In message , John Rumm
writes
chris French wrote:
In message , John Rumm
writes
chris French wrote:

I'm thinking that maybe my RCD isn't doing it's job properly? (We
have a TT earth system with just one main incoming RCD - about as
old looking as the CU) The test button works ok though.

Are you sure it is a RCD and not an older "voltage operated" ELCB?

No I'm not.

There is a picture of a common one he
http://wiki.diyfaq.org.uk/index.php?title=RCD#ELCB

In fact it looks exactly like that.....

Aha, the plot thickens... ;-)

It's an old house, the plot is always thick....


At some point I did consider that it could be an ELCB, but seemed to
forget about the option at this point.

Like Andy said these can fail to operate for a number of reasons. So it
is possible to have a live to earth fault and not have it trip.

First job sounds like finding the live to earth fault. You can worry
about replacing the ELCB with something else after!


I think I've found the fault, after much rummaging behind sockets.

A live wire in one has a small bit of damaged insulation - just like a
cut or maybe getting trapped and damaged at some point - this must have
been in contact with an earth wire (old-ish installation - no sleeving)
or maybe the backbox. There was a little tiny bit of what looked like
heat damage, but only slight, I was expecting a bit more.

Just need to put everything back now, and see if it's ok.


--
Chris French