insulation resistance

[oohthatslive!!]

when u test IR surely you have to take out the cable from the CU. Ive seen examples of this with a probe on the screw of the mcb and croc clip on the earth/neutral bar. When testing for example sockets, wouldnt this give a false reading? Am i doing it wrong by isolating each circuit when i do this test?

 

[comms]

Test across the whole board.
If you get a low reading then isolate each circuit and test individual circuits to find the problem circuit or you could get low IR reading because of circuits in paralell.

Am i doing it wrong by isolating each circuit when i do this test?

No it's what you feel is best practise for you, so long as it's done right.

 

[Adam_151]

You can test the whole installation as a whole, if the whole lot is above 2 meg then all is good

If you want to test the circuit in isolation, then its only the neutral you are going to have to drop out, the phase is broken by the MCB/fuse, and as long as the other two are not connected to the rest of the installation then it doen't matter that the CPC is (unless you are trying to track down some kind of weird problem)

 

[tim west]

With the main switch in the CU off (for obvious reasons= dead circuit)
the neutral should be isolated from earth so no need to drop it out, total isolation of a circuit should not be necessary unless a fault has been discovered and breaking up of the installation is necessary for diagnostic purposes.