Sparks Electrical News June 2018

CONTRACTORS’ CORNER

7

A SIMPLE TESTER ANY ELECTRICIAN CAN MAKE

T o test an electrical installation, an electrician needs to use test equipment such as an earth leakage tester, loop impedance tester, pro- spective short circuit tester or an insulation tester, amongst others. There is another way: A ‘test plug top’ is a simple tester that any electrician can make up. At the back of the test plug top, there are test points, which make it possible to determine different values and allow the registered person to perform different tests as per the Certificate of Compliance (CoC) requirements. Let’s look at SANS 10142-1 (Edition 2): 8.6 Testing [Certain tests shall not be carried out in hazardous locations. Due to the characteristics of the intrinsic safety features of equipment, such equipment can be damaged by certain tests. Certain tests might be im- practical in existing installations already under power.] 8.6.3 Resistance of earth continuity conductor Use a resistance meter to measure the resistance of the earth continuity conductors between the con- sumer’s earth terminal and the earthing terminals of all points of consumption and switches. The values shall not exceed those given in Table 8.1. For example, a 20 Amp circuit breaker needs 0.55 Ω resistances to be functional. By using a test plug top, it will make it easier for the registered person to perform this test and he/she could save valuable time when testing an installation. 8.6.4 Continuity of ring circuits Remove both ends of each live conductor, sepa- rate them and test the circuit for continuity. Ensure that the two ends of the live conductor are connect- ed to the same terminal after the test (see 6.6.1.13). After separating the two conductors (live and neutral) it would be easy to determine a break in the ring circuits by using the test plug top to test back to the distribution board. This saves time by determining the position of a possible break without the unnecessary opening of socket- outlets. Remember, the size of the conductor may be reduced in ring circuits and, therefore, this test is important as it eliminates the overloading of the reduced conductors. 8.6.8 Insulation resistance NOTE 1: Before power is connected to any new or altered circuit, the test for insulation resistance should be carried out to ensure there are no short- circuit or high impedance faults in the installation, and that it is safe to energise. NOTE 2: In the case of existing installations where the power may not be switched off from certain circuits in order to carry out this test, the fact that the circuits are subject to the supply volt- age can be regarded as evidence that the insula- tion resistance is compliant. 8.6.8.1 When carrying out insulation- resistance tests; a) Use an ac or dc voltage of at least twice the nomi- nal voltage, with a minimum of 500 V. NOTE: The working voltage is taken as the maxi- mum of the voltages measured. a) In the case of ac, between each phase conductor and either the neutral or the earthing conductor, and b) In the case of dc, between positive and negative

possible to do this with or without power, and, at the same time, you will also be able to determine that a socket-outlet’s tube makes proper contact with a plug top. Remember that special care needs to be taken when testing with the power on. Using the test plug top will reduce the time spent testing all the socket outlets in an installation because it’s not necessary to open each one – and, at the same time, confirming that the socket outlets and circuits are safe.

conductors. b) Ensure all fuses are in place and switches and circuit-breakers are in the closed positions. Loads may be disconnected. NOTE: To prevent damage, ensure that voltage-sensitive electronic equipment such as dimmer switches, touch switches, time delay devices, power controllers, electronic starters for fluorescent lamps, earth leakage units, surge arresters and certain appliances are disconnected so that they are not subjected to the test voltage. Reasonably safe To perform the above-mentioned tests, the socket-

outlets must be opened; and, in the case of new installations, it is possible to perform these tests without a test plug top (8.6.8.1 and 8.6.8.2). How- ever, when older installations need to be certified as reasonably safe, using the test plug top will eliminate the need to open socket-outlets and this will prevent any damage to the client’s struc- ture – such as paint, plaster, tiles, etc – that can happen when opening the socket outlet for the inspection test. In section 4 of the Certificate of Compliance – Inspection and Tests, item 16 asks for the testing of ‘all switching devices, make-and-break circuits …’ Now, using this easily made ‘test plug top’, it’s

By Chris Koen, Regional Director, ECA(SA) Highveld Region

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