Switchboard Replacement - Incoming PEN and main earth same stud

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JamieP
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Switchboard Replacement - Incoming PEN and main earth same stud

Post by JamieP »

I understand in most cases switchboard replacement is low risk

I also know certain things can change this, like installation a MEN link when there original switchboard had a single bar for both N and E (although I'm also aware it could infact be kept this way in regards to ESR113 avoiding the high risk installation of MEN but why would you)

My main question is actually if I have a switchboard with the incoming PEN and MEC on the same stud on the N bar, does moving said earth to the E bar in the new board trigger it being high risk? Or is this still low risk? (Once again, I know ESR113 would allow me to connect the MEC in the same way but I feel you may as well change to current standard in this situation, also probably cause you more trouble due to uneducated people reporting you as they believe it's not compliant)

I can't get my head around if this still constitutes replacement or if you'd consider it an alteration, I mean if in doubt I'd rather get an inspection because better to do more than less but as always it's a case of is it actually a requirement or not?

Appreciate any input
AlecK
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Re: Switchboard Replacement - Incoming PEN and main earth same stud

Post by AlecK »

It's certainly not "maintaining" or "repairing"; as it changes the configuration of the way the installation's earthing is connected.

It affects the MEC, so it's "mains work"; and as non-maintenance mains work ESR 6A classifies it as high risk PEW.

As with any classification system, there are always some things that are only slightly one side or the other of the demarcation point(s).
JamieP
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Re: Switchboard Replacement - Incoming PEN and main earth same stud

Post by JamieP »

Interesting, but am I correct in ESR113 would allow me to connect both back together on the N bar in the new board as low risk? But only via a lug with a nut and lock nut as per original requirements? (Is that right? Correct me if I'm wrong)

I personally wouldn't go down that route but just making sure I'm thinking the right way about these things
Dan L
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Re: Switchboard Replacement - Incoming PEN and main earth same stud

Post by Dan L »

seeing as everything is being replaced the same, fitting for fitting, e for e bar, n for n bar etc. And the mains conductors are the same, no settings changed and nothing new added.

Coukd the relocating the MEC to earth bar count as to facilitate the replacement
of a fitting with the modern switchboard which is designed for the MEC to go on e bar terminal. And this move does not affect the existing installation.

"(b) includes relocation or extension of a conductor to facilitate replacement
of a fitting"

? Just a thought
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AlecK
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Re: Switchboard Replacement - Incoming PEN and main earth same stud

Post by AlecK »

ESR 113 doesn't apply when fittings are replaced.
It's about items remaining in service ("may continue to be .... used"); and when you replace something it's not continuing to be used.
You stop using the old and start using the new.

The regulation that applies for replacement is ESR 59(3); which allows for 3 ways of maintaining an existing installation.

Option (a) is to maintain so it complies with '3000"; ie for replacement of N&E bars, the MEC has to go on the E-bar.
Option (b) is restoring to / maintaining in "original condition"; and this would allow the MEC to be connected to same stud as the incoming N, under nut and locknut as per 1976 Regs.
Option (c) is by following MIs for the fittings concerned, but for N&E bars there aren't likely to be any MIs.

Yes ESR 6A (1)(b) includes repositioning a conductor to facilitate replacement of a fitting as low risk PEW. Presumably the fitting it's connected to, but could also be an adjacent fitting.
It allows for cases where it's necessary to move the conductor for the new fitting to be functional. Eg where the terminals of the new are in a different configuration compared to the old ; at least one of these conductors will need to be partially re-routed, and may need to be shortened or extended. Or for replacement of switchboard, extending the mains to reach the new main switch. Also, since conductors are also fittings, it covers replacement of old VIR mains with eg N/S or TPS along substantially the same route, but eg applying larger radius bends for increased size.
For replacing N&E bars, often the new bars will be longer, which may require mains N and / or MEC to be re-positioned / extended to teach the appropriate terminal(s). Moving and / or extending these conductors is "mains work", and in absence of this provision would be classified as high risk.

Could also apply where conductors associated with a different fitting need to be moved within a switchboard or meter enclosure in order to accommodate the replacement of an adjacent fitting with a larger item (bearing in mind that unless the conductors concerned are either mains or MEC, there's no issue).

Note that "replace" only extends to the new item being in substantially the same location as the original; not to cases where the new fitting is moved to a new position. I believe the footprints of old & new fittings would need to at least partially, and preferably substantially, overlap; else it risks being a case of moving rather than replacing.

Clearly there's an intent that some minor work that would otherwise be 'high risk' - and so require inspection - doesn't justify that additional step (and cost). But we can't just extend that to everything that we believe doesn't justify inspection. Our personal assessment of risk level doesn't come into it. The words matter; whereas the intent is something we interpret from the words. So to apply this provision, we need to meet BOTH parts of it. Not only must the work be "repositioning or extending conductors"; but it also must be for the stated purpose of "to facilitate replacement of a fitting". "Facilitate" means "make easy or easier" [Concise Oxford]; and in most cases it would be hard to make a convincing case that moving the connection point from one bar to the other makes the replacement process any easier than re-connecting to the N-bar would be.So in my view it can't generally apply for moving the connection point of the MEC from one bar to the other.

Even if in a particular case we assess that this provision could apply; we need to ask ourselves whether, if challenged, EWRB would agree. Reviewing their decisions certainly doesn't suggest that they take a liberal view.

I'd agree that the potential risks of moving the MEC connection from N-bar to E-bar are no greater than for re-positioning & extending to get to the new N-stud. But one of them is specifically classified as being low risk, and the other isn't.
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