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Posted By Topic: green/yellow core used as 24v control

Aug 09 2019 11:47

Hi All, A colleague has identified some field cabling on an HVAC installation where the green/yellow core in a tps cable has been used for 24v control purposes. I'm aware that its not compliant to use a green/yellow as a live conductor in a low voltage installation but I'm unsure if that still applies to extra low voltage. Can anyone advise please?

Aug 09 2019 13:49

ESR 57(1) - Every installation that operates at low voltage or extra-low voltage must comply with either Part 1 or Part 2 of AS/NZS 3000:2007.

Table 3.4 in Part 2 of AS/NZS 3000:2007 states that green/yellow may be used as a PEC or EBC. The same table states that Active cannot be green, yellow or green/yellow.

This leads me to believe that green/yellow can only be used as a current carrying conductor under Part 1 of AS/NZS 3000:2007, in which case I believe it would need an approved certified design.

Aug 09 2019 15:24

Being ELV does not "switch off" the rules.
People can do prety much what they like for conductor ID in equipment; but as part of an installation ELV must comply same as LV (some rules modified i.a.w section 7)

Aug 09 2019 19:25

I'm just an apprentice.
Reading this makes me ask a question, what about Cat 5, Cat 6 cable where they have a green core for data(Green, Orange, Blue, Brown)? Have I missed some thing?

Aug 10 2019 16:18

That's not part of an electrical installation; it's communications.

Aug 10 2019 17:23

and thats green in a data cable, not green/yellow.

Aug 10 2019 21:17

3.8.1 also says "Conductors with green, yellow or green/yellow combination coloured
insulation or sheathing shall not be used as active or neutral conductors in
installation wiring."

So that covers green.

I've heard that there's rules around comms that override/are different to the electrical ones, but haven't looked closely.

One wonders how PoE plays into this...

Aug 10 2019 21:43

easy, the poe voltage uses the blue and brown pairs

Aug 10 2019 22:42

Go to the search box above and put in “green/yellow”. There’s 2 hits.
I had the same question a few years back and there’s some good reading there.

Aug 11 2019 00:47

More recent iterations of PoE use all four pairs to deliver more power.