mains wiring colour code

[andy257]

Hi All,

Just wondering if someone can clarify the following

In the UK the standard for wiring is Neutral = Blue, Earth = yellow/green, Single phase is brown, three phase is brown/black/grey.

If some of my equipment is single phase and i use one of the three phases and a neutral what colour should the live be.

for example: i use the black phase with neutral to power a PSU. Should i wire this with brown cable as it is now single phase or continue with black becasue its off one of the three phase lines?

thanks

 

[mab2]

I should probably advise you if you're not qualified to be very careful, esp. with 400v 3ph supplies. And make sure you're not breaking the law.

To answer the question - your single phase cct should be wired with Brown live, regardless of which phase it's connected to.

Be VERY careful if your connecting into a 3 phase supply with the old colours (red, yellow, blue for live and neutral black), as your new wiring will have blue as neutral and the existing wiring has blue as live - get it wrong and you'll have 400v instead of 230v!

mab2

 

[RODALCO]

The correct colour for the neutral wire should be light blue, often normal blue is used in flexible leads.

 

[Diver300]

for example: i use the black phase with neutral to power a PSU. Should i wire this with brown cable as it is now single phase or continue with black becasue its off one of the three phase lines?

Three phase equipment usually splits to single phase in a distribution box. The three phase cable comes in with the three phases coloured brown/black/grey but all the single phase circuits have live wires brown.

Most single phase loads are in equipment that is fed with a single phase, so the live is brown, just like the cables that feed it.

The fact that the power to your PSU is on the black phase implies that it is inside an item of three phase equipment. If that is right, you can use any colour you want. The colour that I would use depends on the physical arrangement. If you have lots of brown/black/grey single core wires inside the equipment, I would keep with those. If you want to run a 2 or 3 core cable with for live and neutral and maybe earth, then you have to use brown/blue as you can't buy black/blue cable.

In that case, there will be some sort of distribution connector where the three phase supply enters the equipment, and there may be a fuse there. That would be where you could change the colour without confusion.

You could post a photo of what you are making.