RCCB not tripping when test button pushed

[James W]

Hi

I have a newly installed Mem2000 split load consumer unit. When first installed the RCCB tripped when the test button was pushed. I have added a new socket and now the test button does not trip the RCCB. I remember though that the first time I went to switch back on the socket MCB (after the first part of my socket change), the RCCB had tripped. After finishing the socket changes, I tested the RCCB and it wouldn't trip. I have tested all my sockets with a 13amp socket tester and they all look fine. Any idea what to test now?

Thanks in advance

James

[Andrew Gabriel]

If the RCCB has an earth wire connection, check that it is still connected (not all RCCB's have an earth connection). Otherwise, the RCCB is dead -- it does happen. It might be that you have a wiring fault with your new socket which tripped the RCCB, but that shouldn't destroy it even so.

[John Watson]

Interestingly, I have got a MEM one on my (long) list of repairs to do. Its at a relatives house, at it too does not trip when the button is pressed, nor does my RCD tester trip it.

I believe all MEM RCCBs (RCDs & RCBOs) are electronic-based devices - they almost certainly will be if they have the extra functional earth wire. These can be damaged by an insulation test (so called Megger test) on the wiring if they are left in circuit. Was an insulation test done when the CU was fitted? John

[Benjamin Aldred]

Quick pressing and releasing of the test button may not make it trip, try holding it in for a few seconds, a count of ten, to see what happens. If it doesn't trip after that, then you do have a fault on either RCCB or in the configuration of the connections.

Good luck with it.

[Chris Oates]

Wouldn't you die if trips took 10secs to pop ?

[BigWallop]

Hee Hee !!! Most certainly Chris, but I have known a couple of these things to take a little time to respond to the test facility, don't know why, just a couple that took a couple of seconds to trip on the test button but responded immediately under fault condition. That's why I mentioned it.

[James W]

Yep, tried this, that didn't work.

Well, it did trip when first installed, so I "presume" the configuration is OK. I opened it up today to check the little wire coming out of it was connected to earth and indeed it was. Im presuming (doing that too much these days) that my earth is OK, as the socket tester Im using says earth is OK.

Is there anything else I can try? Or some test to prove for sure it is the actual RCCBO that is knackered?

[BigWallop]

If all the connections are made correctly and it still isn't tripping out on the test button, then it's knackered. It is a safety device which should work correctly to its job right, so I wouldn't take a chance with it. Replace it for your own sake.

You need expensive kit to test these properly, so to find buy something like this for one job is not worth it. The simple tests you have already carried out on it prove that it is not doing what it says on the tin, so it's knackered and needs replaced.

[Christian McArdle]

If the RCBO has incoming power and doesn't trip when you press 'T', it is knackered. It should trip even if there is nothing connected to the load terminals. Throw it away.

Christian.

[Sparks]

Not sure if this is a good test, but I remember at school, if you got a plug, and connected the Neutral and the earth together, it would trip RCCBO quite nicely (without causing big bang, and sparks!

Maybe you could try this, and see if your RCCBO is truly shagged.

I would suggest you wait until this has been confirmed or flamed by some more people though ;-)