BS7671 18th Edition Draft out for comment

[ARW]

You know they will f*ck it up

[John Rumm]

Someone obviously took that old joke to heart - you know the "Don't bother trying to get it out Doc, just change the batteries" ;-)

[Tim Watts]

Well - properly worked on, for some definition of "properly". As you're here, would you do the honours :)

[tabbypurr]

Yup. And my point was that existing work meeting some old regs is legal, and to some other regs it's not. 1st edition wiring would definitely not be, 16th would.

NT

[John Rumm]

Some old regs, and some other regs? - I can't make sense of that sentence!

All work done correctly to old standards is "legal". The difficulty comes when you want to modify it now.

[Tim Watts]

Agree.

It does also help with scenarios where one might run temporary from a genny or UPS and the supplier's earth is in doubt during a power failure.

But does it say "and you must have 100% RCD protection"? Without that it's pointless.

I know the other parts require 100% RCD coverage (if I read it right?) for new installations, but if this part of earthing and bonding is made retrospective on any major works being done (in the same way that verifying main EB and supplementary EB where applicable is), then it would be a bit odd.

[tabbypurr]

Let's try to explain again... An existing installation conforming to 1st edition of the wiring rules is definitely not legal today. Anyone using such may land themselves in prison. An existing installation conforming to 16th edition is perfectly legal.

NT

[Robin]

Not another rant (I promise).

I have TN-S with the supplied main earth soldered to the lead sheath.

If the DNO converts me to PME so the supplier's main earthing terminal is no longer using that, I wonder if I can use the sheath as a supplementary earth within 542.2.2.2

"(vi) Lead sheaths and other metal coverings of cables, where not precluded by Regulation 542.2.5"

given 542.2.5 doesn't seem to bar it:

"542.2.5 The use, as an earth electrode, of the lead sheath or other metal covering of a cable shall be subject to all of the following conditions:

(i) Adequate precautions shall be taken to prevent excessive deterioration by corrosion (ii) The sheath or covering shall be in effective contact with Earth (iii) The consent of the owner of the cable shall be obtained (iv) Arrangements shall exist for the owner of the electrical installation to be warned of any proposed change to the cable which might affect its suitability as an earth electrode."

I have a feeling though I'm probably in Baldrick "cunning plan" territory.

[ARW]

Anything that requires an installation certificate (say a new circuit adding) would require the main bonding to be brought up to spec.

Minor works such as swapping a light fitting would not.

However I would not swap0 a shower for a like for like if there was no RCD protection and the main bonding was poor (others might)

[John Rumm]

In theory it sounds like it would be ok. The only difficulty I suppose is ensuring it stays that way. All the time the DNO is supplying your earth via that route you know they will maintain it. Once they convert you to PME, you have no guarantee that they will, and they would be unlikely to feel the need to tell you if they re-cabled a great lump of the supply without the lead sheath. I suppose if you periodically tested as one ought with a TT earth, then you could argue its ok.

[Tim Watts]

Thanks for that Adam. I knew it lay somewhere with more major works but I could not put my finger on it...

[Tim Watts]

On a related note, I have one more job to do under an open building control job, which is to add lighting to a new shower room and supplementary bonding. Could you help me please with the paperwork?

I'm fine with the work and the testing, but I am not sure how to do the certification, given I've already signed an EIC and handed in, plus I hired a sparky to lay in the lighting in the rest of the place to save time and his bit is directly notified.

Is this a MWC or an EIC - and if an EIC, do you just record the one circuit affected or do you record all circuits - and if the latter are you expected to retest all of them?

Cheers,

Tim

[ARW]

There is no need to retest all of the circuits MWC or EIC, just the ones you worked on.

If the work you are doing is under the 16th edition then you can still carry on under the 16th edition. However if you have handed in a certificate saying all the electrical work was complete then you may have to do the new work under the 17th edition.

This one is probably down to your BCOs judgement as to if the EIC you handed in was a final document or not. If he knew there was extra electrical work to be done then you should be able to carry on with the

16th.

All the best mate but this one is down to your BCO unless you think I have missed something in my reply.

[Tim Watts]

Cheers mate,

I've been working to the 17th the whole way - it was just the procedure of certification that I'm not sure of:

Is this an MWC or an EIC for additions in a special location to an existing circuit? Never been sure what a MWC is actually for...

Unsurprisingly a 4 day Part P course does not cover such nuances!

BTW - I'd designed to not have supp. bonding. But after reading your views on the matter, I'm putting SB on the shower room and probably retro fitting to the main bathroom - albeit it will be externally applied as allowed by the regs, rather than the more conventional approach. Your theory makes sense - nothing much to go wrong with simple SB, but the other approach both relies on RCDs working AND plumbers not coming along later and inserting insulating sections in the pipework ruining the continuity.

Having spoken to a GasSafe fitter who will be doing my boiler, apparently the GasSafe certifications don't cover much to do with bonding, which seems a bit weak...

[ARW]

No but the NICEIC Testing and Certification book does.

And in the check list for MWC the first one on the list is

"Additional (non emergency) lighting points (luminaires and switching on a single existing circuit)." And it says a MWC is acceptable.

So unless it's a new circuit from the CU you can use a MWC.

Actually you could probably hand in your old school reports and no one would notice or care.

[Tim Watts]

Cheers - I'm off to amazon...

Thanks Adam. I'll do that then...

That's pretty much the case... Literally all I have to do now is plumb in a bog (after tiling) and this lighting and it should be building certificate time.

[ARW]

Just to make sure you buy the right book

[spuorgelgoog]

Do I have to have my own earthing rod, or can eg 100+ flats in a high-rise block share an earthing rod?

Does it differ if the flats' supply is provided by a DNO or a BNO (building network operator)?

Owain

[spuorgelgoog]

Woo! Points mean prizes!

Manufacturers of NCR pads will be pleased.

Owain