps when new Regulationsare brought out.

Legislation

2

The Management of the Health & Safety atWork Act Regulations 1999

In order that the H&SWA can be effectively implemented inthe workplace, every employer has to carry out a risk assessmentto ensure that employees and those not in his/her employ, arenot subjected to danger.

The Provision & Use of Work EquipmentRegulations 1998

Work equipment must be constructed in such a way that it issuitable for the purpose for which it is to be used. Once again,the employer is responsible for these arrangements.

The Electricity at Work Regulations 1989

These regulations, in particular, are very relevant to theinspection and testing of in-service electrical equipment.

There are two important definitions in the EAWR: theelectrical system and the duty holder.

Electrical system

This is anything that generates, stores, transmits or uses electricalenergy, from a power station to a wrist-watch battery. Thelatter would not give a person an electric shock, but couldexplode if heated, giving rise to possible injury from burns.

Duty holder

This is anyone (employer, employee, self-employed personetc.) who has ‘control’ of an electrical system. Control in thissense means designing, installing, working with or maintainingsuch systems. Duty holders have a legal responsibility to ensure

Legislation

3

their own safety and the safety of others whilst in control of anelectrical system.

The EAWR do not specifically mention inspection andtesting; they simply require electrical systems to be ‘maintained’in a condition so as not to cause danger. However, we onlyknow if a system needs to be maintained if it is inspected andtested, and thus the need for such inspection and testing of asystem is implicit in the requirement for it to be maintained.

Anyone who inspects and tests an electrical system is, inlaw, a duty holder and must be competent to undertake suchwork.

Prosecutions

Offences committed under The Electricity at Work Regulations1989 may be liable for: £20,000 fine for each offence inMagistrates’ Court Unlimited fines/prison sentences in CrownCourt.

Here are just a few examples of the many prosecutionsunder the Electricity at Work Regulations 1989 that take placeevery year.

Case 1

A greengrocer was visited, probably for the second time, bythe Health and Safety Executive inspectors, who found elevenfaults with the electrical installation. They were:

1 a broken fuse to a fused connection unit;2 a broken three-way lighting switch;3 a broken double socket outlet;4 a broken bayonet light fitting;5 a missing ceiling rose cover;6 the flexible cord feeding the beetroot boiler went under

the casing and not through the proper hole in the side;7 there was no earthing to a fluorescent fitting;

Legislation

4

8 there was no earthing to a metal spotlight;9 block connectors were used to connect some bulkhead

lights;10 block connectors were used to connect the fluorescent

lights;11 block connectors were used to connect a spotlight.

He was subsequently fined £4,950, and although he was ‘onlya greengrocer’, he was also a duty holder, and as such had aresponsibility for the safety of the staff working in the shop.

Case 2

An electrician received serious burns to his face, arms andlegs after he was engulfed in a ball of flames whilst testing anold motor control switch-board. He was reaching into the boardto test contacts located only a few inches away from exposed,live, 400V terminals when the accident happened. He wasapparently using inappropriate test leads that were un-fusedand had too much exposed metal on the tips. He was alsoworking near live terminals because no arrangement had beenmade for the board to be made dead.

His company was fined a total of £1,933 because they didnot prevent work on or near live equipment. They were dutyholders. The electrician, however, also a duty holder, carriedthe main responsibility for the accident, but would not havebeen prosecuted, as he was the only one to be injured.

Case 3

A young foreman on a large construction site was electrocutedwhen he touched the metal handle of a site hut which hadbecome live. An employee of the company carrying out theelectrical contracting work on the site had laid inadequatewiring in the hut which had later been crushed by its weight,causing a fault. Consequently the residual current device (r.c.d.)protecting the hut kept tripping out, as it should have. However,

Legislation

5

another of the electrical contractor’s employees by-passed ther.c.d. so that it would not trip. This caused the site hut tobecome live.

The construction company was fined £97,000 for failing tomonitor site safety, the electrical contractors were fined £30,000,and the contractor’s managing director was fined £5,000 anddisqualified from being a company director for three years.

7

2Setting up

There are two ways for an organisation to ensure that in-service electrical equipment is regularly maintained:

• employ a specialist company to provide the inspection andtesting service, or

• arrange for ‘in-house’ staff to carry out the work, trainedand competent to deal with Regulation 16.

In either case, the first step is for the organisation to appointa ‘responsible person’ – who will, therefore, be a duty holder– to whom staff and/or outside contractors should report theresults of any inspection and test, including defects etc. Sucha person could be the manager of the premises or a member ofstaff: they will need to be trained and competent, both in themanagement of the appliance testing process and in theknowledge of relevant legislation as discussed in Chapter 1.

The second step is for the ‘responsible person’ to carry outan inventory of all equipment that may need testing and/orinspecting, and make decisions as to the frequency of suchwork. Some advice may be needed here from an experiencedcontractor in order to achieve the most effective time scheduleand to make decisions on which equipment should be involved.

Table 2.1 gives some examples of recommended periodsbetween each inspection and test.

Sitting up

8

The ‘responsible person’ should have in place a procedurefor users of electrical equipment to report and log any defectsfound.

Whether the inspection and test is to be carried out bycompetent staff or by outside contractors, it is advisable thatvarious forms be produced to record:

• details of equipment that may need to be inspected andtested (Form 1)

• the results of formal visual inspection or combined inspectionand testing (Form 2)

• details of faulty equipment taken out of service and sent forrepair (Form 3).

Previous records must be kept and made available to any personconducting routine inspection and testing of in-service electricalequipment.

Form 1

EQUIPMENT REGISTER

COMPANY: Jones Footware Ltd., Blacktown.

Frequency ofInsp. & Test

Register Equip. Class I, II Normal Formal CombinedNo. Equipment No.* or III Location visual Insp. Insp. & Test

1 Kettle 12 I Kitchen 6 mths. 12 mths.

2

3

4

5

6

7

* This could be the serial No. or a number allocated by the company or the contractor anddurably marked on the equipment

Table 2.1. Sample of suggested frequencies of inspection and testing

Equipment Class Inspection and tests Offices and shops Hotels Schools

Handheld Class I and II User checks Before use Before use Before useClass I Formal visual insp. Every 6 months Every 6 months Every 4 months

Combined insp. and test Every year Every year Every yearClass II Formal visual insp. Every 6 months Every 6 months Every 4 months

Combined insp. and test None None Every 4 years

Portable Class I and II User checks Weekly Weekly WeeklyClass I Formal visual insp. Every year Every year Every 4 months

Combined insp. and test Every 2 years Every 2 years Every yearClass II Formal visual insp. Every 2 years Every 2 years Every 4 months


Moveable Class I and II User checks Weekly Weekly WeeklyClass I Formal visual insp. Every year Every year Every 4 months

Combined insp. and test Every 2 years Every 2 years Every yearClass II Formal visual insp. Every 2 years Every 2 years Every 4 months


Stationary Class I and II User checks None None WeeklyClass I Formal visual insp. Every 2 years Every 2 years None

Combined insp. and test Every 4 years Every 4 years Every yearClass II Formal visual insp. Every 2 years Every 2 years Every year


IT Class I and II User checks None None WeeklyClass I Formal visual insp. Every 2 years Every 2 years None

Combined insp. and test Every 4 years Every 4 years Every yearClass II Formal visual insp. Every 2 years Every 2 years Every year


Form 2

INSPECTION AND TESTING RECORD

COMPANY: R.F. Bloggins & Son Ltd., Whiteford

Equip. Class I, NormalEquipment No. II or III location

Floor polisher 8 1 Store room

Make: Lynatron Voltage: 230 V Purchase date: 1.2.99 Frequency ofModel: KPX2 Power: 700 W inspection and testing

Serial No: 13579 Current: N/A A Formal CombinedFuse: 5 A visual insp. & test

Weekly 12 mths

Inspection Testing

Correct Insulation resistanceenvironment Permission to Earth continuity App. Voltage E. Leakage OK

Date for use disconnect* Socket Plug Flex Body Ohms OK M-ohms mA Functional to use Signature

1.2.2000 Yes N/A OK OK OK OK 0.07 Yes 200+ N/A OK YES A. Mann

8.2.2000 Yes N/A OK OK OK OK YES A. Mann



* Applies to business and IT equipment which may need downloading first

Form 3

FAULTY EQUIPMENT & REPAIR REGISTER

COMPANY: Mr. Baldys Hairdressing Emporium, Thintown

Date removed Equip. Equipment Normal Date sent Date Suitable for use from service Equipment No. register No. location Fault for repair Repairer returned OK Signature Comments

13.3.2000 Hair dryer 9 4 Main salon Frayed flex 20.3.2000 N.O. Good 28.3.2000 Yes N.O. Good

15.3.2000 Curling tongs 11 18 Room 2 Cracked handle 20.3.2000 T.O. Bad 1.4.2000 No T.O. Bad Not repairable

13

3Equipment to beinspected and

testedAs mentioned in the Preface to this book, it is not just portableappliances that have to be inspected and tested, but all in-service electrical equipment. This includes items connected tothe supply by 13 A BS1363 plugs, BS EN 60309-2 industrialplugs or hard wired to the fixed installation via fused connectionunits or single or three-phase isolators.

It is perhaps wise at this stage to comment on the twomethods of receiving an electric shock – direct and indirectcontact – and the different classes of equipment (Class 0,Class 01, Class I, Class II and Class III).

Direct contact

This is touching intentionally live parts. Protection is generallyachieved by applying basic insulation to such parts and/orenclosing them to prevent contact.

Indirect contact

This is contact with exposed metalwork of electrical equip-ment that has become live due to a fault, e.g. breakdown ofbasic insulation. Protection is generally by adequate

Equipment to be inspected and tested

14

earthing or the use of double or reinforced insulation(Class II).

Class 0 equipment or appliances

Almost everyone can remember those old-fashioned, ornatebrass table lamps, wired with either flat PVC-insulated twinflex or twisted cotton-covered rubber-insulated twin flex. Inother words, equipment with a non-earthed metal case, theprotection against electric shock being provided by insulatinglive parts with basic insulation only. Breakdown of this insulationcould result in the metal enclosure becoming live and with nomeans of disconnecting the fault. The Statutory ElectricalEquipment Safety Regulations introduced in 1975 effectivelyban the sale of Class 0 equipment.

Class 01 equipment or appliances

This is the same as Class 0. However, the metal casing has anearthing terminal but the supply cable is twin and the plug hasno earth pin.

Class 0 and 01 equipment may be used but only in specialcircumstances and in a strictly controlled environment. Generallythese classes should not be used unless connections to earthare provided on the item and an earth return path via a supplycable that has a circuit protective conductor (c.p.c.) incorporated:this would convert the equipment to Class I.

Class I equipment or appliances

These items have live parts protected by basic insulation anda metal enclosure or accessible metal parts that could becomelive in the event of failure of the basic insulation (indirectcontact). Protection against shock is by basic insulation and


15

earthing via casing the c.p.c. in the supply cable and the fixedwiring.

Typical Class I items include toasters, kettles, washingmachines, lathes and pillar drills (see Figs 3.1 and 3.2).

Figure 3.1

Figure 3.2


16

Class II equipment or appliances

Commonly known as double-insulated equipment, the itemshave live parts encapsulated in basic and supplementaryinsulation (double), or one layer of reinforced insulationequivalent to double insulation (Figs 3.3 and 3.4).

Even if the item has a metal casing (for mechanicalprotection) it does not require earthing as the strength of theinsulation will prevent such metalwork becoming live underfault conditions. The cable supplying such equipment willnormally be two core with no c.p.c. (Fig. 3.5).

Figure 3.3

Figure 3.4


17

Examples of Class II equipment would include most moderngarden tools such as hedge trimmers and lawn mowers andalso food mixers, drills, table lamps etc. All such items shoulddisplay the Class II equipment symbol:

Equipment with grills or openings, e.g. hair dryers, need topass the standard finger entry test (Fig. 3.6).

Figure 3.5

Figure 3.6


18

Class III equipment or appliances

This is equipment that is supplied from a Separated Extra LowVoltage source (SELV), which will not exceed 50 V and isusually required to be less than 24 V or 12 V. Typical itemswould include telephone answer machines, and other items ofIT equipment. Such equipment should be marked with thesymbol:

and be supplied from a safety isolating transformer to BS3535which in itself should be marked with the symbol:

These transformers are common and are typical of the typeused for charging mobile phones etc. Note there are no earthsin a SELV system and hence the earth pin on the transformeris plastic.

Equipment types

The Code of Practice defines various type of equipment/accessory that needs to be inspected and tested and that aregenerally in normal use. Advice from the manufacturer shouldbe sought before testing specialist equipment. The equipmenttypes are as follows:

• portable equipment/appliances• hand held equipment/appliances• moveable equipment/appliances• stationary equipment/appliances• fixed equipment/appliances

III


19

• built-in equipment/appliances• information technology equipment• extension leads.

Portable equipment/appliances

These are items which are capable of easy movement whilstenergised and/or in operation. Examples of such appliancesare:

• chip fryers• toasters• coffee percolators• tin openers.

Hand held equipment/appliances

These items are of a portable nature that require control/useby direct hand contact. Examples include:

• drills• hair dryers• hedge trimmers• soldering irons.

Moveable equipment/appliances

There is a thin dividing line between this and the previous twotypes, but in any case still needs inspecting and testing. Generallysuch items are 18kg or less and have wheels or are easilymoved. Examples would include:

• tumble dryers• the old fashioned twin-tub washing machine• industrial/commercial kitchen equipment.


20

Stationary equipment/appliances

This is equipment in excess of 18 kg and which is not intendedto be moved about, such as:

• ordinary cookers• dishwashers• washing machines.

Fixed equipment/appliances

These items are fixed or secured in place, typically:

• tubular heaters• lathes and other industrial equipment• towel rails.

Built-in equipment/appliances

This is equipment that is ‘built-in’ to a unit or recess such as:

• an oven• an inset electric fire.

Information technology (IT) equipment

In general terms, this is business equipment such as:

• PCs• printers• typewriters• scanners.

Extension leads

These include the multi-way sockets so very often used whereIT equipment is present, as there is seldom enough fixed socketoutlets to supply all the various units. These leads shouldalways be wired with 3 core (phase neutral and earth) cable,and should not exceed:


21

• 12 m in length for a 1.25 mm2 core size• 15 m in length for a 1.5 mm2 core size• 25 m in length for a 2.5 mm2 core size.

The latter should be supplied via a BS EN 60309-2 plug, andif any of the lengths are exceeded, the leads should be protectedby a BS7071 30 mA r.c.d.

23

4Inspection

Inspection is vital, and must precede testing. It may revealserious defects which may not be detected by testing only.

Two types of inspection are required: user checks and formalvisual inspection.

User checks

All employees are required by the Electricity at WorkRegulations to work safely with electrical appliances/equipmentand hence all should receive some basic training/instruction inthe checking of equipment before use. (This training needonly be of a short duration.) Generally, this is all commonsense: nevertheless, a set routine or pre-use checks should beestablished. Such a routine could be as follows:

• Check the condition of the appliance/equipment (look forcracks or damage).

• Examine the cable supplying the item, looking for cuts,abrasions, cracks etc.

• Check the cable sheath is secure in the plug and the appliance.• Look for signs of overheating.• Check that it has a valid label indicating that it has been

formally inspected and tested.

Inspection

24

• Decide if the item is suitable for the environment in whichit is to be used, e.g. 240 V appliances should not be used ona construction site.

• If all these checks prove satisfactory, check that the applianceis working correctly.

If the user feels that the equipment is not satisfactory, it mustbe switched off, removed from the supply, labelled ‘Not to beused’ or words to that effect, and reported to a responsibleperson. That person will then take the necessary action torecord the faulty item and arrange remedial work or have itdisposed of.

No record of user checks is required if the equipment isconsidered satisfactory.

Formal visual inspection

This must be carried out by a person competent to do so, andrecorded on an appropriate form. This inspection is similar to,but more detailed than, user checks and must be conductedwith the accessory/equipment disconnected from the supply.

General

• Check cable runs to ensure that cables will not be damagedby staff or heavy equipment.

• Make sure that plugs, sockets, flex outlets, isolators etc.are always accessible to enable disconnection/isolation ofthe supply, either for functional, maintenance or emergencypurposes. For example, in many office environments, socketoutlets are very often obscured by filing cabinets etc.

• Check that items that require clear ventilation such asconvector heaters, VDU’s etc. are not covered in paper,

Inspection

25

files etc. and that foreign bodies or moisture cannotaccidentally enter such equipment.

• Ensure that cables exiting from plugs or equipment are nottightly bent.

• Check that multiway adaptors/extension leads are notexcessively used.

• Check that equipment is suitable for both the purpose towhich it is being put and the environment in which it isbeing used.

• Ensure that accessories/equipment are disconnected fromthe supply during the inspection process, either by removingthe plug or by switching off at a connection unit or isolator.

• Take great care before isolating or switching off businessequipment. Ensure that a responsible person agrees thatthis may be done, otherwise this may result in a seriousloss of information, working processes etc.

The accessories/equipment

• Check the cable for damage. Is it too long or too short?• Is the supply cable/cord to the appliance the right size?• Is the plug damaged? Look for signs of overheating etc.• Is the fuse in a BS1363 13 A plug the correct size? Are the

contacts for the fuse secure? (This requires dismantling ofthe plug. The fuse should be approved, and ideally have anASTA mark on it. Some fuses made in China and markedPMS are dangerous and should be replaced. Fuse and cordsizes (in accordance with BS1363) in relation to appliancerating are generally:

Appliance rating Fuse size Cord size

Up to 700 W 3 A 0.5 mm2

700–3000 W 13 A 0.75–1.25 mm2

• If a plug is damaged and is to be replaced, ensure that the

Inspection

26

replacement has sleeved live pins. The Plugs and Socketsetc. Regulations 1994 makes it illegal to sell plugs withoutsuch sleeved pins. However, this requirement is notretrospective, in that it does apply to plugs with un-sleevedpins already in use.

27

5Combined

inspection andtesting

Combined inspection and testing comprises preliminaryinspection as per Chapter 4 together with instrument tests toverify earth continuity, insulation resistance, functional checksand, in the case of cord sets and extension leads, polarity aswell. In some low-risk areas such as offices, shops, hotels etc.,Class II equipment does not require the routine instrumenttests.

Testing

This has to be carried out with the appliance/equipment isolatedfrom the supply. Such isolation is, of course, easy when theitem is supplied via a plug and socket, but presents somedifficulties if it is permanently wired to, say, a flex outlet, aconnection unit, or an isolator etc. In these cases the testermust be competent to undertake a disconnection of the appliance,if not, then a qualified/competent electrical operative shouldcarry out the work.

Additionally, the permission of a responsible personmay be needed before isolating/disconnecting businessequipment.

Combined inspection and testing

28

Preliminary inspection

This must always be done before testing as it could revealfaults that testing may not show, such as unsecured cables inappliance housings, damaged cable sheathing etc. The inspectionprocedure is as detailed in Chapter 4.

Testing

This may be carried out using a portable appliance tester, ofwhich there are many varieties, or separate instruments capableof measuring continuity and insulation resistance.

Portable appliance testers

These instruments allow appliances, fitted with a plug, to beeasily tested. Some testers have the facility for testing appliancesof various voltage ranges, single and three phase, although themajority only accept single phase 240 V or 110 V plugs (BS1363and BS EN 60309-2).

Generally, portable appliance testers are designed to allowoperatives to ‘plug in’ an item of equipment, push a test button,view results and note a ‘pass’ or ‘fail’ indication. The operativecan then interpret these results and, where possible, makeadjustments which may enable a ‘fail’ indication to be changedto a ‘pass’ status.

Some portable appliance testers are of the GO, NO-GOtype where the indication is either a red (fail) or green (pass)light. As there are no test figures associated with this type oftester, no adjustment can be made. This could result in appliancesbeing rejected when no fault is present. This situation will bedealt with a little later.


29

Continuity/insulation resistance testers

These are usually dual instrument testers, although separateinstruments are in use. Multimeters are rarely suitable forthese tests.

For earth continuity, the instrument test current (a.c. ord.c.) should be between 20 and 200 mA with the source havingan open circuit voltage of between 100 mV and 24 V. Forinsulation resistance the instrument should deliver a maintainabletest voltage of 500 V d.c. across the load. Note: All test leadsshould conform to the recommendations of the HSEGuidance Note GS 38.

So, what are the details of the tests required?

Earth continuity

This test can only be applied to Class I equipment, and thepurpose of the test is to ensure that the earth terminal of theitem is connected to the casing effectively enough to result inthe test between this terminal and the casing giving a value ofnot more than 0.1 Ω.

Clearly, it is not very practicable to have to access terminalsinside an enclosure and hence, it is reasonable to measure theearth continuity from outside, via the plug and supply lead.This also checks the integrity of the lead earth conductor, orc.p.c.

Testing in this way will, of course, add the resistance of thelead to the appliance earth resistance, which could result in anoverall value in excess of the 0.1 Ω limit, and the tester mayindicate a ‘fail’ status. This is where the interpretation of resultsis so important in that, provided the final value having subtractedthe lead resistance from the instrument reading is no morethan 0.1 Ω, the appliance can be passed as satisfactory.

The use of a GO, NO-GO instrument prohibits such anadjustment as there are no test values available.

The following table gives the resistance in ohms per metre


30

of copper conductors, at 20°C for flexible cords from 0.5 mm2

to 4.0 mm2.

Conductor size (mm2) Resistance (Ω/m)

0.5 0.0390.75 0.0261.0 0.01951.25 0.01561.5 0.0132.5 0.0084.0 0.005

Hence the c.p.c. of 5 m of 1.0 mm2 flexible cord would havea resistance of:

5 × 0.0195 = 0.0975 ΩIt is unlikely that appliances in general use will have supplycords in excess of 1.25 mm2 as the current rating for such acord is 13 A, which is the maximum for a BS1363 plug.

Example

The measured value of earth continuity for an industrial floorpolisher, using a portable appliance tester, is 0.34 Ω. The supplycord is 10 m long and has a conductor size of 0.75 mm2. Thetest instrument also indicates a ‘fail’ condition. Can the resultbe overruled?

Resistance of c.p.c. of lead = 10 × 0.026 = 0.26 ΩTest reading, less lead resistance = 0.34 – 0.26 = 0.08 Ω

This is less than the maximum of 0.1 Ω, so, yes the applianceis satisfactorily earthed, and the test reading can be overruledto ‘pass’.

The only problem with this approach is that most portableappliance testers have electronic memory which can bedownloaded to software on a PC, which would record 0.34 Ω


31

and a ‘fail’ status. Unless the instrument or the software includesthe facility to include lead resistance, the appliance still fails(something to be said for paper records?).

Having made the above comments, it must be said thatonly low power appliances with very long cables having smallsize conductors, cause any problems.

Conducting the earth continuity test

Portable appliance tester

Having conducted the preliminary inspection:

• Plug the appliance into the tester and select, if possible, asuitable current. This will be 1.5 times the fuse rating (ifthe correct fuse is in place) up to a maximum of 25 A.

• Connect the earth bond lead supplied with the tester, to asuitable earthed point on the appliance. (Remember thatjust because there is metal, it does not mean that it isconnected to earth.) A fixing screw securing the outer casingto a frame is often the best place, rather than the actualcasing, which may be enamelled or painted and maycontribute to a high resistance reading. If a high reading isobtained, other points on the casing should be tried.

• Start the test, and record the test results.• Do not touch the appliance during the test.

Figure 5.1 illustrates such a test.

Continuity tester

The method is in general as for the portable appliancetester:

• Zero the instrument.• Connect one lead to the earth pin of the plug.• Connect the other lead to the appliance casing.• Start the test and record the test results.• Do not touch the appliance during the test.


32

Figure 5.2 illustrates such a test.For the purpose of conducting an earth continuity test using

a separate instrument, it would be useful to construct a simplemeans of ‘plugging-in’ and measuring, rather than trying tomake contact with plug pins using clips or probes.

The resourceful tester will make up his/her own aids totesting. Such an aid in this case could be a polypropylene box

Figure 5.1

Figure 5.2

Continuity tester Metal casing

Appliance

0.1 ohms max.

E

Supply cord

E


33

housing a 13 A and a 110 V socket, with the earth terminalsbrought out to a metal earth stud suitable for the connection ofa test lead (Fig. 5.3).

Again, in the case of testing items of equipment that haveto be disconnected from the supply, special test accessoriesare useful to aid the testing process. Such an accessory wouldbe, for example, a plug, short lead and connector unit, towhich a disconnected item could be connected. This is especiallyuseful when using a portable appliance tester, whereas acontinuity tester can be connected easily to the exposedprotective conductor of the equipment.

Figure 5.3


34

Multiway extension sockets and extension leads are to betreated as Class I equipment. However, there is some difficultyin gaining a connection to the earth pin of socket outlets andfemale plugs. Poking a small screwdriver into the earth socketis not good working practice.

For Class I cord sets, why not use the arrangement shownin Figure 5.3 and add a selection of recessed sockets to housethe range of female plugs found on cord sets? All their earthpins would be connected to the earth stud. For extension leadsincorporating a socket or sockets, use the earth pin from anold plug, as this is designed to enter the earth pin socket.

Insulation resistance

Realistically, this test can only be carried out on Class Iequipment. It is made to ensure that there is no breakdown ofinsulation between the protective earth and live (phase andneutral) parts of the appliance and its lead.

For Class II items, there are no earthed parts and one testprobe would need to be placed at various points on the bodyof the appliance in order to check the integrity of the casing.

Items that have a cord set, e.g. a kettle, should have thecord set plugged into the appliance and the appliance switchshould be in the ‘on’ position.

There are two tests that can be made, using either the appliedvoltage method or the earth leakage method.

The applied voltage method

This is conducted using an insulation resistance tester, set on500 V d.c. The test is made between the phase and neutralconnected together, and the protective earth. (For three-phaseitems, all live conductors are connected together.) This is bestachieved using the same arrangement as shown in Figure 5.2,but with the addition of a phase/neutral stud connected to thesockets phase and neutral (Fig. 5.4).


35

Care must be taken when conducting this test to ensure thatthe appliance is not touched during the process. Also, it shouldbe noted that some items of equipment have filter networksconnected across phase and earth terminals and this may leadto unduly low values. The values recorded should not be lessthan those shown in Table 5.1.

Figure 5.4

Table 5.1. Insulation resistance values

Appliance class Insulation resistance

Class I heating equipment less than 3 kW 0.3 MΩGeneral Class I equipment 1 MΩClass II equipment 2 MΩClass III equipment 250 kΩ


36

The earth leakage method

This is achieved using a portable appliance tester that subjectsthe insulation to a less onerous voltage (usually 250 V) thanthat delivered by an insulation resistance tester. Here, the leakagecurrent across the insulation is measured, and appliance testersusually set the maximum value at 3.5 mA.

Whichever method is used, there is a chance ofpessimistically low values occurring when some heating orcooking appliances are tested. This is usually due to moistureseeping into the insulation of the elements. In this case it iswise to switch such equipment on for a short while to dry theelements out before testing.

NOTE: Many portable appliance testers have the facility toconduct a ‘dielectric strength’ or ‘flash’ test, which is basicallyan insulation resistance test at 1250 V for Class I equipmentand 3570 V for Class II. Such voltages could cause damage toinsulation and should not be carried out for in-service tests.

Touch current

This is an alternative to insulation resistance testing and isonly available on the more expensive/comprehensive types ofPAT tester. The exact method of conducting this test is not atall clear in the Code of Practice, and as it is quite unusual toperform such a test in normal circumstances it has been omittedfrom this volume.

Functional checks

If testing has been carried out using separate instruments, justswitch the equipment to ensure that it is working. If a portableappliance tester is used, there is usually a facility for conductinga ‘load test’. The equipment is automatically switched on andthe power consumption measured while the item is on load.This is useful as it indicates if the equipment is working to itsfull capacity, e.g. a 2 kW reading on a 3 kW heater suggests abroken element.

37

Appendix 1:Shock risk

As we have seen in Chapter 1, all who are involved withelectrical systems are ‘Duty holders’ in Law. For those operativeswho have only a limited knowledge of electricity, but arenevertheless charged with their company’s appliance test-ing, an understanding of electric shock will help to givemore meaning and confidence to the inspection and testprocess.

Electric shock

This is the passage of current through the body of suchmagnitude as to have significant harmful effects. Figure A.1illustrates the generally accepted effects of current passingthrough the human body. How, then, are we at risk of electricshock and how do we protect against it?

1 mA–2 mA Barely perceptible, no harmful effects5 mA–10 mA Throw off, painful sensation10 mA–15 mA Muscular contraction, can’t let go20 mA–30 mA Impaired breathing50 mA and above Ventricular fibrilation and death

These are two ways in which we can be at risk.

Shock risk

38

1 Touching live parts of equipment or systems that are intendedto be live. This is called direct contact.

2 Touching conductive parts which are not meant to be live,but which have become live due to a fault. This is calledindirect contact.

The conductive parts associated with indirect contact can eitherbe metalwork of electrical equipment and accessories (Class1) and that of electrical wiring systems (e.g. metal conduit andtrunking), called exposed conductive parts, or other metalwork(e.g. pipes, radiators and girders), called extraneous conductiveparts.

Figure A.1

Shock risk

39

Protection against direct contact

How can we prevent danger to persons and livestock fromcontact with intentionally live parts? Clearly we must minimizethe risk of such contact and this can be achieved by

• insulating any live parts• ensuring any uninsulated live parts are housed in suitable

enclosures and/or are behind barriers.

The use of a residual current device (r.c.d.) cannot preventdirect contact, but it can be used to supplement any of theother measures taken, provided that it is rated at 30 mA or lessand has a tripping time of not more than 40 ms at an operatingcurrent of 150 mA.

It should be noted that r.c.d’s are not the panacea for allelectrical ills, they can malfunction, but they are a valid andeffective back-up to the other methods. They must not be usedas the sole means of protection.

Protection against indirect contact

How can we protect against shock from contact with live,exposed or extraneous conductive parts whilst touching earth,or from contact between live exposed and/or extraneousconductive parts? The most common method is by earthedequipotential bonding and automatic disconnection of supply(EEBADS).

All extraneous conductive parts are joined together with amain equipotential bonding conductor and connected to themain earthing terminal, and all exposed conductive parts areconnected to the main earthing terminal by the circuit protectiveconductors. Add to this, overcurrent protection that will operatefast enough when a fault occurs and the risk of severe electricshock is significantly reduced.

Shock risk

40

What is earth and why and how we connect to it

The thin layer of material which covers our planet – rock,clay, chalk or whatever – is what we in the world of electricityrefer to as earth. So, why do we need to connect anything toit? After all, it is not as if earth is a good conductor.

It might be wise at this stage to investigate potential difference(PD). A PD is exactly what it says it is: a difference in potential(volts). In this way, two conductors having PDs of, say, 20 Vand 26 V have a PD between them of 26 – 20 = 6 V. Theoriginal PDs (i.e. 20 V and 26 V) are the PDs between 20 Vand 0 V and 26 V and 0 V. So where does this 0 V or zeropotential come from? The simple answer is, in our case, theearth. The definition of earth is, therefore, the conductive massof earth, whose electric potential at any point is conventionallytaken as zero.

Thus, if we connect a voltmeter between a live part (e.g.the phase conductor of a socket outlet) and earth, we may read230 V; the conductor is at 230 V and the earth at zero. Theearth provides a path to complete the circuit. We would measurenothing at all if we connected our voltmeter between, say, thepositive 12 V terminal of a car battery and earth, as in this casethe earth plays no part in any circuit.

Figure A.2 illustrates this difference.So, a person in an installation touching a live part whilst

standing on the earth would take the place of the voltmeterand could suffer a severe electric shock. Remember that theaccepted lethal level of shock current passing through a personis only 50 mA or 1/20 A. The same situation would arise if theperson were touching a faulty appliance and a gas or waterpipe (Fig. A.3).

One method of providing some measure of protection againstthese effects is, as we have seen, to join together (bond) allmetallic parts and connect them to earth. This ensures that allmetalwork in a healthy installation is at or near 0 V and, underfault conditions, all metalwork will rise to a similar potential.So, simultaneous contact with two such metal parts would not

Shock risk

41

result in a dangerous shock, as there would be no significantPD between them.

Unfortunately, as mentioned, earth itself is not a goodconductor, unless it is very wet. Therefore, it presents a highresistance to the flow of fault current. This resistance is usuallyenough to restrict fault current to a level well below that of therating of the protective device, leaving a faulty circuituninterrupted. Clearly this is an unhealthy situation.

In all but the most rural areas, consumers can connect to ametallic earth return conductor, which is ultimately connectedto the earthed neutral of the supply. This, of course, presents

Figure A.2

Shock risk

42

a low-resistance path for fault currents to operate theprotection.

In summary, connecting metalwork to earth, places thatmetal at or near zero potential and bonding between metallicparts puts such parts at a similar potential even under faultconditions. Add to this, a low-resistance earth fault return path,which will enable the circuit protection to operate very fast,and we have significantly reduced the risk of electric shock.We can see from this how important it is to check that equipmentearthing is satisfactory and that there is no damage to conductorinsulation.

Figure A.3

43

Appendix 2:Basic electricaltheory revision

This appendix has been added in order to jog the memory ofthose who have some electrical background and to offer abasic explanation of theory topics within this book for thoserelatively new to the subject.

Electrical quantities and units:

Quantity Symbol Units

Current I Ampere (A)Voltage V Volt (V)Resistance R Ohm (Ω)Power P Watt (W)

Current

This is the flow of electrons in a conductor.

Voltage

This is the electrical pressure causing the current to flow.

Basic electrical theory revision

44

Resistance

This is the opposition to the flow of current in a conductordetermined by its length, cross sectional area and temperature.

Power

This is the product of current and voltage, hence P = I × V.

Relationship between voltage, current andresistance

Voltage = Current × Resistance V = I × R or,Current = Voltage/Resistance I = V/R or,Resistance = Voltage/Current R = V/I

Common multiples of units

Current I amperes kA mAkilo-amperes milli-amperes1000 amperes 1/1000 of an ampere

Voltage V volts kV mVkilovolts millivolts1000 volts 1/1000 of a volt

Resistance R ohms MΩ mΩmegohms milli-ohms1,000,000 ohms 1/1000 of an ohm

Power P watts MW kWmegawatt kilowatt1,000,000 watts 1000 watts

Resistance in series

These are resistances joined end to end in the form of a chain.The total resistance increases as more resistances are added(Fig. A.4).


45

Hence, if a cable length is increased, its resistance willincrease in proportion. For example, a 100 m length of conductorhas twice the resistance of a 50 m length of the same diameter.

Resistance in parallel

These are resistances joined like the rungs of a ladder. Herethe total resistance decreases the more there are (Fig. A.5).

The insulation between conductors is in fact countlessmillions of very high value resistances in parallel. Hence anincrease in cable length results in a decrease in insulationresistance. This value is measured in millions of ohms, i.e.megohms (MΩ).

The overall resistance of two or more conductors will alsodecrease if they are connected in parallel (Fig. A.6).

The total resistance will be half of either one and would bethe same as the resistance of a 2 mm2 conductor. Henceresistance decreases if conductor cross sectional area increases.

Example

If the resistance of a 1.0 mm2 conductor is 19.5 mΩ/m, whatwould be the resistance of:

Figure A.4

Rtotal = R1 + R2 + R3 + R4

R1 R2 R3 R4

1Ω 2Ω 10Ω 4Ω

Ω

Rtotal = 1 + 2 + 10 + 4 = 17Ω


46

Figure A.5

Figure A.6

3Ω

6Ω

8Ω

2Ω

Ω

1/Rtotal = 1/R1 + 1/R2 + 1/R3 + 1/R4

1/Rtotal = 1/R1 + 1/R2 + 1/R3 + 1/R4

= 1/3 + 1/6 + 1/8 + 1/2

= 0.333 + 0.167 + 0.125 + 0.5

∴ Rtotal = 1/1.125


47

1 85 m of 1.0 mm2 conductor2 1 m of 6.0 mm2 conductor3 25 m of 4.0 mm2 conductor4 12 m of 0.75 mm2 conductor?

Answers

1 1.0 mm2 is 19.5 mΩ/m, so, 85 m would be 19.5 × 85/1000= 1.65 Ω

2 A 6.0 mm2 conductor would have a resistance 6 times lessthan a 1.0 mm2 conductor, i.e. 19.5/6 = 3.35 mΩ

3 25 m of 4.0 mm2 would be 19.5 × 25/4 × 1000 = 0.12 Ω4 12 m of 0.75 mm2 would be 19.5 × 12/0.75 × 1000 =

0.312 Ω.

49

Appendix 3:Sample 2377

questions

The management of electrical equipmentmaintenance

1 Which one of the following is a statutory document?

a. A British Standardb. IEE Wiring Regulationsc. IEE Codes of Practiced. Electricity at Work Regulations.

2 Which one of the following regulations states: ‘Everyemployer shall make a suitable and sufficient assessmentof the risk to the health and safety of his employees andto persons not in his employment’?

a. The Electricity Supply Regulationsb. The Electricity at Work Regulationsc. The Provision and Use of Work Equipment

Regulationsd. The Management of Health and Safety at Work

Regulations.

Sample 2377 questions

50

3 Certain sections of The Health and Safety at WorkRegulations put a duty of care upon:

a. employees onlyb. employers onlyc. both employees and the general publicd. both employers and employees?

4 Which one of the following regulations state: ‘As may benecessary to prevent danger, all systems shall be maintainedso as to prevent, so far as is reasonably practicable, suchdanger’?

a. The Electricity at Work Regulationsb. The IEE Wiring Regulationsc. The Provision and Use of Work Equipment

Regulationsd. The Management of Health and Safety at Work

Regulations.

5 The scope of legislation of inspection and testing ofelectrical equipment extends to distribution systems upto:

a. 230 Vb. 400 Vc. 11 kVd. 400 kV?

6 The Code of Practice for In-service Inspection and Testingof Electrical Equipment does not apply to:

a. shopsb. officesc. caravan sitesd. petrol station forecourts?

7 The safety and proper functioning of certain portableappliances and equipment depends on the integrity of the


51

fixed installation. Requirements for the inspecting andtesting of fixed installations are given in:

a. BS2754b. BS7671c. BS EN 60947d. BS EN 60898?

8 Transportable equipment is sometimes called:

a. hand-held appliance or equipmentb. stationary equipment or appliancec. moveable equipmentd. portable appliance?

9 An electric kettle is classified as:

a. a portable applianceb. moveable equipmentc. a hand-held applianced. equipment for ‘building in’?

10 Which one of the following domestic electricalappliances may be regarded as an item of stationaryequipment?

a. A bathroom heaterb. A visual display unitc. A washing machined. A built-in electric cooker.

11 A portable appliance that is supplied by a flexiblecord incorporating a protective conductor, is classifiedas:

a. Class Ib. double insulatedc. metal clad Class IId. Class III?


52

12 Stationary equipment/appliances are defined as notbeing provided with a carrying handle and have a massexceeding:

a. 10 kgb. 12 kgc. 15 kgd. 18 kg?

13 A freezer is classified as:

a. a stationary appliance or equipmentb. a hand-held appliance or equipmentc. moveable equipmentd. a portable appliance?

14 A BS3535 safety isolating transformer having a voltagenot exceeding 50 V is used to supply certain equipment.The class of such equipment is:

a. Class 0b. Class Ic. Class IId. Class III?

15 Which size of the following three-core extension leads istoo large for a standard 13 A plug?

a. 2.5 mm2

b. 1.5 mm2

c. 1.25 mm2

d. 1.00 mm2.

16 Which one of the following arrangements would not meetthe requirements of the IEE Code of Practice?

a. Class I equipment supplied by a 1.5 mm2 three-coreextension lead connected into a 13 A three-pin socketoutlet.


53

b. Class II equipment supplied by a 1.5 mm2 two-coreextension lead connected into a 13 A three-pin socketoutlet.

c. Class I equipment supplied by a 2.5 mm2 three-coreextension lead connected into a BS EN 60309-2 socketoutlet.

d. Class III equipment supplied by a two-core flexiblecord connected into the secondary of an isolatingtransformer supplying SELV lighting equipment.

17 Which one of the following size and length extensionleads should be used in conjunction with an r.c.d. usedfor supplementary protection?

a. 1.5 mm2, 10 m longb. 1.5 mm2, 15 m longc. 2.5 mm2, 20 m longd. 2.5 mm2, 30 m long

18 During the inspection and testing process, which of thefollowing is not required:

a. Preliminary inspectionb. Earth continuity tests (for Class I equipment)c. Insulation testingd. Earth continuity test on Class II equipment?

19 Which one of the following would not be conducted duringroutine inspection and testing of appliances:

a. Preliminary inspectionb. Earth continuity testsc. Type testingd. Functional checks?

20 When performing in-service testing on Class I equipment,which one of the following is not required:


54

a. Type testing to a British Standardb. Earth continuity testc. Insulation testingd. Functional checks?

21 Details of which of the following must be recordedwhen carrying out a safety check on an electricalappliance:

a. Manufacturer’s name and addressb. Combined inspection and testc. User check revealing no damage to equipmentd. Applicable British Standards?

22 Which one of the following will not affect thefrequency of inspection and testing for an electricalappliance:

a. The integrity of the fixed electrical installationb. Environment in which it is to be usedc. The userd. The equipment class?

23 Recorded testing but not inspecting of equipment may beomitted if the:

a. equipment is of Class I construction and in a low-riskarea

b. equipment is of Class II construction and in a low-risk area

c. user of the equipment reports damage as and when itbecomes evident

d. equipment is a hand-held appliance.

24 The table of suggested frequency of inspection and testingfor electrical equipment gives details of:

a. the forms required for such testingb. maximum and minimum values of test results


55

c. the required sequence of visual checks to be maded. types of premises within which electrical equipment

is operated and user check requirements?

25 The suggested initial frequency for a formal visualinspection of a hand-held Class II electric iron in a hotelis:

a. one monthb. six monthsc. 12 monthsd. 24 months?

26 The suggested frequency for user checks for children’srides in a fairground is:

a. weeklyb. monthlyc. dailyd. 12 months?

27 Which one of the following tests should not be appliedroutinely to equipment:

a. Earth continuityb. Insulation resistancec. Polarityd. Dielectric strength?

28 The first electrical test to be applied to Class I equipmentis:

a. insulation resistanceb. earth continuityc. dielectric strengthd. polarity?

29 When information regarding test procedures is unavailablefrom the manufacturer or supplier of IT equipment which


56

one of the following electrical tests should not beundertaken?

a. Earth continuityb. Polarityc. Functionald. Insulation.

30 The purpose of an equipment register is to ensure:

a. compliance with the Electricity at Work Regulationsb. that maintenance procedures are recordedc. the frequency of inspection and test is reviewedd. inspection and testing is performed?

31 Identification of all electrical equipment within a dutyholder’s control is required in order to produce:

a. ‘pass’ safety check equipment labelb. faulty equipment registerc. equipment registerd. repair register?

32 Which one of the following items of information is notrequired on an inspection and test label?

a. An indication of whether the equipment has passedor failed the safety tests

b. Details of previous test resultsc. Date at time of testingd. Appliance or equipment number.

33 All electrical equipment should be marked with a uniqueserial number to aid:

a. disconnectionb. identificationc. risk assessmentd. interpretation of test results?


57

34 Information provided for equipment which requires routineinspection and/or testing should consist of:

a. an indelible bar-code systemb. an identification code to enable the equipment to be

uniquely identifiablec. operating instructions regarding the test equipmentd. an indication of the results which may be expected

during inspections and/or tests?

35 Which one of the following is not required to be testedwithin the scope of the IEE Code of Practice?

a. Fixed equipmentb. Fixed installationsc. Electrical toolsd. Portable appliances.

36 The Memorandum of Guidance on the Electricity at WorkRegulations 1989 advises that equipment records:

a. should be kept throughout the working life of theequipment

b. only be kept where the equipment is used in high-riskareas

c. are not required where the equipment is used in low-risk areas

d. are not required if the equipment is fed from a 110 Vsafety supply?

37 Records of all maintenance activities relating toelectrical appliances must be kept, including details ofthe:

a. initial costb. procurement of equipmentc. estimated replacement dated. estimated replacement cost?


58

38 The person responsible for carrying out an inspectionand test on an appliance should have made available tothem:

a. a list of all the users of equipmentb. a copy of the Electricity at Work Regulationsc. a copy of the Health and Safety at Work Actd. previous inspection and test results?

39 Which voltage must be used when carrying out aninsulation resistance test on a Class I toaster?

a. 3750 V a.c.b. 500 V d.c.c. 1000 V d.c.d. 500 V a.c.

40 An insulation resistance tester should be capable of:

a. delivering a minimum voltage of 1000 V d.c. to theload

b. testing the continuity of an earthing circuitc. delivering a maximum voltage of 25 A through the

loadd. maintaining the test voltage required across the

load?

41 Where a user check reveals damage to equipment, it mustbe reported to:

a. the equipment manufacturerb. the Health and Safety Inspectoratec. a responsible persond. a manager of an inspection and test organisation?

42 The manager of an inspection and test organisation shouldbe able to:

a. repair faulty electrical equipment


59

b. instruct untrained persons in the use of portableappliance testers

c. know their legal responsibilities under the Electricityat Work Regulations

d. demonstrate competence in the use of appliance testers?

43 Which one of the following is outside the scope of theIEE Code of Practice for Inspection and Testing of In-Service Electrical Equipment?

a. Those who inspect and testb. The user of electrical appliancesc. Managers of the inspection and test organisationd. The hirer of electrical portable appliances and

equipment.

44 Earth continuity testing may in certain circumstances becarried out by means of:

a. a low resistance ohmmeterb. an insulation resistance testerc. a bell set and batteryd. an instrument complying with BS EN 60309?

45 Test leads and probes used to measure voltages over 50 Va.c. and l00 V d.c. should comply with:

a. BS 7671b. Health and Safety Executive Guidance Note GS 38c. BS 5490 Specification for Classification of Protectiond. IEC Publication 479?

61

Appendix 4:Sample 2377

questions

Inspection and testing of electricalequipment

1 Where protection against electric shock from equipmentis provided using a protective conductor in the fixed wiring,the equipment classification would be:

a. Class Ib. Class IIc. Class IIId. Class 0?

2 A safety isolating transformer for Class III equipmentmust conform to:

a. BS 3456b. BS 3535c. BS 4533d. BS 5458?

3 A substantially continuous metal enclosure associated withClass II equipment, would be classified as:

a. insulation encasedb. isolation encased


62

c. metal-casedd. metal insulated?

4 There is no provision for protective earthing or relianceupon installation conditions for which one of the followingequipment?

a. Class Ib. Class IIc. Class IIId. Class 01.

5 Which one of the following is the Class III constructionmark?

a. b.

c. d.

6 Which one of the following is the Class II constructionmark?

a. b.

c. d.

7 The suggested initial frequency of user checks, relevantto a children’s ride sited in the entrance of a large store,could well be:

a. dailyb. monthlyc. every 3 monthsd. every 6 months?


63

8 Which voltage should be applied when conducting aninsulation resistance test on an electrical appliance?

a. 230 V a.c.b. 230 V d.c.c. 500 V a.c.d. 500 V d.c.

9 User checks of stationary equipment installed in industrialpremises should be conducted:

a. before useb. dailyc. weeklyd. monthly?

10 When assessing the level of safety of an electrical appliance,the most important check would be:

a. visual inspectionb. flash testingc. earth linkage currentd. the minimum acceptable values of insulation resistance?

11 Which one of the following checks should the user becompetent to undertake?

a. Combined inspection and testingb. Tests using a portable appliance testerc. Visual inspection of the flexible lead and plug fitted

to an applianced. Formal visual inspection.

12 A user of equipment should be competent to inspect:

a. terminal screwsb. socket outletsc. equipment fusesd. protective conductors?


64

13 During a formal visual inspection it should be confirmedthat the equipment is being operated:

a. at the correct voltageb. by a skilled personc. by an instructed persond. in accordance with manufacturer’s instructions?

14 If a standard 13 A plug became overheated the most likelycause would be:

a. a loose connection at one or more of the terminalsb. reversed polarity of the cable conductorsc. inadequate earthing connectionsd. the use of an incorrectly rated cartridge fuse?

15 Before isolating the supply to a computer system, theinspector should ensure that:

a. all recent data is downloaded and savedb. permission is obtained from the equipment userc. permission is obtained from the responsible persond. any static electricity is discharged?

16 When conducting a combined inspection and test, thevisual inspection should determine:

a. the nature of the tests to be conducted when theequipment is not allowed to be disconnected from thesupply

b. whether all 13A fused plugs fitted to portableappliances should be to BS4343 or BS EN6039-2

c. if any disconnected optical fibre cabling should haveexposed ends dipped in a scaling solvent in order toexclude moisture

d. whether the equipment and/or its flexible cord hassuffered any physical damage?


65

17 When conducting insulation resistance tests on newhousehold electrical appliances to BS3456 Class Iinsulation, the minimum value would be:

a. 0.5 megohmb. 1.0 megohmc. 2 megohmd. 7 megohm?

18 Which test should be carried out on low voltage electronicequipment within a computer suite?

a. Earth continuity test at 12 Vb. Insulation resistance test using the earth leakage methodc. Flash testd. Functional test with equipment on load.

19 The maximum permitted length of a 1.25 mm2 extensionlead fitted with a standard 13 A plug should not exceed:

a. 6 mb. 12 mc. 15 md. 25 m?

20 Which one of the following would not be applicable fora test on a two-core cord set?

a. Visual inspectionb. Earth continuity testc. Polarity checkd. Insulation resistance test.

21 An ohmmeter used to measure the resistance of an earthcontinuity conductor, must be capable of producing ashort-circuit current between:

a. 2 and 10 mAb. 10 and 20 mA


66

c. 20 and 200 mAd. 200 and 500 mA?

22 An insulation resistance test of a Class I household portableappliance to BS3456 is to be carried out using the earthleakage method. The maximum acceptable value is:

a. 0.25 mAb. 0.5 mAc. 0.75 mAd. 1 mA?

23 A Class II portable electric drill is to be tested. Theminimum acceptable value of insulation resistance whentested would be:

a. 0.5 MΩb. 1.5 MΩc. 2.0 MΩd. 7.5 MΩ?

24 Which one of the following is not required on an equipmentinspection and testing label?

a. Date of checkb. Identification numberc. Age of equipmentd. Re-test period.

25 Equipment found to be faulty must not be used but mustbe:

a. labelled and reportedb. labelled and withdrawn from servicec. reported and withdrawn from serviced. labelled, reported and withdrawn from service?

26 A 2-cord set is to be tested separately from the appliance.Which one of the following is not applicable?


67

a. Visual inspectionb. Earth continuityc. Insulationd. Polarity.

27 The length of a 1.5 mm2 extension lead should not exceed:

a. 10 mb. 12 mc. 15 md. 25 m?

28 A 1.25 mm2 extension lead 15 m long should be protectedby a:

a. 30 mA residual current deviceb. semi-enclosed fusec. miniature circuit breakerd. cartridge fuse?

29 IT equipment which is not constructed to BS EN 60950may be damaged by an applied voltage insulation resistancetest. The test that should replace it is:

a. a polarity testb. a dielectric strength testc. a continuity testd. an earth leakage test?

30 Equipment with an earth leakage current designed to exceed3.5 mA shall:

a. have a label permanently fixed indicating the value ofleakage current

b. have internal protective conductors of not less than0.5 mm2 c.s.a.

c. be permanently wired or supplied by a plug and socketto BS4343 (BS EN 6030-2)

d. only be used in industrial situations?


69

Appendix 5:Answers to test

questions

Answers to Appendix 3 questions

1. d 2. d 3. d 4. a 5. d6. d 7. b 8. c 9. c 10. c

11. a 12. d 13. a 14. d 15. a16. b 17. d 18. d 19. c 20. a21. c 22. a 23. b 24. d 25. b26. d 27. d 28. b 29. d 30. c31. c 32. b 33. b 34. b 35. b36. a 37. b 38. d 39. b 40. d41. c 42. c 43. d 44. a 45. b

Answers to Appendix 4 questions

1. a 2. b 3. c 4. b 5. d6. b 7. a 8. d 9. b 10. a

11. c 12. b 13. d 14. a 15. c16. d 17. c 18. b 19. b 20. b21. c 22. c 23. c 24. c 25. d26. b 27. c 28. a 29. d 30. c

71

C

Class of equipment 13–18Combined Inspection and Testing

27–36Conductor resistance 30Continuity/Insulation testers 29, 31Current 43

D

Direct contact 13, 39Duty holder 2, 7

E

Earth continuity 29, 31Electrical system 2Electricity at Work Regulations 1, 2Equipment register 8Equipment repair register 11Equipment types 18–21

F

Flash test 36Formal visual inspection 24Frequency of testing 9Functional test 36Fuses for BS1361 plugs 25

H

Health & Safety at Work Act 1, 2

I

Indirect contact 13, 39Inspection 23–26Inspection and Testing record 10Insulation resistance 34Insulation resistance tests 34–36Insulation resistance values 35

Index

Index

72

L

Legislation 1–5

M

Management of The Health &Safety at Work Act 1, 2

P

Plugs and Sockets Regulations 26Portable Appliance Tester 28, 31Power 44Preliminary inspection 28Provision & Use of Work

Equipment Act 1, 2

R

Resistance 44

Resistance in parallel 45Resistance in series 44Responsible person 7, 8, 27

S

Shock risk 37

T

Testing 27, 28Testing extension leads 33

U

Units 43User checks 23

V

Voltage 43

24231881 Elsevier Portable Appliance Testing 2003 Edition

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Transcript of 24231881 Elsevier Portable Appliance Testing 2003 Edition