Earth Bonding / Equipotential woes....

[itsallaboutyou]

Afternoon all. Firstly - I should preface this comment with the fact that I have a sparky coming next week - but I'm just trying to get my head around it so I don't look like an idiot when he comes round!!

The situation is thus... I'm in the process of putting a new bathroom in for the mother in law. All has gone well. I've used a mix of copper piping and these new fangled push fit tee's and elbow's and everything is plumbed in and working perfectly.

The main supply from the street is metal and has a corresponding earth strap on it - which I assume may either a) terminate at the CU, or b) is the end of an earth bond and the pipe itself is the termination.

The next section of pipework is also copper, up into the toilet, where it is joined to some UPVC fittings that were already in situ. This branches up into the loft to supply the header tank (in copper) and also into the bathroom through the wall (in UPVC), where I have connected copper pipe to it. All of the remaining pipework is copper, but with UPVC fixtures and fittings, including the sink taps, bath taps, and shower.

I've tried to do some research, but normally only dealing in wood - the electrical side of things has me perplexed, somewhat! I understand that the reason for earth bonding is to introduce a continuous ground - but surely the use of these plastic fittings, renders that useless?

Should I have done the whole bamming thing in UPVC, thus removing the need for the earth?

As I said - I have a sparky coming round - but forewarned is forearmed.. .and if there is anything that I can do relatively easily to make it less work for the sparky might be beneficial!

Cheers all,

Tom

 

[EFLImpudence]

I understand that the reason for earth bonding is to introduce a continuous ground - but surely the use of these plastic fittings, renders that useless?

No. The bonding is to equalise potential(voltage) during a fault of metal parts which are already earthed.

If your plastic pieces have disconnected pipes from any earth then they do not require bonding. Measurements will determine this.

Should I have done the whole bamming thing in UPVC, thus removing the need for the earth?

It would have removed any doubt.

However, if all the circuits of the bathroom have RCDs then bonding is unlikely to be required.

 

[JohnW2]

Afternoon all. Firstly - I should preface this comment with the fact that I have a sparky coming next week .... The main supply from the street is metal and has a corresponding earth strap on it - which I assume may either a) terminate at the CU, or b) is the end of an earth bond and the pipe itself is the termination.

If a metal water supply pipe enters your property from outside, then it needs to be main-bonded 'as close as practicable' to where it enters your property. It sounds as if that is probably already the case, but your electrician will be able to confirm.

No other main bonding of any other water pipework within the building is required. It is just possible (but pretty unlikely) that 'supplementary bonding' might be required within the bathroom - but, again, your electrician will be able to advise.

Any electrical circuits 'supplying' the bathroom (e.g. lights, shower etc.) need to be RCD protected. Is that already the case?

Kind Regards, John

 

[ericmark]

Big question is if everything is RCD protected or not. When the 17th Edition came out a lot of the requirement for bonding or earthing was removed, however only if whole of house complies with 17th or 18th edition. With the 16th Edition both BS7671:1992 and BS7671:2001 the bathroom lights did not need RCD protection, only from BS7671:2008 was RCD protection extended to bathroom lighting, so it all depends on version of BS7671 that the house is wired to.

 

[itsallaboutyou]

Thanks all.

I think its safe to assume (you know the old saying!) that the electrics are (mostly) compliant as its been rewired periodically over the last few years. I know that the hot water tank is also the proud owner of an earth strap..

From my very, admittedly, limited knowledge the lights are on the RCD side, and the shower i think is on a 40/45A?

Wish I'd taken up a trade now..

Cheers for the advice!!

 

[JohnW2]

From my very, admittedly, limited knowledge the lights are on the RCD side, and the shower i think is on a 40/45A?

If there are 'two sides' to your CU, with some circuits being RCD protected and some not, if the shower is on the non-rcd side (which would seem unlikely), that is an issue that your electrician would need to address, since the shower (as well as the lights) need to be RCD-protected.

Kind Regards, John

 

[itsallaboutyou]

Sorry John, both the lights and the shower feed are on the protected side as far as I know. I’ll have a look later! Just a look, mind.

Thanks for your replies!

 

[AndyPRK]

I believe if you have RCD protection on all circuits, then you don't require any green/yellow wires in the bathroom.
Maybe an easier and more useful way forward

 

[JohnW2]

I believe if you have RCD protection on all circuits, then you don't require any green/yellow wires in the bathroom.

... there are a couple of other requirements (in addition to RCD protection) for omission of supplementary bonding, although those other requirements will usually be satisfied - that's why I told the OP that the need for SB was "just possible (but pretty unlikely).

In any event, if the bathroom is being 're-done' it may well not be possible to avoid the requirement for all circuits serving the bathroom (or even 'passing through' zones of the bathroom) to be RCD-protected.

Kind Regards, John