Decorative Metal Sockets

Ive fitted over 100 metal switches/sockets this year so here are my views on the subject.

Brass sockets can oxidize and go green if coming in to contact with damp or certain paints, so any gasket is giving a small bit of clearance between the surface and anything else.
I've only fitted the more expensive types and they usually have a foam/soft material? backing.
Also if the wall is not 100% flat it allows a good fixing.

I always earth the metal box, whether plastic or metal plate fitted, as this is an 'extraneous' metal part.
Sure if its a plastic patress or cavity box the leave the Earth in a connector.
I believe there is a guideline for this, just one of those things you know but don't know where from.
Anyway I justify it by knowing that when screwing back the plate, if the grommet pops out and the insulation is cut into by the box, then rcd will trip.
Otherwise you risk the plate screws becoming live.
Oh, and the NIC inspector will probably pull you on it!

 

this came up in a guidence note iirc

provided the box has at least one fixed lug and the socket has provision for earthing the screws (most do) you do not need an earth link

most still consider it good practice though

 

I've always been a bit baffled by this, in fact I was going to start a thread:

The regulations state that the (metal) backbox must be earthed, and as far as I know you are supposed to provide an earth link between the earth terminal on the socket and the backbox.

But the socket screw on the fixed lug is effectively earthing the backbox so why is there a need to provide an additional link (assuming of course that the socket earth terminal does have provision for earthing the screws, and as plugwash says, most do)?

 

this did come up in a guidence note though i can't remember which one

an earth link wire is not required (and you should connect earth wire directly to socket) provided the following are true:

1: the socket has an earthing bar on the back
2: the box is not being relied upon to carry the earth (pyro/swa/conduit)
3: the box has at least one FIXED lug

 

That's exactly the way I understand it too, and that's why I'm baffled - on the odd occasion I have to provide an NICEIC certificate (yeah, I know), and as I am not an NIC member I have to have these jobs inspected by an NIC member.

There are three NIC guys that I occasionally use for this purpose, and all three insist that a separate earth link must be provided. WHY??? Nobody seems to know why...

 

probablly just cering thier arses

imo its sensible to anyway though as it helps maintian protection in the event of damage

 

Agreed, I always do it anyway. I'd still like somebody to clear up the issue though.

 

Always run a earth loop wire between metal box and all socket plates.

 

Well as I said above, once you've stripped the cores of the outer pvc it is only singly insulated and the metal box can be construed as an 'extraneous' metal part.

I have pushed back sockets before and nicked a core on the back box and tripped the RCD. Not 'All' plate screws join to earth.
Some sockets dont have the earth bar go that far.

An old Spark once told me 'You can never bond too much'.

 

It is to do with the chemical reaction between the brass plate and the plaster which may have a partial component of lime simple chemistry. What type of sparks are we employing.

 

You must be of the old school like myself

 

see septic's rely

 

Well as I said above, once you've stripped the cores
of the outer pvc it is only singly insulated and the
metal box can be construed as an 'extraneous' metal
part.

I have pushed back sockets before and nicked a core
on the back box and tripped the RCD. Not 'All' plate
screws join to earth.
Some sockets dont have the earth bar go that far.

An old Spark once told me 'You can never bond too
much'.

the problem with bonding is that if you DO touch something live then a good earth path is going to be bad for you

and at least domestically bonding means bonding to the earth system or to stuff attached to the earth system

there is a good argument for earth free equipotnential bonding in the bathroom but it would require carefull appliacation to be safe

 

Yes Plugwash, I do agree that certain things should not be bonded.
For instance, a metal free standing table in a kitchen if bonded is unnecessarily introduced into the electrical system.
But I guess there is no right or wrong, just circumstances.

 

It is to do with the chemical reaction between the
brass plate and the plaster which may have a partial
component of lime simple chemistry. What type of
sparks are we employing.

no, it isnt.
you wont get anything happening with a brass plated socket outlet and any lime that may be present in the building fabric.

an earth link has to be used only where there isnt a fixed lug present, as the knowledgable plug has already stated! after that its just best practice.

 

Yes it is. This happens with mirrors too. Screw a silvered mirror to the wall in your bathroom and it starts to corrode. Certainly the damp helps, but i think there is also something in the emulsion paint. And with a nice earthed metal plate you may get exciting electrolytic effects too.

Ultimately though, those stupid plastic surrounds look awful and you might as well not have them and accept having to redecorate.