RCD/MCB tripping, nothing plugged in.

[SJRSJR]

Hi. Yesterday evening (TV and lamps has been on a few hours) the RCD in the consumer unit tripped taking out the MCBs on the downstairs and upstairs sockets. I re-set it which worked for 5 minutes until it tripped again. This happened several times sometimes with the downstairs MCB alone. So I left that one off and connected the TV/freeview box and two lamps to upstairs sockets via a couple of extension boards. That works fine. There is/was nothing else plugged in to the downstairs circuit (kitchen sockets are on the upstairs one) but now the RCD and downstairs MCB are tripping instantly.

Before I call an electrician tomorrow could anyone give me an idea of what the problem might be? Thanks.

 

[mikeyd]

It could be a neutral to earth fault somewhere. Unfortunately as the MCB only isolates the live and leaves the neutral connected it can be a bit of a nightmare (especially without proper test equipment) to pinpoint the location, as even if the fault is on a circuit isolated by the MCB it will still trip the RCD.

Has any work been done in the house lately, for example screwing shelves to walls, or even putting picture hooks up?

 

[SJRSJR]

Nothing done at all, does that mean (assuming no breaks in the cable) it could be a problem at the sockets? I could check them to see if anything has come loose?

What will an electrician do?

 

[deadshort]

Check all outdoor electrics if you have any as water ingress is often the culprit.

DS

 

[SJRSJR]

Thanks. I have an outdoor PIR light which has been flickering recently but it's not on that circuit. Of the downstairs circuit only two sockets are used regularly. I've checked (visually that is) them both and they're fine.

 

[crystal ball]

I would always try and eliminate the fridge/freezer, and central heating boiler / pump had a few of those causing intermittent trip problems

 

[SJRSJR]

Do you mean on any circuit or just the problem one?

 

[EFLImpudence]

All the circuits which go off when the RCD trips.

 

[JohnD]

now the RCD and downstairs MCB are tripping instantly.

The MCB is actually tripping, you say? Not just losing power because the RCD has tripped?

Have you nailed or screwed into walls or floor recently? Do you have rodents?

 

[EFLImpudence]

He did say:

the RCD in the consumer unit tripped taking out the MCBs on the downstairs and upstairs sockets.

 

[SJRSJR]

My mistake - it's just the RCD that's tripping. With the downstairs MCB off the RCD and upstairs circuit (which includes kitchen and outside light) is working okay.

 

[SJRSJR]

When I first investigated I could have sworn both (upstairs/downstairs) MCB toggles were down. Now it's just the RCD that trips when I try to put the downstairs one on.

 

[deadshort]

You need to physically unplug every item on the circuit , if the boiler is on the circuit switch it off at the FCU.

DS

 

[SJRSJR]

I've already done that. The only other thing that's on the circuit which I can't unplug is a light in the understairs cupboard.

 

[deadshort]

Is it on a FCU?

DS