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CestLaGalere

I have a new breaker panel fitted (March), mostly new appliances, and some from an existing house.
The house is divided into 2 sections with an RCD for each, each section has a ring main and lighting as well as a couple of other breakers on it. One of the RCDs trips infrequently time between trips has been 11.5 days, 84d, 40.5d, 47d. No pattern that I can determine - sometimes trips when we are not in the house. This RCD has the kitchen (so fridge/freezer on it so I have to run an extension for it just in case which is annoying). I haven't spoken to electricity supplier to try and match it to spikes / power issues but this was one of my thoughts.
New meter fitted about 1/2 way through this timeline.
Any ideas on how best to isolate the problem?
replace RCD and wait?
swap the 2 RCDs over and see if it trips the other section?

The problem is that it happens so infrequently, I can only be happy it is fixed if either a) I have found the problem or b) have waited about 6 months with no trip...
 
Good question, thanks - it is new (i.e. at same time as panel) with new oven / hob / microwave / washing machine all on same ring main. If I swap the fridge onto other ring main via extension lead the other ring main is OK however the first one still trips so about the only thing that I do know is that it is not the fridge/freezer!
 
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You need to have insulation resistance tests done on the faulty RCD side.It's no use just guessing what it can be.I would think it could be damp or water getting into something (eg joint box under the floor) and depending on how damp it is as to when it trips.Also the RCD's them selves need ramp testing to see if they are faulty.
Finally it could be an appliance that causes a fault now and again as in the washing machine as it reaches a certain cycle.
Either way proper testing with someone who has the experience on what to look for should get to the bottom of it.
 
Did you get an Electrical Installation Certificate when you had your fuse board changed? If not then I would recommend you get an Electrical Installation Condition Report done, done properly this test should highlight any problems with you electrical installation/
 
If you suspect the fridge freezer, could you run it on an extension lead to a socket circuit on the other RCD?

You really need somebody with a clamp meter - you could be running with a lot of earth leakage, then a small issue could trip the RCD.

These are the most difficult ones to find, especially if they are so infrequent
 
Did you get an Electrical Installation Certificate when you had your fuse board changed? If not then I would recommend you get an Electrical Installation Condition Report done, done properly this test should highlight any problems with you electrical installation/
.....or, seeing as you only had it done in March, get those who did it back in .....after reporting the problem to them.
 
You shouldn't need to swap or change the rcd just get an electrician to run a few years but it doesn't sound like it is nuisance tripping as said above it does sound like damp ingress possibly at a joint but there is absolutey no way to tell without having an EICR carried out
 
Did you/they have an RCD before .
Electric Kettle ,centre pin spinning base ?
Try a different style for a while !
( Someone may be throwing water about -half asleep)
 
This type of problem requires the right kit, a logical approach, a certain amount of experience, the ability to ask the right questions (and listen to the answers!), and sometimes a bit of luck, to resolve.

I've solved (from memory) 4 similar faults such as this, the causes were:

- twin and earth routed directly into concrete floor, presume damp/movement
- faulty washing machine
- damp in metal back box in kitchen (possibly from next door/party wall)
- dodgy lights in conservatory

I have also seen 3 or 4 RCD failures - failing to trip, or failing to reset - but none (so far!) causing nuisance tripping.

Other causes that I've not personally come across but which are common:

- dampness in outside lights
- general weather/wetness-related causes
- floorboards/nails pressing against cables, such that insulation resistance breaks down only when pressure is applied in a certain place
- vermin

Get someone in to do an initial assessment - insulation resistance readings of the circuits concerned, RCD ramp test, possibly earth leakage - to see if the fault is "visible" even when the RCD is not tripping. If there's a low/high (as applicable) reading that an electrician can chase, they will be able to narrow it down to a part of a circuit and hopefully fix it (or perhaps say: "The problem's under the floor between this socket, and that socket. How do you feel about pulling your floorboards up?"). If everything checks out, and looks good on the day - it's one of those pesky intermittent faults.

You're doing good by keeping a record of when it trips - this sort of information, and anything else you can think of, will be of massive help for solving the problem.

Good luck! :)
 
I would just add a couple i have come across. Very high "normal|" leakage, a/c units are particularly bad. very noisy communal earth.
Basically with a clamp meter you can see straight away what the RCD is seeing in its "happy" state. Below 5mA i am generally happy, 5-15mA , think about breaking ccts down, above 15mA , trace leakage and either break ccts down or change appliance for a less leaky alternative. Any problem with the wiring installation should show its face with IR BUT i have encountered ants living in an outside drive light which knew when i was coming and unlinked their arms so i got a good IR only to join back up when i leave, the little buggers. Ha Ha
 

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