I replaced a couple of socket face plates - straightforward like-for-like replacements - and when I came to test the sockets, the RCD tripped. I now cannot switch the RCD on even when the individual MCBs that it protects are all swiched off no matter how often I try or how long I wait. I even tried turning of the main switch but that makes no difference. Any ideas ? Is it simply a faulty RCD ? I'm pretty p****d of as the CU is only a few months old !
Can't Switch on RCD
- Thread starter BotchItYourself
- Start date
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What make of CU is it?
I was called out to a problem recently with exactly the same situation that was a faulty RCD. I think it was energised against a fault and gave up. It was a very cheap looking make of CU that was only four months old with no name. Just a logo like a small circle and triangle of different colours, anyone know the make??
I was called out to a problem recently with exactly the same situation that was a faulty RCD. I think it was energised against a fault and gave up. It was a very cheap looking make of CU that was only four months old with no name. Just a logo like a small circle and triangle of different colours, anyone know the make??
CU is a Wylex NHRS12SL 12 way split-load adjustable board.
I was thinking Neutral-Earth fault, most likely on the new socket fitting, until I read "I even tried turning of the main switch but that makes no difference. "
If it won't reset even with no power, then I think it must be the RCD at fault.
Presumably you meant "turning off the main switch and leaving it off" while you tried to reset the RCD?
And it isn't one of those where you have to push the switch all the way to "off" before you can switch it back "on"? MEM are like that.
If it won't reset even with no power, then I think it must be the RCD at fault.
Presumably you meant "turning off the main switch and leaving it off" while you tried to reset the RCD?
And it isn't one of those where you have to push the switch all the way to "off" before you can switch it back "on"? MEM are like that.
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Yes, I left the main switch off while trying to reset the RCD.
I don't recognise the feature mentioned in your last sentence so I guess that the answer is no.
Since having the CU installed, I have had to carry out various bits of work on some circuits. One thing that I noticed was that if I was working on the socket of a protected ring main circuit, then even though the MCB was switched off, the RCD would still trip the other circuits. Is this normal ? When I tried to reset the RCD, it always took a couple of attempts before it bit. Was this a warning sign that it was dodgy ?
I don't recognise the feature mentioned in your last sentence so I guess that the answer is no.
Since having the CU installed, I have had to carry out various bits of work on some circuits. One thing that I noticed was that if I was working on the socket of a protected ring main circuit, then even though the MCB was switched off, the RCD would still trip the other circuits. Is this normal ? When I tried to reset the RCD, it always took a couple of attempts before it bit. Was this a warning sign that it was dodgy ?
JohnD said:
What I mean is, if "up" is "on" and "down" is "off", some of them trip to an intermediate position, not all the way down, and you have to push them right down before they will latch up.
BotchItYourself said:
the RCD trip is (loosely speaking) operated by an electromagnet, so if there is no electricity, it can't trip. So it sounds faulty to me.
BotchItYourself said:
Could be, the RCD would trip when you were working on the socket circuit as only the phase is normally isolated when you turn off the MCB. This means a neutral to earth fault causing enough current to flow will trip the RCD. Quite normal for this to happen.
Just wondering if it is worth disconnecting the RCD from the CU and seeing if it will reset? If it still wont then it is broken.
I know this is a long shot but check you haven't "Nicked" the cable when screwing the sockets and face plates back to the wall, i have done this and it was the smallest of " Nicks" but the RCD tripped everytime i turned the circuit on.
but the RCD is tripping in the absence of any power i.e. I cannot reset it. Also, the socket plates are (at the moment) not screwed tightly to the wall just in case they need any further attention.
I'm working on the assumption that the RCD is faulty and needs replacing.
I'm working on the assumption that the RCD is faulty and needs replacing.
Sounds to me like you have a neutral to earth fault if the rcd trips when all phases are isolated.
The only way to know for sure is to either, isolate the power completely to the rcd and see if it will reset or drop neutrals out the rcd protected neutral bar one at a time and keep trying to reset it each time the rcd will reset when the faulty circuit neutral is removed.
Think its time you get an electrician in as removing the cover off a live consumer unit is potentially dangerous.
The only way to know for sure is to either, isolate the power completely to the rcd and see if it will reset or drop neutrals out the rcd protected neutral bar one at a time and keep trying to reset it each time the rcd will reset when the faulty circuit neutral is removed.
Think its time you get an electrician in as removing the cover off a live consumer unit is potentially dangerous.
RMS said:
Yeah but the RCD would hold in even with a N-E fault providing the main switch is off, which is what the OP said happens.
No point.
If the RCD will not reset with the main switch off then isolating the RCD or removing neutrals will make no difference.
Yeah, but if the main switch is off, and care is taken, then it is not too much of a hazard to a competent DIYer.
Sounds like the RCD is knackered. First thing to try is replace the RCD. If this one still trips, you can always return it anyway.
I have myself managed to destroy a wylex RCD while testing it. Brand new board aswell it was. B****y annoying. I don't normally fit new wylex either.
I appreciate all of the comments so far; seems like the general consensus is that the RCD needs replacing.
Supplementary question: the RCD protects 3 ring mains each on a 32A MCB. What minimum rating should the RCD be ? The current one is 80A but B&Q only have a 63A in stock.
Supplementary question: the RCD protects 3 ring mains each on a 32A MCB. What minimum rating should the RCD be ? The current one is 80A but B&Q only have a 63A in stock.
I'd swap it for another 80A
see here: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331832&ts=09321&id=77076# Probably be cheaper than the orange and black shed as well
see here: http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331832&ts=09321&id=77076# Probably be cheaper than the orange and black shed as well
You will be able to get one at an electrical supplier - there is bound to be one in your town. 80A is preferable, though 63A would almost certainly do (unless you have a shower or a cooker on it - other circuits rarely run at capacity).
However, it is most important to buy the same brand. Others may fit, some better than others, but the type-testing will have been done by the CU maker with his own parts. the busbars do not always line up with different brands, even different ranges by the same maker.
However, it is most important to buy the same brand. Others may fit, some better than others, but the type-testing will have been done by the CU maker with his own parts. the busbars do not always line up with different brands, even different ranges by the same maker.
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