Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

Thanks

Gerry.

On 6 July, 09:33, GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

I assume that you've earthed them, right?

GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

If you connect the metal socket, but leave it hanging on the wires and
don't screw it to the backbox, does it still trip?

I take it there have been no other changes other than the sockets? (no
re-wiring etc or new circuits)

Is this a split load CU, or one with a single RCD protecting all the
circuits?

Some metal sockets are quite low profile and hence leave less room in
the box. This can compress the wires more, and also allow the fixing
screws to penetrate deeper. That makes it more likely that any small
nicks in the insulation could cause problems. Check the wires carefully
- especially where they pass into the box (it ought to have a rubber
grommet if its a metal back box to protect the wires - but these are
often omitted)


--
Cheers,

John.

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

John Rumm wrote:
GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed.
As soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related
to the RCD tripping but I dont understand why, can anyone explain this
to me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

If you connect the metal socket, but leave it hanging on the wires and
don't screw it to the backbox, does it still trip?

I take it there have been no other changes other than the sockets? (no
re-wiring etc or new circuits)

Is this a split load CU, or one with a single RCD protecting all the
circuits?

Some metal sockets are quite low profile and hence leave less room in
the box. This can compress the wires more, and also allow the fixing
screws to penetrate deeper. That makes it more likely that any small
nicks in the insulation could cause problems. Check the wires carefully
- especially where they pass into the box (it ought to have a rubber
grommet if its a metal back box to protect the wires - but these are
often omitted)


The socket is earthed exactly the same as it was with the plastic sockets.

The socket does still trip if i leave it hanging on the wires.

The CU is a split load in a fairly new build.

There have been no other changes at all, just the socket swap.

I did notice that there was a rubber grommet where the cable enters the
back box but did not scrutinise the cables for nicks etc.

I dont understand how it works ok with the plastic units but trips with
the metal ones! Google did not have much to say about it either!

Thanks for the help so far.

On Mon, 06 Jul 2009 09:33:45 +0100, GMC had this to
say:

Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

This might sound silly, but have you checked that you've connected the
wires to the right terminals? The layout of the terminals can vary
from one make to another.

--
Frank Erskine

Frank Erskine wrote:
On Mon, 06 Jul 2009 09:33:45 +0100, GMC had this to
say:

Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

This might sound silly, but have you checked that you've connected the
wires to the right terminals? The layout of the terminals can vary
from one make to another.

Not silly at all. I did check this and it all looks correct.

On 6 July, 10:14, GMC wrote:

The socket does still trip if i leave it hanging on the wires.

What if you remove it (carefully!) and test it with no socket
connected at all?

What if you do this without the socket faceplate, but with the earth
bonded to the back box?

If you've damaged insulation and you've physically moved the cable
ends, then there's a possibility you've now got a short onto the back
box where the cable enters.

Andy Dingley wrote:
On 6 July, 10:14, GMC wrote:

The socket does still trip if i leave it hanging on the wires.

What if you remove it (carefully!) and test it with no socket
connected at all?

What if you do this without the socket faceplate, but with the earth
bonded to the back box?

I will try what you suggest.


If you've damaged insulation and you've physically moved the cable
ends, then there's a possibility you've now got a short onto the back
box where the cable enters.

But it trips with the faceplate hanging loose and no earth connection
back to the back box.

I will scrutinise the wires for nicks etc.

Thanks

GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

Thanks

Gerry.
Ok, further to a few suggestions I have checked the insulation on the
cables for nicks etc and cannot find any, indeed it all looks perfectly
normal.

As a test i decided to fit a new faceplate to a *different* socket. Same
result, RCD trips. This is with the socket hanging on its own not
screwed to the backbox and not earthed to the backbox.

Im confused.

GMC wrote:
GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed.
As soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related
to the RCD tripping but I dont understand why, can anyone explain this
to me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

Thanks

Gerry.
Ok, further to a few suggestions I have checked the insulation on the
cables for nicks etc and cannot find any, indeed it all looks perfectly
normal.

As a test i decided to fit a new faceplate to a *different* socket. Same
result, RCD trips. This is with the socket hanging on its own not
screwed to the backbox and not earthed to the backbox.

Im confused.

Sounds like the faceplate may be faulty. Can you take the faceplate off
and measure neutral-earth resistance at the connection terminals. This
should be infinity. If it is low or zero, then there is a connection
between neutral and earth on the faceplate that shouldn't be there.

"GMC" wrote in message ...
GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought the
relevant 2 gang sockets from Screwfix, a brushed stainless Volex socket
which will replace the white plastic ones currently installed. As soon as
I connect either of the new metal sockets the RCD in the consumer unit
trips when the power is turned back on. I have triple checked that I am
connecting it up correctly. The fault goes away as soon as the plastic
socket is reinstated. I initially thought that the socket may be faulty
(!) so used the second one which gave exactly the same behaviour. It
seems that the metal sockets are directly related to the RCD tripping but
I dont understand why, can anyone explain this to me or offer a solution
please? (my solution may be to replace the sockets with plastic ones!)

Thanks

Gerry.
Ok, further to a few suggestions I have checked the insulation on the
cables for nicks etc and cannot find any, indeed it all looks perfectly
normal.

As a test i decided to fit a new faceplate to a *different* socket. Same
result, RCD trips. This is with the socket hanging on its own not screwed
to the backbox and not earthed to the backbox.

Im confused.
It is odd, I can only suggest they are both faulty or have been
exposed to moisture or other contaminant.
Disconnect them completely and use a multi-meter set to its
highest resistance range between L&E and N&E. If there is any
measurable leakage at all, take them back.

--
Graham.

%Profound_observation%

On Mon, 06 Jul 2009 11:15:18 +0100, GMC had this to
say:

Andy Dingley wrote:
On 6 July, 10:14, GMC wrote:

The socket does still trip if i leave it hanging on the wires.

What if you remove it (carefully!) and test it with no socket
connected at all?

What if you do this without the socket faceplate, but with the earth
bonded to the back box?

I will try what you suggest.


If you've damaged insulation and you've physically moved the cable
ends, then there's a possibility you've now got a short onto the back
box where the cable enters.

But it trips with the faceplate hanging loose and no earth connection
back to the back box.

I will scrutinise the wires for nicks etc.

Is it actually the RCD that trips, or the MCB? An MCB trips to
over-current, and an RCD trips to a L/N current imbalance.

--
Frank Erskine

On Jul 6, 11:36*am, GMC wrote:
GMC wrote:
Hi there.

I needed to replace two socket plates in my parents kitchen, i bought
the relevant 2 gang sockets from Screwfix, a brushed stainless Volex
socket which will replace the white plastic ones currently installed. As
soon as I connect either of the new metal sockets the RCD in the
consumer unit trips when the power is turned back on. I have triple
checked that I am connecting it up correctly. The fault goes away as
soon as the plastic socket is reinstated. I initially thought that the
socket may be faulty (!) so used the second one which gave exactly the
same behaviour. It seems that the metal sockets are directly related to
the RCD tripping but I dont understand why, can anyone explain this to
me or offer a solution please? (my solution may be to replace the
sockets with plastic ones!)

Thanks

Gerry.

Ok, further to a few suggestions I have checked the insulation on the
cables for nicks etc and cannot find any, indeed it all looks perfectly
normal.

As a test i decided to fit a new faceplate to a *different* socket. Same
result, RCD trips. This is with the socket hanging on its own not
screwed to the backbox and not earthed to the backbox.

Im confused.

maybe your nw metal sockets are a faulty batch. I'd test them. A
multimeter will pick up basic faults.


NT

On Mon, 6 Jul 2009 12:12:56 +0100, "Graham." wrote:


It is odd, I can only suggest they are both faulty or have been
exposed to moisture or other contaminant.
Disconnect them completely and use a multi-meter set to its
highest resistance range between L&E and N&E. If there is any
measurable leakage at all, take them back.

I'm assuming it is the RCD which is tripping. There is another
possibility which is that somewhere in the house is a neutral/earth
fault. These are commonly introduced when a new split load consumer
unit is fitted to old wiring or when a floorboard nail is put through
a cable.

The new metal faced socket may introduce a very small inductive
current, more than the plastic one will. I had a similar fault once
where simply plugging an extension lead (any extension lead, nothing
connected to it) in to a particular socket tripped the RCD. The fault
was eventually traced to a nail linking neutral and earth in an
entirely different circuit in another part of the house. The trip was
caused by the small transformer effect the extension was producing.

It was found by isolating all the neutrals in the CU and measuring
each individually for insulation to earth.

On 6 July, 12:12, "Graham." wrote:

Disconnect them completely and use a multi-meter set to its
highest resistance range between L&E and N&E.

Use a high voltage resistance meter to check this, not just an average
multimeter. Don't complete electrical installation work without one.
If you don't have one, eBay's your friend.

For this sort of fault, a cheap DVM wil probably find the fault,
However I wouldn't "test" the system and claim it didn't have other
faults unless I'd tested the insulation at high voltage. You don't
need a few hundred quids' worth of 17th-ticketed Part-P-tricorder to
do this, just an old hand-cranker or a tenner's worth of cheap Robin
from eBay.

Are the sockets illuminated ? maybe they are badly constructed and use a
neon between switched live and earth ?

Andy Dingley wrote:

Use a high voltage resistance meter to check this, not just an average
multimeter. Don't complete electrical installation work without one.
If you don't have one, eBay's your friend.


I want one...
like this one?

http://cgi.ebay.co.uk/Digital-Insula...71410002r29602

Item number: 360165628074

Digital Insulation Meter Volt Resistance Tester 1000V £50.90

[g]

george (dicegeorge) wrote:
Andy Dingley wrote:

Use a high voltage resistance meter to check this, not just an average
multimeter. Don't complete electrical installation work without one.
If you don't have one, eBay's your friend.


I want one...
like this one?

http://cgi.ebay.co.uk/Digital-Insula...71410002r29602


Item number: 360165628074

Digital Insulation Meter Volt Resistance Tester 1000V £50.90

[g]


Yes, like that, but if you're going to buy one, you should consider
getting one that is compliant with the wiring regulations (introduced in
the 16th Edition). This requires (among other things) that the short
circuit current is a nominal/minimum of 1mA. You will note that all
major branded product will either state "16th/17th edition compliant" in
the general features or state this explicitly in the specification:

e.g. from Megger website:

"Test Current on Load = 1 mA at min. pass values of insulation (as
specified in BS7671, HD 384 and IEC 364)."

The unbranded Chinese model you have seen does not explicitly state
this, which *may* mean that the 500V generator circuit is not capable of
delivering a nominal 1mA into a short circuit, which may in turn mean
that under certain circumstances it's readings may not be trustworthy.

Dave Osborne wrote:
george (dicegeorge) wrote:
Andy Dingley wrote:

Use a high voltage resistance meter to check this, not just an average
multimeter. Don't complete electrical installation work without one.
If you don't have one, eBay's your friend.


I want one...
like this one?

http://cgi.ebay.co.uk/Digital-Insula...71410002r29602


Item number: 360165628074 Digital Insulation Meter Volt
Resistance Tester 1000V £50.90

[g]


Yes, like that, but if you're going to buy one, you should consider
getting one that is compliant with the wiring regulations (introduced in
the 16th Edition). This requires (among other things) that the short
circuit current is a nominal/minimum of 1mA. You will note that all
major branded product will either state "16th/17th edition compliant" in
the general features or state this explicitly in the specification:

e.g. from Megger website:

"Test Current on Load = 1 mA at min. pass values of insulation (as
specified in BS7671, HD 384 and IEC 364)."

The unbranded Chinese model you have seen does not explicitly state
this, which *may* mean that the 500V generator circuit is not capable of
delivering a nominal 1mA into a short circuit, which may in turn mean
that under certain circumstances it's readings may not be trustworthy.
/\
Sorry for the aberrant apostrophe.

Dave Osborne wrote:

Sounds like the faceplate may be faulty. Can you take the faceplate off

Indeed.

and measure neutral-earth resistance at the connection terminals. This

Check the live to earth resistance. If it were a neutral to earth bridge
then it would probably cause a trip even with the circuit MCB off.
(assuming the RCD is shared between a few circuits)

--
Cheers,

John.

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

John Rumm wrote:
Dave Osborne wrote:

Sounds like the faceplate may be faulty. Can you take the faceplate off

Indeed.

and measure neutral-earth resistance at the connection terminals. This

Check the live to earth resistance. If it were a neutral to earth bridge
then it would probably cause a trip even with the circuit MCB off.
(assuming the RCD is shared between a few circuits)


Yes, I thought that, but a live to earth fault would make the plate live
and the OP would probably have noticed the tingle. Probably worth
checking both as Graham said.