Global Insulation Resistance & RCBO's

[m4tty]

Hi,

If you wanted to do an Insulation Resistance test on the whole installation at once (domestic) and there were RCBO's, is this test still possible and will it damage the RCBO.

Thanks

Matt

 

[revjames]

As you would have to subject them all to 500V then yes. 250V would be ok

 

[tom1]

would shorting L and N and testing to earth damage them?

 

[m4tty]

Hi thanks for replying do you happen to know if when doing IR testing at 250v are the results as good as 500v results. Are the results far apart when comparing 250V/500V?

Im finding it hard to explain what I mean so if you cant understand what im on about dont worry

Cheers

 

[sellers]

yes there is a difference, you have to test at twice normal voltage and you will notice the difference in Megohm when doing so.

 

[nicks electrix]

The regs state where possible you should do the IR test at 500v, where not possible because of voltage sensitive items you can use 240v but this should be noted on certs. If i test at 240v my megger reads >99.9Mohms if all clear. If i test at 500v my megger reads >299Mohms.

 

[vandalay]

Could you not link out the RCBO in this situation?

 

[m4tty]

Suppose you could but sorry I was meaning if the cu had more than just a few maybe if all circuits were covered by RCBO's

Cheers

 

[PC Electrics]

On some manufacturers instructions for RCBOs it says that if you IR test with the RCBO still connected you can:

1. get false (low) readings due to the electronic section, and

2. possibly damage the RCBO.

Ergo, a true reading of circuit IR can only be obtained by disconnecting the RCBO.

Spotted this recently on the instructions for an MK RCBO I was fitting.