On 1 Jun 2004 14:47:25 -0700, (Geoff) wrote:

(Geoff) wrote in message . com...
I would be grateful for some advise regarding a fitted dish washer. I
was in the process of removing it from its kitchen cabinet when I had
an electric shock on touching both the washer's metal interior and the
stainless steel sink. I checked which was live and using one of those
cicuit testing screw drivers it was the dishwasher. Neither the
circuit breaker or the main RCD tripped. I have had a good look at the
wiring in the dishwasher and can find no obvious fault. I have also
tested the diswasher regularly and it has not been live again. I
assume the shock was caused by me shorting the circuit between the
then "live" dishwasher and the sink which I again assume is
connected to earth via the cold water pipe. Can anybody offer any
advice as to what could have caused the fault as I would have thought
that if the dish washer was faulty it would be "live" on a regular
basis.

Thanks for all the replies they are extremely helpful.

We have only recently moved into the house and the wiring although all
PVC and also with a modern consumer unit is pretty old. There is on an
odd collection of circuits with one single socket on its own circuit!

That's permissible as long as the MCB is no more than 20A. If you
have a split consumer unit with RCD, this circuit could be upstream of
it and supply a freezer, for example.

Also, there is no earth in the lighting circuits

In the early days of PVC wiring, that was not a requirement. I
believe earthing of lighting circuits became a requirement in the 70s.

and there appears to
be no earth bonding for any of the metal objects in the house,
including the sink next to the dish washer. This will have to be
rectified as I have recently purchased an electric shower.

It should be done anyway.



I thought there was a problem with the RCD as several times it has
tripped when I was doing work to individual circuits. I had assumed
that as I had popped the circuit breaker for the circuit then that
ciruit was comletely "dead". However from reading this news group I
now understand that, if you short the earth and neutral then the RCD
will trip. I stand to be corrected!

With regard the problem the supply cord did initially appear to be
trapped at the back of the washer, but on inspection the cord was not
damaged, but it had some black "tar" like subsidence. This had
attached itself to the wire from the back of the washer. I assume
that this was caused by the heat of the dish washer softening the
materail and then attaching itself to the cable where it came into
contact with the cable.

I can't recall whether there were any other appliances running at the
time although I dont think there were. As to the "shock" it was more
of a jolt. The machine was not actually on at the time.

Notwithstanding a faulty dishwasher, I would suggest by your replies
that the problem would appear to lie with the earth circuit either in
the dish washer itself or the socket or circuit it is plugged into.

Another possibility is if there is a radio interfence suppressor
employing capacitors in the dishwasher. WHere these are used, the
appliance needs to be grounded or there can be an effect of the
chassis acquiring a voltage level at about half of mains but with no
real current behind it. This can explain a non sustained jolt such
as you experienced.

I would suggest getting a simple continutiy tester/digital meter.
They are pretty inexpensive. You can then do an earth continutiy
test from the dishwasher chassis all the way back to the main earth
terminal near the consumer unit.

Mains testing screwdrivers do not really give reliable results one way
or the other.





..andy

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