RCD tripping randomly over the past few weeks

[Paul.M]

If the mcbs are on and the rcd won't reset, that could be cumulative earth leakage on start up (computers, fridge etc).

The random tripping on what you have said, the socket circuits, points towards high earth leakage just below the tripping point of the rcd until an electrical item requires more current, eg fridge or something on a timer.

It also could be damp/condensation at a socket or switch with all this heavy rain we have been getting?

As said before it needs professional investigating and I wish him good luck. Please come back and tell us how it goes.

 

[sedgy34]

My money is on the appliance he mentioned the fan clogged with ice on round it

 

[DaveyD]

I know the outside lights been turned off - but just by a SP switch?

 

[GOLLUM]

I know the outside lights been turned off - but just by a SP switch?

I have now isolated the outside light by disconecting wires from int connector so have to wait and see if it trips again, just a case of narrowing down possible cause one by one.

 

[GOLLUM]

Think i might have narrowed it down to a 2 gang socket, the socket in question just has the washing machine plugged in to it. i tried to plug in the freezer to same socket and it trips yet when i plug freezer into its original socket it fine, yet when i plug the washing machine into it it fine as well. I have a spark coming round on Monday so at least he has a starting point.

Cannot understand why it trips when i plug in freezer but not the washing machine, if it was a fault with the freezer would that not trip it when plugged into its original socket. weird

 

[GOLLUM]

It is defo the freezer causing the problem as i put both the washer and the freezer on ind RCd's and the last two trips of the main rcd the washer has been ok but freezer rcd tripped as well. So now i need to find someone to look at that,i have looked at compressor and no damp there so no idea what the problem there is.

 

[telectrix]

new freezer?

 

[GOLLUM]

You got to be kidding its a 2k usa type, and believe it or not works perfectly apart from blowing the god dam rcd. I know somwone local who services them so il just have to spend Sparkys money on that.

new freezer?

 

[Darkwood]

Remember here Gollum your confusion has arised from the simple fact you can plug the freezer in and it may not trip, but the freezer has a control circuit and may not call the compressor for hours so can be misleading, some freezers have more complex controls too so can hide the fault until certain criteria is met e.g. some models have heating coils to maintain the freezer has differing temp as the fridge all from one compressor circuit.

 

[kenny james]

have you considered having the freezer put onto its own dedicated circuit run seperately from the consumer unit?.

 

[GOLLUM]

Remember here Gollum your confusion has arised from the simple fact you can plug the freezer in and it may not trip, but the freezer has a control circuit and may not call the compressor for hours so can be misleading, some freezers have more complex controls too so can hide the fault until certain criteria is met e.g. some models have heating coils to maintain the freezer has differing temp as the fridge all from one compressor circuit.

Thanks for your replys,

Yes i understand that the appliance does use the compressor and heater on demand but it trips the RCD very random, sometimes twice in a couple of hours and as now has not tripped it since Sat evening so it must be a intermitant problem in the appliance and not everytime it is using the compressor or defrost heater.

I have contacted Smsung and am awaiting there reply.

 

[Adam Monkhouse]

Hi there,

iv just done a second fix on a house and installed a dual rcd board and the downstairs lighting circuit keeps tripping the rcd. I have done all the dead tests and everything is fine on paper but as soon as i turn the light on form any downstairs switch it trips the rcd. circuit stays on with out a lamp installed and switches all work fine but as soon as i put a load on it trips straight away!! went to first light and disconnected the leg feeding the other lights and also diconnected the leg from the DB to the first fitting put a new trailing lead straight into the db and it still tripped!! Need some help on this one guys.....head is battered!!

 

[kenny james]

hi adam,

sounds as though you have the classic problem of a borrowed neutral were the upstairs lighting shares the same neutral for downstairs lighting this will happen if you have the upstairs and downstairs circuit breakers on seperate rcd's on your dual board.

 

[Darkwood]

i would firstly divide the circuit up downstairs you may have a trapped or damaged cable, this can lay unoticed till load is applied so its down to IR tests and dividing the circuit till it stops tripping i assume from the fact you second fixed it you also first fixed too and you haven't got any crossed neutrals in the board between the 2 rcd's which again im assuming you have in the board.

 

[technospark]

See the following analysis
1.Within your distribution board there are 2 types ofd protection MCB and RCD.
2. The MCB measures load and trips out if the circuit is overloaded.
3. The RCD measures leakage to earth on any of the MCB protected circuits downstream of it.
4. The RCD monitors the current going up the positive and compares it with that returning down the negative, and discrepancy and it trips . The threshold for it to trip is 30 milliamps leaking away to earth so it does not take much.
5. Remember that although the RCD is a double pole device the MCBs are just single pole so all the neutrals downstream of the bank of MCBs in the db. are commoned.
6. The RCD will trip if the total leakage to earth exceeds 30 ma. from either L to E or N to E or a combination of the two.

Therefore a tripping problem can arise from a number of appliances on the circuits downstream of the MCBs each with a small leakage to earth giving a cumulative earth leakage in excess of 30 ma.


Also note that a double insulated appliance (no earth wire) will not trip the RCD unless the electricity is leaking away through a body!!!! or owing to water ingress.


Most electricians find this sort of problem a nightmare and try to run away from it or approach it on a trial and error basis but there is no substitute for testing out each circuit and appliance with an insulation resistance tester which applies a 500 or 1000v spike to check the appliance/circuit.

Apart from the surge arrestors the other common fault is water leaking into something, often a motorised valve, a problem within the boiler, a shower pump, central heating pump etc. If the pipework is copper look for greenish blue staining, crystallisation etc.


The type of distribution board which you probably have is notorious for this sort of thing and in the section of the industry we work in (commercial landlords/ housing associations etc) we always now use a distribution board where the earth leakage and overload protection is combined in a discrete unit for each circuit ( known as a RCBO board) In that way at least if there is a fault on one circuit then only one circuit trips off. It is less troublesome and makes diagnosis much easier. RCBOs are available for your board at around £30 each and if all else fails my next move would be to reconfigure the db with RCBOs

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