Weird MCB trip

[gbasl0]

Had a call from wife the MCB tripped and each time she went to reset it instantly tripped again.
When I got home I traced it to my wine fridge. Strange thing is I have had this switched on for at least 3 years. More strange if I plug it into a different socket on the same circuit it does not cause the MCB to trip !!
The only thing I can think of is the socket has suddenly gone faulty or the cable to the scoket has suddenly develeoped a leaky earth - but I do not understand how this can suddenly go wrong? The socket is in a cupboard and never gets touched, the wiring is under the floor and there has been no work to affect the wires?
I tried plugging my printer into the socket that the fridge trips on but the printer still works in that socket - so I am very confused now??!!
Any ideas?
I'm going to try replacing the scoket with a new one and if that doesn't work I think I will have to run new wires to the socket but that will be a real pain! I cannot see how it could be the fridge itself since it does not trip in another socket on the same circuit - plus it has worked for last few years.

 

[phatboy]

I think you are getting a bit ahead of yourself talking of replacing the cabling.

I would isolate the circuit, and remove the socket front. Check for loose connections. Regardless if there are or arent any, remove the socket totally and check the terminals on the back for any damage, and also try to check the front.

Also worth checking the plug on the wine fridge, it might be slightly dodgy, and over time has got worse, and damaged itself or the socket, or both.

It seems very unlikely the fixed cabling would be faulty

 

[Taylortwocities]

The only thing I can think of is the socket has suddenly gone faulty or the cable to the scoket has suddenly develeoped a leaky earth -

A leaky earth won't cause an MCB to trip. It may cause an RCD to trip though.

Does the device that trips have a button on it marked "TEST"?

 

[gbasl0]

apologies for confusion - yes it was RCB that tripped not MCB (now you know how little I know!).
I think I found it - the wires behind the socket are chaffed, in fact I can see the wire in the Live cable as plastic covering is cut through. I assume that even though it is in a hidden and untoched place the wires were probably tight on a rough edge and slowly over time this edge cut through the wire plastic cover? Anyway now looking at putting tape over the chaff to recheck. It's a very tight spot and wire disappears behind a built in cupboard then goes under floor so unable to see what wires were caught on and can only pull an inch or two out. Not sure what to do if this does not work.

 

[wingcoax]

DO NOT put tape over, can you pull a little more cable out and re terminate?
As a last resort use heat shrink sleeving of the correct colour over the core/s

 

[gbasl0]

fortunately I cannot pull any more cable out, very restricted.
I did put tape on but still have same problem.
My logic was flwaed anyway
- why would the socket work for other appliances eg I put kettle in which I believe is high drain and it works without tripping. This would imply the wine fridge has a fault not the socket - but again why when I plug the fridge (via extension cable) into another socket does it work without tripping (the other socket is on the same circuit obviously with same RCB).
I cannot see the logic behind the issue, it makes no sense?

 

[mysteryman]

Check the appliance first - it's easier and more likely. Could be condensation somewhere in the fridge.

 

[gbasl0]

..but it does not make sense why would it work plugged into another socket? If the appliance is faulty it would trip in any socket. That is what I do not understand

 

[Spark123]

Check your extension lead has all 3 cores connected, if it doesn't then cut it up.

 

[Taylortwocities]

apologies for confusion - yes it was RCB that tripped not MCB (now you know how little I know!).

Its an RCD or an RCCB, not an RCB.

Untitled

• Taylortwocities
• 27 Mar 2010
• 43

 

[gbasl0]

Yes RCD not RCB
OK - so I have tried plugging the fridge into 3 different extension leads all of which work in other socikets, but plugging the extension lead (with fridge connected) into the original socket and it trips!! However other appliances in the same socket (eg kettle) do not cause a trip.
I have tried changing the scoket face, and also the firdge plug but still same symptoms.
It appears to be combination of fridge and socket - socket ok with other appliances, fridge ok in other sockets.
Does not make sense to me.
Can the fridge have very minor fault not big enough to trip the RCD, and socket also have minor problem not big enough to cause a trip but put the two together and you get a trip????!!
Very frustrating as wires are so buried behind socket as will be nightmare to re-wire.

 

[JohnW2]

OK - so I have tried plugging the fridge into 3 different extension leads all of which work in other socikets, but plugging the extension lead (with fridge connected) into the original socket and it trips!! However other appliances in the same socket (eg kettle) do not cause a trip.

Are you sure that the other sockets you've plugged the fridge into (via extension leads) are protected by an RCD?

Kind Regards, John.

 

[gbasl0]

Yes - it is very weird. My main box has 2 RCD's one for downstairs and one upstairs. I traced the trip by switching off individual circuits until I found which one was tripping. In that room there are a number of scokets - the one that fails with the fridge as well as others. I plugged a light into one of the others just to check it is on the same circuit and it did go off when I switched the circuit off. The fridge does work in the other socket on the same circuit protected by the same RCD !! AAARrrghh !

 

[JohnW2]

Yes - it is very weird. My main box has 2 RCD's one for downstairs and one upstairs. I traced the trip by switching off individual circuits until I found which one was tripping. In that room there are a number of scokets - the one that fails with the fridge as well as others. I plugged a light into one of the others just to check it is on the same circuit and it did go off when I switched the circuit off. The fridge does work in the other socket on the same circuit protected by the same RCD !! AAARrrghh !

What you are describing is, indeed, very weird. When that happens, it's often because "there's something we're not being told", but it's hard to think of what that could be. It obviously makes little sense that the same fridge can trip the same RCD via the same circuit when plugged into one socket, but not when plugged into a different socket on the same circuit. Are you absolutely certain that the extension leads you used to plug the fridge into other sockets did have satisfactory 'earth' (CPC) connections (e.g. that they are not 2-wire ones intended for outdoor double-insulated garden tools)? If they weren't connecting the 'earth', that could result in what you're seeing. I suppose it's not possible to plug the fridge into a different socket without using an extension lead, is it? .. and do I take it that nothing (other than the fridge) has ever tripped the RCD when plugged into the 'fridge socket'?

Kind Regards, John.

 

[securespark]

Yup, get checking that lead to make sure it's correctly wired, then move the fridge and plug it in direct to the other socket.