Insulation Resistance Test for FICA

[rob1993]

Hi guys sorry for posting as I know there is a lot of posts similar to this.

my problem Is for my trade test I am a little confused about insulation resistance test. I know most of it for example

lock off at main switch
remove all sensitive equipment
test between live-neutral live-earth earth-neutral
make sure results are okay.

the things im not sure of are when testing the whole board and it has RCBO's In it do I leave all RCBO's on and just disconnect earth and neutral links and test at main switch?

if testing individual circuit do I switch RCBO off and then again disconnect earth and neutral links and test at outgoing of RCBO? or do I also need to disconnect the wiring of the circuit?

I have also heard people speaking about disconnecting the main neutral why would this be needed?

thanks for any help.

 

[Octopus]

Do not, and I repeat do not IR the circuit with the RCBO's or any loads connected!

 

[rob1993]

yeah so either way I need to disconnect the earth and neutral links! but when testing individual circuit do I need to take out the wiring from the RCBO?

 

[Octopus]

I wouldn'try a global IR on a board with RCBO's

You have to remove the cables from each RCBO in turn.

 

[rob1993]

okay so your saying to take out the cabling from the RCBO's when doing the test?

I remember at college being told to do a global test even with RCBO's just cant remember what needed disconnected

 

[Plonker 3]

Yes disconnect all electronic loads, that includes anything at source.

Think how a RCD/RCBO works.

 

[rob1993]

okay thanks. what about disconnecting the main neutral? is this ever needed?

 

[Plonker 3]

No, simply disconnect each individual cable from the DB. A lot safer than disconnecting the incoming neutral.

 

[trev]

You're going to test on the load side mate with everything disconnected so no.

 

[rob1993]

okay thanks again, what if I am asked to test the whole installation? what would be the best way to do this?

 

[Octopus]

With a RCBO board, if you do this

a. You will get very odd unreliable readings

b. You may ruin the RCBO's

c. Decline to do it for the 2 reasons above

 

[Plonker 3]

okay thanks again, what if I am asked to test the whole installation? what would be the best way to do this?

Test each individual circuit as you would normally do.

 

[Engineer54]

Unless you are just doing a quick installation check, a global IR test is pretty pointless these days!! I'd want to see IR test values for each circuit recorded on any official test certificate, not a pointless global IR value that basically tells you little and is useless as an indicator of say, a particular circuits deteriorating insulation circumstances over a period of time, that can otherwise be clearly seen when comparing previous circuit test certificate values!!