RCD tripping every three to four days

Comer1

Hi all

I've been having an ongoing problem for over a year or so now. Initially the MCB tripped but now the RCD for sockets trips (never the MCB anymore.)

I though it was the freezer as when I'd unplug it for 12 hours, the problem would go away for about three or four days but then it would start tripping again as often as three to four times in the day until I unplug the freezer again.

It tripped once when the freezer was not plugged in and I changed the freezer but still it tripped again after four days. So I turned off the MCB and it didn't trip for a week and a half which confirmed that it is very likely on that circuit.

I then unplugged everything from that circuit and switched on the MCB to determine if its the circuit or something plugged in there. The RCD tripped twice this morning after only two days.

From reading about similar problems on here, it is probably going to be either a faulty cable or MCB (unlikely).

Whats confusing me is the way it doesn't happen for a few days and then starts to trip frequently. Could this behaviour give a hint as to the cause?


Any ideas, greatly appreciated.

brightspark

Damaged insulation, dampness?

An electrician with the correct test equipment (megger) should easily find the problem.

Alternatively visually check all the cables and connections on that circuit.

GooglePlus

brightspark wrote: »

Damaged insulation, dampness?

An electrician with the correct test equipment (megger) should easily find the problem.

Alternatively visually check all the cables and connections on that circuit.

What would the solution be if it was dampness? I've a similar problem to the OP, tripping RCD caused by a leak, which has since been fixed but obviously damp in behind the wall.

brightspark

GooglePlus wrote:

What would the solution be if it was dampness? I've a similar problem to the OP, tripping RCD caused by a leak, which has since been fixed but obviously damp in behind the wall.

You may need to replace the cable and any thing else damaged by the water. But you should sort out the dampness first.

meercat

I’d check that the immersion is turned off first

The mcb tripping may just be coincidental to this issue

Neutral to earth fault most likely

Agree with poster who said a competent rec should find this fault with a few tests.

Chicoso

Shouldn't be too hard to find

I would probably plug out the 2 wire electronic appliances

Leave some of the other appliances in-circuit and test at 250v

Comer1

Chicoso wrote: »

Shouldn't be too hard to find

I would probably plug out the 2 wire electronic appliances

Leave some of the other appliances in-circuit and test at 250v

Thanks, I had all appliances unplugged from the circuit and it still tripped

Chicoso

Comer1 wrote: »

Thanks, I had all appliances unplugged from the circuit and it still tripped

Unless you can nail it down you'll need a rec to test

Comer1

Chicoso wrote: »

Unless you can nail it down you'll need a rec to test

Seems like that's my only option now, thanks.

Comer1

Just to update in case this is found in a search, solved by changing the RCD.

meercat

https://www.boards.ie/discussion/comment/118350886#Comment_118350886

Cheers for the update. Did your rec do an insulation resistance test and an rcd test to confirm

Comer1

https://www.boards.ie/discussion/comment/118353567#Comment_118353567

No, we spent a month isolating different circuits and it continued to trip, so I asked him to change the rcd three months ago and it hasn't tripped since.

meercat

That’s great.

press the test button regularly (once a month is recommended)to ensure proper mechanical operation

Risteard81

https://www.boards.ie/discussion/comment/118354539#Comment_118354539

There's still every chance that there was an intermittent fault. It's more likely than a faulty RCD in my opinion.

Atlantic Dawn

I'd a similar problem, turned out to be the pump for the boiler on the way out tripping it, very difficult to diagnose, the replacement sorted it,

Comer1

https://www.boards.ie/discussion/comment/118359396#Comment_118359396

Perhaps you are correct but it was a very quick and cheap fix to change the RCD. Every search I made came back with the same opinion, very unlikely to be the RCD, so I didn't change it. Perhaps if I had followed my own (uninformed) instinct and changed it, I could have saved myself years of hassle and stress. This is why I've updated the thread, to let others know that it could be a faulty RCD.

Comer1

https://www.boards.ie/discussion/comment/118359404#Comment_118359404

One of my fixes was to replace my pump too

Andrea B.

https://www.boards.ie/discussion/comment/118359460#Comment_118359460

But has the MCB tripping been resolved? This is downline from RCD (faulty/shorted RCD should not trip MCB) and is designed to trip once its current rating exceeded.

With this, I suspect an issue still exists. This could be a seasonal related issue or other.

Comer1

https://www.boards.ie/discussion/comment/118359578#Comment_118359578

The MCD hasn't tripped for years. That was my initial problem so I assumed that when the RCD started tripping, it was related to the MCD tripping. When the RCD started tripping instead of the MCD, I turned off that MCD but the RCD continued to trip. I know, too much of a coincidence for them not to be related but there has been no logic to this problem over the past three years. You are correct, it could be seasonal. It stopped for one winter when I only use a stove so when it started again in the summer, I thought it was the pump on the central heating. Disconnected that and it stopped so after a few weeks, I changed that. But after a while, tripping returned, even when I only used the stove. It had gotten very bad a few months ago so I started leaving MCDs off to isolate the problem. It continued to trip with every MCD off so that's when I changed the the RCD. What's a real mystery is that I have made so many changes over the past few years and the problem would go away for a while and then return. None of these changes were related so why almost all of them would have temporarily improved the situation makes no sense.

I'm not saying it won't come back, but I'm daring to hope we have solved it, time will tell I suppose. Just to let people know that changing the RCD years ago could have saved me a lot of hassle. If it does start tripping again, I will report back and so you can say "told you so"😁

Andrea B.

https://www.boards.ie/discussion/comment/118360059#Comment_118360059

No, not a case of "i told you so".

I like problem solving, that's why i stuck my nose in.

+the excellent detailed history you gave, made it all the more tangible.

Other things may have been corrected while he changed out RCD ( eg. A bad/hot terminal on MCB, causing it to trip / spreading loads from MCBs etc).

Fingers crossed.