On Jun 25, 12:17*pm, cynic wrote:
On 25 June, 09:45, "Dave Liquorice"
wrote:





On Thu, 25 Jun 2009 00:04:55 -0700 (PDT), Bear wrote:
When it trips, only the electrical sockets in the house are knocked out.

You use the abbriviation "RCB", I'm not sure what you *exactly* mean
by that. A consumer unit can contain three different types of breaker
(excluding the main switch...).

Minature Circuit Breakers (MCB) for each individual circuit (socket
rings, lights, cookers etc), this provides overload protection only.
This just has a toggle to reset it.

Resdiual Current Device (RCD) which monitors the live ane neutral
wires and trips whne there is more than the specified current going
than is coming back. No overload protection just dection of "earth
leakage". This will have a "test" button and toggle to reset.

Residual Current Breaker Oveload (RCBO) these combine the function of
an MCB and RCD into a single unit and provides both earth leakage and
overload protection to the circuit passing through it. Again test
button and reset toggle.

We need to know exactly what type of device is tripping.

--
Cheers
Dave.

It gets worse if you have an old Voltage operated Earth Leakage
Circuit Breaker :-(

Taking a giant leap of faith and assuming you have either an RCBO or a
separate RCD serving the socket circuit(s) only then it is possible to
test your RCD using an RCD tester which will check the operating
current and time of operation. Also assuming the problem is down to
leakage currents rather than fault (milliamps not hundreds of amps)
There are other possible causes such as dampness/condensation ocurring
under certain weather conditions or having a kettle blowing steam into
a socket outlet above a worktop.
Insects/small mammals can give rise to such a problem also.
If you have the test equipment and the knowledge you can test the
insulation values of the circuit and subject to vulnerability the
apparatus you have plugged in.
Some indication of your skill level would help but I can't help
thinking that if you have to ask you may not be able to meet the
requirements of testing the system and you really need a decent
electrician to find the fault.

Thanks for the replies.

My skill level is reasonable competence with electrics but anything
which requires testing beyond a standard digital meter or common
sense, I leave to the experts. I think the device is an RCCB (is this
the same as an RCBO?). Indeed the smaller switches are MCBs, and there
is a main master switch on the consumer unit. I also considered the
option of dampness - but ripping the kitchen apart (where it's most
likely to come from) is not a viable option. If it is dampness then I
should be able to determine this by investigating the electrical
sockets inside the kitchen - it has to get in somewhere!

When tripped, the MCBs remain in place - only the RCCB trips. My next
course of action is to try the test button (duh - I know I should've
tried this before posting) to make sure the RCCB is working correctly.
Then I will systematically go through the MCBs to see if there is one
where I have nothing powered which I can turn off. That will isolate
one more part of the house to narrow down the problem. Also, I am
trying to source some power breakers which shut off at 20ms or below.
I read that consumer units are usually 30ms. I can plug these into the
suspect devices and hopefully they will then trip (if faulty) before
the consumer unit.

Perseverance.....