RCD trips when back of fridge touches copper CH pipes

[dave2506]

Hoping for a bit of advice please so I can call the right person to fix a problem.

RCD tripped overnight and have isolated the cause to be when the back of the fridge freezer touches the copper central heating pipes that run behind it. This is because it only happens when the fridge is pushed back into position and is due to contact, rather than pressure on the socket for example. Worryingly, there appears to be carbon deposits on both the pipes and back of fridge where they have touched.

The fridge has been in this exact position for over 2 years so it seems odd that this has only just happened. Basically, please could someone advise whether this sounds like a fault with the appliance or the house electric wiring as I want to call the appropriate tradesman to fix the problem. My gut feel is it's the appliance but would appreciate a more educated opinion!

 

[winston1]

Appliance.

 

[EFLImpudence]

Do you mean a faulty appliance which is not actually earthed - until it touches the pipe?

 

[dave2506]

I'm not sure. As far as I'm aware the earthing to the appliance is fine. If there were an issue with the earthing in the ring main, would it earth to the pipes behind? The obvious answer is yes I suppose but why would that, on its own, cause the RCD to trip?

 

[EFLImpudence]

I was referring to winston's curt reply.

If the machine is faulty it should trip the RCD on its own as the case should be earthed.
If it only trips the RCD when it touches (presumably) earthed pipes, that would indicate the machine is itself is not actually earthed.

 

[stillp]

Sounds as if the fridge has an insulation fault and is not properly earthed, which might be a fault in the appliance or the CPC in the ring might be faulty.

 

[chivers67]

Bit of a strange one. I'd check the socket it's plugged into first.

 

[flameport]

It's probably a fault with the appliance, but that requires two separate failings - the fridge is not earthed and there is a fault with the fridge causing the rear metal parts to become live.
The lack of earth could be due to the appliance or a fault with the socket it is connected to. If the socket has no earth, other sockets may also be affected. It would be dangerous to use other appliances in those sockets.

Less likely but not impossible is that the pipes have some voltage other than earth on them and are being connected to earth via the fridge, in which case the fridge is not faulty but something else is. Also a dangerous situation.

You should get someone to check the socket that the fridge is connected to as well as the fridge itself, and that the pipes behind the fridge are actually at earth potential.

 

[dave2506]

Thank you for your replies. I think I will call a local electrician first to investigate the wiring and pipes, especially if it is a problem that may affect other areas of the house. It may still turn out to be the appliance but 2 faults in a fairly new appliance seems odd.

I will report back with the cause once resolved.

 

[AdrianUK]

It is also possible that the fridge itself is not faulty, but another appliance connected to the ring is.

Consider the scenario that the earth cores in the twin & earth forming the ring are not connected to the earth terminal in the consumer unit. If another appliance on the ring develops a fault it could liven up the 'earth' conductors (and hence the case of the fridge) until the fridge becomes earthed by touching the water pipe.

In fact it may not even be faulty appliance at all, just an accumulation of earth currents on the ring (from devices with filters, like PCs) coupled with a bad CPC in the ring - the fridge completing the connection to true earth via the water pipes.

The are many scenarios which could explain this. Hopefully you'll have a visit from a knowledgeable spark who can quickly identify the problem.

 

[SteveP86]

Would be nice for an update once resolved. Too many threads just seem to stop with no resolution.

 

[OwainDIYer]

Would be nice for an update once resolved.

or even so we know the OP is still alive ...