Supplementary Earth Bonding

[Richard C]

When supplementary bonding a bathroom does a metal base ceiling light fitting inside zone 3 still require bonding if operated by a pull cord?

 

[JohnD]

I don't think you've expressed it right. The pipework needs to be bonded to the earth of all the circuits entrering the bathroom.

So (1) the metal light fitting needs to be connected to the earth of the lighting circuit (2) the other stuff needs to be connected to the earth of the lighting circuit.

You do not have to run a separate G&Y to every light fitting and switch as they will (should) already have the CPC of the circuit inside them and metal fitttings earthed to it.

Have a search on "supplementary bonding" - there are lots of posts and a download which explains it better than me.

 

[sm1thson]

as john says everything only needs connecting once to daisy chain them together and the cpcs count. theres a nice diagram in this link

 

[JohnD]

That's the one

Great link.

 

[Richard C]

Thanks John; I took it for granted I meant the pipe work (& not the bathroom) but with some of the posts on here maybe I should have been clearer! I already have IEE recommendations but it’s not the easiest of documents to follow for a non spark; or I suspect some that are! The fitting is within 0.6m of the edge of the bath which puts it in zone 3 so I suspected I needed to include it but was unsure if it applied to ceiling fittings.

One other doubt you may be able to clear up for me; does the toilet cistern pipe need to be separately bonded? It’s a feed off the same C/W pipe that’s part of the bath pipework bonding 2m away, or is that sufficient!

 

[Richard C]

Opps sorry guys wasn’t expecting additional replies to come in while I was replying to the first. I'l download the other doc.

 

[JohnD]

If it's a copper pipe, continuous, with metal joints, you only need to bond it once, at the point where it comes into the bathroom (you can even do it just outside, e.g. in an adjacent airing cupboard, for neatness). It is not necessary to bond the same pipe multiple times, e.g. at every tap, though some people do. If you have a cast-iron soil pipe, or lead waste pipes, bond them too.

You can even use the copper pipe as if it was part of the wire (if it is continuous copper it is a good conductor) to save you running G&Y about the bathroom.

 

[Richard C]

This is where I find some of the documents I have confusing; my electric were upgraded last year with new C/U, earth provision & main equipotential bonding of all the services pipework (H/C/CH) inside the airing cupboard. The airing cupboard is just across the hall from the bathroom (probably around 8m of pipe to the bath/sink), does this mean I don’t have to daisy chain everything together again within the bathroom itself & just make one connection from the light earth terminal down to the one of the pipes?

 

[dingbat]

If it's that close, do some measurements:

If the resistance between the CPCs of all circuits in the bathroom zones is less than 0.05 ohms, then they are effectively already bonded. (And if there's onlt the light circuit... sorted!)

If the resistance between all extraneous parts (pipes, etc) is less than 0.05 then they, too, are already bonded, by virtue of their continuous connections

If this is the case then, yes, all you need is one bit of 4 sq mm green-and-yellow between any point on the light circuit to any point on the pipework.

 

[Richard C]

I’ll get prodding with the multi-tester then; I’m sure this is contained somewhere in the relevant docs. but it’s nice to have it explained in easy to understand chunks & what you’ve said certainly makes more sense to me; thanks again guys.