RCD tripping – electrical advice

Having some issues with my RCD tripping at random. Unfortunately this is not predictable so my attempts to find the fault have been fruitless and it has been going on a while.

I’ve been doing some reading and was wondering if any of the following ideas are practical (and/or suicidal).

I think everything is on the RCD since it is positioned at the far left of the consumer unit and everything goes off when it trips! Would it be possible to fit another RCD or simply take some things off the one RCD so not everything goes off. I’m mainly interested in keeping the fridge freezer running and the boiler and I gather these are common causes anyway. Is it possible to tell which breakers are on the RCD?

Unfortunately all the sockets in the kitchen are on one breaker. Without rewiring and destroying the room is it possible to put the fridge on its own non protected circuit – probably house dependent?

Is it worth getting the one RCD changed – are there some that are better than others and more reliable – are some a bit sensitive and trip at 25mA not the stated 30mA?

Can you fit ones with a higher “rating”. Screwfix has ones in that are 100mA – but I assume the standard domestic ones are 30mA for a good reason?

Is there an easy way for me to test earth leakage? Motors are the likely culprit from what I read so I’d like to check a few things there. But I’m also living in an old house and have a suspicion that a socket, somewhere is on a wall that is damp. Without going round and taking them off and looking for corrosion is there a simple way to check?

I’ve seen you can buy plug in RCDs. IF I stick my Fridge Freezer on one of these (and that is the cause) is that likely to stop the whole house tripping?

Anything else I can check? I’m going to call a sparky at some point but last time they found nothing. The problem is intermittent which in itself gives me some clues.

Not sure if its compliant with current regs, but my fusebox is fitted with a non-rcd main switch, and then every circuit as its own RCD, so if something trips I only loose one circuit.

You can get an RCBO’s as an alternative to RCD’s, I believe (could be wrong) that these are more tolerant to things like power tools, popping lightbulbs etc. Previous occupier has fitted an RCBO to the feed to the garage.

It’s tripping for a reason. Could be a number of things such as wiring, dodgy appliance, faulty heating controls, faulty rcd.
Don’t be tempted to fit a 100mA rcd to try get over the problem as it will still be there and will probably still trip the 100mA.
Try another sparky if the last one couldn’t find anything.
You need proper test equipment to fault find properly, patience and perseverance is key.
I had a call out Monday to a house tripping and the customer swore it was a problem with the boiler/heating. Turned out to be a cable had been chewed by a rodent in the cellar….

Jonba,

A 30mA rcd is required for shock protection so changing to a 100mA one as a direct replacement shouldn’t be done.

Depending on the age/condition of the consumer unit it is probably worth having a new one fitted. This could divide up the circuits between 2 RCDs or each circuit could go on an RCBO – essentially a combined MCB and RCD in one unit – which is more expensive but does give the benefit of only one circuit tripping in a fault scenario.

RCDs can be tested with a suitable meter. Some can be a bit sensitive but none should trip at a fault current of less than 15mA – 25mA is pretty much around the level I would expect to see.

An RCD for the fridge/freezer may work but it’s not necessarily the local RCD that will trip first. The most sensitive/fastest may still be the one at the consumer unit so you may not solve it this way.

RCD nuisance tripping is a pain to find. It can take minutes or days. First action for me in a situation like yours is to check vulnerable areas for water ingress – outside sockets, lights etc.

Wind blowing loose cables hung across to an outbuilding?

I’ve also had random tripping at a property that I pinned down to a faulty neutral on the overhead pole. Western Power did a “visual check” (a cursory look from the ground even though they had a cherry picker to take a proper look) and said it was all ok. A couple of months later after continual tripping and they were back and fixing the broken connection! Being an old property you may still have an overhead supply so that is a consideration.

Keep a track of when it’s tripping. What’s on/off. Rain/wet/windy. This might give you some clues as to what might be causing it.

Any questions, just post here.

Rich.

I had this a while back and it was very annoying but eventually sorted out.

We had the chest freezer put onto a separate (RCD-protected) circuit, as it got very boring throwing out ice cream every few weeks.

There was never a single thing that fixed it – I suspect we had several things connected (washing machine, a damaged extension cable, a very iffy light) all of which were just a bit leaky and pushed up the overall leakage to just short of the 30mA trip current, so that we then only needed a few mA extra to trip it.

Fixing just one on its own wasn’t enough to cure the problem, annoyingly.

Good luck!

How intermittently is it tripping? Would it be practicable to unplug one thing after each trip and see if it still trips?

Of course this won’t catch it if it’s a wiring fault…

Intermittent electrical faults are well annoying, and most electrical faults are intermittent.

I had this last week. I turned off all the protected circuits. Then turned them back on one by one until it tripped again. Turned out to be the washing machine.

RCDs can be tested with a suitable meter. Some can be a bit sensitive but none should trip at a fault current of less than 15mA – 25mA is pretty much around the level I would expect to see.

The brand new consumer unit I bought for my Workshop had a faulty 30mA RCD, tripped below 15mA. Luckily I had a spare kicking about, so could swap it out to pass the BC inspection…

It happened a couple of times last night but it normally goes off 4 or 5 times a year. It did spike in frequency a couple of years ago. Shortly afterwards our Fridge-Freezer died so I assumed that was the cause. Never had it in a previous house. It has been a mild annoyance meaning all the little clocks on the microwave, oven etc. need to be changed. But I’m always concerned it’ll go off the first day of a 2 week holiday. Never happened while I’ve been up and about before. Normally I come home to it or it happens overnight.

I think we might have too much on the kitchen circuit. I’m sure the Boiler, washing machine, Fridge-Freezer, Dishwasher and oven are all on there so it could be a cumulative thing.

We’ve tried turning things off but because it isn’t reliable it is virtually impossible.

Our RCD used to trip out whenever my son would turn on (and even turn off) his desktop computer. I *suspect* that a dodgy USB extender was the culprit, or possibly graphics board – never really got to the bottom of it.

Then it was a dodgy uplighter, again I think a cable was loose / rubbed / worn. Eventually moved to the shed, and got another lamp!

100mA rcd is for protection from fire only, so don’t swap the 30mA one for a 100mA one. I had an issue years ago which after some fruitless fault finding I changed the rcd itself. Problem solved, I don’t think it’s that common for the rcd to go faulty but it can happen.

The capacitor in a tumble dryer tracking across the terminals is one of the classic RCD trips – I assume the can of the capacitor is earthed.

Solved by (switching off first then) polishing the area between the terminals with a tissue / some kitchen roll.

as above, switch off all circuits then put then back on one by as you use them

when it trips you know the circuit

after that further simple faulting as described above should let you track down something which is contributing to the trip

as above, switch off all circuits then put then back on one by as you use them

when it trips you know the circuitWith it tripping about every 2 months how long will that take? How long do you leave each circuit off before deciding it isn’t that one? 😀