RCD occasional tripping


A friend of mine rents a flat out and the tenant has just advised that the RCD tripped out whilst the tenant was on holiday (result - fridge/freezer defrosted). Apparently it has tripped on occasions before but the tenant can't remember when (and obviously decided not to bother telling my friend).
The installation has been safety checked/certified before it was re-let, and had not been a problem with the previous tenant.
How are faults like this normally diagnosed? Seems to me an electrician could come along and test it and find nothing, since its so intermittent. None of the breakers had tripped apparently.
TIA, Midge.
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Annoying I agree. The trouble with intermittent faults (if there is a fault) is that they never develop the fault whilst been tested. Sometimes you have to just accept that the RCD is perhaps a little too sensitive and replace it. If it's on the fridge / freezer circuit it may be that the 'kick in' draws too much power for the RCD and whilst it's not a fault it may be enough for it to trip.I'm sure there's some sophisticated piece(s) of equipment which you can use to bench test the RCD but at the end of the day it's probably cheaper and quicker just to replace it.
We used to have a problem with our lighting circuit - whenever a bulb expired it blew the RCD and plunged us into darkness ... we replaced the RCD with one of the same rating and never had a problem with it.
Ash
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Ash wrote:

Been there, done that, got the tee-shirt...

Could be a new device has been added so that the earth leakage current is now marginal, and the device is doing what it ought to do. Or an old one is failing. I'd go for looking at earth leakage currents first, in case something is on the way out.
Except I just googled and the testers seem to be 200 squid plus!
Andy
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Certainly the cheapest initial option - I wasn't sure whether they suffered any particular issues or not.
Ta, Midge.

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sounds like insurance fiddle

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It did make me wonder - esp as the tenant was apparently quick to try and blame the fact its an old victorian house.....

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If the fridge/freezer is on an RCD it might be worth connecting it to the other side of the board with its own less sensitive mcb (assuming that it's a split load CU of course). This may involve running a new cable depending on how it is connected to the circuits at the moment.
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Hmmmm might be worth a go I guess esp. if the alternative is to spend a few hundred quid on a sparky and find nothing......
Midge.

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You may be able to get an electrician to test the RCD for a call out fee. In my experience RCDs tend not to trip at all rather than trip too quickly (the x1/2 x1 and x5 tests)
As the tenants were on holiday when the RCD tripped then not many appliances would be running. The CH and fridge are be more likely to trip an RCD than the mains wiring having a fault in such circumstances.
The electrical inspection that was done before the place was first let should have been be a PIR test complete with insulation readings. PIRs do cost you money but you do not need a PIR with every change of tenant. A change of tenant may just need a visual inspection but that is something any clued up landlord can do.
If an PIR was done then your friend will have a certificate to show that.
Adam
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Thanks Adam.
I've since found out there may have been a general power outage in the area. Is it possible an RCD could trip on power up?
Midge.

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An RCD on a consumer unit should not trip on powering up.
However, when power is applied then all the appliances that are plugged in and turned on will start up together. The total amount of earth leakage from these appliances may trip the RCD.
Adam
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