Crabtree Consumer Unit - Electricians Advice Please!

[moggie 939]

My neighbour and I have 2 yr old apartments and they have these consumer units. My neighbour's RCD (the small one) keeps tripping and I notice then that the sockets are still on but the ceiling lights and the boiler goes off!.

From the left it is as follows:

2 main sockets then a double RCCB marked split load 363/S030. Then there are 4 black trip switches marked kitchen sockets, living room sockets, bedroom sockets and another marked store socket!

Then there is a single RCCB marked 363/030. THIS IS THE ONE THAT TRIPS!.

To the right of this are 4 more small black trip switches marked cooker, Boiler, living room and kitchen lights , doorbell and finally bedroom sockets (but believe these should be marked bedroom lights?)

When this RCCB trips all these last 4 mentioned (inc bedroom lights) go off.

But the wetroom light which also works the wetroom fan stays on.

The detail under each switch is scribbled in biro when the apartment was built so could be wrong.

Any ideas why it keeps tripping? It does seem to happen a lot to my elderly neighbour after she has used her electric cooker to warm plates.

The wall sockets never go off at all, neither does the light over the cooker.

Any ideas at all.

Thanks all

[Buenchico]

I'm not an an electrician but it seems to me that anything which was permanently overloading a circuit (e.g.through a short) would trip the RCCB as soon as it was reset. So you should be looking for something that only momentarily causes a problem. If the problem was related to turning a light on or off, resulting in a current surge, your neighbour would have almost certainly noticed that the circuits trip out as she operates a switch. Since that's not happened, the only other thing you've mentioned is the boiler. I suspect that it's a dodgy thermostat that's causing the problem, through arcing occurring when it cuts in or out. (It could also be a dodgy time switch, with a similar fault, but then your neighbour would have noticed that the problem always occurs at the same time).

However, while you've told us that there might be a link to the cooker, it's not clear from your post whether the power to that cooker actually goes off when the problem occurs. If it does, then it could be a fault within the cooker (with a dodgy thermostat still coming quickly to mind).

[Old_Geezer]

Wow, I think I'd need to draw a picture to get the image of what does and doesn’t trip.

It may prove completely unrelated but when I had plumbing issues end of Dec / start of Jan the issues were multiple. The “plumber” I got in spotted and fixed a leaking joint which may have caused problems with a valve electrics; but the RCD for the circuit the boiler was using, was still intermittently blowing. Eventually got BG to look at it, and a replacement pump sorted the issue. It was not clear to me that was the problem, but it fixed it.

Apparently it isn’t uncommon for an older pump to intermittently blow the RCD.

[Old_Geezer]

Apaprently that is a 63A 30mA RCD.

It sounds to me the sort of thing that would go to a shower, or maybe a cooker. Maybe an electrical boiler (mine is gas and uses very little electricity).

Does her cooker fail when the thing blows ?

[moggie 939]

Thanks everyone - yes old geezer the boiler is on this circuit and did go off and came back on when the trip switch was switched back on.

Will investigate further

[BRIGHT SPARK]

These rccb trips dont trip on overload,they only trip when there is a fault of 25ma or more between live and earth or neutral and earth.If the trip can be reset without switching anything off then its caused by an appliance reaching a certain temperature at which point the fault occurs and trips the rccb.It then cools down the fault clears and allows you to reset.Have you got a fridge or freezer on the affected circuits...this would be my first check....then the boiler.If you suspect the fridge or freezer then unplug and using an extension lead re-feed from a socket not affected by the tripping and see what happens.

[The Builder]

For His Brightness .............

BS, Just thinking of something else to try.

Moggie mentions tripping after cooker use. Since they're known for earth leakage, would it be worth switching off the cooker at the wall switch, then see how it goes while it's disconnected?

[BRIGHT SPARK]

...yes as TB says ...unplug the fridge and freezer and use the cooker for a while.Its all trial and error.However once the source of the fault is determined it will need rectification...........sometimes by replacement.
There is also the chance that the rccb is at fault but IMO its a slim one.

[moggie 939]

Thanks BS and TB. Further checking with this elderly lady shows that it always trips at about the same time - when she has switched on the (old) electric cooker to warm her dinner plates (she only uses it for this as she has microwave meals and the MW is ok.

As it is the ceiling lights that go out in liv. room, kitchen and bedroom if she has not got these on she would not notice until later!

If I can see her before she switches on the cooker I will switch the lights on and see if they go out?

Thanks again

[moggie 939]

.The Builder

Well - you were right! Before she warmed her plates today I watched and as soon as she turned the switch for the top oven it threw the trip on the consumer unit. I reset the trip and all ok and then tried the other cooker switches for the plates and each one tripped the switch!

It is a very old cooker and she will get a new cooker fitted by an electrician. I have switched it off at the isolator switch on the wall.

The boiler and the ceiling lights also went out, but as I said previously, these are all operated by this trip switch.

Thanks again and everyone.