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On a commercial switchboard the MEN link (which was connected by lug not a screw type) was bolted onto the same stud as as another conductor on the earth and neutral connection.

The other conductors where extensions to a second earth and neutral bar of the the same enclosure.

To me this seemed wrong, bad practise and inconvenient if anything.

I can only find ref 2.9.4.3

provided with a separate terminal for—
(i) the incoming neutral conductor terminating at the switchboard;
and
(ii) the neutral conductor(s) associated with each outgoing circuit
originating at the switchboard.

(not sure if the conductors used for extended to another bar counts)

And possibly 5.3.5.1
Which may suggest a dedicated earthing terminal is required on the neutral bar.

Any other ref I'm missing is this compliant or not?

I tried to upload publics hopefully it worked

Not very good practice; but I believe 'compliant'.

In 2018 edition, 5.3.5.1 is amended to require that the MEN must be "located in an accessible position for disconnection and testing purposes".
Which emphasises the fact that we have to be able to remove the MEN easily.

The links between sections of busbar are effectively part of the bar.
They should be connected such that they don't get removed / disconnected / loosened when the MEN link is removed.
So if they are 1st on stud, secured by a nut, and therefore remain firmly connected when link is removed from above the nuts, then no problem.

But this case appear to just have the one nut per stud, so anything connected to 2nd set of bars risks being disconnected by removal of link.
Even worse; looks like the lugs for the linking conductors are over the top of the MEN.
Very poor practice; and defeats the point of having a removable MEN.
But not actually in breach of any clause.

There's also 2.9.5.34; which requires the terminals for the MEN to be "legibly and indelibly marked"
Since the MEN is NOT at one extremity if the bar, and the main N is not immediately next to it; the Exception can't apply.
I can't see the required marking, so non-compliant in that regard.

Thanks I really appreciate the feedback.