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Posted By Topic: 3 phase extension

Jul 03 2017 16:17

Hi all,
I was recently supplied 5mm2 4 core flex to create a 3 phase extension lead for as 16 Amp machine.
The colours on the supplied flex are black, brown, blue and green/yellow.
In the wiring rules it has red, white, blue for the phases and black as the neutral and I had an electrical trainer inform me that I could not use these colours for the 3 phase lead as it contained a black and the black is a neutral.
The chap who needed the lead just complained and informed me the company he usually takes it to uses this lead without any dramas.
Who is correct?
Kindest regards


Jul 03 2017 16:37

There\'s nothing wrong with those colours.

You need to read all the details in 3.8.1, 3.8.2 and 3.8.3. But the basics are, those rules are for installation wiring only, but even so, the black can be sleeved as red or other colour. What to do with your \"blue\" will depend if it is light blue or not.

However there is an exception for flexible cable which refers to ( European colours, where black is an active and blue is Neutral.

Jul 03 2017 16:40

Your being quoted fixed wiring colours. Which exept for earth you can sheath.
Now for flexible leads for which this is g/y is earth. Beyond that a bit of a choice. Recommended is found in AS/NZS 3191:2008 2.2.4.

Jul 03 2017 16:41

The part of wiring Rules you are referring to (Clause 3.8) relates to installation wiring. So unless you are using the flex for that purpose, that particular rule doesn\'t apply.

If you look at Fig 3.2 you\'ll see that black, brown, grey blue and green/yellow are the standard colours for European flex.

What your trainer is telling you is simply not true. Clearly he has failed to understand either what the relevant Rules say, or why they were made that way.

There is a rule - in ESRs - that makes Black mandatory for Ns in installation wiring of domestic installations. Being in ESRs this over-rides the Wiring Rules for those particular installations - the effect being that alternative colours, such as light blue for N (as listed in Table 3.4), are not allowed in domestic installation wiring. But it has NO effect at all on extension cords.

Your trainer has not only missed the fact that rules for ID of installation wiring do not apply to equipment wiring - including extension cords; he has failed to note that black is specifically listed as an active colour for flexes


Jul 03 2017 17:33

There is a version of 5 core flex with the following colours,
Brown, black, black, blue, green/yellow.
Imagine the confusion when making up a lead if you have to identify which black was the neutral.
Using the blue as the neutral solved the problem and to change the rotation if it was incorrect you simply swap the black cores at one end of the lead.

Jul 03 2017 18:48

The blue is the neutral.
The blacks are identified by the first next to the brown as P2 then next black as P3.

Jul 03 2017 19:02

Thanks Guys,
Can the phase colours be terminated into any socket \"line\"numbers as long as they match at the other end?

In regard to the electrical safety test of a three phase extension - this would be the same as a single phase test with addition of phase to phase insulation ?

Much appreciated.

Jul 03 2017 20:36

You would want to try and follow a colour standard and L1-L1, L2-L2 ect is required. Same as a single phase lead. Transposing A&N will still work but its a fail for obvious reasons

Aug 07 2019 08:34

Hi guys,
Has AS/NZS 3191:2008 been removed or has it been renamed and incorporated into another standard?

Aug 07 2019 08:53


Aug 07 2019 12:30

Odd that It wasn't available to me but have had to request to add to online portfolio.

Aug 07 2019 17:39

I didn't check if it was included in the EWRB portfolio.
If it's not already in there, you'll probably have to pay for it.

Clicking the request to add button will do nothing. You may as well bang your head against a wall.

Aug 08 2019 08:24

The Standards available via EWRB are mostly those directly cited in ESRs Schedule 2, plus a couple of others (eg 3017 & 3008)that are essential for electrical workers.
The list doesn't include many manufacturing Standards like 3191.

There's another bunch, relating to building, now available free because of other sponsorship. Some of these are useful for electrical workers also, eg 3604 for timber framing.