Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

On Saturday, 15 December 2018 09:20:55 UTC, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips.

can be caused by either oven element leakage or a faulty RCD. The former is much more common.

FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

there's no such thing as either. And no reason to change from MCB to fuse.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

90%+ likely the oven is faulty.


NT

On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

--
Adam

On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

Apologies for the thread hijack, but that reminds me. I added a bit to
the RCD article to cover the different sensitivity / detection type
classes of RCD:

http://wiki.diyfaq.org.uk/index.php/...haracteristics

It could probably do with some more practical guidance on selection.


I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?



--
Cheers,

John.

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

Delay time?
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.!
"Grumps" wrote in message
news
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and said
"You need a class A fuse. You've got a class B". They're my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type from
B to A make a difference?

Thanks, and a Merry Christmas!

On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.

Normally when a RCD trips on a switch off event, it indicates that the
RCD is "sensitised" i.e. there is already lots of leakage being seen by
it, and it is close to its tripping point. The step change in current
demand then only needs cause a little extra leakage in the system to
cause a trip. Hence the fault may be elsewhere, or for that matter may
just indicate too many circuits protected by a single RCD.

The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

Hard to say what that might have been about. Perhaps the Neff engineer
just wanted something to blame and get out quick.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

There are different types of MCB; Type B, C, or D. They differ in how
tolerant they are to switch on surges. Typically you use type B devices
on most domestic circuits. Can't see that being an issue here -
especially on switch off.

There are also different types of RCD. The basic one we know and love is
a type AC. Other types include a type A, F, and B. Each of those adds
abilities to detect additional leakage scenarios that the lower level
device may not respond to. Again it seems unlikely that there is an
issue here.

--
Cheers,

John.

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

On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

On Saturday, 15 December 2018 20:57:38 UTC, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

So if power to everything was lost, it has to be the RCD that tripped. That leaves 2 possibilities:
Oven element leaky near the neutral end
RCD faulty.
The 1st is more likely.
Hipot or PAT test the oven & you'll know which it is.
One thing's for su a class A fuse has nothing to do with it.


NT

On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my
FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with a
30mA trip threshold, a maximum switching capacity of 80A, and no time
delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to the
right of the big red switch?

If there is another bit we can't see, does that have another RCD?

Either way, it has quite a number of circuits protected by the same RCD...



--
Cheers,

John.

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

On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my
FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with a
30mA trip threshold, a maximum switching capacity of 80A, and no time
delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to the
right of the big red switch?

If there is another bit we can't see, does that have another RCD?

That is half of the CU. The other half has a similar number of circuits
and another RCD. I'll get another photo later.

Either way, it has quite a number of circuits protected by the same RCD...

Is having lots of circuits on one RCD bad?

On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my
FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with a
30mA trip threshold, a maximum switching capacity of 80A, and no time
delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to the
right of the big red switch?

If there is another bit we can't see, does that have another RCD?

Either way, it has quite a number of circuits protected by the same RCD...

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

On 16/12/2018 08:27, Grumps wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with
a 30mA trip threshold, a maximum switching capacity of 80A, and no
time delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to
the right of the big red switch?

If there is another bit we can't see, does that have another RCD?

That is half of the CU. The other half has a similar number of circuits
and another RCD. I'll get another photo later.

Either way, it has quite a number of circuits protected by the same
RCD...

Is having lots of circuits on one RCD bad?

When you say the oven is been switched off when it trips is that at the
oven or at the switch on the wall?

--
Adam

On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my
FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with a
30mA trip threshold, a maximum switching capacity of 80A, and no time
delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to the
right of the big red switch?

If there is another bit we can't see, does that have another RCD?

Either way, it has quite a number of circuits protected by the same RCD...



And an odd layout. That looks like a new CU and MK main switches are on
the left.

--
Adam

On 16/12/2018 08:55, ARW wrote:
On 16/12/2018 08:27, Grumps wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device,
with a 30mA trip threshold, a maximum switching capacity of 80A, and
no time delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to
the right of the big red switch?

If there is another bit we can't see, does that have another RCD?

That is half of the CU. The other half has a similar number of
circuits and another RCD. I'll get another photo later.

Either way, it has quite a number of circuits protected by the same
RCD...

Is having lots of circuits on one RCD bad?

When you say the oven is been switched off when it trips is that at the
oven or at the switch on the wall?

On the oven itself.

On 15/12/2018 20:57, Grumps wrote:
Thanks. Hope this works: https://ibb.co/TbSsw1t

I'm impressed the electrician printed a nice custom label (I'm going out
on a limb and say it looks like Brother P-Touch tape) instead of
scribbling on the manufacturer supplied paper strip

--
Email does not work

On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

--
Email does not work

On 16/12/2018 09:47, Grumps wrote:
On 16/12/2018 08:55, ARW wrote:
On 16/12/2018 08:27, Grumps wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A
MCB. There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device,
with a 30mA trip threshold, a maximum switching capacity of 80A, and
no time delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to
the right of the big red switch?

If there is another bit we can't see, does that have another RCD?

That is half of the CU. The other half has a similar number of
circuits and another RCD. I'll get another photo later.

Either way, it has quite a number of circuits protected by the same
RCD...

Is having lots of circuits on one RCD bad?

When you say the oven is been switched off when it trips is that at
the oven or at the switch on the wall?

On the oven itself.




Then I would be wanting a polarity test on the oven terminals.


--
Adam

On 16/12/2018 09:50, Tim Watts wrote:
On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

https://www.mkelectric.com/Documents...gue/Sentry.pdf

see the picture on the 3rd page down, would be the more traditional
internal set up for these CUs.

Looks to me like the sparks has modified the setup to match the incoming
cables.

--
Adam

On 16/12/2018 08:27, Grumps wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with
a 30mA trip threshold, a maximum switching capacity of 80A, and no
time delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to
the right of the big red switch?

If there is another bit we can't see, does that have another RCD?

That is half of the CU. The other half has a similar number of circuits
and another RCD. I'll get another photo later.

ok that makes sense (the labels seemed to suggest there were circuits
missing). The layout is a bit strange though... Other than that, it
looks like a fairly standard 17th edition style "split" CU with a pair
of RCDs and the circuits distributed between them.

Either way, it has quite a number of circuits protected by the same
RCD...

Is having lots of circuits on one RCD bad?

Its not "bad" as such, but if you assume that each circuit may have a
small amount of natural leakage[1], then when you add up lots of them
you can get close to the tripping point of the RCD. At that point they
are also more sensitive to being tripped by switching loads.

Do you still get a trip if the oven is turned off at the cooker point /
isolator switch?

[1] For example, socket circuits will often have electronic devices
connected with modern switch mode PSUs, and those will tend to have a
mains input filters that have a small capacitor across the supply, which
will leak a tiny amount at normal mains frequency.


--
Cheers,

John.

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

On 16/12/2018 08:40, Grumps wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with
a 30mA trip threshold, a maximum switching capacity of 80A, and no
time delay.

The circuit breakers are all normal type B devices...

Nothing there that should have any compatibility problem with an oven.

Is that photo of the whole CU, or are there more circuit breakers to
the right of the big red switch?

If there is another bit we can't see, does that have another RCD?

Either way, it has quite a number of circuits protected by the same
RCD...

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

In some cases it could be (and is in fact what I did on my own CU to
move the kitchen off the 30mA trip RCD and give it its own). However
with the setup I am guessing is here it might be tricky to get the RCBO
in there so that its not still being fed from one of the existing RCDs.

ISTM that a check on the oven circuit polarity, and insulation
resistance test on it might be a good start before looking further. Also
testing that RCD with a "ramp test" would be worthwhile.


--
Cheers,

John.

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

On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my
FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with a
30mA trip threshold, a maximum switching capacity of 80A, and no time
delay.


And a 7880s RCD is a bog standard AC type.

A ramp test would be interesting.


--
Adam

On 16/12/2018 11:17, ARW wrote:
On 16/12/2018 01:36, John Rumm wrote:
On 15/12/2018 20:57, Grumps wrote:
On 15/12/2018 09:41, ARW wrote:
On 15/12/2018 09:20, Grumps wrote:
Hi
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.

The problem is, that when the oven is switched off, sometimes the
RCD trips. FIL just says "the fuse blows", but other circuits are
also affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit
and said "You need a class A fuse. You've got a class B". They're
my FIL's words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD
type from B to A make a difference?

Thanks, and a Merry Christmas!

This must be a RCD thing. There is and has never been a type A MCB.
There are however type A and type B RCDs.

I would be surprised if your FiL has a type B RCD unless he has an
electric car charging point..

Any chance of a photo?

Thanks. Hope this works: https://ibb.co/TbSsw1t

ok so that tells us the RCD is a bog standard double pole device, with
a 30mA trip threshold, a maximum switching capacity of 80A, and no
time delay.


And a 7880s RCD is a bog standard AC type.

A ramp test would be interesting.


Seems to be an echo in here this morning John:-)

--
Adam

Grumps wrote:

Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

Older ovens used to have lazily designed electronics power supplies
using a dropper capacitor from the mains. If this is the case, on
switching off a transient from discharging the DC supply at the bottom
of the capacitor to earth could pass through the capacitor via the (now
disconnected) live circuitry of the oven which may be fairly low
resistance to neutral, and via the intact neutral oven connection
through the RCD to incoming neutral. This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

An annoying workaround would be to always turn the oven off at the
isolating switch on the wall.

--

Roger Hayter

ARW wrote:

On 16/12/2018 09:50, Tim Watts wrote:
On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

https://www.mkelectric.com/Documents...gue/Sentry.pdf

see the picture on the 3rd page down, would be the more traditional
internal set up for these CUs.

Looks to me like the sparks has modified the setup to match the incoming
cables.

Why do you need a main switch when all the cirtuits are RCD protected?
Is it just to isolate the live busbar instead of using the main supply
switch, if any?

--

Roger Hayter

On 16/12/2018 15:51, Roger Hayter wrote:
ARW wrote:

On 16/12/2018 09:50, Tim Watts wrote:
On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

https://www.mkelectric.com/Documents...gue/Sentry.pdf

see the picture on the 3rd page down, would be the more traditional
internal set up for these CUs.

Looks to me like the sparks has modified the setup to match the incoming
cables.

Why do you need a main switch when all the cirtuits are RCD protected?
Is it just to isolate the live busbar instead of using the main supply
switch, if any?


There need not be a main switch as part of the CU but AFAIK you do need one.

--
Adam

On Sunday, 16 December 2018 15:36:20 UTC, Roger Hayter wrote:
Grumps wrote:

Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

Older ovens used to have lazily designed electronics power supplies
using a dropper capacitor from the mains. If this is the case, on
switching off a transient from discharging the DC supply at the bottom
of the capacitor to earth could pass through the capacitor via the (now
disconnected) live circuitry of the oven which may be fairly low
resistance to neutral, and via the intact neutral oven connection
through the RCD to incoming neutral. This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

An annoying workaround would be to always turn the oven off at the
isolating switch on the wall.

Not true of course.

On 16/12/2018 09:50, Tim Watts wrote:
On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

Here's the rest of the CU:
https://ibb.co/XXz2rXf
https://ibb.co/gDLKSCc

On 16/12/2018 16:34, Grumps wrote:
On 16/12/2018 09:50, Tim Watts wrote:
On 16/12/2018 08:40, Grumps wrote:

If there are too many circuits on this RCD, is a simple solution to
replace the oven MCB with an RCBO?

Not at is - the busbar would still be supplied from the RCD that would
be equally likely to trip as the RCBO.

Unless the other side (assuming a split load board) is non RCD - that
would work, if the wires had enough slack to be moved over.

Here's the rest of the CU:
https://ibb.co/XXz2rXf
https://ibb.co/gDLKSCc

I should add that the red lights are a result of the flash on the
camera, and they are not actually illuminated.

wrote:

On Sunday, 16 December 2018 15:36:20 UTC, Roger Hayter wrote:
Grumps wrote:

Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

Older ovens used to have lazily designed electronics power supplies
using a dropper capacitor from the mains. If this is the case, on
switching off a transient from discharging the DC supply at the bottom
of the capacitor to earth could pass through the capacitor via the (now
disconnected) live circuitry of the oven which may be fairly low
resistance to neutral, and via the intact neutral oven connection
through the RCD to incoming neutral. This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

An annoying workaround would be to always turn the oven off at the
isolating switch on the wall.

Not true of course.

It does assume the oven has a mains switch in the live supply which,
come to think of it, my last two cookers didn't have. If it does, it
*could* be true.

If the OP is just talking about switching the oven heating off, with the
electronics and switches still live, then it is clearly a leaky element,
which could easily be checked with a Megger or similar with a bit of
dismantling. My old grill did precisely this, tripped on turning off
one of the elements. I also didn't think if through and changed the one
that *wasn't* being switched off first!

--

Roger Hayter

On 16/12/2018 15:36, Roger Hayter wrote:

This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

From the picture he has a type AC RCD, and they are insensitive to
unipolar currents. So switching to any of the other types would make
that kind of trip more likely.


--
Cheers,

John.

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

John Rumm wrote:

On 16/12/2018 15:36, Roger Hayter wrote:

This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

From the picture he has a type AC RCD, and they are insensitive to
unipolar currents. So switching to any of the other types would make
that kind of trip more likely.

Ok, sorry, I got type A and type AC the wrong way round. I'll go with
everyone else that it is a defective component, very probably a heater
element, especially given that it happens on switching off.

--

Roger Hayter

On 16/12/2018 20:57, Roger Hayter wrote:
John Rumm wrote:

On 16/12/2018 15:36, Roger Hayter wrote:

This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

From the picture he has a type AC RCD, and they are insensitive to
unipolar currents. So switching to any of the other types would make
that kind of trip more likely.

Ok, sorry, I got type A and type AC the wrong way round. I'll go with
everyone else that it is a defective component, very probably a heater
element, especially given that it happens on switching off.



Switching on and tripping would suggest a defective heating element.

--
Adam

ARW wrote:

On 16/12/2018 20:57, Roger Hayter wrote:
John Rumm wrote:

On 16/12/2018 15:36, Roger Hayter wrote:

This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

From the picture he has a type AC RCD, and they are insensitive to
unipolar currents. So switching to any of the other types would make
that kind of trip more likely.

Ok, sorry, I got type A and type AC the wrong way round. I'll go with
everyone else that it is a defective component, very probably a heater
element, especially given that it happens on switching off.



Switching on and tripping would suggest a defective heating element.

Absolutely, but having recently investigated a switching *off* and
tripping problem in my cooker I know that a leaky element can do this!
I can't explain it convincingly, but perhaps the leak was so near the
neutral end the leakage was equal in both wires when switched on. The
observation, and the cure with the new element, was completely
consistent though. The measured leakage was quite low, about 50kohms at
100v when cold. Which really means nothing much about when it was hot
at 240v except that it wasn't a dead short.

--

Roger Hayter

On Sunday, 16 December 2018 20:14:00 UTC, Roger Hayter wrote:
tabbypurr wrote:
On Sunday, 16 December 2018 15:36:20 UTC, Roger Hayter wrote:

Older ovens used to have lazily designed electronics power supplies
using a dropper capacitor from the mains. If this is the case, on
switching off a transient from discharging the DC supply at the bottom
of the capacitor to earth could pass through the capacitor via the (now
disconnected) live circuitry of the oven which may be fairly low
resistance to neutral, and via the intact neutral oven connection
through the RCD to incoming neutral. This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

An annoying workaround would be to always turn the oven off at the
isolating switch on the wall.

Not true of course.

It does assume the oven has a mains switch in the live supply which,
come to think of it, my last two cookers didn't have. If it does, it
*could* be true.

It can't possibly be true. Capacitor power supplies don't run live to earth, but live to neutral. And no new appliance passes enough i to E to trip an RCD.

And there's nothing lazy about capacitor PSUs.


NT

On Sunday, 16 December 2018 21:03:27 UTC, ARW wrote:
On 16/12/2018 20:57, Roger Hayter wrote:

Ok, sorry, I got type A and type AC the wrong way round. I'll go with
everyone else that it is a defective component, very probably a heater
element, especially given that it happens on switching off.



Switching on and tripping would suggest a defective heating element.

Yes. So does tripping on switch off. I'll leave it to the electrician to explain how.


NT

"Roger Hayter" wrote in message
...
Grumps wrote:

Hi
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.

The problem is, that when the oven is switched off, sometimes the RCD
trips. FIL just says "the fuse blows", but other circuits are also
affected - hence I'm guessing he means the RCD.
The NEFF engineer turned up and took a look at the consumer unit and
said "You need a class A fuse. You've got a class B". They're my FIL's
words.

So, can anyone decipher this and say what needs changing and why?
Can you even get a class/type A MCB? Why would changing the RCD type
from B to A make a difference?

Thanks, and a Merry Christmas!

Older ovens used to have lazily designed electronics
power supplies using a dropper capacitor from the mains.

Trouble is that it’s a NEW oven.

If this is the case, on
switching off a transient from discharging the DC supply at the bottom
of the capacitor to earth could pass through the capacitor via the (now
disconnected) live circuitry of the oven which may be fairly low
resistance to neutral, and via the intact neutral oven connection
through the RCD to incoming neutral. This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

An annoying workaround would be to always turn the oven off at the
isolating switch on the wall.

--

Roger Hayter

On 16/12/2018 20:57, Roger Hayter wrote:
John Rumm wrote:

On 16/12/2018 15:36, Roger Hayter wrote:

This probably should not be
enough to trip if the RCD is not already carrying a leakage current, but
would be a design fault. It is true that an RCD insensitive to
unipolar currents (?? type A) would prevent this tripping, but you
shouldn't have to change it!

From the picture he has a type AC RCD, and they are insensitive to
unipolar currents. So switching to any of the other types would make
that kind of trip more likely.

Ok, sorry, I got type A and type AC the wrong way round. I'll go with
everyone else that it is a defective component, very probably a heater
element, especially given that it happens on switching off.

Dodgy heater elements are well known for RCD trips, however I would
expect it to do it either at switch on, or while running. Not
necessarily at switch off. So while a dodgy heater element is possible,
there are other possible causes.


--
Cheers,

John.

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

John Rumm wrote:

Dodgy heater elements are well known for RCD trips, however I would
expect it to do it either at switch on, or while running. Not
necessarily at switch off.

Turn off all the other MCBs on the left side of the CU, then see if
turning the oven on/off still reliably trips the left RCD, will tell you
if some other circuit is taking the RCD to the brink, or whether the
oven alone can trip the RCD ... might save finger pointing between John
Lewis and the sparky

On Mon, 17 Dec 2018 11:44:41 +1100, cantankerous trolling geezer Rot Speed,
the auto-contradicting senile sociopath, blabbered, again:

Older ovens used to have lazily designed electronics
power supplies using a dropper capacitor from the mains.

Trouble is that it¢s a NEW oven.

Trouble is that you really are an OLD cantankerous trolling geezer, Rot
Speed!

--
FredXX to Rot Speed:
"You are still an idiot and an embarrassment to your country. No wonder
we shippe the likes of you out of the British Isles. Perhaps stupidity
and criminality is inherited after all?"
Message-ID: