What Tests Should Be Carried Out on Electrical Installation? - Lceted

TESTING OF ELECTRICAL INSTALLATION IN BUILDINGS

It is good to test the electrical wiring of a building after the wiring is completed. Electrical installation of buildings should satisfy at least the four tests which are discussed further.

 

How to do an insulation resistance test?

Test for insulation resistance:

This test is made with all links in place, all lamps in position and all switches on. The insulation resistance is measured between the earth and the whole system of the conductor or any section thereof. The insulation resistance of the installation in megaohm should not be less than 50 divided by the number of points in the circuit except that it need not exceed 1 megaohm for the whole installation.

 

How to do a Test for resistance between the conductors?

Test for resistance between the conductors:

When making this test, all the switches must be on but the lamps and other loads should be removed. This test is made between all the conductors connected to one pole (or phase conductor of the supply) and all the conductors connected to the other pole (or neutral phases of the supply). Leakage at cable ends is one of the common causes of low reading so before this test, care should be taken to see that the switches, etc. are clean. The result of the test shall not be less than the one specified in the insulation resistance test with the load on as stated above.

 

How to do the Earth continuity test?

Earth continuity test:

The total resistance measured from the earth electrode to any point in the earth continuity conductor in the complete installation should not exceed one ohm.

 

How do Check the polarity of single pole (SP) switches?

Checking polarity of single pole (SP) switches:

The following checks are needed for the polarity of single pole switches:

(a) In a two-wire installation, all non-linked single pole switches should be checked to see whether they are all connected to the phase conductor. (This will ensure total cut off of the current when the switch is in the off position.) It is an important check.

 

(b) If the installation is three-phase (four-wire installation), then a test should be made to verify that every non-linked single pole switch is fitted to a conductor connected to one of the phases and that any two of the phases are not exposed within the specified distance of two metres. (This ensures that there is no chance for a phase-to-phase connection.)