It is not a guide to the Regulations or a replacement for them; nor does it seek to interpret them Regulation by Regulation. It should, in fact, be read in conjunction . 17th Edition. IEE Wiring Regulations: Design and Verification of Electrical. Installations. Seventh Edition. Brian Scaddan, IEng, MIET. AMSTERDAM • BOSTON. “Give and Take is brimming with life-changing insights. “One of the great secrets of life is that those who win mo 17th Edition IEE Wiring Regulations.
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Guide to the Wiring Regulations. 17th Edition IEE Wiring Regulations (BS ). Darrell Locke IEng MIEE ACIBSE. Electrical Contractors' Association. IEE Wiring Regulations Inspection, Testing and Certification By the same DOWNLOAD PDF CONTENTS Preface Introduction: the IEE Wiring Regulations. 16th Edition IEE Wiring Regulations. Explained & Illustrated. Brian Scaddan 7th Edition. Used alongside the regulations themselves, this book is the key to safe.
Every socket-outlet adaptor us. Protection against both direct and indirect contact One method of protecting against shock from both types of contact relies on the fact that the system voltage must not exceed extra low 50 V AC, V ripple free DC , and that all associated wiring etc. SA see Appendix 3 Mthout intermediate support. F'GIi PnJ! M than one Ii'v. Iafety ommission C i l For fuabet guidance on the applkat: Nou 2.
Hoofs IHl requirements of Regulations t exceeding I j amperes. Dr alternativety. S sockes- tii! Jc 1Fi00ldomes! See B. Jamps to Iifl. The rating at the fuse shan not exceed that of the cable forming the spu r of pOInts.
The total current demand by a fused spur shall nOI[ Icxl.! Stir seeker-outlet. AilSa An. For an appliance fitted with heating elements which can be 'touched Dr into which. The switch required b, R,egularion A.. Sa ttuty be in! Dce or lumin;airce can be d. Any' conductors orcables,whlch. The lI. Dltm;, When: Brtakj g sho u ld. Nng and. S1,1I b: I9-Unn A. Q n agaln. Choke of conductof. Fla mmabmll: Segtega tlon tl f ei rcuits.
EU25 Specht I requirements for consumers' undergnlnnd wlrin,g between buildings; etc, ,, 8. R UJ-I ;9 Special reqairemenrs for he: OI wiltS and. J'ld "on!.
OF p having a h Any of the types of cablesheathed. Jtions lof taese: This requ tremel1 t.. Busbars and busbar connections on switchboards shall. NOll-armoured p. December 1' Braided travellingcables for Hfts 0. II S An 'cables. Et] I. S"tiOQ'1' B. The lype of insulation..
Uwl' wtron5 of a. Such rubber insu]aticdfkxible cables and. This regulation does nat apply to a flexible cord forminl part of 11 portable appl. Il9 Single-core c: I J Fle. Twisted twin noa-sheathedr fer the wiring o: AVO sed to be of a. J and flexTble cords in normal use are I"Te[J I r- '8. Al PnJ. U conductors and cables shall be adequately protected against any risk of med1o. Where a cabJe 'traverses a wooden jo.
S made for diversity In accordance wIth Regu'fa. J the declared or OIOD1 inal o voltage when.: B may be necessary 1. J'rs form ing' part of [he equipment of switchboards shall comply as regards:. Flexible cables and flexible t. Roors or above ceilings: Th is regulation d oes not ap'ply to pos ltlons e. H less than the apprhpriete value stated in Table B. U be taken to avotd risk of mechanical damage to the cables duri ag haodling see also Rlegu: Cables of Ijft in stallatiens.
Nun-metal-sheathed cables installed in positions duct o: Table R. Copper 0. Nen-arttmured copper or s. J'r p. TABLE 8. I Col. Q til!
Forflexible cords used as pendants. Barriers againsr. Fur rubber. S ill for a rubber.! SILl ppnrt shall not exceed ]. For cables sheathed with rubber. For gUlidance c. For a cable Installed in a heated rloor or other heated p: For cables of the lypes described in J terns [i and iji of Regulario n n. Ii Lead-sheathed. J hig. Hi 'Minera t-insulated CD pper -sheathed: R"f39 lf it i'iii necessary toinstall cables in asituation where flamm.
Keflil to th:. CQntmuous exposure uf P. J8 Tcrmmations cf rnineral-trrsu lated cables shal [be provided witb sleeves haying a temperature rating similar to that of the seals The use of heat-r.
SIJC may. Cloud uits or eond ueto rs are ins tailed in ehaanels.
This regulation doesnot. If a run ccnduit must pass from a danger area to a safe area. R cabi In damp situ. Armoured pl. Code con t. J Cables having a seamless aluminium sheath. N orIE'. Parts E and 2. A6 For the purposes of Regulations B..
Y fixed screens orbarriers. Category 2 circuits. Fire-alarm circuits. Category 1 ci.. With the exception of fire-alarm circuits. T are containcdi in: C'p 3: CP HL'R ' additi. Where term in. JJ of Idel1lifi'!: F'GIi PnJ! Y circumstances be contained in: J corn men m ul tieore cable. J ai 10w vQ. I voided. CDl'e cable rO. In preparing eopperelad aluminium conductors for cennection to. The colQur com binatlon green and ye.. SJ 7'Ul. Y Any scheme of colouring used in a. Regulation oth..
IS an altf'rn. For armoured p. A] or by painting w-ith moee coleurs.
Cop pe rei ad. PLE H. A 'Colour i. B of 3-pha8e a. Colour idel'l.. Dr three-Dhase. Q'[ or ea hie cpre.!! ThiS regulation insulated cables. Ir tbe bi[uecere is!. BA51 and Regula. DId '! I' Numbe. Hon shall. Neutral Live Neui'l'al Brown.. Uered n'ot eoh ur. J Iqtl:!. DieutrnJ cODdjuctCl! Live Neutral Earthi: H'and nell trod" are colouf. M than one Ii'v. AltemativeiYi Jtm. IlS'Ure' that the temperature or the exceed 3 kg see aiJ: The mass suspended from tire box shall aot V explosive dust.
Parr J. Cable glands shall securely retain the outer sheath or armour of the cables without damage to these. The enclosure. Boxe-s or enclos: EOfil"menie' m. The construction efterminaticns for mineral-insulated coppersheathed cables shall comply with B. Edering fluxes which. L joined. Soldering fl. II meehanical clamps and eompression-type or. Part 4. IL" Earth-continujty conductors. J 01 nts i11 non-flexlble cables shall be accessible for inspection.
For the purpose of this regulation. For joi nts irr paper-insulated metal-sheathed cables. W here joints in. CJ rtI'pl iance or flexibl: Joints in non- sockets shall securely retain all the wires the cond uctors.
S0 which are "necen. Iow-voltage systems.. Collector wires for travelling cranes or trolleys.. Protected rising-mal nand busbar systems. BJI'l Bare er l'ightly At each strain position for such wires. BS AU metal sheaths and armour 'of cables a. S6 Paper-insulated. This requirement does not apply to prefabricated t1e. Tables B. Fot short. The number of cables drawn in shall not be greaterthan the appropriate number giv.
For types of cables having largeroverall. SM and 8. IJJ ColQ ttl t. AU unused cond'Oit entries sbaH be blanked off. U be such as. For the purpeses or these Regu!. If the conduit IS used as an earthcontinuity coaduetor. Metal conduit. Part 1 sha:: U fol'rigi: II reduc. Induits andadapters or or zinc-base-alloy Br. Part 1 a.
M rna. J Type B E'O. Non [0 R. Whflre the ulie of p. I0l In situ. Flgs for US. S appropriate. Conduit s. Cables of a. ThiS' s. An removable 'covers shaU be securely fbu: Every bend formed in a concrete duct whether or not formed by' chaoneis er Iormers ref. Ois drawn to the risk 'of che: I[ times the diamete'c of the completed duct.
This requirement does B Jit pn! The resistance of the bonding conductor shan not exceed thatspecified ill Re. For short. Dr having [he Internal conduetora connected iuparaile]. IM At every joint in the external conductor! Cit ii 'where it is supplied by a. Laid direet in the ground: Such wiring. The use of cable covers I pre.. Dlcssboildd be. FQI" CIl'fn: SA see Appendix 3 Mthout intermediate support. FQf cuu. ViDI' all ojl. S" Qv. Jl covering of p. Rl3lJli of Slab! Available fWjliI If''.
Irom or below. H 03 recornmends that in ex:. Of mm l. R 0guia.
NO'TE 2. Jgauge siee. I J II" 'traffic 2 cables shea rbed wiU. In pos. W tely i. E 'oo: No limit.. Wg sn oH- with catenary' wire'.. CI' Gcne. C" over cDndutwr NyloD over cQnductor. CeiUngroses Laenpbolders with Table C.
Apparatus jlahle to cause overheating D. S and. Three-phase electrode wa: Regulation C. I Flameproof eaclosures. D'lfflP C. Intrinsically-safe o. AU appa. Non to C. I CIJf[. I see Re. Viczyttcm of apparatus shan be of t'he da: Section C C. Uydevelop under fault cenditions. C'ontBjns reC l. Di '1'UiUS overheating shaU cnmpl'y with.
U j]iari: Full details of the' thre. WJUlI B. Dhdsions D 2 are. C'xcluding im: U Fixed. ID In places where petrol-driven v6hJc1el's are stored or repaired.
Regu I'arion C. Dor level to. Q't apply to apparatus. S A ceiHng rose shan not be installed in any eireuit ope. Any shade or guard used for this purpose shall be su.. D guarded as to prevent igf'litk. This regulatioo does J1.
British g. DY ftammable materials. Where such la. The earthing terminal or every eeiBn. Z4 or o. Ilparatus "a'S a. HOOf Jevei. SO rnm lm'l11lLh! Is open. Live couducror or E. Wberever noxious Fumes are Uke'y to be emitted fn. U'I it.. NOTE' 2. Every capacitor. E1cCllrodc C.. An aute-transformer ha V iug an output in the extra-to w" voltage range shall not be used to su. J7 The. This requirement shall not app.
A time delay may be incoEpu. SC the apparatus. Rln 'enH: G When: I] that of'toti' larges't phase: Of where an.. Uirs e. Ii'equiremeilrs orR'egu. J1tted in 'the'. J agd A. NO'TI 3. Y alltholiity will be TCquIred. The parts of the. Qtheearth-eonUnuity 'conductor of the final sub-cireuit su. Je' earth-cnntinuity conducter referred to in Regulation C. Im mer setJ. CAS incoming water su. OQm confa1ning a.
Euthlng leads. S ecnon D". Connootion of earthIng Ilead with ea. This regulation does not a. OIt or in. Board for HousehoLd are ope: Q[l doesnot app: Jy toisotated metal par'tsf'efer-red to in Regnlation.
Metalwork other than current-carrying p"arts and one poinr of the secondary windrlng of. IO The co nsumer's earthing terml'naJ required by Regnlation 0.
Connections to the pipes of other services s.
NOTE 2. The bonding connections D. The instaUati: Il the premises. C'oQccrned should be C'O. Iv Sm3. Uie connection 5. Metal dips used fQr fixing cables. PJiiimcea ex.
NOI stationary appltance having heating elements which can be touched shaU be installed within reach a person usi. Wnere P. Cepper bonding! Ieads shaU be of ceoss-sectiona] area not less than Uu: Regulations D. FnunBwork of mobile equipment ' ul whicl1 elect't'icaJ ap: O'rd'er ttl obviate th.
As an aU. These s. This reqll. Jtl0n 0. S"30S2 req'll-l.: NOTIE 2. EbI51 rcqil. The earthing of the consumer's installation sha. Table D. Regulati lnS ['Lf. Nou 2. Every veltage-operated eaerh-Ieakage circuir-breaker shal] be arranged to have its operating ceil connected between the consumer's earthing terminal Which ma..! Where such a circuit-breaker is used.
J the test requirements of Regulation E. Jlaled ate to be mu. J iii Every cable sheath a. SS or D. It should have a resolution i. The instrument should only allow an earth fault to exist for a maximum of 40 ms, and a resolution of 0.
Above this circuit rating, the ohmic values become too small to give such accuracy using a standard instrument, and more specialized equipment may be required. The test instrument should not be operated for longer than 2 seconds, and it should have a 10 per cent accuracy across the full range of test currents. A typical approved test lamp is as shown in Figure 1. The Health and Safety Executive, Guidance Note 38, recommend that the leads and probes associated with test lamps, voltage indicators, voltmeters etc.
Proving unit This is an optional item of test equipment, in that test lamps should be proved on a known supply which could, of course, be an 22 An overview Figure 1. However, to prove a test lamp on such a known supply may involve entry into enclosures with the associated hazards that such entry could bring. A proving unit is a compact device not much larger than a cigarette packet, which is capable of electronically developing V DC across which the test lamp may be proved.
The exception to this are test lamps incorporating V lamps which will not activate from the small power source of the proving unit. Test lamps must be proved against a voltage similar to that to be tested. Hence, proving test lamps that incorporate an internal check i. This does not restrict such maintenance to just a yearly calibration, but requires equipment to be kept in good condition in order that it is safe to use at all times. Whilst test instruments and associated leads probes and clips etc.
Keep test gear in a separate box or case away from tools and sharp objects and always check the general condition of a tester and leads before they are used. Information required Assessment of general characteristics sections , and together with information such as drawings, charts etc. Documentation required and to be completed Electrical Installation Certificate signed or authenticated for the design and construction could be the same person and then for the inspection and test.
A schedule of test results and an inspection schedule must accompany an Electrical Installation Certificate. In order to comply with these requirements, the Regulations give a check list of some eighteen items that, where relevant, should be inspected. However, before such an inspection, and test for that matter, is carried out, certain information must be available to the verifier. This information is the result of the Assessment of General Characteristics required by IEE Regulations Part 3, Sections , and , and drawings, charts, and similar information relating to the installation.
It is at this point that most readers who work in the real world of electrical installation will be lying on the floor laughing hysterically. Let us assume that the designer and installer of the installation are competent professionals, and all of the required documentation is available. Interestingly, one of the items on the check list is the presence of diagrams, instructions and similar information. If these are missing then there is a departure from the Regulations.
How on earth can this be verified without all the information? A 30 A Type B circuit breaker CB protecting a length of 4 mm2 conductor may look reasonable, but is it correct, and are you prepared to sign to say that it is unless you are sure?
Let us look then at the general content of the check list. So, we have now inspected all relevant items, and provided that there are no defects that may lead to a dangerous situation when testing, we can now start the actual testing procedure. For main equipotential bonding there is no single fixed value of resistance above which the conductor would be deemed unsuitable. Each measured value, if indeed it is measurable for very short lengths, should be compared with the relevant value for a particular conductor length and size.
Such values are shown in Table 3. Table 3. In the case of construction sites and agricultural or horticultural installations the 50 is replaced by For example, suppose a 45 A BS fuse protects a cooker circuit, the disconnection time for the circuit cannot be met, and so a supplementary bonding conductor has been installed between the cooker case and an adjacent central heating radiator.
How then, do we conduct a test to establish continuity of main or supplementary bonding conductors? Quite simple really, just connect the leads from a low resistance ohmmeter to the ends of the bonding conductor Figure 3.
One end should be disconnected from its bonding clamp, otherwise any measurement may include Figure 3. Remember to zero the instrument first or, if this facility is not available, record the resistance of the test leads so that this value can be subtracted from the test reading. If the installation is in operation, then never disconnect main bonding conductors unless the supply can be isolated. Without isolation, persons and livestock are at risk of electric shock.
The test is conducted in the following manner: A reading indicates continuity. Figure 3. In these cases, continuity tests may have to be carried out at the installation stage before accessories are connected or terminations made off as well as after completion.
Although it is no longer considered good working practice to use steel conduit or trunking as a protective conductor, it is permitted, and hence its continuity must be proved.
The enclosure must be inspected along its length to ensure that it is sound and then the standard low resistance test is performed. If the verifier has any doubt as to the soundness of the conductor, a further test is made using a high current test instrument which has a test voltage not exceeding 50 V and can deliver up to 1. This test can cause arcing at faulty joints and hence should not be carried out if there is any chance of danger. What then are interconnections in a ring circuit, and why is it important to locate them?
Figure 4. The most likely cause of the situation shown in Figure 4. The problem arises if a break occurs at, say, point Y, or the terminations fail in socket C or P.
Then there would be four sockets all fed from the point X which would then become a spur. A simple resistance test between the ends of the phase, neutral or circuit protective conductors will only indicate that a circuit exists, whether there are interconnections or not. The following test method is based on the philosophy that the resistance measured across any diameter of a perfect circle of conductor will always be the same value Figure 4.
The test procedure is as follows: This is quite easy with sheathed cables, but with singles, each conductor will have to be identified, probably by taking resistance measurements between each one and the closest socket outlet. This will give three high readings and three low readings thus establishing the opposite legs. Record this value. The readings obtained should be, for a perfect ring, substantially the same. If an interconnection existed such as shown in Figure 4. If a break had occurred at point Y then the readings from socket S would increase to a maximum at socket P.
One or two high readings are likely to indicate either loose connections or spurs. A null reading, i. These faults would clearly be rectified and the test at the suspect socket s repeated.
This difference, due to the phase and cpc being different sizes, will not be significant enough to cause any concern. As before, loose connections, spurs and, in this case, P — N cross polarity, will be picked up. Table 4. In this case the CPC will be approximately 1. As already mentioned null readings may indicate a reverse polarity. They could also indicate twisted conductors not in their terminal housing. The examples shown in Figure 4.
It also indicates whether any short circuits exist. Insulation resistance, as just discussed, is the resistance measured between conductors and is made up of countless millions of resistances in parallel Figure 5. The more resistances there are in parallel, the lower the overall resistance, and in consequence, the longer a cable the lower the insulation resistance. Add to this the fact that almost all installation circuits are also wired in parallel, it becomes apparent that tests on large installations may give, if measured as a whole, pessimistically low values, even if there are no faults.
Under these circumstances, it is usual to break down such large installations into smaller sections, floor by floor, sub-main by submain etc. This also helps, in the case of periodic testing, to minimize disruption.
Remove any items of equipment likely to be damaged by the test, such as dimmer switches, electronic timers etc. Remove all lamps and accessories and disconnect fluorescent and discharge fittings. Ensure that the installation is disconnected from the supply, all fuses are in place, and MCBs and switches are in the on position.
In some instances it may be impracticable to remove lamps etc. Alternatively, test between each live conductor and earth in turn. For three phase systems, join together all phases and test between this join and neutral.
Then test between each of the phases. Alternatively, test between each of the live conductors in turn. Installations incorporating twoway lighting systems should be tested twice with the two-way switches in alternative positions.
Example An installation comprising six circuits have individual insulation resistances of 2. They also require special test equipment.
In consequence, the requirements for these tests will only be briefly outlined in this chapter. Site applied insulation When insulation is applied to live parts during the erection process on site in order to provide protection against direct contact, then a test has to be performed to show that the insulation can withstand a high voltage equivalent to that specified in the BS for similar factory built equipment. If supplementary insulation is applied to equipment on site, to provide protection against indirect contact, then the voltage withstand test must be applied, and the insulating enclosure must afford a degree of protection of not less than IP2X or IPXXB.
Protection by separation of circuits When SELV or PELV is used as a protective measure, then the separation from circuits of a higher voltage has to be verified by an insulation resistance test at a test voltage of V and result in a minimum insulation resistance of 0.
If the circuit is at low 41 Special tests voltage and supplied from, say, a BS transformer the test is at V with a minimum value of 0. Protection by barriers or enclosures If, on site, protection against direct contact is provided by fabricating an enclosure or erecting a barrier, it must be shown that the enclosure can provide a degree of protection of at least IP2X or IPXXB.
Readily accessible horizontal top surfaces should be to at least IP4X. An enclosure having a degree of protection IP2X can withstand the ingress of fingers and solid objects exceeding 12 mm diameter. IPXXB is protection against finger contact only. IP4X gives protection against wires and solid objects exceeding 1 mm in diameter. One end of the finger is connected in series with a lamp and live parts in the enclosure.
When the end of the finger is introduced into the enclosure, provided the lamp does not light then the protection is satisfactory.
The test for IP4X is conducted with a rigid 1 mm diameter wire with its end bent at right angles. Protection is afforded if the wire does not enter the enclosure. Protection by non-conducting location This is a rare location and demands specialist equipment to measure the insulation resistance between insulated floors and walls at various points. The requirements are: Although polarity is towards the end of the recommended test sequence, it would seem sensible, on lighting circuits, for example, to conduct this test at the same time as that for continuity of CPCs Figure 7.
Figure 7. For radial socket outlet circuits, however, this is a little more difficult. The continuity of the CPC will have already been proved by linking phase and CPC and measuring between the same terminals at each socket. Whilst a phase-CPC reversal would not have shown, a phase-neutral reversal would, as there would have been no reading at the socket in question. This would have been remedied, and so only phase-CPC reversals need to be checked. This can be done by linking together phase and neutral at the origin and testing between the same terminals at each socket.
A phase-CPC reversal will result in no reading at the socket in question. When the supply is connected, it is important to check that the incoming supply is correct. This is done using an approved voltage indicator at the intake position or close to it.
So let us remind ourselves of the component parts of the earth fault loop path Figure 8. Starting at the point of fault: In the latter case the metallic return is the PEN conductor. Overcurrent protective devices must, under earth fault conditions, disconnect fast enough to reduce the risk of electric shock.
This is achieved if the actual value of the earth fault loop impedance does not exceed the tabulated maximum values given in the IEE regulations. The purpose of the test, therefore, is to determine the actual value of the loop impedance Zs , for comparison with those maximum values, and it is conducted as follows: Consumers earth electrode I Figure 8. If a neutral is not available, e. It must be understood, that this instrument reading is not valid for direct comparison with the tabulated maximum values, as account must be taken of the ambient temperature at the time of test, and the maximum conductor operating temperature, both of which will have an effect on conductor resistance.
So, our measured value of Zs must be corrected to allow for these possible increases in temperature occurring at a later date.
This requires actually measuring the ambient temperature and applying factors in a formula. Clearly this method of correcting Zs is time consuming and unlikely to be commonly used. Table 8. Never short out an RCD in order to conduct this test.
As a loop impedance test creates a high earth fault current, albeit for a short space of time, some lower rated MCBs may operate resulting in the same situation as with an RCD, and Zs will have to be calculated.
It is not really good practice temporarily to replace the MCB with one of a higher rating. External loop impedance Ze The value of Ze is measured at the intake position on the supply side and with all main equipotential bonding disconnected. Unless the installation can be isolated from the supply, this test should not be carried out, as a potential shock risk will exist with the supply on and the main bonding disconnected.
If this value cannot be measured it must be ascertained by either enquiry or calculation. Connection to earth is made by an electrode, usually of the rod type, and preferably installed as shown in Figure 9. In order to determine the resistance of the earth return path, it is necessary to measure the resistance that the electrode has with earth.
If we were to make such measurements at increasingly longer distances from the electrode, we would notice an increase in Lid Ground level Label Earth electrode Earthing conductor protected from corrosion and mechanical damage Figure 9. The maximum resistance recorded is the electrode resistance and the area that extends the 2. There are two methods of making the measurement, one using a proprietary instrument, and the other using a loop impedance tester.
Method 1 — protection by overcurrent device This method is based on the principle of the potential divider Figure 9. In Figure 9. The method of test is as follows: What is the value of the electrode resistance and is the accuracy of the measurement acceptable?
The value obtained is added to the cpc resistance of the protected circuits and this value is multiplied by the operating current of the RCD. The resulting value should not exceed 50 V. If it does, then Method 1 should be used to check the actual value of the electrode resistance. The RCD testers used are designed to do just this, and the basic tests required are as follows: Set the test instrument to half rated trip.
Operate the instrument and the RCD should not trip. Set the instrument to deliver the full rated tripping current of the RCD. Table In all these cases and apart from conducting the tests already mentioned, it is required that the RCD be injected with a current five times its operating current and the tripping time should not exceed 40 ms.
Operating this test facility creates an artificial out of balance condition that causes the device to trip. This only checks the mechanics of the tripping operation, it is not a substitute for the tests just discussed. All other items of equipment such as switchgear, controlgear interlocks etc.
General reasons for a periodic inspection and test 1 To ensure the safety of persons and livestock. General areas of investigation Safety; wear and tear; corrosion; damage; overloading; age; external influences; suitability; effectiveness.
Sequence of tests 1 2 3 4 5 6 7 Continuity of all protective conductors. Earth fault loop impedance. Insulation resistance. Operation of isolating and switching devices. Operation of RCDs. Prospective fault current. Earth electrode resistance. Manual operation of RCDs. Protection by separation of circuits.
Insulation of non-conducting floors and walls. This could be so simple. As it is, periodic inspection and testing tends to be complicated and frustrating. On the domestic scene, I doubt if any house owner actually decides to have a regular inspection. It is usually only when there is a change of ownership that the mortgage companies insist on an electrical survey. The worst cases are, however, industry and commerce. Periodic inspections are requested, reluctantly, to satisfy insurers or an impending visit by the HSE.
Under the rare circumstances when an inspection and test is genuinely requested it is difficult to convince the client that, as there are no drawings, or information about the installation, and that no switchgear is labelled etc. If it is felt that it may be unsafe to continue with the inspection and test, then drawings and information must be produced in order to avoid contravening the Health and Safety at Work Act Section 6. A periodic inspection and test under these circumstances should be relatively easy, as little dismantling of the installation will be necessary, and the bulk of the work will be inspection.
Inspection should be carried out with the supply disconnected as it may be necessary to gain access to wiring in enclosures etc. This is also the case when testing protective conductors, as these must never be disconnected unless the supply can be isolated.
This is particularly important for main equipotential bonding conductors which need to be disconnected in order to measure Ze. In general an inspection should reveal: As was mentioned earlier, dismantling should be kept to a minimum and hence a certain amount of sampling will take place.
From the testing point of view, not all of the tests carried out on the initial inspection may need to be applied. This decision depends on the condition of the installation. The continuity of protective conductors is clearly important as is insulation resistance and loop impedance, but one wonders if polarity tests are necessary if the installation has remained undisturbed since the last inspection.
The same applies to ring circuit continuity as the P—N test is applied to detect interconnections in the ring, which would not happen on their own. It should be noted that if an installation is effectively supervised in normal use, then Periodic Inspection and Testing can be replaced by regular maintenance by skilled persons.
This would only apply to, say, factory installations where there are permanent maintenance staff. This is done on electrical installation certificates, inspection schedules, test schedules, test result schedules, periodic inspection and test reports, minor works certificates and any other documentation you wish to append to the foregoing. This documentation is vitally important. It has to be correct and signed or authenticated by a competent person.
Electrical installation certificates and periodic reports must be accompanied by a schedule of test results and an inspection schedule for them to be valid. It should be noted that three signatures are required on an electrical installation certificate, one in respect of the design, one in respect of the construction and one in respect of the inspection and test. For larger installations there may be more than one designer, hence the certificate has space for two signatures, i.
It could be, of course, that for a very small company, one person signs all three parts. Whatever the case, the original must be given to the person ordering the work, and a duplicate retained by the contractor.
One important aspect of the electrical installation certificate is the recommended interval between inspections. This should be evaluated by the designer and will depend on the type of 61 Certification installation and its usage.