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Posted By Topic: Wiring System

Dec 01 2019 09:22

I don't know if there is an official definition of wiring system but I believe that a insulated, sheathed cable is its own wiring system, correct? As is cables installed in conduit/capping etc what ever method is chosen

Basically what I want to know is if said insulated, sheathed cable gets installed in let's say a conduit, does it still remain its own wiring system or does it become part of the conduit wiring system?

For example if there were other cables in the conduit that were insulated, unsheathed so they were part of the conduit wiring system does that mean all the cables inside are one wiring system of the conduit or does the insulated, sheathed cable still get regarded as its own wiring system, inside the other

I hope this makes somewhat sense

I'm just trying to work out where certain rules stand with regards to things that are or aren't allowed in the same wiring system

Dec 01 2019 09:33

section 3

Dec 01 2019 09:49

Any specific part? I was reading through it earlier and couldn't find the answer to my question

Dec 01 2019 11:54

I'm really not sure what your question is.

The wiring system is the wiring system - as per "description" in table 3.1.

Cable types are a different animal, but become part of the wiring system where they are allowed in whichever system.

Dec 01 2019 12:42

Hmmm, I'll try break it down

Is a sheathed cable on its own a wiring system?

I believe so but correct me if I'm wrong

Cables installed in conduit are a wiring system?


If said sheathed cable is then installed in conduit, does it still remain its own wiring system or does it become classes as the conduit wiring system?

For further example, let's talk about colouring for the purpose of what I'm asking

You're not allowed to mix the colouring of NZ and the Euro colours in the same wiring system. If I had a sheathed cable and using the light blue as N run inside the conduit but also had some single, uninsulated cores in the same conduit but used black as a N, would this be compliant? Is this non-compliant because they are all inside the conduit classing as one wiring system? Or is it compliant because the sheathed euro colours are classes as there own wiring system contained in the sheathed cable, regardless of the fact it's in the conduit too?

(Note I understand sleeving to change colours etc and all that, I'm just curious if what I'm asking above would be compliant or not)

Dec 02 2019 09:34

2018 edition has added a definition; though i doubt it will help your particular example.

What you're dealing with is a mixture of wiring systems using a common wiring enclosure.
That gets a bit complicated, but only if you allow yourself to get bogged down in stuff that doesn't actually affect the outcome.

TPS by itself is one sort of "wiring system" [insulated & sheathed conductors]. TPS in conduit (or trunking) is another sort of wiring system [insulated & sheathed conductors in wiring enclosure]. Conduit wires in conduit / trunking is another again [insulated conductors in wiring enclosure].

There are other factors that can also affect the designation of the wiring system; including location & method of installation.

You might have a simple run of TPS, and along one part you want support across a span, or additional protection against mechanical damage, and so may choose to tun that particular section inside a conduit. Same cable, but now this is a different type of 'wiring system" for that part of the run.

If you install a mix of conductor types into a common wiring enclosure; you make life complicated for yourself; so to avoid complication just avoid doing the mix. Failing that; apply each rule according to the stated objective. The fundamental requirements are in Bold typeface (check the Foreword), and 1st para of 3.8.1 is in bold; so that's the outcome we must achieve: ID of each conductor's function. No requirement to ID the circuit, just the function.

Para 2 says that if we choose to use colour to achieve this, then we must use the colours of Table 3.4; and as you've spotted, there is a choice when it comes to Ns (unlike for PEs & EBs; which MUST be green/yellow). There's even more choice for as; but the choice for N's is limited to either black or light blue.
Limited further, in NZ, by ESR 20;so that only black is acceptable in domestic.

The Table includes several Notes. A Note to a clause is always simply advice; but a Note to a mandatory Fable or Fig can similarly be guidance. But a Table / Fig Note that's expressed in mandatory terms is a requirement. So Note 3, statement that the AS/NZS & European colour identification systems "shall not" be used within the same wiring enclosure is a rule.
There's nothing in the Table to identify any of the colours as either AS/NZS or European, but clause & Fig 3.2 provide the info.

What we must avoid is combinations of colours that might lead to individual conductors being mis-identified. Mixing European & AS/NZS colours within one cable isn't going to happen within one cable; but within a wiring enclosure it could.

So you've got a bit of trunking along the plant-room wall, containing a mix of several TPS cables and some conduit wires. Those TPS cables have black Ns. So do the several circuits of conduit wire. No problem so far.

You want to add another circuit, perhaps using flex that has a light blue N. Light blue is an accepted colour for an N in the Table. And, from Fig 3.1; we can see it's an AS/NZS colour for N in flexible cords, flexible cables, and equipment wiring. Absolutely compliant.More importantly, no-one will be confused.
The rule isn't about black Ns vs light blue Ns.

But if you start mixing AS/NZS blue actives and European blue neutrals, there could be confusion; especially if it's in conduit wire. That's what Note 3 is about.

The ID rules aren't applied to each individual wiring system; they're applied to ALL of the wiring systems that share the same wiring enclosure. So if somehow you do end up with both colour-code systems; what you have to do is keep them in different wiring enclosures.