Earth bonding - can I crimp short lengths?

[Brian {Hamilton Kelly}]

Errm, by 'spring' do you mean helix?

(There's nothing springlike about BTC)

[Andy Wade]

[OSG note (i) to Figs, 4a, 4b & 4c]

I'd suggest it is meant to maintain the bonding to the other services in the event that the clamp to an intermediate service is removed (temporarily or permanently) in connection with work being done on that service. E.g. if a metal service pipe is replaced in plastic the clamp can be removed safely and continuity is maintained without the need for any electrical knowledge by the plumber/gasfitter etc. The plumber (etc.) would have to deliberately cut the wire to disrupt the bonding.

I don't see that this in any way forbids the use of a properly-made in-line joint in a bonding conductor. In any case the main bonding conductor(s) have to be disconnectable from the main earth terminal for test purposes - so there's one joint to start with...

I agree, but there's nothing in section 543-03 of BS 7671 - "Preservation of electrical continuity of protective conductors" that specifically bans such joints. There are only 6 regulations in this group:

543-03-01 requires suitable protection against mechanical and chemical deterioration, and electrodynamic effects; 543-03-02 requires separate protective conductors (PCs) up to and including 6mm^2 to be insulated and requires sleeving of the bare PC of a multi-core cable (e.g. T&E) at terminations; 543-03-03 requires connections to comply with the accessibility requirements of section 526-04 (i.e. as for live conductors). Joints in metal conduit or trunking systems used as PCs are excluded from this; 543-03-04 forbids the use of switching devices in PCs (with certain exceptions). It also says "Joints which can be disconnected for test purposes are permitted in a protective conductor circuit." 543-03-05 is concerned with earth monitoring systems with pilot wires (not usually relevant to TN systems or house wiring). 543-03-06 requires joints in metal conduit to be screwed or to use "substantial mechanical clamps" and forbids the use of "plain slip or pin-grip sockets."

[Martin Angove]

Good point, hadn't thought of that. I'm not sure how often that is likely to happen though; on the incoming side, perhaps, but on the outgoing side it'd have to be a pretty major refurbishment to warrant replacing with plastic right back to the tap. Mind you, I can't see one of those straps coming loose without an earthquake either :-)

A point arising though is what to do with the disconnected bond? You'll be left with a length (inch to inch and a half) of G&Y which has been stripped of insulation and hence requires protecting from damage and the elements and accidental shorting on something it shouldn't. Would a tape wrap be sufficient, or would we be looking at enclosing in some kind of a box? Would a plumber necessarily think of such things?

Had a job last week where I renewed the bond to the water pipework. The kitchen fitters (about 2 years ago) had simply disconnected the original bond and left it dangling behind a unit. It was green 6mm2 and I needed (for other reasons) to upgrade to 10mm2, but why on earth (sorry) did they just leave it dangling when presumably it was previously attached?

No, and I think I said that, or at least implied that, in my post. I was just trying to avoid quoting large chunks of BS7671 ;-)

Hwyl!

M.

[Tony Williams]

A 'spring' is what it was known as.