Consumer unit trips without reason that I can find

[teddysnips]

Apologies in advance for length of post.

As part of our nearly-complete building work, the old fuseboard (as I still call it) was replaced by an all-singing, all-dancing consumer unit. Whizzo, I thought, as I recalled our last house where every time a light bulb blew the consumer unit arranged for the whole house to be plunged into darkness and a joyous festival of resetting the blinking 12:00s was on the cards.

The new unit behaves differently, but it does have one very, very annoying habit. Every so often without any rhyme or reason that I can tell, part of the thing trips and all the sockets in the house go dead. The lights are fine, but nothing else. I asked the electrician to test it, but he simply suggested unplugging things until it stops happening. Yet more blinking 12:00s to play with.

Fine, except that it might happen four times in one day, and then not happen again for three days, whereupon it might happen another six times in three hours.

We recently went away for a week and fretted about this happening ten minutes after driving away and all the food in the fridge spoiling, so we unplugged everything and switched everything off except the fridge, the DVD recorder and one or two other essentials. When we got back everything was fine, no power outages (as the Merkins have it), and gradually we plugged things back in and switched things back on as and when required. And it all seemed fine for a few days, and then suddenly they all went off again and the whole merry cycle began anew.

The only appliances that are running 24/7 are fridge, cookers (well, the clocks anyhow), alarm clocks and whatever controls the boiler. Plenty of other appliances are plugged in, and on at the wall, but not in use (washing machine, dishwasher, TV (never left on standby) etc. etc).

I don't have the correct terms for all the bits and bobs of the consumer unit, but it's divided into two rows of eight trips (what would, I suppose, have been fuses in the old days, what I think are now called MCBs) with each row having a master "trip" (an RCD?) and an over-arching master "trip" (a super RCD?) for the whole shooting match.

It's the lower master "trip" that trips - the one controlling the second row of individual trips. These trips are labelled "Hob", "Sockets - kitchen", "Sockets - Upstairs", "Sockets - Garage", "Sockets - Extension", "Immersion Heater", "Cooker", "Hall/Lounge sockets downstairs".

Given that the rate of failure is so low and MTBF so long (for elimination purposes), and that the sub-master trip is what goes (rather than the individual trip for the misperforming part of the system), which doesn't exactly narrow possibilities down, does anyone have any ideas how we could go about finding the problem? Electrician thinks the prime candidate is the fridge, which is the one thing that we can't realistically turn off and see if everything carries on working (plus it didn't trip for the 9 days we were away). Would using an RCD on the fridge tell us anything - such as this

?Could it be a fault in the consumer unit itself?

Thanks

Edward

[Adrian]

teddysnips ( [e-mail]) gurgled happily, sounding much like they were saying:

Silly question - it couldn't just be being overloaded, could it? What rating's that master got, and what's the sum of the ratings below it?

[adder1969]

On Feb 15, 2:41=A0pm, [e-mail] wrote: off and see if everything carries on

If you're not worried that there's an actual hazardous fault anywhere then you could move a circuit from the RCD side to the non-RCD side, perhaps starting with the fridge circuit. (It sounds like you have a split load unit - sockets on the RCD, lights on the non-RCD)

The consumer unit is just a box of components so I guess it could be a particular component in there isn't right.

[teddysnips]

I'm not worried that there's an actual hazardous fault anywhere, but that's only because none of us has been electrocuted recently. I think you're right, we do have a split load circuit. Presumably it's an electrician's job to do the circuit moving as you suggest?

Thanks

Edward

[teddysnips]

Not at all a silly question - I'll take a look when I get home. Thanks

Edward

[dom]

It sounds like you're describing an RCD tripping on a split load consumer unit (post a pic so we can verify this). Does the switch that trips say something like "30mA" and have a test button it?

As your electrician says, it's probably a faulty appliance that's passing a little too much earth leakage - combined with the small allowable leakages that is normal with many appliances.

[Jim Alexander]

The system designer (your electrician?) hasn't done you any favours if he didn't ask if you ask if you wanted your freezer on a dedicated circuit, ditto your boiler, though where that is connected is not clear. For little extra cost you could have had a RCBO for each socket ring, the garage on non sockets RCD but RCD'd in the garage. Can't undrerstand the Immersion Heater being on a sockets RCD either. Ditto cooker and hob unless there is a control unit socket. Find out why the electrician did it this way and maybe think about a different electrician.

Jim A

[Tim Lamb]

In message , " [e-mail]" writes

Dishwasher.

In my case, heater element, although I am concerned about steam getting places it shouldn't via the bottom door seal.

regards

[John Rumm]

It sounds like you have a nuisance trip issue with a split load CU. This is not common, can happen and is as you have discovered a pain to fix!

Of the two "master" trips to which you refer, chances are one is just a main switch, and the other is the RCD (you can have RCDs in both positions but that is currently not that common unless you are out in the sticks).

A photo would be handy.

Tracking the cause of these trips can be time consuming. You can read some background on the subject here:

I don't have the correct terms for all the bits and bobs of the

Your naming sounds about right. The "super" RCD may just be a switch as mentioned before.

It sounds like there are some design failings to be addressed there - the arrangement of circuits is not ideal with various things that represent low electrocutions risk, but high nuisance trip risk being connected to the RCD side of the CU.

The individual trips will only trip under different circumstances anyway

- when something draws too much current. The RCD trip results from a different cause.

Not really - even if it was the main source of leakage it might not on its own cause a trip.

Not very likely. It could just be a fault in the house wiring though. (e.g. neutral to earth short)

[mogga]

We had problems with random tripping and it turned out to be a bit of the dishwasher causing it. Even when it was just plugged in and not in use. Sussed it cos of a bit of burnt electrical smell in the kitchen which narrowed it down. Bits been replaced now and problem solved.

[<me9]

I'd rather put the boiler on the RCD side, that way when you have the (inevitable) leak into the electrics it trips /before/ it burns anything up, and also gives an earlier of a problem.

[Andrew Gabriel]

The problem is that tripping by something else would leave the house without frost protection, which would could be a serious disaster if you are away at the time.

If you really want an RCD protected boiler, I would ensure it is dedicated -- easiest way is probably an RCD protected spur on a non-protected circuit.

[mick]

Also, there is no need for a 30mA sensitivity RCD in this case. You could use a much less sensitive device.

[Andrew Gabriel]

There's no need for the RCD at all. However, the reason B Thumbs gave for wanting might not be satisfied with a higher current one.

[teddysnips]

[original post snipped]

Here are photos of the misperforming parts.

The whole consumer unit is here:

strip that fails is here:

button that flips up is on the far left.

Thanks again everybody.

Edward

[The Natural Philosopher]

Yup. classic piece of regulatory s**te.

So did mine till `I put in a 100mA trip for the whole house.

I recommend you do teh same, and then fit RCBO's to the circuits that need them - typically IIRC those with outside sockets.

100mA is abit on the high side to stop you being electrocuted when grabbing e.g. a live light fitting,but if you are already marginal due to earth leakage from multifarious RFI filters in the computers, TVS, radios and all the other gubbins one has, in reality its only 60mA more..and will trip if you have a serious earth fault. Then stay legal with RCBO's on the places that really need them.

[Appin]

The message

from [e-mail] contains these words:

Photo's not too clear. Looks like a Chint box, but they usually have translucent covers to the breakers. So what make is it?

30mA trip and you've got the hob, cooker and immersion heater on it? Recipe for frequent tripping. As has been suggested, the very LEAST you should do is swop that trip for a 100mA one.

You may actually be able to use a split busbar in that box, in which case you could fit a switch-disconnect at the other end of the same row and cut the busbar appropriately.

And there's actually a spare way in the top row of breakers which are on a switch-disconnect.

[meow2222]

RCCB =3D RCD, and I gather that's whats tripping. The problem is RCD nuisance tripping. The wiki article John pointed to would be a start. In short there are probably 2 issues:

1. You've got a lot of equipment on the RCD that shouldnt really be on it, and that makes your setup liable to these kind of problems. Its not verboten to have it this way, but it is a recipe for nuisance trips.
2. Some appliance somewhere may be electrically slightly leaky - but with all that kit on one RCD that isnt necessarily so, the setup is a bad design.

Solutions:

1. Resistance test all appliances, from E to L+N. A multimeter will do for a start, they arent perfect but usually pick up the offender if there is one. Write down all the R readings, and the lowest Rs are your prime suspects. Theres a fairly good likelihood this will solve the current problem - but you will still be left with an installation where this is liable to recur in future.
2. Reconfigure your CU layout to move items that dont need to be on an RCD to the other non-RCD supply.
3. It is possible as an alternative to change the RCD and MCBs, but depending on the details this will either breach regs or be costly.

9x RCBOs =3D about =C2=A3300.

A separate electrical feed for the f/f would have been a good idea, preferably not from the RCD, but if the decor's all finished its poor timing to put one in now.

NT

[John Rumm]

OK this makes it clearer. Looks like you have your "split load" consumer unit built up from two different CUs. With the lower one being RCD protected and the top one just having a simple switch (which I presume also cuts power to the whole lower CU as well).

There are a number of circuits on the CU that are known to be potential causes of trouble: The hob, cooker, & immersion heater. Moving those to the top CU might be better (you would need to combine a couple of circuits on the top one to make space since you only have one free way up there). Having said that there are many people with "whole house" RCDs feeding many more circuits than that without any problem. So while an appliance fault is the most likely scenario, don't assume that the cause of the trip is minor and should be ignored.

Other than that, your best line of approach is following the fault finding section in the wiki article.

[Appin]

The message from John Rumm contains these words:

I think that though it looks as if it makes use of some of the tooling and components for separate CUs it's actually one phsyical plastic box. We'd be a lot further on if the OP will just tell us what make it is. My guess is it's Chinese and probably a Chint or clone of one.

Possibly -- but it might well be a simple split unit with the RCD for the entire lower busbar fed from live side of switch disconnect.

Agreed as to the most probable sources of trouble, especially with a

30mA RCD. However there are two spare ways in the bottom so there's room to put in a second switch-disconnect and split the busbar in the bottom row, always assuming that parts to fit are available.

If only the OP would come back with a bit more info.