Need a bit of help regarding the RCD tripping on my consumer unit.
At the weekend the RCD tripped, knocking off the sockets. Tried resetting
but it wouldn't, kept flicking back to the OFF position. Turned off all the
sockets and narrowed it down to the fused spur which feeds the central
heating control panel which was causing the RCD to trip. Turned the fused
spur back on and it would trip again. Waited a couple of minutes, then
tried again and this time the RCD did not trip.
This morning, the same happened again, the RCD tripped and again, leaving
the fused spur turned off I could reset the RCD. This leaves us with no
central heating. I switched off the cooker switch and turned on the fused
spur and it did not trip the RCD.
Anyone any ideas?
The device detects the sum of all the earth leakage currents on all the
circuits connected through it. It is very possible to get a number of
faults, none with a large enough current, yet, to trip the device but
together they do.
For example - the insulation within the cooker has deteriorated such
that 20mA of leakage current is now flowing. This won't be enough to
trip the device, if it is a 30mA one. The insulation within, say, the
central heating pump has also deteriorated such that 18mA of leakage
current is now flowing. Again, insufficient to trip a 30mA unit, on its
own. Switch them both on, 48mA flows and the device trips.
Or it could be that you have half a dozen devices all leaking 4mA -
giving 24mA and not tripping the device. Switch the cooker on and it
adds another 5 mA - still not enough total current leaking to earth. Now
switch the central heating on, another 5mA - and the trip operates..
Switch either the central heating or cooker off and the total leakage
current drops below the trip level.
You really need to know what the situation is and get it fixed.
The principal still holds (well spotted Sue), but the OP said s/he lost the
power to the sockets. Maybe a clearer view of the OP's CU layout could shed
more light but I will still put money on a dodgy pump.
Has your next door neighbours been doing an electrical work in their houses
I ask, because, a friend of mine put a socket in his living room and
everytime he used it, it tripped the electrics next door. He asked me to
have a look at it for him and I discovered that he had wired it incorrectly.
Once put right, next door had no problems.
Wierd I know.
I had a very similar problem after a storm was in the area. After what
seemed like hours of disconnecting circuits, I traced it to the fused spur
itself...i.e. the fuse casing. Replaced it, and all was fine. I can only
conclude that somehow, during the storm, the insulation had deteriorated to
such an extent in the fuseway that it caused the tripping out.
If the RCD trips when the boiler fires, not just when the fused spur is
turned on then you are probably looking at a pump problem. Ideally central
heating systems should be on the non RCD side of a CU
Rubbish, if there's an EL fault you want the fault detected. Who wants a
bit (or more) mains stuck on their heating pipes to save a problem tripping
their power. It is indeed annoying, can be tricky to locate, but if working
the RCD is doing it's job.
Reminds me of the Spanish hotel who inserted an earth isolation plug (I kid
you not) because we complained that if the cooker was on (and heating) and
we touched the sink we felt a sharp tingle (made you jump) !!
My money is only the CH circuit/s having a fault, pump yes, diverter valve
yes, controller fault yes.
I have, in the past, comprehensively tested an 'external' ELB for an
outhouse, both when new and after a number of years. The trip value was as
low as 6mA (reliably) and whilst I can't remember the timings was also well
below the maximum spec. Good job really as a 30mA rating may stop nuisance
tripping but 25mA is the rated danger current through the central body (and
heart) and you do not want to get near that.
I had a problem with my Baxi Bermuda backboiler. The heat exchanger was
clogged so when it lit the flames went round the side instead of up the
middle . This burnt the insulation on the mains cable to the control unit
and caused the RCD on the consumer unit to trip. Unfortunately the burnt
insulation was inside a duct in the boiler so it wasn't visible immediately.
I checked out the pump and all sorts of things before I found it.
I disagree. If mine had not been on the RCD it could have caused a fire.
 Lack of servicing, now sorted.
It has been fine since yesterday. CH on and the cooker plus the usual tv /
pc on as well and the RCD has not tripped. Seems to be an intermittent
problem. Turning the CH on and the cooker on at the same time does not
always trip the RCD. Just when the RCD trips, turning the CH fused spur off
allows me to reset the RCD. Turning this back on will trip the RCD. Wait a
while and I can turn it on and it will be ok for a while
It hasn't "been fine" - it is simply that the fault currents haven't
added up to enough to trip the device.
This "intermittent" problem could be water leakage/condensation only
being in present in sufficient quantities and in contact with
power-carrying conductors under certain conditions and, say, not present
or evapourating off under others. Even when not tripping, there could
easily still be enough water to be present to be corroding wiring and
electrical units - until the damage becomes so great that a permanent
What I would do is to isolate parts of the system and test them with an
insulation tester - which will localise the problem(s). At this stage it
could be extremely inexpensive to fix - just a displaced seal needing to
be repositioned, a bit of silicone sealant needed, a compression fitting
needing tightening, etc. Leave it and you risk expensive repairs later..
Possibly but I don't know where my controller gets its power from. The cable
appears from somewhere in a cupboard. I presume it's wired direct into the
ring main like my immersion heater. If that's the case then the cable which
looked to be less than 13 amp might be backed up by a 30 Amp (or whatever
the ring main breaker is) breaker. In which case a fault might cause the
cable to burn out before the breaker went.
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