MCB without appliances keeps tripping

[holy85]

Hello,

The downstairs MCB ring main that controls the sockets keeps on tripping after around 4mins even when no appliances are plugged in?

I've been told it could be a live and neutral wire touching somewhere?, can this fault be found with a plug in electrical tester?

Any other tests i can do before calling in an eletrician?

Thanks

 

[holy85]

just to add its a old plug in wylex board without rcds

 

[stillp]

It could also be a live touching an earthed conductor somewhere. You're unlikely to find it with a socket tester.

 

[Robin0577]

If you're lucky, you might be able to narrow down the search by listening for a fizzing/crackling noise, especially if water ingress has caused the problem, as it will then be producing some steam somewhere.

It is vital to remember to switch off the power once you have located the general area, before you proceed to search manually

 

[ban-all-sheds]

If a B32 MCB is tripping after 4 minutes that means there's a current of about 60A flowing.

So wherever the fault is, there's about 14kW being dissipated.

Robin - imagine the heat from 14 1-bar electric fires concentrated in a very small spot.

You need to get an electrician ASAP, and in the meantime DO NOT turn the circuit back on.

 

[JohnW2]

If a B32 MCB is tripping after 4 minutes that means there's a current of about 60A flowing. ... So wherever the fault is, there's about 14kW being dissipated.

Indeed - although I would probably have expected 14kW for 4 minutes to 'show itself' (as smoke, flames or smell). The MCB could be faulty. Nevertheless ...

You need to get an electrician ASAP, and in the meantime DO NOT turn the circuit back on.

That it definitely the only sensible course.

Kind Regards, John

 

[stem]

Even though there is nothing plugged into the circuit, is anything else connected to it via a permanent connection or FCU. Central heating? Exterior lighting / garage? Cooker hood? Oven?

Have you carried out any DIY recently that involved nailing down loose floorboards, drilling any holes or similar activities?

 

[deadshort]

It's gone quiet, that's never a good sign

DS

 

[eveares]

Has a insulation resistance test sprung to anyone's mind? My first bet is you get a low reading of around 3.8-4.0 ohms. (Yes you read right, ohm - 1 millionth of a mega ohm.)

Also how long has the problem existed and is their any outside equipment/lights/cables fed from the circuit what could be causing the issue?

i.e. Has water got in any junction box/perished cable somewhere?

Also agree with others, unless your skilled, competent and have the right test gear; just get a qualified electrician in.

 

[Robin0577]

If a B32 MCB is tripping after 4 minutes that means there's a current of about 60A flowing.

So wherever the fault is, there's about 14kW being dissipated.

Robin - imagine the heat from 14 1-bar electric fires concentrated in a very small spot.

and in the meantime DO NOT turn the circuit back on.

It was precisely the point I had in mind that a fault of that magnitude has to be producing some visible or audible signals.
However, I accept that it was foolish of me to suggest anyone take such a course of action without pointing out the dangers involved.