Circuit Identification

[JamieP]

"2.9.5.4 Terminals of switchboard equipment
Terminals of bars, links, circuit-breakers, fuses and other electrical
equipment mounted on a switchboard shall be marked or arranged to
identify the corresponding active and neutral connection for each circuit."

I understand arrangement can be used but what's the best way to mark the terminals if you choose that method such as bars etc? Is a label on the cable right by where it goes into the terminal sufficient to meet this clause?

[DougP]

Neutral bars usually have numbers on them. You would have to mark the circuit protective device with the associated neutral number.
For 3 terminal RCD neutral bars, some type identifying number mark on the RCD and the associated neutral bar.
I'm sure you'll be able to think of a compliant way to do it, depending on the type of fittings that you use.

Just a side note, for the line side feed to RCDs or RCBOs, the clause doesn't apply.
And for the load side of RCBOs, as the A & N are connected to the same device, it is easily identifiable.

[AlecK]

"for the line side feed to RCDs or RCBOs, the clause doesn't apply."

I don't think that's true. I can see nothing that exempts these connections from being required to be identified.

[JamieP]

Basically what I'm wanting to know is do you consider a marking on the cable (such as a heat shrink label) directly by the terminal sufficient to meet this clause or must the actual terminal be marked?

[gregmcc]

When I was doing that kind of work we would label each phase/neutral/earth with a slide on label at the termination point, came across heaps of commercial panel that had absolutely no circuit identification, it made for a real nightmare trying to identify the corresponding neutral and earth for each phase.

[DougP]

"for the line side feed to RCDs or RCBOs, the clause doesn't apply."

I don't think that's true. I can see nothing that exempts these connections from being required to be identified.

I think it might be a matter of the writers not using consistent wording in various clauses?

(Working from 2007A2 clauses)

2.9.4.3(d)(ii) refers to "each outgoing circuit" so obviously can't apply to the line side of any device.
2.9.5.4 uses the wording "for each circuit" - so if you include the line side of an RCD or RCBO as part of the circuit, then presumably yes, they should be identified. I don't think I would have ever seen that happen though. And it certainly would be difficult to identify the corresponding active, with a separate neutral, if the actives and/or neutrals were looped around the devices?

And if the line side supplying RCDs or RCBOs was included as part of the "circuit", wouldn't 2.9.5.5 then also apply on the line side in that case?

Also, 2.9.4.3 allows for "A neutral conductor or busbar connection may be used between the neutral bar or link and a number of multi-pole devices mounted on the switchboard."
So I'm not sure how those arrangements could comply with 2.9.5.4 to identify corresponding actives and neutrals?

Personally, I think that the defined term "final subcircuit" should have been used in place of just "circuit" in some instances.
But it's late, and your response surprised me, so maybe I'm just not thinking clearly

[AlecK]

I think the key is in your final comment; WRT the wording being 'outgoing circuit" and not referring to "final subcircuits" - which would have limited the effects.

WRT 2.9.4.3; I see the wiring between main switch and circuit protection devices as a outgoing circuit from the main switch; or WRT 2.9.4.3 the N side is outgoing from the n bar - and therefore those Ns need to be identified.
An inference can be taken that "outgoing" means "out from the switchboard", but there's nothing in the words that actually supports that interpretation.
In this case, the 2.9.4.3 is about N-bars, so "outgoing" has to mean outgoing from the N-bar in question.

Similarly there are some who believe that a "final subcircuit' has to leave the switchboard it originates at - but again the relevant definition doesn't support that interpretation.
We all have a tendency to interpret WRs in terms of our own individual experiences; and it can be difficult to let go of the safety net of what we've long understood and just read what's actually written.

WRT 2.9.5.4; the clause is about labelling of switchboard equipment. NOT limited to only switchboard equipment at which final subcircuits originate.
Again the conductors feeding the circuit protection can be seen as part of a circuit (though NOT part of any "final subcircuit"); so the Ns feeding RCCBs / RCBOs must be identified.
This interpretation is also supported by the exceptions. Taken overall, the clause MUST mean that EVERY N on any N-Bar must be identified, except those specifically exempted by an Exception.

So for both, once we stop thinking that "circuit" means "final subcircuit or submain", and think of these interconnecting conductors as being outgoing from something upstream instead of being on line side of something else; it falls into place.

And yes 2.9.5.5 applies to these conductors as well; though it won't apply very often. Eg when feeding a set of RCDs; we can take individual Ns to each, or we can use a "common N configuration - and if we do that then we have to follow 2.9.9.5. However just looping the Ns ( a practice 2018 edition will restrict) doesn't necessarily set up a 'common N"; it's only "common N" if the various As come from different sources.

[ShaneR]

I work better with pictures

So what doesn't need to be labelled/identified

[Daniel2]

Looking at the picture, I'm a bit unsure of the neutral configuration 'A' corresponding to the first and the second circuit breakers on the left: is there a neutral missing?

[AlecK]

MEN connection is at ends of both N-bar & E-bar, so Exception 1 applies

I assume 'A' is N of incoming supply; and if so then - being in terminal next to MEN - Exception 2 applies.

"B" is outgoing N to "RCD 1, so must be either labelled or identified by the arrangement.
"C" is incoming N to RCD 1; and if RCD is so labelled then NFA needed (it's the terminal that must be labelled, not the conductor)
Trouble is it's hard to mark a brass bus-bar (even though "legibly & indelibly" isn't specifically required except for incoming & MEN)
However most bars have numbers stamped on them ex-factory; so instead of trying to write "RCD-A" on the bar; just write "N #1" or similar on the RCD incoming N terminal.

If using "arrangement" as means of ID of N-bar terminals, then "A" should be one terminal to the right, so that left hand terminal (after MEN & incoming N) is for the mcb beside incoming isolator. IE, left-most terminal for left-most circuit.

"D" must be the outgoing N of RCD-A , so must be identified as to where it goes - presumably to the 2nd N busbar; but how can we tell for sure, even when - as here - there are only 2 "extra" busbars?
Easy if using the type of bars that connect directly to RCD terminal.
But using "remote" busbars (as supplied with most domestic-type DBs), best option may be to provide these subsidiary N-bars with an ID that can also be written on the relevant RCD terminal. As indicated above, better to use letters, rather than numbers, to avoid confusion between the terminal numbers & the busbar ID.
Active feed from RCD to mcb group also needs labelled unless arrangement makes it clear; in this case having the mcbs immediately beside the RCD should be enough; especially if A-busbars are used.

Repeat for second RCD + busbar combination.

Now to the outgoing RCD-protected final subcircuits.
If the RCDs' outputs are labelled A, B, etc, then the outputs from mcbs are A1, A2, A3, & B1, B2, B3; and with the N-bars labelled a & B to match then N # A1 must be the N from mcb output A1 - etc. (I'm assuming thisois what your "E" relates to?)

hope that makes sense.
A super-fine felt-tip pen is very handy, eg Stabilo OHP (permanent, not erasable)

[JamieP]

Trouble is it's hard to mark a brass bus-bar (even though "legibly & indelibly" isn't specifically required except for incoming & MEN)

Judging by this comment I would take it that you'd consider a label on the cable directly by the terminal to not technically be sufficient to meet this clause?

"Basically what I'm wanting to know is do you consider a marking on the cable (such as a heat shrink label) directly by the terminal sufficient to meet this clause or must the actual terminal be marked?"

[AlecK]

The wording calls for "terminals" to be marked / arranged; so technically a conductor ID wouldn't comply with the letter of the rule.
But in practice I believe conductor ID that achieves the stated function would comply with the spirit of it.

[JamieP]

I see, then again though, like you say it calls for the terminal to be marked, doesn't actually say the marking has to be on it does it, so I guess you could argue such method used on the cable directly beside the terminal is marking what each terminal is for?

[gregmcc]

I have noticed that some N & E bars are numbered, would this meet the requirements of identification?

[JamieP]

I believe so Greg, as long as you mark the other end of the cable with the appropriate number

[Daniel2]

So, then, what does the neutral at 'A' correspond to? Incoming supply or an outgoing C40 or C32a MCB?

[JamieP]

I thought A was incoming then the 2 Ns to the right of it were the RCD Ns that dropped straight into the top of them but I just realised then I have no idea where the 32A N is haha

[gregmcc]

I'm having a close look at the picture and seen a few things not quite right.
1) The 2 RCD's, the live side, the phase conductor - they should both go to the load side of the main switch, I would assume the 40A MCB is the main switch, neither terminal has 2 wires in it.
2) The load side of the RCD's the phase conductor, this should go to the live side of the 3 MCB's (from each RCD) and a link bar should be fitted, can't see either.
3) The 32A MCB, this appears to be non-RCD protected, so where does the phase for this (the live side) come from? and where is it's associated neutral, does not seem to be on the non-RCD neutral bar and none of the other neutrals appear to be big enough.
4) The main earth - appears to be in the same terminal as the MEN link, personally I would have put it in its own terminal down the other end of the earth bar, don't see any "Main Earth do not disconnect " tag.

[AlecK]

WRT item 4:
While they are a good idea; there's no requirement for a MEC label at switchboard.
And, unlike Ns, Es don't require separate terminal for each.
That said, I don't like the idea of MEC & MEN sharing same terminal; 'cos either one should be able to be disconnected for testing without affecting the other. So any doubling-up should be among the PECs.

The form of labelling / arrangement isn't specified; so what matters is whether the required purpose of matching A(s) to N is fulfilled.
So yes the number stamped on a N-bar could serve the purpose; provided the same number is marked on the terminal of the relevant A(s).
And my personal opinion is that wire labels wouldserve the required function; however I believe they are not identifying a terminal, so non-compliant on a technicality

[DougP]

"for the line side feed to RCDs or RCBOs, the clause doesn't apply."

I don't think that's true. I can see nothing that exempts these connections from being required to be identified.

This question came up again recently in another forum, regarding a combined A & N busbar being used on the line side of dual pole devices.

While I always appreciate Alec's detailed and well thought out responses, they are sometimes difficult to convey to the average electrician on the tools.

With the digression above to a very confusing looking switchboard photo, I think the answer and reason for the original question got lost.

The way I explained it on the other forum was that there's only one purpose for the marking of the neutral connection, which is detailed in clause 2.10.5.4. as "marked or arranged to identify the corresponding active and neutral connection for each circuit".
That phrase has been in the book since the '90s, if not earlier.

So where the corresponding active and neutral are in adjacent terminals on an RCBO, they meet that requirement and no further marking is required. And this has nothing to do with the line side neutral supplying an RCD or busbar.

[AlecK]

Agree that arrangement can be equally valid as marking,
What I was getting at was that when eg a number of RCCBs are fed from the main N-bar by individual wires, we need to be able to ID, at the N-bar, which N-feed goes to which RCD. The Actives will generally all come from same terminal typically the main switch, in which case individual ID isn't needed