Nuisance tripping RCD - down to oven I think?


L

Lobster

Am having a hell of a time with nuisance tripping at the moment. It
happens intermittently, and when it does, you can just immediately flip
the breaker back and it works again. So it's very hard to localise.
It's definitely in the kitchen; and I'm fairly sure it happens when the
oven's on; but seems it may be more likely when the microwave's on as well?

When it does trip, it's the main RCD which goes; however sometimes an
individual MCB flips as well. I hadn't particularly noticed which one,
but I this morning I spotted that it was the main ringmain for all
sockets in the house *other* than the kitchen! (the oven has a
dedicated radial, and the kitchen sockets - including microwave - are on
another MCB).

First question - do the above observations add up at all? The MCB thing
makes no sense to me at all; I wonder if today's observation was just a
one-off oddity today?

The first time this happened I thought (well, assumed, as I'd
experienced this before) the problem was a duff element in the oven and
just ordered a new one; when it arrived though (during which time
there'd been no more trips) I checked the old and new with a multimeter,
found identical resistance across terminals (20 ohms IIRC) and to earth
(open circuit) and decided I'd been wrong, so returned the new element
unused. Now wondering if I was incorrect in doing so. Could there be
undetected earth leakage (which I don't have kit to detect? Could it be
somewhere else in the oven? Or the house wiring? Oven is a built-in one
about 10 years old; main element was replaced about 9 months ago.

Right now I'm really confused - I don't know whether I should be looking
at appliances (which!?) or wiring. I'd happily buy a new bloody oven if
that would definitely solve it, but I am concerned it might not!

Problem's really made worse by being intermittent, and because it seems
to involve appliances we really can't do without.

Any advice on how to proceed most welcome!
 
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B

Bob Minchin

Lobster said:
Am having a hell of a time with nuisance tripping at the moment. It
happens intermittently, and when it does, you can just immediately flip
the breaker back and it works again. So it's very hard to localise.
It's definitely in the kitchen; and I'm fairly sure it happens when the
oven's on; but seems it may be more likely when the microwave's on as well?

When it does trip, it's the main RCD which goes; however sometimes an
individual MCB flips as well. I hadn't particularly noticed which one,
but I this morning I spotted that it was the main ringmain for all
sockets in the house *other* than the kitchen! (the oven has a
dedicated radial, and the kitchen sockets - including microwave - are on
another MCB).

First question - do the above observations add up at all? The MCB thing
makes no sense to me at all; I wonder if today's observation was just a
one-off oddity today?

The first time this happened I thought (well, assumed, as I'd
experienced this before) the problem was a duff element in the oven and
just ordered a new one; when it arrived though (during which time
there'd been no more trips) I checked the old and new with a multimeter,
found identical resistance across terminals (20 ohms IIRC) and to earth
(open circuit) and decided I'd been wrong, so returned the new element
unused. Now wondering if I was incorrect in doing so. Could there be
undetected earth leakage (which I don't have kit to detect? Could it be
somewhere else in the oven? Or the house wiring? Oven is a built-in one
about 10 years old; main element was replaced about 9 months ago.

Right now I'm really confused - I don't know whether I should be looking
at appliances (which!?) or wiring. I'd happily buy a new bloody oven if
that would definitely solve it, but I am concerned it might not!

Problem's really made worse by being intermittent, and because it seems
to involve appliances we really can't do without.

Any advice on how to proceed most welcome!
It is quite likely that you have a number of devices each with small
leaks to earth, none of which will cause a trip in its own right but in
combination can add up to enough to cause a trip.
The only real way is to measure the differential current in the likely
candidates and fix them 1 by one.
Immersion heaters are another favourite problem source. Even when not
used, can give an earth to neutral leak. Disconnect completely if you
are not using it whilst testing.

Some electrical leaks will only be present when a voltage is present and
perhaps say a heating element is hot.
 
B

Brian Gaff

This never happened with fuses. I'm often suspicious that these detectors
are now more electronic than mechanical and as such prone to all sorts of
interference causing them to trip for an invalid reason. Can you not try
some alternative trips just in case its fooling you?
Brian
 
A

ARW

Lobster said:
Am having a hell of a time with nuisance tripping at the moment. It
happens intermittently, and when it does, you can just immediately
flip the breaker back and it works again. So it's very hard to
localise. It's definitely in the kitchen; and I'm fairly sure it happens
when
the oven's on; but seems it may be more likely when the microwave's
on as well?
When it does trip, it's the main RCD which goes; however sometimes an
individual MCB flips as well. I hadn't particularly noticed which one,
but I this morning I spotted that it was the main ringmain for all
sockets in the house *other* than the kitchen! (the oven has a
dedicated radial, and the kitchen sockets - including microwave - are
on another MCB).

First question - do the above observations add up at all? The MCB
thing makes no sense to me at all; I wonder if today's observation
was just a one-off oddity today?

The first time this happened I thought (well, assumed, as I'd
experienced this before) the problem was a duff element in the oven
and just ordered a new one; when it arrived though (during which time
there'd been no more trips) I checked the old and new with a
multimeter, found identical resistance across terminals (20 ohms
IIRC) and to earth (open circuit) and decided I'd been wrong, so
returned the new element unused. Now wondering if I was incorrect in
doing so. Could there be undetected earth leakage (which I don't
have kit to detect? Could it be somewhere else in the oven? Or the
house wiring? Oven is a built-in one about 10 years old; main
element was replaced about 9 months ago.
Right now I'm really confused - I don't know whether I should be
looking at appliances (which!?) or wiring. I'd happily buy a new
bloody oven if that would definitely solve it, but I am concerned it
might not!
Problem's really made worse by being intermittent, and because it
seems to involve appliances we really can't do without.

Any advice on how to proceed most welcome!
Check that the labels actually do match the MCB circuits! And make sure who
ever resets the MCB when it trips notes which one it is.

Any outside circuits on the RCD? I am thinking wet weather and NOT the oven
may be the cause. If it was the oven I would (in most cases) expect it to
happen every time the oven was used.

Good luck.
 
J

Jim K

Check that the labels actually do match the MCB circuits! And make sure who
ever resets the MCB when it trips notes which one it is.

Any outside circuits on the RCD? I am thinking wet weather and NOT the oven
may be the cause. If it was the oven I would (in most cases) expect it to
happen every time the oven was used.
also if a multi-element oven (fan, conventional top/bottom, grill etc)
it may be only when a certain (failing) element is in use...

Jim K
 
B

Bill

ARW said:
Any outside circuits on the RCD? I am thinking wet weather and NOT the
oven may be the cause. If it was the oven I would (in most cases)
expect it to happen every time the oven was used.
My son had the oven occasionally powering down in the middle of cooking
his tea.
We discovered that the oven RCD also fed the "plant room" at the other
side of the garden and the lights up his path. The plant room had
another set of breakers feeding (we think) a faulty light on the garden
wall, a summerhouse (with leaking roof that we still haven't fixed) and
on from there to the pump in the fish pond via a weatherproof box.

It took an awful lot of walking before we isolated the problem to the
weatherproof box. He rewired this and he is now able to rely on hot
meals again.

I may be asking about pond pumps later, because the took the opportunity
to replace the impeller/rotor assembly in the pump. The new one looks
identical to the old, but not worn, turns freely on its shaft and seems
to have equally strong magnets in the same places on the rotor, but the
pump doesn't run when we install it. The old one is now back in there
and the fish seem happy again.

The house has some other rather eccentric wiring.
 
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M

meow2222

Am having a hell of a time with nuisance tripping at the moment. It
You need to troubleshoot, or your efforts will mostly be in vain. I'd insulation test every appliance first.


NT
 
L

Lobster

On 18/03/2013 15:20, Lobster wrote:

You may be barking up the wrong tree.
Hmm, I've just been advised there's been a bit of domestic confusion
about what's causing the trip; apparently our temporarily resident
daughter has been trying to switch to grill mode without realising[1],
when using the oven which (a) may have damaged something and (b)
accounts for some of the muddle. In the interim no more trips so
hopefully it's the grill element. But need to investigate further when
I have a bit of time.
What test equipment do you have access to?
Just an ordinary multimeter. And a lump hammer...

[1] to be fair the icons on the oven dial are completely bizarre and
incomprehensible - I just use it at the "4 o'clock" position without
paying any attention to the icons)
 
C

charles

Hmm, I've just been advised there's been a bit of domestic confusion
about what's causing the trip; apparently our temporarily resident
daughter has been trying to switch to grill mode without realising[1],
when using the oven which (a) may have damaged something and (b)
accounts for some of the muddle. In the interim no more trips so
hopefully it's the grill element. But need to investigate further when
I have a bit of time.
What test equipment do you have access to?
Just an ordinary multimeter. And a lump hammer...
a multimeter almost certainly won't show leakage from the element of the
grill. You will need a "megger" or PAT tester which uses at least 250v
 
R

robgraham

You need to troubleshoot, or your efforts will mostly be in vain. I'd insulation test every appliance first.

NT
I seem to have done my usual of writing to the thread and then failing
to Send it ---dohhh!

About a year or so ago a neighbour was having bother with his barn
lighting. It was an excuse for me to buy one of the Ebay ~£30
insulation testers. Inevitably in the time it took to arrive, the
problem was found and I've never found a further excuse to use it.
Has anyone had any experience of these - do they work - are they to be
relied on?

If there is a favourable answer, then that David, is your solution !!

Rob
 
L

Lobster

About a year or so ago a neighbour was having bother with his barn
lighting. It was an excuse for me to buy one of the Ebay ~£30
insulation testers. Inevitably in the time it took to arrive, the
problem was found and I've never found a further excuse to use it.
Has anyone had any experience of these - do they work - are they to be
relied on?
This type of thing I presume?:
http://www.ebay.co.uk/itm/321021300857

I'm quite interested... (if only to keep in a cupboard as a guarantee of
no further occurrences, like you!)

Are they straightforward to use - are the basically like using a
multimeter on a very high-range resistance setting?

Pitfalls for the unwary, etc?
 
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Z

zaax

Am having a hell of a time with nuisance tripping at the moment. It happens intermittently, and when it does, you can just immediately flip the breaker back and it works again. So it's very hard to localise. It's definitelyin the kitchen; and I'm fairly sure it happens when the oven's on; but seems it may be more likely when the microwave's on as well? When it does trip, it's the main RCD which goes; however sometimes an individual MCB flips as well. I hadn't particularly noticed which one, but I this morning I spotted that it was the main ringmain for all sockets in the house *other* than the kitchen! (the oven has a dedicated radial, and the kitchen sockets - including microwave - are on another MCB). First question - do the above observations add up at all? The MCB thing makes no sense to me at all; I wonderif today's observation was just a one-off oddity today? The first time this happened I thought (well, assumed, as I'd experienced this before) the problem was a duff element in the oven and just ordered a new one; when it arrived though (during which time there'd been no more trips) I checked the old and new with a multimeter, found identical resistance across terminals (20 ohms IIRC) and to earth (open circuit) and decided I'd been wrong, so returned the new element unused. Now wondering if I was incorrect in doing so.. Could there be undetected earth leakage (which I don't have kit to detect? Could it be somewhere else in the oven? Or the house wiring? Oven is a built-in one about 10 years old; main element was replaced about 9 months ago.. Right now I'm really confused - I don't know whether I should be looking at appliances (which!?) or wiring. I'd happily buy a new bloody oven if that would definitely solve it, but I am concerned it might not! Problem's really made worse by being intermittent, and because it seems to involve appliances we really can't do without. Any advice on how to proceed most welcome! -- David
How about one of the heaters. It sounds like that something is expanding (getting hot) then tripping the RCD, like a dry joint in a curcuit board
 
A

ARW

Lobster said:
This type of thing I presume?:
http://www.ebay.co.uk/itm/321021300857

I'm quite interested... (if only to keep in a cupboard as a guarantee
of no further occurrences, like you!)

Are they straightforward to use - are the basically like using a
multimeter on a very high-range resistance setting?

Pitfalls for the unwary, etc?
Well I always get a new apprentice to hold the cables at the other end to
the tester when I am doing a 500V test:)
 
F

Flowerpotgirl

We had this problem with our light circuit, it kept randomly tripping but
then would sometimes go straight back on. It went on for weeks. We ended up
testing all the lights on the circuit but still could not isolate the fault.
Our friendly local electrician and his mate visited and were in the house
for four hours before they finally diagnosed the fault.....a mouse had
nibbled through one of the cables in the crawl space between the first and
second storey. There were burn marks around the nibbled area. Cable was
replaced and all is well now. This also happened to a friend, and her house
burnt down. We got off lightly.

"zaax" wrote in message

Am having a hell of a time with nuisance tripping at the moment. It
happens intermittently, and when it does, you can just immediately flip
the breaker back and it works again. So it's very hard to localise. It's
definitely in the kitchen; and I'm fairly sure it happens when the oven's
on; but seems it may be more likely when the microwave's on as well? When
it does trip, it's the main RCD which goes; however sometimes an
individual MCB flips as well. I hadn't particularly noticed which one, but
I this morning I spotted that it was the main ringmain for all sockets in
the house *other* than the kitchen! (the oven has a dedicated radial, and
the kitchen sockets - including microwave - are on another MCB). First
question - do the above observations add up at all? The MCB thing makes no
sense to me at all; I wonder if today's observation was just a one-off
oddity today? The first time this happened I thought (well, assumed, as
I'd experienced this before) the problem was a duff element in the oven
and just ordered a new one; when it arrived though (during which time
there'd been no more trips) I checked the old and new with a multimeter,
found identical resistance across terminals (20 ohms IIRC) and to earth
(open circuit) and decided I'd been wrong, so returned the new element
unused. Now wondering if I was incorrect in doing so. Could there be
undetected earth leakage (which I don't have kit to detect? Could it be
somewhere else in the oven? Or the house wiring? Oven is a built-in one
about 10 years old; main element was replaced about 9 months ago. Right
now I'm really confused - I don't know whether I should be looking at
appliances (which!?) or wiring. I'd happily buy a new bloody oven if that
would definitely solve it, but I am concerned it might not! Problem's
really made worse by being intermittent, and because it seems to involve
appliances we really can't do without. Any advice on how to proceed most
welcome! -- David
How about one of the heaters. It sounds like that something is expanding
(getting hot) then tripping the RCD, like a dry joint in a curcuit board
 
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