Work on MEN in outbuilding - Inspection

[JamieP]

So I believe an outbuilding with separate MEN switchboard has a main earthing system hence work on this being high risk

But I'm curious about work solely involving the MEN connection

ESRs says "main earthing system means an earthing system of an installation that—
(a) operates at standard low voltage; and
(b) comprises an earth electrode, an earthing conductor that is connected
between that earth electrode and a MEN switchboard, and a removable
link between the neutral and earth conductors within that MEN switch-
board"

This clearly includes the MEN connection as part of the main earthing system

"mains work—
(a) means any of the following:
(i) work on mains (including connecting the conductors of mains at a
MEN switchboard):
(ii) work on main earthing systems (including connecting the conduc-
tors of main earthing systems at a MEN switchboard):
(iii) work on the connection between earth and neutral made by the
removable link within the MEN switchboard closest to the point
of supply;"

Under mains work (iii) says work on the MEN closest to the PoS

This feels like it's indicating only the one closest to the PoS? But (ii) already includes other MENs under main earthing system?

Any input?

[AlecK]

Yes the earthing systems for some outbuildings include all three components that make ip a 'main earthing system"; and therefore these are also "main earthing systems".
Accordingly (installation) work on these MESs is classified as high risk PEW and requires inspection.

I believe the minor anomaly you've noted arises from the several revisions there have been of ESRs since 2010; in particular the fact that the definition of MES has substantially changed (the original had the effect of making any earthing conductor within an installation part of the MES, and therefore work on it required inspection).

I also believe that it may not have been the intent to include these "outbuilding" MESs under "mains work"; but that's the unavoidable effect of the current words.
But there are significant safety issues when outbuilding MESs are installed incorrectly, same (or very similar) as for the MEN closest to pint of supply;
which in my view make it entirely proper for them to be "mains work".

[JamieP]

So in your opinion under the current words do you believe installation work on a MEN outbuilding requires inspection?

For example if you found an outbuilding that the a MEN outbuilding had been established but they forgot MEN link and it had to be remedied, would this installation require inspection?

Obviously this would mean both the person who did the work and the inspector (provided they got it inspected) would have to have to have missed this etcetc

I saw someone mention they had picked up on a MEN link missing but everything else was in place and just wondering if inspection would be required by installating one

Main earthing system points to yes so I believe so even though mains work (iii) points to just the closest to PoS so no

[AlecK]

The logic simply goes like this:
ESR 4; "mains work; (a)(ii) says work on any "MES" is "mains work".
ESR 6A(2) (b) says installation / alteration PEW that is mains work is high risk.

The fact that ESR 5; mains work, (a)(iii) only talks about the N-E connection in the MEN switchboard closest to supply can reinforce this.
It may also provide a glimpse as to what may have been intended.
Or it may simply indicate that the (several?) writers got themselves confused.
But such speculation is just speculation, and any inference taken based on speculation can't outweigh the clear line of logic;
it can't alter the fact that installation / alteration (ie non-maintenance) PEW on any MES is mains work under (a)(ii)and therefore high risk.

[gregmcc]

FYI @AlecK, the reason for this question is because there is a posting on Facebook - Electrician Q & A regarding this. Professionally I'm with AlecK on this.

[JamieP]

Yeah it was the age old debate of inspection of MEN outbuilding haha I also agree with you both

But that's what made me notice the indiscrepancies in the clauses that made me ask the question above about the MEN connection solely

[AlecK]

when you look closely there are a number of areas where ESRs don't fully line up internally.
Sometimes it's just that the writer(s) haven't used the right words to fully & accurately give effect to the intent.
I believe the incorrect older definition of "main earthing system" was one of those.

Always assuming they have a clear & coherent intention in the first place; and one which covers all eventualities.
Often the intent is not published; leaving us to deduce it.

Sometimes it's the effect of the number of different people who have a finger in the pie.
Example: when they went through changing "inspect" & "inspection" to "assess" & Assessment' for everything that wasn't about ESR 70 "third-party" inspection of high-risk PEW.
The (presumed, not declared)intent was to differentiate between inspection of HR PEW, and other sorts of inspection such as (now) periodic assessments & WoEFs.
But they changed one too many "inspect"s, that should have been left alone; and now only people who are authorised to "assess" PEW are allowed to do PAs under ESR 75
but if you look at your PL, and at limits of work for each class, there's nobody "authorised" (by their PL) to "assess".

So while I generally believe in following the words strictly as they are written;
sometimes - where there's no way to extract a clear meaning - the only practicable way forward is to deduce what we think the intent probably was, and follow that.

Back to the case of MESs in outbuildings, the safety issues from getting it wrong are pretty much the same for outbuilding supplied by PEN submain as for a MSB.
Exactly the same risk of leaving a "mantrap" under earth fault conditions.
And to me that justifies having such work inspected