shaver sockets and bathroom bonding

[Ronald Raygun]

What supply earth to the shaver socket? It's a two pin plug - no earth.

[Fred]

Hi,

My newserver has a lot of old posts made here about shaver sockets and I have tried to read them all.

It seems that shaver sockets with an isolating transformer can be connected in the bathroom to the ring main via a FCU but as the ring is often not available the more common approach is to connect it to the light radial, where a FCU is not necessary but some people chose to fit them for isolation purposes.

So far so good. However the supply earth to the shaver socket needs to be bonded and this is where I begin to get confused. My questions are:

What size cpc do you use? Some posts suggested big fat earth cable (10mm^2, 16mm^2?), whereas others said the cpc of the T&E would be fine. Which is right?

The bath, radiators, and basin taps are bonded with "big fat" earth cable as far as I can see. I don't know where the cable runs under the floorboards so I don't know whether it stays in the bathroom only, or whether it goes back to the CU. This would have been done some time ago, so possibly is not up to the current regs? Also some of the copper pipe would have been replaced with plastic since then, so it could probably do with someone having a look at it all.

Where do you connect the earth from the light radial to everything else? Some posts suggested that if they both ran back to the CU's earth bar, that would be fine, but other posts seemed to contradict this and suggest it had to be done locally. Having a yellow and green cable down the wall would not look pretty imho. I am pretty sure that my light is not earth bonded at the moment so if I had a socket, this would have to be done. Does it need doing even if I don't have a socket fitted?

TIA

[ARWadsworth]

It would be 4mm^2 cable OR the cpc. You would use 4mm^2 cable between the hot and cold pipes, the bath (if metal), the radiator and to the cpc of every electrical circuit in the bathroom. However this is where the cpc comes into play. You would typically have a pull switch and a light in the bathroom. You would not need to run a 4mm cable between the two - the cpc will act as the bonding between the light and the switch. The same will apply to your shaver socket if it is supplied from the lighting circuit - the cpc will act as the bonding provided the lighting circuit is supplementary bonded.

The bonding needs to be attatched to the cpc of each seperate electrical circuit that enters the bathroom - eg if you also have an electric shower that would need to be bonded.

Supplementary bonding need not run back to the CU.

The usual method is to run a 4mm under the floorboards from the bathroom and up the airing cupboard to the bathroom light. Easier said than done.

How are you going to run the 1mm T&E down to your shaver socket without it looking as ugly as a green/yellow wire running down the wall?

Cheers

[ARWadsworth]

?????????????

[Ronald Raygun]

What I meant was that there are only two wires to the shaver socket, to engage with the two pins on the shaver plug. Neither of the two wires/contacts is ever live relative to earth because they are coming from a transformer and so both should have high impedance to mains. There are usually no other metal parts on a shaver socket (are there?) and so no earthing is required (for the same reason the shaver flex is

2-conductor earthless despite the shaver itself having metal parts).

[Tim..]

I've heard it all now!!!

Tim.

[ARWadsworth]

Are you not going to give Jerry and Harry their say before jumping to that conclusion:-)?

[John Rumm]

There is a wiki article for that:

(perhaps we should trademark that phrase before apple gets any ideas!)

The key is that it is the circuit earth that is bonded rather than the shaver socket specifically. So if it is on the lighting circuit, then a bonding connection can be made at any convenient place.

You can use the CPC of the supply cable flex. If you need a discrete wire (say to pipe clamps) then 4mm^2 green/yellow single is the stuff.

It does not need to go back to the CU explicitly (although usually does by virtue of the bonds to the circuit CPCs)

Sounds ok so far. The key question to ask for each bit of metal is "can it introduce a potential into the room?" i.e. is it connected (electrically) to anything outside the room that could be earthed, or could become live under fault conditions.

The purpose of the EQ bonding is to limit the maximum touch voltage one can be exposed to. If the bond is too far away or made using too thin a wire then this voltage could exceed the 50V allowed. Hence the requirement that it is "close" to the room. That can mean in the rood adjacent etc. If the CU were the other side of the wall or in the room below, then you could make a fair case for that being close enough.

Under the 17th edition it is permissible skip EQ bonding in a bathroom altogether so long as all circuits that enter the room are protected by a 30mA RCD, and the main EQ bonds to incoming services are in place elsewhere.

If you do go the supplementary bonding route, then you may find the that lighting circuit supply cable is available under the floor for example (perhaps on its trip up to the loft), and hence connection could be made here between its CPC and your other bonding conductors.

In the shower room I did in my loft on the last place, I had the supply ascending to the ceiling running up through a small airing cupboard in the corner of the room. Hence it was easy to introduce a junction box and make connection there.

[ARWadsworth]

As you seem to be using the 16th edition not the 17th edition (nothing wrong with that BTW) here is everything you need to know

[cpvh]

I presume by "could be in the rood adjacent" you meant the room adjacent, rather than the road adjacent (which is what I first thought of) you might like to correct the wiki if the error is there also.

Cheers

Chris (not normally picky, but it pays to get electrickery right).

[John Rumm]

Indeed - my fingers are not fully under my control sometimes!

True, although I would quite like to see an attempt to wire supplementary equipotential bonding in the adjacent road! ;-)

[geoff]

"... Your honour..."