insulation res. test and RCD

[psychicwarrior]

Hello folks - cheers for reading and responding (if you do).

consider a main distribution board (DB) which has a distribution circuit; the circuit is to a 2nd final circuit DB that has a 30mA 40A rcd as its main incoming switch/protective device.

insulation testing (500v, using 3 tests: n-cpc, l-cpc, l-n) the main DB first as a whole (inc. the distrib circuit to DB2), is it likely to damage the rcd on DB2 (fed by the distrib circuit) if the rcd on DB2 is 'open'?

what is the 'best practise' in this scenario for the test?

i would say best to test main DB as a whole with protective device for distrib circuit to DB2 'open'. Then test distrib circuit separately by disconnecting at RCD-end on DB2 and connecting insulation res. tester at that end?

cheers for any views

best wishes all

PW

 

[Bez]

I'm sure someone with greater knowledge than I will be along shortly, and welcome to the forum

Bez

 

[NozSpark]

As you are doing an IR test then you need to disconnect all loads or equipment which is sensitive to IR tests such as RCD's, flourescent lighting, SELV transformers, neons, lamps, boilers, etc...

so while you are doing this disconnect the incomming cable from the second DB

 

[kme]

Would concur with Noz here - the RCD "may" be damaged by insul test.

 

[revjames]

As I am fairly new to inspecting and testing having only recently done the 2391 I can admit that I have done a few tests now and afterwards gone 'whoops' as I realised RCDs were still connected and I had put 500Vdc across them on the IR tests. However none of them broke - phew!

 

[ADS]

Hi everyone

New to the forum and just want to extend this question if I could.

I'm faced with this exact scenario in January (my 2391 prac).

Would it not work to just open the main switch/rcd on db2 then

do your IR test at db1 - this will then test the distribution cable as well.

Then, on completion of these tests, IR test on the outgoing side of

the main switch/rcd (still open) to test the db2 installation.

Surely this wouldn't damage the Rcd as it's open circuit both times?

I'd appreciate your thoughts coz I have to decide which way to approach

this in my prac.

Thanks

 

[ADS]

Hello again,

Does nobody know the answer to this or do you just not want to talk to me

Got my 2391 prac in two weeksPray

Thanks

 

[revjames]

Pretty sure thats what I did on my prac back in Nov and I passed.

 

[batty]

I have never had problem insulation testing RCD's, RCBO's are different though and should not be tested through but why not test on 250 volts.

Batty

 

[Lurch]

I think in general insulation testing RCD's is to be avoided, but manufacturers instructions usually make some mention of it, generally only if it's to prohibit it though.

 

[NozSpark]

I have never had problem insulation testing RCD's, RCBO's are different though and should not be tested through but why not test on 250 volts.Batty

It's OK as an initial test to check for connected loads, but insulation testing on 230v should be carried out at 500v as required in the regs..

You should be disconnecting or linking out sensitive equipment!

 

[ADS]

I think in general insulation testing RCD's is to be avoided, but manufacturers instructions usually make some mention of it, generally only if it's to prohibit it though.

Hi,

Thanks for the replies, everyone.

So what's the best way to IR test a DB? (whole board - without doing individual circuits) -

1/ With split board RCD's (17th edition)

2/ With one or two RCBOs installed

Thanks