rcd tripping

colshaws · Nov 1, 2011

Hi All
Called in to see a friend today and was asked to check out an rcd fault. The house has a 16th edition board with kitchen, downstairs and upstairs sockets on the rcd side,all on 3 seperate 32A mcb's. He regularly has the rcd trip out which resets straight away and then trips out about 11/12 hours later, by disconecting appliances he has narrowed it down to a socket feeding a fridge freezer in the kitchen/diner.There are 2 sockets in the kitchen/diner that are on the downstairs ring ( not kitchen) on one socket he has an american style fridge freezer, on the other the the offending fridge freezer, or so I thought. If he plugs the offending fridge into the same socket as the american fridge freezer the rcd will trip after the 11/12 hours but if he plugs the offending fridge into a socket in the hall which is on the same ring via an extension lead the rcd does not trip (been ok like this for over a month). I have ramp tested rcd, checked I.R and R1-R2 on circuit and all good. I dont have an earth leakage clampmeter to test appliance but I dont understand why it trips if direct into socket but not if plugged into extension lead to a different socket on same ring. THe socket supplying the fridge has been replaced and I checked the wiring to make sure all was ok. Any ideas

Richard Burns · Nov 2, 2011

Just some ideas to think about:

Have you IR tested the fridges/freezers (probably at 250V) this may highlight the problem.

From your description there may be a problem in the supply cable for the fridge, if it is in the local socket the cable may be at a different angle than when it is stretched out to the extension.

The 11/12 hours delay maybe a problem when an auto defrost / frost free control operates.

I think there is a recent thread on here about Fridge freezers tripping RCDs but cannot remember the outcome.

MarkieSparkie · Nov 2, 2011

A PAT test of the offending fridge/freezer may reveal an insulation breakdown. The sort of event you are describing is typical of a compressor whose insulation is breaking down when it gets hot and this situation is usually due to refridgerant leakage over time from the cooling system. This means the compressor has to work harder for longer to do the required cooling, hence the compressor gets hotter than normal. Eventually breaking down the compressor windings insulation, this tends to happen gradually with the first signs being the RCD dropouts after extended periods of operation.

mogga · Nov 2, 2011

MarkieSparkie said:
A PAT test of the offending fridge/freezer may reveal an insulation breakdown. The sort of event you are describing is typical of a compressor whose insulation is breaking down when it gets hot and this situation is usually due to refridgerant leakage over time from the cooling system. This means the compressor has to work harder for longer to do the required cooling, hence the compressor gets hotter than normal. Eventually breaking down the compressor windings insulation, this tends to happen gradually with the first signs being the RCD dropouts after extended periods of operation.

in other words Go to currys n get a new fridge,freezer
WHY O WHY O WHY do people allways insist "it must be the wiring thats at fault I NEED to test this and test that When its been proven buy unplugging (90% of the time) that the faulty appliance trips RCD had this god knows how many times even a 2 day old washing machine ( cable inside loose and rubbed against case)
Fridges freezers washimg machines ,irons kettles are first suspects but sometimes ok when plugged in but run through programme and HEY PRESTO this is 4th thread today same thing same advice

colshaws · Nov 2, 2011

I agree it is most likely to be the appliance but why does it not trip the rcd when plugged into extension lead.

Chr!s · Nov 2, 2011

If it has a defrost timer you could place a flat screw driver and turn the dial until it clicks, its now in defrost mode, and hopefully trip(the elements may be down to earth)

Regards Chris