Bathroom supplementary bonding question

[Lobster]

Sorry but I'm sure it must be *hours* since we last had one!

I'm currently applying the bonding to an all-copper plumbed bathroom. It's going to have a separate self-contained shower cubicle (still awaiting delivery of that) with its pipework emerging from within a stud partition.

Now, practically speaking I would apply bonding clamps to the shower's H&C pipes where they emerge from the wall, however they will be concealed behind the shower paneling once I've installed it. Therefore, how will the bathroom pass its electrical inspection, if the inspector can't see the clamps?

The shower pipes themselves travel down below the bathroom floor and emerge again at the bath taps, where there will be another couple of clamps. In theory, I understand that I shoudn't need to bond at every tap in the room (I'm doing the basin and toilet feed too), as the copper pipe will do the job - but as the inspector won't be able to see it all, will he accept that there's no plastic pipes anywhere?

Separate issue - also in the bathroom is a white-painted towel rail, connected to the CH via 10mm copper tubing. The picture in the OSG just vaguely shows the bathroom rad being bonded, without details... Do I need to fit clamps to both supply and feed pipes (and not the towel rail itself - don't know where I'd fit one anyway?)

Thanks David

[Andy Burns]

By looking at the photos you take of them before boxing them in?

[Owain]

Photos are one idea, but screw terminals in general aren't acceptable if they're inaccessible.

Ideally you need to bond close to where the shower pipes enter the bathroom - can you get a bond at the opther side of the stud wall, or in the loft above or floor void of an adjacent room?

IMHO if the pipes are bonded where they enter the room at the shower they don't need to be bonded again at the basin /provided/ they don't leave the equipotential zone. If the pipes do leave the equipotential zone then they do need to be bonded again at the basin. It's up to you whether you consider 'below the bathroom floor' to be within or outwith the equi. zone.

If you had >1m of plastic pipe at the edge of the equi. zone the basin wouldn't need bonding anyway, because plastic pipe isn't considered to be a risk of introducing a potential.

IMHO yes at the supply pipes as that is where the potential may be introduced (and join that up to all the other bonding, and then the cpc of the lighing circuit etc. I've seen a lot of bonding where the sparky things "green wire between hot and cold taps and the job's a good'un")

Owain

[Lurch]

On Sat, 17 Feb 2007 14:50:51 GMT, Lobster mused:

Intermediate inspection or he'll just have to believe you.

Who knows, should be fine but depends on the inspector and this weeks revision to acceptable practices.

[Grumpy owd man]

The Inspector could always give it a **category 5 classification** ie

'.....does not comply with current regulations but give it a few weeks and it probably will when they next decide to change their minds about how things should / should not be done....' ;)

[David Hansen]

On Sat, 17 Feb 2007 14:50:51 GMT someone who may be Lobster wrote this:-

Does the towel rail have an electric element?

If it does then it must be bonded as it is part of the electrical system. Assuming that the cord to the element is short and unlikely to be damaged then this can be done by running the bonding cable just to the cord outlet and connecting it to the protective conductor there. The protective conductor in the cord is considered enough (personally I don't like this, but the IEE/IET disagree).

If it does not have an electric element then, assuming all of it is visible, it is unlikely to introduce a potential into the area (just like a radiator, metal window frame or the bit of chain the plug hangs from). However, the pipes to it may introduce a potential (for example an electric cable may be lying on a pipe and the insulation may then melt slowly) so the flow and return pipes should be locally bonded. This only needs to be done once in the bathroom (or nearby) assuming that the pipes are joined by reliable metal to metal contact. Assuming you use proper joints this will actually bond the towel rail as well.

[ARWadsworth]

Snag 33 of the NICEICs "earthing snags and solutions" suggests that you can make the bonding connection out of site by soldering the supplementary bonding cable to the flow and return pipes just below the floorboards as this would be a permant connection and inspection would not be required.

Adam

[Lobster]

Thanks for all the very helpful replies.

The shower pipes travel down from the bathroom taps (which will be bonded there), under the floorboards, along the length of the bathtub and then up into the stud partition behind where the shower unit will stand (ie at the foot of the bath). So I suppose when the bath panel is off, I can ensure the two pipes will be visible through a gap in the floor boards, disappearing under the shower. I could bond there I suppose? But probably overkill anyway given that it's all obviously copper? AIUI providing the inspector is convinced of the integrity of copper between shower, bath, basin and sink, then a single H->C strap would actually be all that's required for the H and C pipework? (and linked to the towel rail).

David

[David Hansen]

On Sun, 18 Feb 2007 13:48:23 GMT someone who may be Lobster wrote this:-

You could do.

Why not run the pipes under the bath, rather than under the floor?

Provided you have proper joints, soldered or compression, then the copper pipes will probably have higher electrical conductivity than a bonding cable. However, some people do want to see bonding near taps and showers, even if a metal pipe is doing the job better.

You also need to connect the bonding cable to the protective conductors of all circuits feeding equipment in zones 1, 2 and 3. This is likely to mean connecting to at least the lighting circuit, though the connection can be made at a suitable junction box near to the bathroom.

I take it that the bath and shower tray are not metallic.

I take it that you have also selected appropriate equipment/switchgear and the wiring system complies with what can be in which zone.

[Lobster]

Well if they weren't already run, I would probably have done so with this issue in mind (but it seemed easier at the time just to put them under the floor out of the way - and the joists run parallel with the bath and all the floorboards were up).

Well, the bathroom electrics are restricted to SELV halogens in the ceiling and a 240V timer fan in the wall (all in Zone 3) wired to a switch on the landing, so my understanding is that I shouldn't be bonding to the cpc of the lighting circuit, right?

Bath is in metal fact, and that will be bonded to its H&C taps.

Thanks David

[David Hansen]

On Sun, 18 Feb 2007 18:07:30 GMT someone who may be Lobster wrote this:-

Which circuit is the fan powered by?

Are they connected by reliable metal to metal contact to the bath itself? Probably not, due to washers. If there is not a suitable bonding point on the bath then a hole can usually be tapped into a suitable bit of the bath.

[Lobster]

The lighting circuit.

Bath has a welded-on tag for the purpose, from which I've scraped away the enamel around the hole in the tag for the reason you describe.

David

[jim]

can you give the source for this document/information please?

TIA

[ARWadsworth]

Sorry, there is no online version.

Adam

[David Hansen]

On Sun, 18 Feb 2007 23:16:15 GMT someone who may be Lobster wrote this:-

Whether the fan is of Class I or Class II construction the protective conductor of the fan circuit must be connected to the bonding.

[Lobster]

Really...? wow. I've had several bathrooms signed off by sparks in the past and that's never been an issue. Anyway, better to find out now rather than in a few days, after the plasterer's been...!

David

[David Hansen]

On Mon, 19 Feb 2007 07:49:41 GMT someone who may be Lobster wrote this:-

Amendment No 3, April 2000, is presumably still available for download. 601-04-01.

[Lobster]

Thanks - new cable duly run, painlessly. I'm glad you raised this! I'll have to educate my sparks on the subject. No, maybe not. (He also insists I supplementary bond the kitchen: I don't argue....

Out of interest though... I'm struggling to work out how either the bathroom or the double-insulated fan up in Zone 3 can possibly be made safer by connecting in the cpc of the fan's circuit to the bathroom's supplementary bonding. In what scenario would it help?

David

[ARWadsworth]

It is there in case the fan is changed to a class I fan. Not very likey I know. The real reason is mainly for the lights. Imagine when SWMBO wants to change the SELV halogens to a 230V class I fitting in a few years time. If the 230V cpc of the lighting is already supplementary bonded you have no extra work to do when you remove it.

Adam

[Andy Wade]

In a few years time (not much more than one year, in fact) the 17th edition will be in force and she'll have the alternative option of putting the lights on an RCD. If all circuits feeding stuff in the bathroom are 30 mA RCD'd and the main bonding is present & correct then no supplementary bonding will be required in the bathroom. At the same time she'll be able to install a 13 A socket or two, provided the room's big enough... (sockets must be at least 3 m horizontally from the edge of zone 1.