we have had huge problems wit our RCD tripping in the house on our
farm for no reason.
We live on a farm and we have a 3 phase supply comming into a shed in
a main consumer unit. it then goes of the the separate buildings. The
main buildings like the house and the workshop have a the 3 phases and
small buildings only have 1 or 2. The house and workshop then have
their own consumer units with 3 phase RCD's in them. Everything is on
the RCD's even the lights (this did once save me when changing a light
The house RCD started tripping about 2 months ago so recently we got
an electrician in. He leakage tested everwhere and had floorboards up
and all the socket faces off. We have been quoted £200ish for a new
RCD device but today we noticed that when you use motorized equipment
in the workshop it trips off in the house. (the workshop is all
working fine and trips off when tested).
You name it really, electric drills, pressure washer, angle grinder,
If we have our fridge, freezer and oven off it trips out less.
What do you recon?
This is a long post, because it was a very long
(and baffling) diagnostic process.
The symptoms sound similar to an RCD-tripping we had
a few months ago, reported in this newsgroup, and with
some useful advice given.
Chaos here at that time, builders working inside and out.
The tripping seemed initially to coincide with the
replacement of the incoming supply cable. Got them back
in, got it tested, no faults found.
Then it seemed that the trip happened when certain
appliances were used. Megger'd all appliances, and even
went to the bother of making a device to measure the
L-N difference current when appliances were powered up.
No perp found.
Finally realised that the RCD trip was *load-related*.
When there was a certain load on the house, then any extra
surge current would cause a trip..... didn't matter what
appliance, Hoover, Henry, fridge motor, oven element, etc.
Finally (finally!) twigged that we probably had an E-N short
somewhere, where our low Neutral voltage was not enough by
itself to cause a trip, but was enough to sensitise the RCD.
Sure enough, an ohmeter measurement in consumer unit showed
that there was an E-N short. Lifted off every Earth off the
busbar and found it was on the kitchen ringmain (somewhere).
A series of low-ohm measurements located the 13A socket that
was nearest the short. And (at last!) located a (new) nail
head that was also connected to E or N, 4ft above the socket
and some distance off to one side.
Pulled the nail, all probs went away.
god knows it seems to have lost the end of my message
i think i said:
if there is a sharp voltage drop what can we do about it?
would the electricity company pay for out electrician if it is there fault?
Almost as desperate/daft as perched on a ladder with an
ohmeter, one lead plugged into Neutral, and the other
probing along a line of nail heads.
The symptoms are so similar that I think the OP could
well have an E-N short (or leakage) somewhere.
Thats what im thinking but would the electrician not have picked that
He was here for nearly 3 days (at a cost of about £700) and he
basically traced all the wiring in the whole house. Surely he wouldnt
have missed a E-N short. He plugged some funnny machine in at the
Could it be the trip itself gone faulty ?
Try replacing the suspected item with another and see if the problem moves with it...
We had similar intermittent problems, and they turned out to be a corroding
washing machine heater element, a dying freezer, and the (still going) toaster
which allows the bread which curls when cooking to touch the elements.
None of these happened before I fitted the RCDs, so the wife suggested
I remove them ( :-) ) I am thinking about it !!!! and going about my daily
chores wearing rubber gloves ! I think we were lucky.
That WAS meant to be a joke ! - When we moved in we had a
voltage-operated breakerb from ? 50 years ago (overhead feed)
which had neither of the earths fitted, either the one to the
house wiring or the one to the earth on the plastic water pipe !!
It is still in circuit as a master switch, but now it goes to a new consumer unit
with two zones of RCD protected breakers and also a small box of two 6A
breakers on non-RCD protected supply for the lights.
The fridge and freezer are also on a further separate RCD spur, so any house trips
take out the fridge/freezer if we are away.
Not sure if that is current regs, but seems logical, safer and
"it was there when we moved in, Guv" if anyone asks.
However, if anyone can comment with constructive suggestions,
I would be grateful, not having a copy of the current regs. (not in the trade ! )
it is ;-) one works, the old one doesn't. The voltage-operated design
works by making the house 'earth' not a 'true earth', but a conductor
to which fault currents flow. When those fault currents make the house
'earth' more than 50V above 'true'/'reference' earth, the voltage-operated
breaker trips. So it protects the house 'earthed' metalwork against
rising above 50V, making it safe-ish, but does nothing for personal
protection in the case of a fault from live to 'true' earth (e.g. out
in the garden, copping hold of a live wire while reasonably well earthed,
etc.) They were an improvement (in most circs) over nothing, in the
case of a no-earth-from-the-supplier feed, but have been superseded by
current-balance types in all applications now.
Responses to yours..... severely snipped for ease of viewing..
As I Understand it, when about 50 volts appears across the earths
the unit trips, isolating the house. It only therefore protects earthed
and did nothing to protect against shock. I guess it was better than nothing
The likelyhood of coming into contact with a lighting circuit is deemed small. I
suppose a compromise would be to separately protect them with say RCBOs.
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