Earth Bonding

[Adrian Brentnall]

HI all We're hoping to sell our bungalow soon in anticipation of an overseas move (Ireland).

With this in mind - I'm looking around the property at things that a surveyor might find fault with. Have already sorted all the little 'nearly finished' bits of decorating that we've lived with for 5 years - and now thinking about the electrics.

Although the electrics are now much improved over the original slightly dodgy, elcb, wire-fused installation - one thing that I never got round to was the earth bonding. I've read up in the faq, and in my Which DIY Electrics book - but I'd like some clarification if possible..?

1) We use Calor (big red cylinders) for gas. Should the incoming small-bore gas pipe be bonded back to the main earth ? - even though the gas hob and the gas cooker are both connected to mains earth via their own 3-core cables....

2) The airing cupboard looks like a good place to connect 'everything to everything' - as the central heating piping, the power-shower pipework, the solar heating pipework, the general hot & cold pipework and the water pipe from the well all pass through here. Is bonding here a good idea / acceptable ?

3) I understand that bonding hot, cold and exposed metalwork is necessary at kitchen sinks and bathrooms - does this bonding need to extend back to the common mains earth by the switchboard ?

4) Anything else I should be thinking of ?? regarding a possible survey...

Thanks Adrian - Suffolk UK ======return email munged================= take out the papers and the trash to reply

[bigcat]

to met 16th edn regs yep

no and no

no, just bathroom needs equi bonding to conform to latest regs.

no

everything.

NT

[Andrew Gabriel]

Yes.

Not necessarily. Bonding of sevices which come in from outside needs to be done where they enter the house, normally within

300mm on house side if the isolating valve. Bonding of bathroom pipework should be done in the bathroom or immediately adjacent to it. If the airing cupboard fits one or both of these requirements, then that's a good option. Otherwise it's a waste of time as you will still need to bond at the required locations.

Only necessary in bathrooms. People often do kitchens too, but there's no requirement to do so in the regs. The bonding should be to the earths of local circuits -- a dedicated earth conductor back to the switchboard is not required for bathroom bonding (it is for the service bonding above). Normally, 4mm² earth cable is used for bonding, but that can be dropped down to 2.5mm² if the cable is protected from damage.

Water supply should be bonded back to the main earth terminal too. Service bonding should be done with 10mm² earth wire. The main earth terminal should be connected to the supplier's earth connection with 16mm² earth wire.

[Adrian Brentnall]

OK - that's going to be a pain ! I can get access to the gas pipe outside near the gas bottles, or inside, near the gas hob. If I connect at the hob then it's going to be a mare to get back to the main earth bonding terminal....

There isn't a meter (obviously) or a valve - other than the ones on the cylinders themselves.

This part of the installation was done by the previous occupant.... - wish I'd known about the need to do the bonding on the gas pipe when I had the kitchen floors up 4 years ago - would have been very easy back then..... not so easy now......

The incoming water supply is in black 'alkathene' pipe from the well

- turns into copper pipe in the airing cupboard....... - I've described the gas supply arrangement above.

I'm interested in the 'immediately adjacent' option. The power shower mixer is fed through the wall from the airing cupboard by copper pipe

- can I bond it in the airing cupboard ? Likewise, the jacuzzi is fed by a short pipe-run from the airing cupboard - should this be bonded at the pipe under the taps... or can it be done in the airing cupboard ?

OK - that's worth knowing - thanks !

OK - I can come throught the bathroom wall to reach a 13A socket in the hall - so I could pick up the earth from there ?

Even in the case of the well-water system I've described. The only place that the water pipe from the well goes is into the cold storage tank in the loft...

OK - so that's just for the gas, then ??

Yes - that's done - but thanks for reminding me...

Adrian Suffolk UK

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[Andrew Gabriel]

The bonding can be done outside the house. Actually this is common for (natural) gas supplies with outside meters. I'm not familiar with how a bottled gas supply is setup.

OK. Just include it in the bathroom bonding then.

Assuming it's all copper pipework, either. The bath (if metal) needs bonding to the tap pipework too, which is normally done under the bath.

It should be to the circuits which supply the bathroom such as the lighting circuit. Ring circuit is less likely to supply anything in the bathroom, but if it does, then bond that too.

Yes.

[usenet]

Hello Adrian!

The bonding in the bathroom is only required to join all the bits of exposed metal (well strictly conductors) together, it doesn't actually need to be connected to any mains wiring earth anywhere.

[Adrian Brentnall]

Aha - that makes it a tiny bit easier....... still another of those 'If only I'd known that when I had the floor up...' jobs.

Ah well - we live & learn......

How's those chickens ??

Adrian

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[usenet]

They're fine, if noisy at times. One is on and off broody but she seems to be in a not broody period at the moment.

[Adrian Brentnall]

Glad to hear that they're both well......

Our remaining flock is promised to a friend in Nacton once we get round to moving house..... ... and we'll have to get some (new) Irish chickens when we get over there....

Adrian

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[Martin Angove]

Err... and I'm sure someone else'll be along in a minute to say the exact same thing, yes it does. For example, fig. 4d and 4e in the OSG:

"The protective conductors of all power and lighting points within the zones must be supplementary bonded to all extraneous-conductive-parts in the zones, including metal waste, water and central heating pipes, and metal baths and metal shower basins."

There's no need to connect to the E of a socket in the hall, unless the circuit supplying that socket also supplies something in the bathroom and that is the best place to connect to it. However the "protective conductors" (earth wires) of all electrical items in the bathroom must be supplementary bonded to the metalwork.

Hwyl!

M.

[usenet]

Yes, quite right, but the bathrooms I've worked in simply don't *have* any power and lighting points within the zones. It's hardly unusual for there to be nothing electrical except lighting which can often be outside the zones.

[Stefek Zaba]

Martin Angove wrote:

There's two reasons for quibbling with your quibble. The narrow, quibbly quibble is that the quote from the OSG itself, and the Figs 4d and 4e (see the luminaire and pull-cord sw in 4d, and the pull-cord sw in 4e), clearly say it's protective conductors *within* *the* *zones*, whereas you wrote 'all electrical items in the bathroom'.

That's the picky-picky reason. The deeper reason is about good teaching/explanation: as I know you know well, bathroom supplementary bonding is about creating a *local* equipontial zone among all the metallic-and-capable-of-introducing-a-potential bits of metalwork within the reach of a numpty in the bath/shower. For that safety purpose, it matters not a jot whether the bonding's referenced to the installation earth or not. In *practice*, 99 times out of a hundred, it will end so referenced, since at least one, overwhelmingly-likely most, and probably all, of those bits of metal will already, in non-fault conditions, be earthed - copper pipework at the water-supply entry, and most likely again through a CH boiler's electricity supply, and again through the water-tank boiler's immersion-heater earth connection; the light(s), switch(es), shaver-point, FCU-supplying-jacuzzi, and so on through their existing Circuit Protective Conductor, the electrickle shower through its circuit-cable protective conductor. And the bonding has an extra handy effect of reducing the resistance to earth should there be an L-to-E fault, making it all the more likely that the fuse/MCB will blow nice and quickly. But in trying to get across the *point* of supp-bonding, it's the bonding-together idea you want to get across, not the idea of 'earthing'. (After all, as I've just enumerated above, they're already 'earthed' in non-fault conditions, right?)

Stefek