You mean if you fix a 2" X 3/4' chunk of brass on the wall with several green and yellow wires going into it you would have to label it "safety electral earth etc"? And should you enclose it to discourage interference?
Yes it makes sense, though my electrican did not bother. Maybe he (or I) might have done if it hadn't been in a workshop.
All I meant was that I agree with those who argue a screwed connection in a main bonding conductor brings it within 514.13.1((ii) ("a point of connection of every bonding conductor to an extraneous-conductive-part") and so requires the warning notice. It can be argued the other way but I was persuaded by the fact that the join must be accessible (else you wouldn't use a screwed connection, would you?) so it makes sense to require a warning notice there as at connections to pipes etc.
What happens in practice is of course another matter. But I've seen labels used where the bonding used a combination of cable and pipe.
I don't know just what your chunk of brass was for but 514.13.1((iii) provides that no label is needed for a MET by switchgear.
Just call it an earth marshalling bar?
Stickers that say "earth warning do not remove" are cheap
I'll be guided by you!
I've seen those labels on EMBs a few times (once inside a CU) but never really understood why they are used instead of BS 951 labels or how they finesse 514.13.1.
That sounds like what existed here on an old installation. Where the incoming lead water main and the sheath to the mains riser provided the rudimentary earth.
If you can use the mains riser for earth it needs the correct clamp - but that's really a job for the supply company to make sure it is up to it.
The electrical installaton here, probably 1920s, got its earth from the incoming cable sheath. However, after a few days of being fed from a generator, tests on reconnection showed an inadequate earth from that cable sheath. The supply company changed things to PME.
Personally I do not think it matters that much.
But some people like to see safety stickers and they get paid to look for non problems.
Leads finally turned up. Ze is 0.2. I moved their clamp gently, and established that it's a) stiffer than I remembered from Monday, and b) didn't affect the measurement. BTW it's not a 951 clamp.
Fair point. I'll put me clipboard away.
It's slighly interesting. The person who wired my house originally took equipotential bonding remarkably seriously and throughout the house (at least in all rooms with any CH pipes or extraneous metal work which I think was everywhere except the conservatory) he ran a network of
10mm insulated earth wire in parallel with every bit of the socket wiring plus to every pipe, even ones connected by copper back to the boiler. If I felt like burning the insulation off I'd have about 10kg of copper I've ripped out doing other jobs. A consequence was an earth terminal block in almost every room and the electrician used one of them which was actually directly connected to the supply earth block, rather than pulling a new wire in from the supply board to do the one bit of bonding the original owner forgot, which was the oil feed into the house- one of very few that was actually required. Though since it goes to the outside oil tank with no earthing to speak of it therefore creates a new PME hazard. In the context a label saying this connection is actually wanted might be sensible, though it would have to say why in the context of dozens of other pointless earth labels.
When you've finally ripped it all out, then the regs will require equipotential bonding in all rooms.
NT
On 29/05/2020 12:38, Roger Hayter wrote: <snip>
Others may know what was behind that. To me it sounds like someone (a) installing high integrity earthing without understanding what was and wasn't required or (b) with an awful lot of 10mm green/yellow single to bill to an unsuspecting client. Any idea when it was done?
About 40 years ago, by the householder. He had other wiring quirks.
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