My daughter has an RCD that keeps tripping and I cannot find the fault. Out
of the blue this evening it just tripped without any particular reason and
she could not identify what she did to cause it to trip.

The RCD is one of two in a split CU with MCBs for the immersion, downstairs ring main, garage feed. Upstairs lights and burglar alarm. I have tried the usual process to at least identify which circuit is at fault by switching
off all the MCBs, resetting the RCD and switching each individual MCB on to
see which is the faulty circuit. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the ring main MCB has no effect but as soon as
a load is applied the RCD trips. Does this suggest that the RCD is faulty
or is there another possible fault? Pressing the test button causes it to
trip as normal.

Richard

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On 26/06/2025 00:07, Tricky Dicky wrote:

t. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the ring main MCB has no effect but as soon as
a load is applied the RCD trips.

Theres your problem.
It could be a neutral to earth fault. Get it tested properly with a good ohmmeter, preferably one that is used for electrical installations,
rather than a cheap £10 one from Wilko.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/06/2025 07:43, Alan Lee wrote:

On 26/06/2025 00:07, Tricky Dicky wrote:

t. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the  ring main MCB has no effect but as
soon as
a load is applied the RCD trips.

Theres your problem.
It could be a neutral to earth fault. Get it tested properly with a good ohmmeter, preferably one that is used for electrical installations,
rather than a cheap £10 one from Wilko.

+1

--
The urge to save humanity is almost always a false front for the urge to
rule.
– H. L. Mencken, American journalist, 1880-1956

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/06/2025 00:07, Tricky Dicky wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out of the blue this evening it just tripped without any particular reason and she could not identify what she did to cause it to trip.

The RCD is one of two in a split CU with MCBs for the immersion, downstairs ring main, garage feed. Upstairs lights and burglar alarm. I have tried the usual process to at least identify which circuit is at fault by switching
off all the MCBs, resetting the RCD and switching each individual MCB on to see which is the faulty circuit. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the ring main MCB has no effect but as soon as
a load is applied the RCD trips. Does this suggest that the RCD is faulty
or is there another possible fault? Pressing the test button causes it to trip as normal.

Richard

It sounds very much like you have an earth neutral short.

I had one for years.

The only way to ID is to first of all ID which ring - switch off the
whole CU and disconnect each neutral in turn and measure neutral to
ground resistance. (You should remove all un-pluggable appliances first) .

Then when you have the circuit Id'ed you need to measure neutral to
ground resistance..as you get closer to the short, resistance will decrease.

After that it is a matter of inspection.

If the rings and spurs check out, it may well be an appliance. Electric
motors have been known to short a turn to ground.

Note that this is a tedious step by step process of elimination and an electrician is going to charge.


--
All political activity makes complete sense once the proposition that
all government is basically a self-legalising protection racket, is
fully understood.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 26/06/2025 00:07, Tricky Dicky wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out >> of the blue this evening it just tripped without any particular reason and >> she could not identify what she did to cause it to trip.

The RCD is one of two in a split CU with MCBs for the immersion, downstairs >> ring main, garage feed. Upstairs lights and burglar alarm. I have tried the >> usual process to at least identify which circuit is at fault by switching
off all the MCBs, resetting the RCD and switching each individual MCB on to >> see which is the faulty circuit. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the ring main MCB has no effect but as soon as >> a load is applied the RCD trips. Does this suggest that the RCD is faulty
or is there another possible fault? Pressing the test button causes it to
trip as normal.

Richard

It sounds very much like you have an earth neutral short.

I had one for years.

The only way to ID is to first of all ID which ring - switch off the
whole CU and disconnect each neutral in turn and measure neutral to
ground resistance. (You should remove all un-pluggable appliances first) .

Then when you have the circuit Id'ed you need to measure neutral to
ground resistance..as you get closer to the short, resistance will decrease.

After that it is a matter of inspection.

If the rings and spurs check out, it may well be an appliance. Electric motors have been known to short a turn to ground.

Note that this is a tedious step by step process of elimination and an electrician is going to charge.

Thanks for the explanation. He has managed to get an electrician in who
should be working on the problem as I type.

Just out of interest when isolating the neutrals do you have to do all of
them as it is a split CU and the the other half of the CU is working as it should?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Tricky Dicky <tricky.dicky@sky.com> wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 26/06/2025 00:07, Tricky Dicky wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out >>> of the blue this evening it just tripped without any particular reason and >>> she could not identify what she did to cause it to trip.

The RCD is one of two in a split CU with MCBs for the immersion, downstairs >>> ring main, garage feed. Upstairs lights and burglar alarm. I have tried the >>> usual process to at least identify which circuit is at fault by switching >>> off all the MCBs, resetting the RCD and switching each individual MCB on to >>> see which is the faulty circuit. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips >>> it. Sometimes switching on the ring main MCB has no effect but as soon as >>> a load is applied the RCD trips. Does this suggest that the RCD is faulty >>> or is there another possible fault? Pressing the test button causes it to >>> trip as normal.

Richard

It sounds very much like you have an earth neutral short.

I had one for years.

The only way to ID is to first of all ID which ring - switch off the
whole CU and disconnect each neutral in turn and measure neutral to
ground resistance. (You should remove all un-pluggable appliances first) . >>
Then when you have the circuit Id'ed you need to measure neutral to
ground resistance..as you get closer to the short, resistance will decrease. >>
After that it is a matter of inspection.

If the rings and spurs check out, it may well be an appliance. Electric
motors have been known to short a turn to ground.

Note that this is a tedious step by step process of elimination and an
electrician is going to charge.

Thanks for the explanation. He has managed to get an electrician in who should be working on the problem as I type.

Just out of interest when isolating the neutrals do you have to do all of them as it is a split CU and the the other half of the CU is working as it should?

An update. The sparky has been and isolated the issue to the upstairs
lighting circuit but owing to the mixture of wiring systems ie loop-in at
the rosette and loop-in at the switch has not been able to solve the
problem yet. Owing to having to go to another job he has isolated the
upstairs lights which has allowed all the other circuits on that RCD to
work and will come back later to do some more testing. My SiL did say he
spent quite a time at one switch on the middle floor.

--- SoupGate-Win32 v1.05
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On 26/06/2025 11:29, Tricky Dicky wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 26/06/2025 00:07, Tricky Dicky wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out >>> of the blue this evening it just tripped without any particular reason and >>> she could not identify what she did to cause it to trip.

The RCD is one of two in a split CU with MCBs for the immersion, downstairs >>> ring main, garage feed. Upstairs lights and burglar alarm. I have tried the >>> usual process to at least identify which circuit is at fault by switching >>> off all the MCBs, resetting the RCD and switching each individual MCB on to >>> see which is the faulty circuit. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips >>> it. Sometimes switching on the ring main MCB has no effect but as soon as >>> a load is applied the RCD trips. Does this suggest that the RCD is faulty >>> or is there another possible fault? Pressing the test button causes it to >>> trip as normal.

Richard

It sounds very much like you have an earth neutral short.

I had one for years.

The only way to ID is to first of all ID which ring - switch off the
whole CU and disconnect each neutral in turn and measure neutral to
ground resistance. (You should remove all un-pluggable appliances first) . >>
Then when you have the circuit Id'ed you need to measure neutral to
ground resistance..as you get closer to the short, resistance will decrease. >>
After that it is a matter of inspection.

If the rings and spurs check out, it may well be an appliance. Electric
motors have been known to short a turn to ground.

Note that this is a tedious step by step process of elimination and an
electrician is going to charge.

Thanks for the explanation. He has managed to get an electrician in who should be working on the problem as I type.

Just out of interest when isolating the neutrals do you have to do all of them as it is a split CU and the the other half of the CU is working as it should?

No. Just the ones associated with the trip

--
"An intellectual is a person knowledgeable in one field who speaks out
only in others...”

Tom Wolfe

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/06/2025 13:20, tony sayer wrote:

In article <103iq6n$3ag63$1@dont-email.me>, Alan Lee
<alan@darkroom.plus.com> scribeth thus

On 26/06/2025 00:07, Tricky Dicky wrote:

t. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips >>> it. Sometimes switching on the ring main MCB has no effect but as soon as >>> a load is applied the RCD trips.

Theres your problem.
It could be a neutral to earth fault. Get it tested properly with a good
ohmmeter, preferably one that is used for electrical installations,
rather than a cheap £10 one from Wilko.

Second that!, it needs some current to flow _before_ that will show up
as a fault as such..

Second to the good multimeter!, if you can find one a second hand Fluke
is a very good choice may not have all the bells and whistles but
manage fine with mine in an Electronics workshop!..

I got an antique AVOMeter Mk II for £45 at a antique shop.
So nice to have a reliable meter with a moving needle again


--
“Progress is precisely that which rules and regulations did not foresee,”

– Ludwig von Mises

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <103iq6n$3ag63$1@dont-email.me>, Alan Lee
<alan@darkroom.plus.com> scribeth thus

On 26/06/2025 00:07, Tricky Dicky wrote:

t. Switching on the immersion and burglar
alarm MCBs leaves the RCD unaffected but switching the other three trips
it. Sometimes switching on the ring main MCB has no effect but as soon as >> a load is applied the RCD trips.

Theres your problem.
It could be a neutral to earth fault. Get it tested properly with a good >ohmmeter, preferably one that is used for electrical installations,
rather than a cheap �10 one from Wilko.

Second that!, it needs some current to flow _before_ that will show up
as a fault as such..


Second to the good multimeter!, if you can find one a second hand Fluke
is a very good choice may not have all the bells and whistles but
manage fine with mine in an Electronics workshop!..
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Peter Johnson <peter@parksidewood.nospam> wrote:

My downstairs RCD tripped one evening a couple of weeks ago, for no
obvious reason. Narrowed the issue down to the outside lighting
circuits so turned if off. Couldn't see anything obviously wrong with
the lighting, and some of it would require ladder work to access, so I changed the screw terminals in various junction boxes for Wagos, not
seeing anything wrong as I did so, and turned the power back on. Been
OK since but it must be a coincidence.

Water getting in? It could trip when it rains and then the fault clears
when it's dried out? Or something similar with a slug or other conductive beastie.

Theo

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Wed, 25 Jun 2025 23:07:52 -0000 (UTC), Tricky Dicky
<tricky.dicky@sky.com> wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out >of the blue this evening it just tripped without any particular reason and >she could not identify what she did to cause it to trip.

My downstairs RCD tripped one evening a couple of weeks ago, for no
obvious reason. Narrowed the issue down to the outside lighting
circuits so turned if off. Couldn't see anything obviously wrong with
the lighting, and some of it would require ladder work to access, so I
changed the screw terminals in various junction boxes for Wagos, not
seeing anything wrong as I did so, and turned the power back on. Been
OK since but it must be a coincidence.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thu, 26 Jun 2025 17:22:42 +0100, Peter Johnson
<peter@parksidewood.nospam> wrote:

On Wed, 25 Jun 2025 23:07:52 -0000 (UTC), Tricky Dicky ><tricky.dicky@sky.com> wrote:

My daughter has an RCD that keeps tripping and I cannot find the fault. Out >>of the blue this evening it just tripped without any particular reason and >>she could not identify what she did to cause it to trip.

My downstairs RCD tripped one evening a couple of weeks ago, for no
obvious reason. Narrowed the issue down to the outside lighting
circuits so turned if off. Couldn't see anything obviously wrong with
the lighting, and some of it would require ladder work to access, so I >changed the screw terminals in various junction boxes for Wagos, not
seeing anything wrong as I did so, and turned the power back on. Been
OK since but it must be a coincidence.

For quite a few years we had an RCD trip, seemingly at random until I
realised it happened when my wife was roasting meat. This in itself
didn't make a lot of sense since there were no problems with baking.
However it then dawned on my that above but not quite to the side of
the hobs was the unswitched oven fuse which got partially covered when
the hob lid was raised. eg:

https://www.wellingtonshomeelectrical.co.uk/images/thumbs/0007339_leisure-cc100f521c-chefmaster-100cm-dual-fuel-range-cooker-with-glass-top-lid-in-cream_600.jpeg

The box was slightly adrift of the wall and taping up the sides has sufficiently sealed it to the wall such that any condensation trapped
by the raised lid would not seep into the fuse. Pulling the oven away
from the wall a fraction also helped any steam arising to escape.
--
AnthonyL

Why ever wait to finish a job before starting the next?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26 Jun 2025 17:26:58 +0100 (BST), Theo
<theom+news@chiark.greenend.org.uk> wrote:

Peter Johnson <peter@parksidewood.nospam> wrote:

My downstairs RCD tripped one evening a couple of weeks ago, for no
obvious reason. Narrowed the issue down to the outside lighting
circuits so turned if off. Couldn't see anything obviously wrong with
the lighting, and some of it would require ladder work to access, so I
changed the screw terminals in various junction boxes for Wagos, not
seeing anything wrong as I did so, and turned the power back on. Been
OK since but it must be a coincidence.

Water getting in? It could trip when it rains and then the fault clears
when it's dried out? Or something similar with a slug or other conductive >beastie.

Don't think so. Not had much rain lately and everything external is
well sealed.

For a few weeks the living room intruder sensor had been triggering
during the night, the alarm sounding long enough to wake me but not
long enough to bother the neighbours. Once that happened at about
8.00am and I went downstairs to find that the RCD had tripped and the
intruder panel battery was flat. No way of telling what the sequence
of events was but it was a bit weird. The alarm installer changed the
battery and so far the sensor hasn't been triggered and the RCD hasn't
tripped so one way or another everything seems to be OK.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)