Likely cause of Consumer unit tripping?

Likely cause of Consumer unit tripping?

Author
Discussion

gmaz

4,400 posts

210 months

Sunday 16th December 2018
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I have this same problem, but the RCD trips randomly about once a week, so its just not practical to leave some appliances unplugged for so long.

An electrician was unable to find the fault, so we just kinda live with it now frown

dhutch

14,388 posts

197 months

Sunday 16th December 2018
quotequote all
OP, if it now trips within a min, but holds if the ground floor sockets are off at the MCB, that sounds like you have narrowed it down, if the kitchen has its own ring that's even more manageable.

Obviously if you haven't already it's worth having a super good think of anything that might be on the gf skt ring you can remove/unplug and trying that. Do you have anything spured off the ring, outdoor socket, garage/shed etc.

Else the electrician will be able to break the ring and test it in parts to further narrow it down, can still be time consuming but atleast you have narrowed it down to one area by the sounds.


Daniel

dhutch

14,388 posts

197 months

Sunday 16th December 2018
quotequote all
gmaz said:
I have this same problem, but the RCD trips randomly about once a week, so its just not practical to leave some appliances unplugged for so long.

An electrician was unable to find the fault, so we just kinda live with it now frown
That's a very annoying fault, anything intermittent is so much harder. However the process is the same if you want to cure it. Else it might in time get worse and show itself.

I would start by doing a week or so where you leave nothing plugged in when not in use (Inc phone charger, hob ignition, hair dryer etc) and then maybe. Pick a circuit a week to disconnect (live at MCB, and neutral out of the busbar) and work through it. Else if your on a single RCD board you could have it swapped to a twin RCD and use that to work out where it is. You could even have a couple of RCBOs and put key circuits on that. Obviously costs time effort and money, but everything going off once a week would do my but and ruin my freezer food!


Daniel

Jazzy Jag

3,422 posts

91 months

Sunday 16th December 2018
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Have you got and dimmer switches on your lighting circuit?

I had a similar problem a few years ago and managed to trace it to an adjustable dimmer switch in the dining room.

Easy and cheap fix.

AlmostUseful

Original Poster:

3,282 posts

200 months

Sunday 16th December 2018
quotequote all
I’ve left one ring (ground floor sockets) off since about 7 am, and it’s been fine since then.
Does that suggest the problem isn’t on any of the other rings? The oven and microwave are wired in behind units and I can turn the fused switches off but can’t unplug them without removing them completely.
Currently the kitchen is all on (plugged in, not literally in!) and the fridge and kettle are in use.
The lights all work.
The ground floor sockets are used for the router, two TVs, 2 skyQ boxes and a few lamps (rarely on) and all these are off (but plugged in, sockets turned off)

Ref the damp, it could be an underground connection on the ring or the wiring in the loft (probably two most likely problem areas, but on different circuits)

We’ve had 4 hours with no outage now so i’ll Maybe get to a whole day and the turn the final ring on I expect it to trip.

AlmostUseful

Original Poster:

3,282 posts

200 months

Sunday 16th December 2018
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Just to clarify my above point, I’m just trying to identify likely problem areas to save my electrician some time and me some money!

Yabu

2,052 posts

201 months

Sunday 16th December 2018
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If you do put it back on make sure everything on that circuit is unplugged so that you can rule out appliances that are plugged into that ring, then it should be down to the wiring.

AlmostUseful

Original Poster:

3,282 posts

200 months

Sunday 16th December 2018
quotequote all
What I’m hoping for is that I turn it back on and it trips, then I know it’s *something* on that ring, then I can unplug everything and turn it back on and start to close the problem down somewhere. Be kind of annoying if I turn it on and it’s all fine and then doesn’t it doesn’t trip for a week!

Alucidnation

16,810 posts

170 months

Sunday 16th December 2018
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Jazzy Jag said:
Have you got and dimmer switches on your lighting circuit?

I had a similar problem a few years ago and managed to trace it to an adjustable dimmer switch in the dining room.

Easy and cheap fix.
I would almost bet money the dimmer was not the problem.

Mr2Mike

20,143 posts

255 months

Sunday 16th December 2018
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AlmostUseful said:
I’ve just watched a YouTube video from a very articulate guy on how the circuit breakers only break the live and still allow flow through the neutral (makes me glad I always turn the full board off when I do anything!)
Neutral should be at earth potential (or very close to it) unless there is a major wiring fault somewhere.

ndg

560 posts

237 months

Sunday 16th December 2018
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gmaz said:
I have this same problem, but the RCD trips randomly about once a week, so its just not practical to leave some appliances unplugged for so long.

An electrician was unable to find the fault, so we just kinda live with it now frown
We had a very similar problem a few months ago, thankfully it went from weekly to full failure after only three weeks. Turned out to be a faulty RCD!

AlmostUseful

Original Poster:

3,282 posts

200 months

Sunday 16th December 2018
quotequote all
1. We do have a dimmer, it’s been in for about 6 months - it buzzes a bit and we never use it preferring a lamp in the corner. I’m going to replace it with a switch anyway but I doubt it’s the cause.
2. We’ve been it all day, the whole house has been functioning since 7am without the ground floor socket ring on.
3. I’ve just unplugged everything from the downstairs sockets, only a few things are plugged in (the playroom runs off a single extension so only 1 to unplug)
4. With nothing plugged in the circuit tripped. Numerous times instantaneously with the breaker being flipped up it turned the ground one off.

I know a few places that I’d be concerned about damp so will check them out and replace items as necessary and then get my spark in.
Cheers for the advice all

dhutch

14,388 posts

197 months

Sunday 16th December 2018
quotequote all
Mr2Mike said:
Neutral should be at earth potential (or very close to it) unless there is a major wiring fault somewhere.
Yes, but equally it's can often be at 5v which is more than enough to generate 35mA and trip and RCD.


ndg said:
We had a very similar problem a few months ago, thankfully it went from weekly to full failure after only three weeks. Turned out to be a faulty RCD!
Yes, that is also very much an option. They do fail and often get more sensitive with age I'm told.


Daniel

ruggedscotty

5,626 posts

209 months

Sunday 16th December 2018
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Mr2Mike said:
Neutral should be at earth potential (or very close to it) unless there is a major wiring fault somewhere.
Yes you are correct, neutral is the same as earth as it is connected together at source. however you can be unlucky and have volt drop across the neutral and this gives you voltage between the neutral and earth at the consumer. Ive seen occasions when a large load has been switched on the neutral spikes. You get to see many weird and wonderful voltages occur from time to time.

If its not obvious then maybe best to get an electrician in to give it a good going over if you are still having problems. I see that the OP says that they had isolated a few circuits and that the problem had not occurred, good. but remember that the neutrals are still linked to the consumer unit and that even if switched off a circuit could still trip your RCD.

AlmostUseful

Original Poster:

3,282 posts

200 months

Sunday 16th December 2018
quotequote all
Out of interest, I’ve been reading more about this and a few people mention across the web that if the main breaker trips immediately when you turn the other switch on that it’s either wiring or the bracket itself may be faulty.
I have a spare breaker (the ones for individual rings) would it be worth swapping a known working one to check if the same ring trips just to disprove that it’s the breaker switch?

dhutch

14,388 posts

197 months

Sunday 16th December 2018
quotequote all
It won't be the MCB that's causing the RCD to trip.

PRTVR

7,102 posts

221 months

Monday 17th December 2018
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I think what the op means is switching out the RCD, my view is yes worth trying everything with
a intermittent fault, RCDs do go faulty.

AlmostUseful

Original Poster:

3,282 posts

200 months

Monday 17th December 2018
quotequote all
To be fair I did actually mean the MCB (if that’s the breaker that’ serves the individual rings) but might get the RCD done anyway. Have a last minute holiday morning from work today so going to have a look for some damp damage or something before getting the electrician in. If nothing else at least I can expose some things which mean I won’t be paying an electrician to break things!

Alucidnation

16,810 posts

170 months

Monday 17th December 2018
quotequote all
What do you think he might break?

AlmostUseful

Original Poster:

3,282 posts

200 months

Monday 17th December 2018
quotequote all
There are connections that I know about behind\under panels that I know how to remove, I can expose them easily so he can check the integrity of the electric components.