Electric Shower earth cable - can I join...

Lukie · 13 Apr 2008

Hello all,

I've just installed the wiring for a new electric shower and run the cable to the consumer unit (CU). I've done the same with the supplemental earth bonding, but the cable is a few metres too short and doesn't quite make the CU! There is, I've noticed, another chunky earth cable running parallel to my new earth cable at the point where it runs out, and I wondered whether it's acceptable to join the two cables together with a junction box, rather than join a few metres additional cable to the end of the short one.

Any views would be appreciated.

Andy

Lectrician · 13 Apr 2008

A supplementary equipotential bonding conductor does not go back to the CU!

It links all the CPC's and extraneous conductive parts within the 'special location'.

GaryMo · 13 Apr 2008

It sounds like you want to cut a main equipotential bonding conductor and join it together with you supplementary bonding conductor. DON'T DO THAT!

For a start supplementary bonding conductors don't run back to the main earthing terminal whether it be in the consumer unit or external.

Check the wiki for supplementary bonding in a bathroom.

Lukie · 13 Apr 2008

ummm... maybe I have the terminology wrong. I thought I was supposed to run an earth cable (10mm) from the loft - connected to the water pipe which feeds the shower - and back to the CU. I think my use of the word 'supplemental' was incorrect.

Andy

Lectrician · 13 Apr 2008

Nope.

No need for any earth wire other than the one in the showers cable is required from the consumer unit to the loft.

You do, however, have to provide supplementary equipotential bonding to the bathroom. This does not connect back to the consumer unit though.

Lukie · 13 Apr 2008

Ok, now I'm a little confused. In a previous house I fitted an electric shower; connected the 10mm twin/earth to the shower, then back to the CU. In the loft, I connected a 10mm earth cable to the pipework, then down to the CU (which was a simple run). I had the whole house electrically inspected before renting it out, and it 'passed' without issue.

So I think I'm reading the the earth bonding I'm doing to the loft pipe (connected to the shower) only has to be bonded to the pipework within the bathroom. However, given tiles etc, this is now impractical. Perhaps overkill, but is there any harm in running the earth cable from the loft as I describe, or MUST in be connected to the bathroom pipes?

Andy

Taylortwocities · 13 Apr 2008

Supplementary bonding must be carried out to comply with 16th edition regs. See the WIKI as suggested above.

Its a shame its tiled but you may be able to bond in the airing cupboard or up in the loft.

Dont bring an extra cable back to the MET and connect it up in the bathroom. This could bring a different potential into the equipotential zone. (again - see the WIKI).

If this was done at the old house then it was wrong and should have been picked up on the inspection.

Lukie · 13 Apr 2008

Blimey! The inspection at the previous place was poor, and I'll have sort out the cable.

I'm now happy with the reasons why I shouldn't bond back to the MET. Having checked the airing cupboard, I can't see any existing bonding straps, but it would be easy to bond the new shower pipe to an existing pipe in the airing cupboard. However, given that the shower/airing cupboard are separate rooms, is it ok to do that? I think you're also saying that I could bond in to the loft to a pipe rising from the airing cupboard.

Thanks all for your help so far. Sorry to keep coming back with questions; just trying to clarify where I'm less than 100% certain.

Andy

GaryMo · 13 Apr 2008

Don't forget to include CPC's from any circuits within zones 1,2 and 3, shower being one of them and possibly your lighting circuit.

Lectrician · 13 Apr 2008

And use 4mm

GaryMo · 13 Apr 2008

Lectrician said:
And use 4mm

Lukie · 13 Apr 2008

CPCs... These are Circuit Protective Conductors right? But that's as far as I know what CPC means! So my bathroom light should have a 4mm earth cable going from it to the pipework in the bathroom/airing cupboard?

I'm getting confused now... Really appreciate help from all.

Andy

GaryMo · 13 Apr 2008

Lukie said:
CPCs... These are Circuit Protective Conductors right? But that's as far as I know what CPC means! So my bathroom light should have a 4mm earth cable going from it to the pipework in the bathroom/airing cupboard?

I'm getting confused now... Really appreciate help from all.

Andy

Yes, if any part of that circuit resides in zones 1, 2 or 3. Same for shower.
For the lighting circuit, if you decide it needs to be included then you only need to bond to one part. This can be light fitting or switch.

Lukie · 13 Apr 2008

It gets even more complicated doesn't it!

I've decided that the light fitting is in zone 3 (less than 60cm from bath and room is only 2.33 metres high), so this should be bonded to rest of pipework in bathroom I believe. Having looked at the light fitting from the loft, there are 4 cables: 2 being the ring, 1 to the shaver socket, and 1 to the light switch. Therefore, no bonding with separate 4mm earth cable is present. (Is this common?) Anyhow, do I just connect a 4mm earth cable to the earth of the light, then run to pipework and bond, or do I need a specific type of light fitting?

Back to the shower and bonding the feeder pipe to existing pipework. I believe it's ok to bond to pipes in the airing cupboard. Would someone just confirm that for me.

And... the bathroom is in the process of being tiled/re-plumbed, and the installer had decided to put the earth bonding of the sink taps below the floor (and has tiled over the top). I'm guessing that this is bad practice, makes inspection impossible and should really be visible.

And finally: the radiator - not quite fitted - is apparently planned to have a piece of plastic pipe inserted between it and the main central heating pipework. Am I correct in saying that the radiator will not need to be bonded as it's not directly connected to the metal pipework?

Andy

GaryMo · 13 Apr 2008

Lukie said:
It gets even more complicated doesn't it!

I've decided that the light fitting is in zone 3 (less than 60cm from bath and room is only 2.33 metres high), so this should be bonded to rest of pipework in bathroom I believe. Having looked at the light fitting from the loft, there are 4 cables: 2 being the ring, 1 to the shaver socket, and 1 to the light switch. Therefore, no bonding with separate 4mm earth cable is present. (Is this common?) Anyhow, do I just connect a 4mm earth cable to the earth of the light, then run to pipework and bond, or do I need a specific type of light fitting?

Yes, 4mm to either the light fitting, shaver socket or light switch - up to you which. This should then be connected together with a 4mm earth from the showers CPC and any pipework in the bathroom, for example, hot water, cold water, CH feed and CH return.[/quote]

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Electric Shower earth cable - can I join...

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