So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven controls.
NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

On Sat, 08 Aug 2020 18:04:06 +0100, Grumps wrote:

So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven
controls.
NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the
wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

First you need to do a systematic check for earth leakage on all major
components when individually disconnected.....that is heating elements,
control unit, fans and any temperature measuring devices.

On 08/08/2020 18:04, Grumps wrote:
So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven
controls.
NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the wiring.

He may have been doing an insulation resistance test, and detected that
there was some continuity between the live on that circuit and earth.

This could be a fault present in one of the circuits being fed from that
RCD that is "sensitising" the RCD and placing it close to its trip
threshold. Any added leakage from the cooker (or in fact just the switch
on/off surge causing harmonics that get bled to earth by mains input
filters on devices connected to the circuit) could then result in a trip.

The fact that it did not trip when on the other RCD suggests that its
unlikely to be the over circuit itself at fault. It could be one of the
others that share that RCD, or it could also be a faulty (over
sensitive) RCD.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

It could for example be a neutral to earth fault on one of the circuits.
Those can be difficult to find because they only manifest when there is
enough load to cause the neutral voltage to rise enough above the earth
voltage to cause a current flow via the main neutral to earth bond
(which would be in the main cutout on a property with a TN-C-S supply,
or at the substation with a TN-S one)

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Normally when you measure L to N and see anything other than open
circuit, you are measuring the resistance of a load that is still
connected to the circuit somewhere. (that something may not be an actual
appliance but could be some kind of electronic device like a lighting
transformer / PSU, smoke alarm etc.

(if there is a neon or other indicator on the cooker switch, they can
cause odd readings - although normally only with an IR tester rather
than the multimeter)

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?

He's understandably near his wit's end!

If the CU can support a three way split[1], the a RCBO for just the oven
circuit would likely solve it.

[1] i.e. the RCBO must not be powered via either of the current RCDs.

Other than that its a case of testing each circuit in isolation with
appliances unplugged etc.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Saturday, 8 August 2020 18:04:09 UTC+1, Grumps wrote:
So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven controls.
NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

Something somewhere is leaking electrically, probably live to earth. It's not hard to check for - if you don't understand how, one way forward is to insulation test all your household appliances.


NT

Maybe there is something like a psu always on, or maybe a clock?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

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Note this Signature is meaningless.!
"Grumps" wrote in message ...
So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven
controls.
NEFF were called in sometime last year and they replaced the oven controls
and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was wired
back to the cooker point.
He then tested the wiring and said (his words) "there is some continuity"
and suggested a sparks should be called in to check the wiring.

Following my 1st post way back, someone suggested switching off all other
MCBs on that half of the CU. My FiL did this and can report that it seems
better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but when
I checked with a simple multimeter I saw that when the cooker wall switch
was off and the oven disconnected, then there was high impedance between
all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like less
than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone, maybe
using an RCBO?
He's understandably near his wit's end!

and timers etc, no matter how powered. In somebody else's house even an old
QED mains filter in one of the sockets occasionally seemed to cause
tripping. as far as I could tell it consisted of a coil and six capacitors.
Luckily my house being old fashioned does not have fancy breakers and from
what I hear from those who have them tripping events are not uncommon for no
apparent reason.
Could there be some of these devices which are just far too open to slight
issues, like switching transients or something. I'd not like 1K across the
mains all the time if absolutely nothing is running.
What is that about 230Ma all the time running between the connections.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Smolley" wrote in message ...
On Sat, 08 Aug 2020 18:04:06 +0100, Grumps wrote:

So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.

This oven often trips the RCD when it is turned off using the oven
controls.
NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the
wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

First you need to do a systematic check for earth leakage on all major
components when individually disconnected.....that is heating elements,
control unit, fans and any temperature measuring devices.

On 09/08/2020 01:36, John Rumm wrote:
I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker
wall switch was off and the oven disconnected, then there was high
impedance between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N
from the cooker wall switch back towards the CU. The reading was low,
like less than 1k. What was I measuring?

Normally when you measure L to N and see anything other than open
circuit, you are measuring the resistance of a load that is still
connected to the circuit somewhere. (that something may not be an actual
appliance but could be some kind of electronic device like a lighting
transformer / PSU, smoke alarm etc.

(if there is a neon or other indicator on the cooker switch, they can
cause odd readings - although normally only with an IR tester rather
than the multimeter)

The cooker switch does not have a neon, and when I made the measurement
the cooker switch was off and the oven MCB was also off.

Maybe I muffed up the test somehow, so will retest again unless FiL has
got it sorted by getting a sparks in.
FiL has not been a sensible boy recently regarding social distancing, so
I'm going to give him a wide berth for a week or so.

Any chance theres a nail or screw through the cable causing a N to E leak? i.e. to house structure not cable cpc. A multimeter isn't ideal for chasing earth leakage. Really you need a megger and experience in using it.

On 08/08/2020 18:04, Grumps wrote:
So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.




This oven often trips the RCD when it is turned off using the oven
controls.


That is an important bit of info. Often caused by live switching before
neutral on a circuit..


NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

How difficult would it be to RCBO it?

--
Adam

On Sunday, 9 August 2020 21:39:43 UTC+1, ARW wrote:
On 08/08/2020 18:04, Grumps wrote:
So this is an old post revisited. Some of you may remember but it was
December 2018.

Father-in-Law had a new NEFF oven installed by John Lewis. Their
installers said that the MCB needed changing to a 32A part. The
electrician called and checked the wiring and swapped the MCB. He said
that the method the JL installers had used to connect wasn't great;
ideally the copper wires should be wrapped around the screw terminals.




This oven often trips the RCD when it is turned off using the oven
controls.


That is an important bit of info. Often caused by live switching before
neutral on a circuit..

Neutral switching before live. It means a DP switch. N opening first exposes the N-most end of the element to live voltage it doesn't usually see, and leakage then occurs there.


NEFF were called in sometime last year and they replaced the oven
controls and left.

Same problem seems to have continued to plague this oven and NEFF were
called before this lockdown hit. They've just visited and replaced ALL
heating elements. The engineer (who spend about 4 hours there) also ran
the oven from a 13A socket on a different RCD (the CU has two RCDs). It
seemed to work fine, but would still trip the other RCD when it was
wired back to the cooker point.
He then tested the wiring and said (his words) "there is some
continuity" and suggested a sparks should be called in to check the wiring.

Following my 1st post way back, someone suggested switching off all
other MCBs on that half of the CU. My FiL did this and can report that
it seems better, but still occasionally trips.

I'm not sure what wiring the NEFF man said "had some continuity" but
when I checked with a simple multimeter I saw that when the cooker wall
switch was off and the oven disconnected, then there was high impedance
between all terminals at the oven end of the cable.
With the oven MCB off I tried to measure the same impedance L to N from
the cooker wall switch back towards the CU. The reading was low, like
less than 1k. What was I measuring?

Anyway, he seems to be back to square one. What's the next step?
Change the tripping RCD, move the oven MCB outside of the RCD zone,
maybe using an RCBO?
He's understandably near his wit's end!

How difficult would it be to RCBO it?

Insulation testing is what I'd do, it can usually find a leakage problem. Putting your electrical loads onto more circuits rather than the one is another option - using RCBOs and a switch rather than MCBs and an RCD does that.


NT