Shaver Socket Question

[rabi_sultan]

I recently did the wiring and was getting the certificate for the work I did and the electrician failed an item in the bathroom.

Apparantly my plastic plated shaver socket which is being supplied by the lights circuit (with the 1.5mm earth) requires supplementary earth bonding. He told me to take a 4mm earth wire from the radiator up the wall and take it into the light switch so the light circuit is bonded.

What I don't understand from electrical theory is why does an isolation transformer, which is what a shaver socket is, require supplementary earth bonding?

 

[GaryMo]

It's the bathroom lighting circuit that may require supplementary bonding.
As the shaver socket is supplied by the same circuit then that circuit should be to current BS7671 regulations.

 

[ColJack]

it's the primary side of the transformer that needs bonding..

it still has 240 going to it..

 

[Inlandrevspy]

Good for him to spot it, in January it will be more expensive to meet the (new) rules but we can only begin to guess what the new rules might be.

Luckily my van is stocked up with guesswork - like doing the lottery really.

Pass me some more of that Merlot - it seems to make more sense at the moment

 

[rabi_sultan]

sorry I failed to mention that the primary side is bonded, 1.5mm onto the light circuit. Would that still not be enough for the current (or next) regs?

 

[RF Lighting]

No, that is the CPC. It is NOT part of the bonding unless the lighting circuit is already included in your supplementary bonding, but if that were the case then I would not have expected your electrician to have told you to add the link.

 

[ban-all-sheds]

This would be an electrician from the group which fully understands the difference between earthing and bonding, what is and is not an extraneous-conductive-part, and would never dream of bonding the pipes going to a CH boiler, or a stainless steel sink, would it?

 

[djrichie_t]

Earthing is a very funny subject because its the only place electricity will be flowing under abnormal conditions, so you need to allow for absolutely every eventuality.

Supplementary bonding also allows for equalisation of any potential difference in the event of a nearby lightning strike, hence the need for a minimum of 4mm cable for this to handle any would-be large currents.

At least it will be safer for a bloke to go for a pee in the loo during a storm

 

[Spark123]

I thought the 4mm figure was more to do with mechanical damage?

 

[djrichie_t]

Its part of the reason, but the main contributor was the current carrying capacity, Knowing what lighning is capable of I would always where possible use 6mm and if a bath is fitted, use a proper cast iron one, faraday cage, much safer.

 

[rabi_sultan]

right I understand about the lightning but surely it doesn't apply to a 1st floor flat that also has further bonding through the metal conduit system (which btw has also been bonded at the mains water tap).

 

[djrichie_t]

A close lightning strike can induce current in the most weird and wonderful places. Its a bit overkill adding this into the regs but from an engineers point of view its common sense. Probably a one in a million chance but there was that girl in the papers who was in the shower when lightning struck, and went round her as she was having a shower. Had it been a plastic bath she wouldnt have been so lucky

 

[ban-all-sheds]

Supplementary bonding also allows for equalisation of any potential difference in the event of a nearby lightning strike, hence the need for a minimum of 4mm cable for this to handle any would-be large currents.

Lightning strikes? FFS.

We're straying from the specific situation of the OP, but in general if you bond metal which is not an extraneous-conductive-part you've actually made things less safe, not more.

Hence my post to RF Lighting - there are people out there, including professional electricians, who do not understand earthing and bonding, and who erroneously think that "if it's metal, bond it" is a can't-go-wrong policy....

 

[rabi_sultan]

Well this is an old flat and from my knowledge of construction it has a lightning conductor/arrestor as part of the structure. Should this not take care of the external lightning strike issue or is it something that electricians/persons making the regs ignoring?

 

[RF Lighting]

Ignore the lightning issue, as it is completely irellevant.

You could have had your link in and forgotten about in the time you've spent looking for a reason not to do it

to BAS when have I advocated an "if its metal, bond it" policy?