Electric Reference

an insulation resistance test is like a pressure test of the circuits. On a 230v circuit, a test voltage of 500 volts is sent down. We do this test to check for current leaks in the insulation, hence “insulation resistance test”. Current leaks could occur from anything such as old age to crushed cables

Information to consider when doing an insulation resistance test

- As 500v volts is being sent down the circuit, if the building is occupied , then all must be informed
- Remember to remove all lamps for fittings because lamps could blow and effect readings
- if it is not possible to remove a lamp from a fitting, ensure the switch is open

Ensure
- dimmer switches are removed (why?)
- Accessories with neon indicator lamps are switched off (why?)
- Pir’s are removed (why?)
- All fixed equipment isolated (ovens, tv’s, why?)
- Shaver sockets removed (why?)
- Electrical portable items are unplugged (why?)

1. Safely isolate the supply
2. remove equipment mentioned above
3. Set insulation resistance tester to 500v
4. Set instrument to 200Mohms if it is not self ranging
5. Test between Neutral & Line
6. Test between Line & CPC
7. Test between Neutral & CPC

note: lighting circuits should be tested with the switches on and while operating all 2 way switching in both positions.

note: If testing the whole board at the tails then you need the supply to the board OFF i.e its main switch and tails de-energised and the board’s main switch in the ON condition.

note: If the supply to the board cannot be removed just lock the main switch off at the board and test the whole installation from the switched side of the isolator. (Now dead/use proving unit before and after