How to fix an RCD fused spur that wont reset

ZeroTools · 6 Jun 2019

Due to some unusual wiring by the previous owner, there is a pair of outdoor sockets wired into a 13A RCD fused spur in my kitchen. Recently the weather cover failed on one of the sockets resulting in water ingress which tripped out the main RCD on my consumer unit. After fixing it and resetting the main RCD, the RCD on the fused spur in the kitchen will now not reset (indicator stays red). The spur is one of these: https://www.screwfix.com/p/british-general-13a-rcd-fused-spur-white/8250P

This may seem like a stupid question, but can I just replace the fuse to sort it? I assume its a standard 13A fuse I replace it with in that case?

AndyPRK · 6 Jun 2019

if you have a 30mA RCD in the CU

you could replace that whole plate with an FCU.

https://www.screwfix.com/p/british-...le-switched-fused-connection-unit-white/86116

you could try replacing the fuse, but I woudn't hold out much hope

sure the outdoor socket is dry now?

ZeroTools · 6 Jun 2019

AndyPRK said:
if you have a 30mA RCD in the CU

you could replace that whole plate with an FCU.

https://www.screwfix.com/p/british-...le-switched-fused-connection-unit-white/86116

you could try replacing the fuse, but I woudn't hold out much hope

sure the outdoor socket is dry now?

I dont have a 30mA RCD in the CU. The fused spur is running off the 32A RCD for the sockets (which is what tripped originally). Pretty sure the sockets are dry, they just popped open one day when it was raining so it wasnt gathering water over a long period. Plus it's been months since it happened and the CU RCD hasnt blown since.

AndyPRK · 6 Jun 2019

Ok. So the 32A is probably an Mcb.

In which case the fuse could well of blown. Yes replace the fuse

EFLImpudence · 6 Jun 2019

I think more clarity is required as to what tripped in the CU. Picture?

Water in a socket will not cause a fuse to blow nor an MCB to trip.

Also, if the outside sockets are still wet or an original fault is still present then the RCD FCU won't reset.

flameport · 6 Jun 2019

ZeroTools said:
will now not reset (indicator stays red).

Red is on, so it has no power, most likely due to the fuse blown.

ZeroTools · 7 Jun 2019

EFLImpudence said:
I think more clarity is required as to what tripped in the CU. Picture?

Water in a socket will not cause a fuse to blow nor an MCB to trip.

Also, if the outside sockets are still wet or an original fault is still present then the RCD FCU won't reset.

As per AndyPRK's correction, it was a 32A MCB on my CU that tripped out (my mistake in the OP). The one for all the sockets in the house. When I first reset it, it tripped out again straight away, so I went round the house and switched off everything plugged into a socket and reset it again. This time it stayed on so I went around the house again turning things on one at a time, assuming I had a faulty appliance somewhere which would trip it again when switched on. With everything switched back on it still didnt trip, which was when I thought to check the outdoor sockets. The weather cover was open and it was chucking it down with rain, at which point I checked the RCD on the fused spur and found it was tripped. I covered the sockets up, waited a few days for them to dry out and tried to reset the RCD but it wouldn't, and that's how it's been ever since (now months later). There's no 'pop' when I press the reset button to suggest it's tripping again, it just wont reset to black at all. I agree that a lot of this is inference, but it seems too coincidental to be anything else.

JohnW2 · 7 Jun 2019

ZeroTools said:
As per AndyPRK's correction, it was a 32A MCB on my CU that tripped out (my mistake in the OP). The one for all the sockets in the house. When I first reset it, it tripped out again straight away, so I went round the house and switched off everything plugged into a socket and reset it again. This time it stayed on so I went around the house again turning things on one at a time, assuming I had a faulty appliance somewhere which would trip it again when switched on. With everything switched back on it still didnt trip,...

OK, so, months ago, something (unknown) caused the MCB to trip twice, but do I take it that this has not happened since?

ZeroTools said:
.... which was when I thought to check the outdoor sockets. The weather cover was open and it was chucking it down with rain, at which point I checked the RCD on the fused spur and found it was tripped. I covered the sockets up, waited a few days for them to dry out and tried to reset the RCD but it wouldn't, and that's how it's been ever since (now months later). There's no 'pop' when I press the reset button to suggest it's tripping again, it just wont reset to black at all. I agree that a lot of this is inference, but it seems too coincidental to be anything else.

Most (all?) RCD FCUs and RCD sockets will not reset if they do not have power. Hence, as has been said, if the fuse in an RCD FCU blows, it will usually not reset. Have you tried replacing the fuse yet?

Of course, if the fuse is blown, then something caused it to blow, and it may be the same thing that caused the 32A MCB to trip (the fuse having survived the first trip) - so it's not impossible that a new fuse would blow immediately you tried it, in which case you would have to seek the cause of that. As has been said, no amount of water ingress is likely to cause a fuse to blow, let alone a 32A MCB to trip.

Kind Regards, John

EFLImpudence · 7 Jun 2019

JohnW2 said:
Most (all?) RCD FCUs and RCD sockets will not reset if they do not have power. Hence, as has been said, if the fuse in an RCD FCU blows, it will usually not reset. Have you tried replacing the fuse yet?

RCD FCU in question is a passive one.

Of course, if the fuse is blown, then something caused it to blow, and it may be the same thing that caused the 32A MCB to trip (the fuse having survived the first trip) - so it's not impossible that a new fuse would blow immediately you tried it, in which case you would have to seek the cause of that. As has been said, no amount of water ingress is likely to cause a fuse to blow, let alone a 32A MCB to trip.

It would appear (thanks to Flameport re: red indicator) that the fuse in the RCD FCU blew and the RCD part of it did not trip and has been ON all the time.

ZeroTools · 7 Jun 2019

JohnW2 said:
OK, so, months ago, something (unknown) caused the MCB to trip twice, but do I take it that this has not happened since?

Correct.

JohnW2 said:
Most (all?) RCD FCUs and RCD sockets will not reset if they do not have power. Hence, as has been said, if the fuse in an RCD FCU blows, it will usually not reset. Have you tried replacing the fuse yet?

Not yet, I wanted to ask if it was the right thing to try before trying it!

JohnW2 said:
Of course, if the fuse is blown, then something caused it to blow, and it may be the same thing that caused the 32A MCB to trip (the fuse having survived the first trip) - so it's not impossible that a new fuse would blow immediately you tried it, in which case you would have to seek the cause of that. As has been said, no amount of water ingress is likely to cause a fuse to blow, let alone a 32A MCB to trip.

Kind Regards, John

Fair enough, and thanks for the response. Any other ideas on what could effect an outdoor socket in a way that would trip the MCB and blow the fuse? The weather covers are in a pretty poor state so I was considering replacing the sockets completely anyway. But I dont want to waste time and money if there's likely to be some other issue lurking there which would make them unuseable.

JohnW2 · 7 Jun 2019

EFLImpudence said:
RCD FCU in question is a passive one.

So it is - as I implied, I wasn't even sure that there were any! However ....

EFLImpudence said:
It would appear (thanks to Flameport re: red indicator) that the fuse in the RCD FCU blew and the RCD part of it did not trip and has been ON all the time.

I didn't realise that's what flameport was suggesting - I thought he was suggesting that a blown fuse was preventing an (I assumed active) RCD from resetting. In any event, as regards the "red indicator" ...

... does that not rather move the goalposts?

Kind Regards, John

JohnW2 · 7 Jun 2019

ZeroTools said:
Not yet, I wanted to ask if it was the right thing to try before trying it!

It would seem the most obvious thing to try - although, as I wrote before, if it has blown and the reason for it blowing persists, then the new one will presumably blow immediately (and/or the MCB will trip).

Kind Regards, John

EFLImpudence · 7 Jun 2019

JohnW2 said:
However ....
I didn't realise that's what flameport was suggesting - I thought he was suggesting that a blown fuse was preventing an (I assumed active) RCD from resetting. In any event, as regards the "red indicator" ...

Not exactly sure what you mean.

OP said RCD FCU wouldn't 'reset' and red indicator was 'still' showing.
Flameport pointed out that the red indicator means it is ON.
Therefore if there is no power to the sockets then the fuse must have blown.

ZeroTools · 7 Jun 2019

Ok, just to clarify my poor description at the start:

The indicator is showing red which is indeed supposed to be ON. If I press the 'test' button, this (from memory) should 'trip' the RCD and set the indicator to black (off). You then press Reset to turn it back on (red indicator). At the moment, neither button does anything. There is a warning that says "If red stays visible, do not use" - presumably this means the power is on but no longer protected by the RCD? Up til now I've not tested the sockets to see if they are on (appreciate that would help) as I've been apprehensive of connecting anything. I have a socket tester somewhere which I'll dig out and connect to them later. Appreciate everyones patience, as you can tell, I'm no expert.

JohnW2 · 7 Jun 2019

EFLImpudence said:
Not exactly sure what you mean. ....

I'm confused. You write ....

EFLImpudence said:
Flameport pointed out that the red indicator means it is ON.

... yet what flameport wrote was ...

flameport said:
Red is on, so it has no power....

Does "has no power" not mean "OFF", rather than "ON"? ... and, as you say, and per the labelling of the item, red means "ON".

Are people assuming that the fuse is upstream or downstream of the RCD? I was assuming the former. I also would have expected that the red/black indicator would be downstream of both fuse and RCD (i.e. indicating whether the output of the item was 'on or off').

Kind Regards, John

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How to fix an RCD fused spur that wont reset

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