RCD Tripping Intermittently

[Ciaran Lang]

Hi,

I have a RCD in the CU connected to 2 x socket circuits (house and kitchen/heating), shower and cooker. This tripped the other night when only the heating and a couple of sockets were on. I reset this and the issue only reoccurred tonight. The RCD would not switch on until the kitchen/heating breaker was off. I thought this was the issue so when I turned the breaker back on I expected the RCD to trip but it stayed on. I tried switching everything off and back on one by one but nothing tripped the RCD.

I discovered that if all the CBs are on the RCD will turn on sometimes but trip when turning on other times. By that I mean repeatedly turning it on until it stays on.

Dos this this sound like a faulty RCD? I am going to buy one to rule this out.

Could it be any other issue?

Thanks in advance for the help

 

[trev]

Ciaran, are you an electrician? Genuine question.
If not, I;d get one to test the circuits and the RCD properly. You're guessing and a consumer unit is no place for the uninitiated to be poking around in

 

[Leesparkykent]

Hi,

I have a RCD in the CU connected to 2 x socket circuits (house and kitchen/heating), shower and cooker. This tripped the other night when only the heating and a couple of sockets were on. I reset this and the issue only reoccurred tonight. The RCD would not switch on until the kitchen/heating breaker was off. I thought this was the issue so when I turned the breaker back on I expected the RCD to trip but it stayed on. I tried switching everything off and back on one by one but nothing tripped the RCD.

I discovered that if all the CBs are on the RCD will turn on sometimes but trip when turning on other times. By that I mean repeatedly turning it on until it stays on.

Dos this this sound like a faulty RCD? I am going to buy one to rule this out.

Could it be any other issue?

Thanks in advance for the help

No it doesn't sound like a faulty RCD, it sounds like you have an intermittent fault possibly on an appliance or the circuit/heating system.

I highly advise that you don't keep on repeatedly Resetting the RCD until it stays on and get an electrician to come have a look and carry out some tests.

 

[ipf]

RCD doing it's job, by the looks. Try living in the cold for a while.

 

[Des 56]

Does this this sound like a faulty RCD?
No it sounds like a system or appliance fault




I am going to buy one to rule this out.
You are going to buy one and probably waste money that could be used to finance the services of an electrician and his test meters

 

[Engineer54]

Where's your earth leakage clamp, or don't you own one??

 

[Ciaran Lang]

I'm an electrical fitter to trade but it was industrial work. (although I'm now an office based electrical designer in the oil and gas industry) So I can do certain domestic work without an issue. I wouldn't go poking around things I know nothing about, especially electricity.

if it's an intermittent fault with something would it be advisable to turn everything off and then leave one thing on eg turn off the heating, cooker etc and leave on the fridge/freezer for a while to see if it trips? I can only imagine being a kitchen appliance as it was only the WiFi router and the telephone that was plugged in elsewhere in the house.

The RCD tripping made me think it was a serious fault but I couldn't understand why it would switch on sometimes but not other times. The only explanation I could come to was a faulty RCD.

I just want to get a grasp of the issue before calling out an electrician.

Thanks again.

 

[Leesparkykent]

If your an electrician, you should be more than aware how an RCD works and what would cause it to trip.

 

[Knobhead]

As an electrical fitter you should at least know the basics. I do know what your job entails and electrical theory doesn’t play a great role.

As an electrical fitter I assume you work for a company, you wouldn’t get far as a freelancer in such a specialised branch of the trade. The company must employ some electricians, why haven’t you asked them?

 

[ChristianG]

Keep everything unplugged including extension leads. Hopefully your boiler is on a fused spur. If it still trips, then turn the boiler off via a fuse spur (hopefully) then the RCD should reset. It sounds like a possible fault with the boiler. Is the boiler on a timed setting? If it is put it on constant and see if it trips. Bare in mind that you really to need to not be tight and just splash out on an experienced electrician. Oh if they walk in with just a screwdriver, tell them to go and get their test gear.

to be honest it could be so many different things, I,ve had a wedding photo picture that's been up for 10 years, then the RCD has started to trip and we found 240v at the picture hook, not in my house btw.

 

[Spoon]

If you don't have a earth leakage clamp meter then the best thing you can do mate is get an electrician in.
Or if you want to find out more about the fault then get your hands on one and do a bit of testing of the circuits and appliances on them.

 

[Octopus]

Kitchen with heating on the circuit - tripping at irregular times. my moneys on the fridge or central heating...

 

[Marvo]

The problem with intermittent RCD tripping faults is it's often the cumulative result of more than one earth leakage fault. If you don't have a megger tester and an earth leakage clamp meter this kinda fault will run you round in circles.

 

[Ciaran Lang]

I know how RCDs operate etc but I have just never came across this problem before.

I'm not an electrician, a common mistake my family and friends make when they have issues with their electrics! And I am also working in an office now doing electrical design, we have "engineers" that I hadn't spoke to as yet as it only reoccurred last night.
I have no issue getting a good electrician out to have a look but I would rather be able to pinpoint the cause to a certain appliance(s)

Since this happened last night when no one was in, I can only imagine it being the central heating (which is timed and had turned off about half an hour before I came home and the house was warm), fridge or washing machine as no other appliance would've been on.
All the appliances in the kitchen except the washing machine are on a fused spur. With these off, the RCD reset but I then turned everything back on and it never tripped. If as you guys suggest it is an appliance intermittent fault I may just need to wait it out and see under what conditions it trips again. I'll go with unplugging the washing machine for now and see if it trips.

Unfortunately I don't have a megger or earth leakage clamp.

Thanks for help. It's much appreciated!

 

[Deleted member 9648]

The problem with intermittent RCD tripping faults is it's often the cumulative result of more than one earth leakage fault. If you don't have a megger tester and an earth leakage clamp meter this kinda fault will run you round in circles.

I cant believe that once again nobody has mentioned an IR test(until post #13)

 

[Engineer54]

I cant believe that once again nobody has mentioned an IR test(until post #13)

Know what you mean, but in this case, it wouldn't have mattered much if it had been mentioned earlier, as the OP doesn't have ANY test equipment!!

 

[LEO]

Hi there Ciaran,

I've experienced these types of faults quite a few times, some decent info above in the previous posts and ideally a IR tester and a earth leakage clamp tester are needed here. You can do your own process of elimination and may get lucky and find what the culprit is, if it is down to one item? Could be quite likely that it is down to more than one item though and a cumulative effect of earth leakage across the circuits protected by the RCD, this is more difficult to diagnose and simply unplugging items won't prove what item is at fault. You could have say 8 items connected for example all producing 3mA of earth leakage, the RCD is just about holding, and everything is fine, then your central heating kicks in at 4pm and your RCD trips, your central heating may have 7mA of earth leakage, the combined amount exceeding the RCD rating and then trips, this doesn't necessary mean the central heating is at fault.

Also when you are switching fused spurs off, if they are not D.P, take into consideration that the neutral is still connected and you could quite easily have a couple of volts or so floating on the neutral, if the earth leakage/fault is on the neutral side of things then this could cause the RCD to trip to(could be a P-E fault or N-E fault or both), even though you have ruled that item out because you have the fused spur switched off. Same goes for plugged in items to sockets, always unplug from the socket not just flick the switch off as you could be in the same scenario if they are not D.P, you could easily end up chasing your tail then and going round in circles. Depending on the nature/origin of this fault they can be time consuming to narrow down. Take into account any supplies to outside, pond pumps, garden shed etc etc that may be connected unknowingly to one of these RCD protected circuits.

Goodluck.

 

[Marvo]

.......You can do your own process of elimination and may get lucky and find what the culprit is, if it is down to one item? Could be quite likely that it is down to more than one item though and a cumulative effect of earth leakage across the circuits protected by the RCD, this is more difficult to diagnose and simply unplugging items won't prove what item is at fault.

This is the problem with no test equipment. Many household items have an acceptable amount of background leakage which isn't a fault because, to a point, the earth is functional as well as protective. If you have a faulty appliance with twenty-odd mA of leakage and you unplug a PC or maybe a Playstation that has a few mA of functional leakage via surge arrestors and the RCD will hang in even though the fault hasn't been eliminated.

Finding RCD tripping faults by elimination is basically guesswork and as I previously said can run you around in circles and may even have you spending money replacing or repairing items that aren't actually at fault.

Beg, borrow, kidnap or steal a megger tester and an earth leakage clamp.

 

[Knobhead]

Beg, borrow, kidnap or steal a megger tester and an earth leakage clamp.

Would you lend someone with no training your test gear?

He would better getting one of the guys he works with to sort the job out.

 

[walsh builders]

Testing equipment alone will not find your problem, you need someone to operate it.

There's no way on this earth that you could guess what the fault is. Take the money that you were willing to spend on an RCD and give it to an electrician. That seems the most sensible (and safe) solution