Terry Pinnell wrote in message
...
"N Cook" wrote:

Terry Pinnell wrote in message
.. .
The house suddenly lost power a couple of days ago and on checking the
circuit breaker box I found the one controlling the immersion heater
had tripped. But that is not switched on (it hardly ever is), so how
could a leak be detected by the circuit breaker?

After resetting that breaker there has been no re-occurrence, but with
a two week holiday imminent I'm nervous that it may happen again. It's
no big deal to return to a house with maybe some of my
electronically-controlled devices switched on (lights, radio, TV,
garden waterfall, etc), as occasionally happens due to storm
lightning, or a widespread power failure, but the fridge and freezer
would be a major issue.

The immersion heater cable from the heater coil on top of the hot
water tank in the airing cupboard goes directly to the switch on the
wall, with no intervening mains plug/socket. So presumably, to get an
ohm reading on this unit to test for leakage, I have to first switch
off at the breaker box, remove the switch panel in the airing
cupboard, unscrew a connection, and work from there?

Any practical advice would be much appreciated please.

--
Terry, West Sussex, UK

Tripped MCB or RCCD/ELCB device?

Thanks for those prompt and helpful replies. I'm responding to the
requests for more info:

The unit is a 'Crabtree', and carries a label '8A/30mA'.

It has two sections:

CIRCUIT BREAKERS:
-----------------
1. Upstairs lights: 2 shaver-sockets in bathrooms; outside security
light (from loft extension)

2. Downstairs lights: hall, kitchen ceiling & under cupboard,
downstairs toilet (and fan), cupboard under stairs (and alarm)

3. Downstairs lights: lounge, dining room

4. Transformer by board (This is an add-on of my own, as part of a
gadget to detect when the front door bell was pressed, to buzz a
garden extension. Not a possible culprit IMO.)

5. Spare

RCD PROTECTED CIRCUITS:
-----------------------

1. Immersion heater. (This is the one that tripped.)

2. Sockets (radial): My office. Too many items to list here.

3. Sockets (ring): Downstairs except kitchen (5); Garage (1); Upstairs
except main bedroom (6)

4. Sockets (ring): Main bedroom including spurs (1): Hall (1); Kitchen
(6), Utility (3), upstairs bedroom

5. Cooker and 1 socket by cooker switch.

I also have two other RCD units
- In garage mains socket, protecting garden and workshop circuits
- In lounge mains socket, protecting garden pond submersed pump

After the failure I thought *all* power was lost. But now I can't be
100% sure whether I had the lights on, and I don't recall checking
them. Certainly things like fridge, microwave, etc were off.

The only switch I reset in the Crabtree unit was the RCD one
controlling the immersion heater.

I haven't unscrewed the immersion heater wall switch yet, so can't
confirm whether it's single or double pole. But doesn't the fact that
this RCD was tripped mean that it *must* be single pole, with a leak?

Hope this helps further diagnosis.

--
Terry, West Sussex, UK

Probably just that that RCD trip is more sensitive to unbalanced inductive
load on another circuit, usually the motor of a washing machine but
theoretically could be due to a neighbour using an arc welder, anything else
very inductive, distant lightening strike etc. If definitely no problem with
the immersion wiring then change the RCD.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/