insulation resistance test

[pevvers]

Easy, main switch off, all MCB's closed or fuses in place, lead with croc clip on both ends from neutral bar to busbar, or if this cannot be done, a nice bit of single between the neutral bar and the outgoing side of any MCB, seeing as they're all connected through the busbar it matters not which one.

This is entirely acceptable for periodics, with limitations noted. You can't always know what sensitive equipment may be hiding here and there, i.e. alarm spurs, TV boosters, so I always go down this route myself.

A new installation should have been tested way before all the final circuits were terminated anyway, so you wouldn't have to think about RCD's in line...

 

[dochisholm]

am i right in thinking that with L=N linked and testing to earth wont damage standard 230 kit even when testing at 500v

 

[pevvers]

That is indeed correct, I have done this test on complete 3 phase boards in offices with all IT equipment plugged in and have never had any problems.

You may be shocked by the low value that you find on most installations though, but if you can remember that parallel paths that you are testing lower the overall insulation resistance (formula 1/Rt=1/R1+1/R2+1/R3) then this will prove that it is correct.

 

[telectrix]

should be OK but if in doubt use 250v.