'Chattering' MCB

[dom]

Hope you have it sorted Chris. Given the potential seriousness, a proper wiring regs full test of all circuits might be advisable.

[Pete C]

Might be worth fitting an RCD instead of the ELCB.

Though Part P probably forbids doing it yourself without hassle >:|

cheers, Pete.

[John Rumm]

Given the nature of the fault I would suggest retesting with an insulation resistance tester if you can borrow one. That way you should find any other latent problems of that nature.

[chris French]

In message , Andrew Gabriel writes

Well, thanks to everyone's help. The socket live > earth fault does seem to have been the problem. Rectified the problem, all seem to be fine now. Replaced a couple of falling part 30-40 year old socket faceplates.

John, you suggested borrowing an insulation tester - if I had any idea where to borrow one I might, but TBH this does seem to have been a one off, the rest of what I've seen generally seems ok

Re your above comments Andrew, well the metal work around the house seemed to be ok. The isn't any main bonding of the water/gad pipes at the moment. The VOELCB seems to be connected properly, I can't see any earth connections that bypass it. It has two 'outgoing' earth connections.

One, to (presumably - I need to remove the base of an old climbing plant to find it) a buried earth rod, the second looks older - connects to an external copper pipe. This looks like an old gas pipe. It rises from the solid kitchen floor, goes out through the wall, runs along the outside, goes back inside to the utility room, where it terminates in what looks like a capped off gas c*ck.

Anyway sorting out the meter/CU area has been on the job list for a while. It's probably up to 40 years old, the main CU is chockerblock and there is the typical hotpotch of extra switch fuses etc. A new bigger CU, a main RCD, sorting out the main earth bonding etc. Probably starting with replacing the VOELCB with an RCD to give more space for the new CU, partly because that can go elsewhere on the mounting board - replacing a great big F-off metal main switch - there presumably because the house has a 3 phase supply. Though only 1 phase is used.

[John Rumm]

I have one in SE Essex if that is any use... Failing that a hire shop may be able to help.

The reason for suggesting it was that if there was one fault of this type it might indicate that other similar faults may be lurking. A high voltage resistance test will shake out the ones that a multimeter will not find.

There are a number of ways of hooking these things up. Some a quite sophisticated with main and sense electrodes, but more commonly you just have them inline with the main earth connection to a single electrode.

Using a gas pipe was not uncommon. I used to have one in my house which just used the gas pipe as a main earth. The danger is that these days they may end up replacing large swathes of pipe with plastic and this can interfere with the operation of your earthing.

In circumstances like that it can often work out simpler to install two CUs fed via split tails from a main switch. You can stick an ordinary

100mA trip RCD in one for all the lights and other circuits that do not need direct contact protection, and then have a 30mA trip RCD in a second CU for the power circuits. Often works out cheaper than having a £100 time delayed RCD cascaded in the same CU as the smaller threshold one.

[chris French]

Thanks, but we are in the middle of Cambridgeshire. I might investigate hire options.

It's unlikely this bit of pipe would get replaced with plastic (more like just removed all together), but anyway, we have a proper earth rod.

Ahh yes, that's a good suggestion, thanks.

[dom]

Ah - you're fixing fenland wiring!

This may explain much.

I removed a wiring run from actually inside the trough of the rainwater guttering in my old fenland bungalow.

[John Rumm]

Novel approach to keeping it cool perhaps!

[chris French]

In message , " [e-mail]" writes

Not quite on the fens, we are high up (approx 10m above sea level)