Guys I need some help please!
Quietly sitting at home this morning and suddenly all the electrics went,
checked the consumer unit and the RCD had been tripped. Done some basic
fault finding and I've managed to identify that the problem is something to
do with the central heating. Everything is fine with just the hot water
switched on but as soon as the CH kicks in, it trips the RCD.
Can I have some pointers as to where the fault might lie.
If it's any help the boiler is about 30years old ! and is a Concord WCF the
controller is a Potterton Ep2001
Bet its earth leakage in the central heating pump.
You could try connecting the pump directly to the mains if you know how
and see if this trips. Isolate the heating circuit while your doing
this. If the trip goes the moment the heating comes on then you could,
if your careful, disconnect the pump and then fire up the boiler and see
if it trips or not. Shouldn't hurt to run it for a very short while with
the pump electrically disconnected....
Humm...just noticed that I'd assumed somewhere that the hot water was
some sort of gravity fed system. Suggest that the motorised valves come
under suspicion. Should be able to hold them open whilst disconnected
and in most systems their fed via the room stat, and a small motor in
them drives the valve part then there is a microswitch that feeds the
boiler depending on your boiler and system. Either way the most likely
culprit is a motor winding leaking to earth and this might not happen
until the unit has warmed up a bit...
I made the same assumption - rightly or wrongly. It seems *quite* likely -
though by no means certain - that a 30-year-old boiler will have gravity hot
water and pumped central heating. If this is the case, the pump is the prime
suspect - since it is turned on when CH is required but not when HW-only is
An RCD trip can be a live to earth or neutral to earth fault. It
usually means a break down in insulation of some kind or wires
The simplest way to diagnose without the use of a lot of test gear is
to disconnect each item in the system one by one.
Before doing that, take the appropriate panels off of the boiler and
see whether there are any signs of cable insulation having melted by
touching something hot, or poorly cut when installed etc.
I would begin furthest from the boiler by disconnecting the pump, both
live and neutral wires. Check again.
If you have a motorised valve or valves disconnect all wires at the
terminal block, noting where they go and check again.
Check which type of control system you have by referring to the
Check thermostats, although these are less likely.
Remove the programmer from its plate and check again. This is not
necessarily rigorous because wiring to other things goes through it,
but it might help in the elimination process.
If you haven't found it by this stage then the fault probably lies in
the boiler wiring or one of the internal components.
However, since that you said it's CH only, if the system is fully
pumped with a motorised valve then the motorised valve would be
suspect. If it's a gravity type HW with no valve, then the evidence
points to the pump (or the attendant thermostats and wiring.
My money would be on the pump or motorised valves first because the
insulation in the motor windings can fail.
To email, substitute .nospam with .gl
Something leaking around the CH boiler, pump, motorised valve(s) or getting
into the wiring centre or other electrics, perhaps? Or damaged cable -
frayed, gone rigid and getting cracked, heat damage?
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