Ring Main cutting wires or not?

[Dave Plowman (News)]

But they are by far the most important part of the circuit, safety wise.

So if cutting the L&N is a bad idea, likewise the earth.

[newshound]

You, me, and Andrew then....

[newshound]

Different function. Of course you want low resistance in the earth circuit for fast tripping, but you want low resistance in conductors to reduce heating *and thermal cycling*. The latter being one of the things which loosens screw terminals and can, eventually, lead to overheating.

Also, it's easy enough to check your earth integrity with a plug-in tester, much more of a faff to check ring circuit resistance.

[newshound]

Folding solid copper once won't break it. I normally do this on the end of spurs, it just feels more secure.

[Dave Plowman (News)]

Eh? Where did you find such wire? If you continually bend it open and closed you will break it eventually. But not once.

[DJC]

I did it when I reired my mother's house about 25 years ago.

>

[Roger Hayter]

But presumably you can put a terminal block nearby and a branch to each service?

[Robin]

Most guidance and books seem to say the bonding "should" be continuous. I've never seen anything in the regs. to justify "must" be continuous but it may be there somewhere.

OTOH:

a. it's easy enough to achieve (with crimping to restore continuity if the cable has been cut) and

b. it seems sensible given the risk of an intermediate clamp being removed and breaking the bonding.

c. the terminal block would need to be accessible as I don't know of maintenance-free connectors for 10mm

[Fredxxx]

I didn't think you were obliged to supply an earth wire to both connections?

They are internally connected in the socket, aren't they?

[Roger Hayter]

You presumably mean maintenance free connectors for for more than two wires, seeing you mentioned crimps in a. above. Noted that terminal block should be accessible. The bonding wire usually terminates at the service entry in a terminal block, doesn't it? I must admit I wouldn't like to run one main bonding link via another even if the wire was folded, it is a bit opaque to a householder. But I am talking moderately conscientious DIY rather then professional. The professional electrician who put in extension wiring for me ran the new main bonding he put in from a terminal block on the inside wall already present connected to the outside meter box. Do you think he acted properly?

[Tim Watts]

You're not - but it is considered good practise (if one falls off, the other still earths the socket) but it's a "+0.01% nice to have".

[Robin]

I had thought - perhaps wrongly - by "a terminal block nearby" you meant a block *in addition* to the main earthing terminal or bar fitted (usually) by the meter. (ANd that sounds like what yuour electricain used for your bonsing.)

An additional block/bar is usually deprecated because it's an unnecessary connection which might become loose over time. But AIUI (from an note I made some years ago) it's not forbidden 'cos the "continuous conductor" thing comes not from BS 7671 but from BS 7430 (Code of practice for protective earthing of electrical installations): "Where both main gas pipes and main water pipes enter a location, a common bonding conductor may be used, but in such cases that conductor should be continuous or should be permanently jointed (by soldering or crimping)" Note "should", not "must".

There's nothing wrong with running separate cables. And I know one couple who were sold new bonding to the gas separate from the water on the basis of the picture in the On Site Guide showing that. But IMO that was a rip-off by a cowboy with a badge.

And running 2 separate cables from the MET can be a waste of copper when (as here) the incoming gas and water pipes are less than a metre apart and - as the cable runs - about 8m from the MET. So I ran one and looped it from water to gas. All clearly labelled as such for whoever comes after.

[ARW]

I see no reason why not.

[Roger Hayter]

You're right. I only mentioned the one by the meter to that suggest crew ferminals can't be totallly forbidden in the bonding conductor.

If soldering counts as continuous then presumably you can just solder the ends of both 10mm cables together in the terminal of one clamp. Easier than messing about trying to put one clamp half way along.

As far as I (and others) am concerned a soft solder joint is not a permanent connection in the absence of mechanical clamping or retention of some kind. Does the standard acknowledge that?

[Robin]

Sorry, I've never used soldered joints. I've no idea if there's a separate standard which deals with it. But there is the generic requirement for strain relief in BS 7671.