ARWadsworth wrote:
"Bear" wrote in message
...
On Jun 25, 8:07 pm, The Natural Philosopher
wrote:
Bear wrote:
Brief description of problem.
Electric sockets only are tripping randomly - happened four times
since moving into our new property on 22/5/09. The first time was two
days after moving in, when barely anything was plugged in. The house
was rewired a couple of years ago and the previous occupants state
they had a similar problem, but it only happened to them a couple of
times in the 2 1/2 years they were there. The most recent trip was at
1am this morning. When it trips, only the electrical sockets in the
house are knocked out.
In locating the fault, I'm making some assumptions: chiefly that if
all of the sockets are turned off (ie. no device is consuming power),
its unlikely that anything could trip the RCB.
Not true.

Any device that DOES draw power anywhere near a neutralearth short
will trip one.

I have the same problem more or less isolated to one ring thats been
extended..anything on a section that one trips the house.

I must get down to fixing it..

Ok - more information:
Consumer unit is a Crabtree Starbreaker. The RCCB (labelled as such)
is split load 63A/30ma (363/S030). The 3 MCBs it protects are 2x 61/
B32 MCBs and 1x 61/B20. The latter is for the extractor fan only. The
other 2 - 1 is for all of the sockets except the kitchen, the other is
the kitchen. I've pulled a few sockets apart tonight in the kitchen
but all connections are tight and no signs of problems; except the
freezer. The live connection wasn't tight and there's a small nick in
the wire which could have connected to the securing screw for the
socket. Doubt this is an issue though.

Next steps - source an earth leak tester cheap on the net and test all
sockets. At the weekend scour the attic for dead/decaying vermin which
may have chewed a cable (beginning to seem like the most applicable
option).

One thing still puzzles me - 2 nights ago it tripped minutes after
boiling a full kettle. Same thing happened when trying this process 5
minutes later. Eventually plugging in the kettle just tripped the
sockets (as soon as the kettle was placed on its base) repeatedly -
even tried sockets in the living room. Hence replaced kettle following
day. That morning tripped around 1am.

I've moved the kettle away from the combi boiler - maybe the steam was
getting inside unseen?


I would not call small nick in a cable insignificant.
I have discovered that to be the most common fault of RCDs tripping.

When trying to find faults like this it is worth remembering that extra
loads (and that includes loads on the non RCD side of the board) can make
the RCD more liable to trip if it is a neutral earth fault.

Before buying a tester you might be better off checking behind every socket
in the house (you have found one potential fault) and seeing how things run
for a while.

Adam


We got a split load board after a neutral to earth fault lost us all
power until it was traced. Problem with neutral earth faults is that
switching off individual circuits does not help to isolate the cause.

I would guess there is an underlying problem which puts the system on
the edge all the time.
Is it the same side of the CU that trips every time? If so trip could be
super sensitive. Can substitution be tried?
Can the trip be reset first time immediately after it trips? I would not
have thought this likely if the cause was very obvious transitory damp.