RCD tripping problem again

[Norv]

A couple of weeks ago I posted on here about a nusiance 30mA RCD tripping problem (upstairs & downstairs sockets). I thought I found the problem, a double adaptor was faulty so I binned it. RCD tripping problem stopped. Now its started up again, so today I went through all the tests on the CU. When I got to testing the RCD it was tripping on the '1/2 x I' & the Megger kept saying 'trp' before it could give me a result. Do you think the RCD is faulty ?

When I was learning about the testing I did a couple of IR tests with the RCD still connected. Do you think that has damaged it ?

Its a Wylex CU

Cheers.

 

[luminaire]

It shouldn't trip on the 1/2 test, so it very much looks like it is faulty and should be replaced.

 

[nozspark]

Norv,

You have to turn off all the MCB's before you test the RCD to be able to tell if is faulty, as what you might have is a 20mA earth fault on one of the circuits and the extra 15mA test current is then taking it ovet the RCD's threshold.

So firstly turn off all the MCB's in the CU and then retest the RCD before you go and replace it.

 

[JohnD]

but if you have a neutral/earth fault, the MCBs will not isolate it. You need to disconnect the RCD and test on its load terminals.

 

[Norv]

OK thanks, never tested an RCD directly onto it before. Do I disconnect the live busbar & test between the live load side on the RCD & earth?

In my Meggers instructions, for testing on the auto sequence setting you have to put the red test lead on the live load terminal of the RCD & the green & black leads on the earth bar.

If the above is correct & I have done this & it tripped on the 1/2 test.

 

[Spark123]

You'd normally put black on neutral & red on phase to power the instrument, green on earth. If your instrument runs from batteries it might not matter where the neutral is connected, if at all. You'll need to read the manual I'm affraid.