I intend to put a shaver socket into our bathroom, and connect it as a spur to the ring main on the wall just outside the bathroom door. Where do I need to connect earths? To the ring main earth? To the nearest pipework?
I'm confuzzled.
Use a 2.5mm csa' T&E Cable which will give you a good enough earth connecting centre back to the earthing on the ring mains circuit.
It needs to be connected to both the earth of the circuit supplying the power and to the bathroom's equipotential bonding, and the bathroom's equipotential bonding must be connected to any metal back box. You must also bring the bathroom's equipotential bonding up to current spec if it isn't.
Of course, the shaver socket must be the type with an isolating transformer built in. Check the instructions to see what type of circuit it can be supplied from -- I wouldn't be surprised if it can't be directly supplied from a 30A circuit without having an additional lower current fuse in the supply.
My understanding is that you don't need to do anything special regarding shaver sockets and supplementary bonding. If the rest of the bathroom is bonded properly it's all joined together at the main earthing terminal anyway - I don't have my OSG to hand, but it's in there somewhere. On top of that, shaver sockets with isolating transformers are specifically designed so that there is no earth path; even if you touched the live conductor of the shaver socket while holding onto (say) the basin tap you shouldn't get a shock as there is no circuit.
Just wire it up as normal.
But do get the rest of the bonding up to scratch - this is worth doing anyway.
HTH.
Hwyl!
M.
No, Andrew was right. What you say above used to be the case prior to the 'zones' amendment, but that's quite a while ago now.
You are now required to bond to the circuit protective conductors (CPCs) of any circuits feeding equipment located within zones 1, 2 or 3 [Reg.
601-04-01]. This applies even if the equipment is Class II (double insulated) like a shaver point. So as well as the traditional things like shower units, heaters and electric towel rails (all of which are usually Class I) we must now bond to the earth terminals of Class II items like light fittings and shaver points, unless they're outside the zones. Diagrams on pages 30 and 31 of the On-Site Guide show typical arrangements.Remember that you are allowed to use a CPC as a bonding conductor. So if you have a light (or lights) and a shaver point fed from the same lighting circuit, as would be usual, then only one point of bonding is necessary. (A exception to this would arise if the wiring between the various items that need to be bonded takes a tortuous route such that it doesn't remain in close proximity to the bathroom.)
I opened up the boxed in pipework over the weekend and discovered that most of the metal pipes are about 25cm long sections that join the plastic pipework to the taps/WC. Do I bond these sections, or treat the whole as a plastic installation? The only other metal pipes are about 1 meter lengths to the towel radiator, and they go back to plastic pipes in the boxed in section, although go directly through the wall to supply the next room. How long does a metal run have to be before it requires bonding?
... but Class II (double insulated) equipment doesn't *have* a CPC or a CPC terminal does it?
Or are you just saying that the CPC conductors of the feeds to things like shaver sockets need to be bonded to the supplementary bonding (if present) in the bathroom?
If there is only plastic plumbing etc. what is there to connect to the CPC conductor of a feed to a shaver socket?
Thinking aloud a bit here, going on from the above, if there's only one thing that should be bonded (I'm thinking of the bathroom I've just plumbed, only metal thing now is a radiator) is there any need for supplementary bonding? I can't see what one would bond it to.
In message , chris French writes
Whoops, I'd meant to ad some more to that.......
The above document can be found on the Hepworth website above.
However, there seems to be two sets of info about Hep2O, one at the hepworth.co.uk address which includes the above, another (possibly newer) at
which does not.
The above page is not dated so I'm not sure if it was applicable only to the older pre-zone system or not.
Maybe the resident Hepworths luker(s) could comment?
There should be an earth terminal in the wiring accessory where the unused CPC in the fixed wiring is 'parked'.
Yes, precisely that.
CPC terminals of electric shower units, heaters, towel rails etc.; extraneous-conductive-parts in contact with metallic structual parts of the building; CPC terminals of luminaires within the zones fed from another final circuits. If none of those apply, then nothing.
The radiator, if it's fed via plastic pipes, doesn't count as an extraneous-conductive-part. What other electrical equipment is there? If the answer to that is "lighting only" then is it inside the zones? If the lighting and shaver socket are on the same final circuit then the supplementary bonding required is automatically in place (via the CPC). No additional bonding would be required in such a case.
I've replumbed everything *except* the radiator, thus we now have a plastic bath, with plastic connections, plastic connections to loo, cistern and washbasin. However the metal radiator is fed by copper pipes.
The flat was either built before supplementary bonding was required or the installations were so cheap and nasty that they didn't bother with regulations. The standard of plumbing and wiring in general tends to make me feel it might be the latter - though, actually, I suppose since most of the *original* plumbing was plastic too it wasn't required and it was only the bodges with copper that made it wrong.
Anyway, what do I do about the radiator? There's no lighting in the zones (low voltage downlighters, transformers in the roof void). I suppose I could bond the radiator to the CPC of the lighting wiring but I think that's not strictly necessary. There's also now some electrics (outside the zones) below the bath feeding a pump and things like that. I could bond to that. I'm not convinced that any of it's required by regulations though.
Thanks for the discussion - it's helped clarify things.
Over the doorway, I have put a double metal backbox (the sort where the two compartments are divided), and will put the fused spur and the fan isolator onto this. This means the lights, extractor and shaver socket will have common earth just outside the bathroom. If I run an earth wire from the copper pipes (for the towel rail) up the doorframe to this box, then I think I'm done! Many thanks s
The article on earth bonding at:-
The Hepworth Plumbing Products Team
-- Tel: +44 (0)1709 856 300 |Hepworth Plumbing Products Fax: +44 (0)1709 856 301 |Edlington Lane, Edlington Email: snipped-for-privacy@hepworthplumbing.co.uk |Doncaster, UK
The D-I-Y FAQ covers shaver points and states that earthing the transformer core is via the input mains cable.
In the FAQ the following example is given:
"Equi-potential Bonding. As mentioned elsewhere, a fault current flowing in the earth wiring will cause the voltage on that wiring to rise relative to true earth potential. This could cause a shock to someone touching, for instance, the case of a faulty washing machine and a water tap at the same time. In order to minimise this risk, an 'equi-potential zone' is created by connecting the services to the main earthing point. Such services are:
Water Pipes Gas Pipes Oil Pipes Central Heating Metallic Ventilation Trunking Exposed Parts of Building Structure Lightning Conductor Any other Metallic Service "
In the example quoted the washing machine case has become live because of a fault. The earth connection must also have failed or the fuse/RCB would have tripped. How does equipotential bonding help in these circumstances? Making sure every bit of metal in the vicinity is connected to a good solid earth doesn't 'minimise the risk', it maximises it.
Sorry if this subject has been done to death in the past, but I really don't see the benefit.
Point taken. I've re-read the appropriate bit :-)
Interesting that the word used is "may" and not "shall" when talking about the bonding being in close proximity to the area (601-04-01, last bit). Does this mean that the letter of the regulation, though probably not the spirit, means that you could count your lights etc. as bonded because their CPCs return to the CU, and the bonding of pipes etc. in the bathroom also returns to the CU?
Hwyl!
M.
Agreed, no bonding necessary there.
Any metal pipework coming up from the pump into the zones? That would need bonding to the rad, otherwise no.
And you'd bond it to the CPC of a shaver point inside the zones, but it sounds as if there isn't one.
Sounds like it -- though I'd put a deliberate strap (only needs to be 1mm^2) between the earth terminals of the two wiring accessories mentioned, rather than relying on connection via the box and screws.
No, I don't think it means that at all. "May" and "close proximity" are giving an alternative to "in the location" (i.e. the bath or shower room). It allows bonding in the loft above or walls nearby, but not via things running back to the CU, which would defeat the whole object.
No, it's all flexible plastic pipe.
No, no shaver point.
OK, it looks as if I don't need any supplementary bonding now, though the old bath should have been as the old hot water pipe was copper.
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