Wiring colours.

JohnW2 said:

if one was wiring in T&E (like my house), really require blue/black and blue/grey T+E to be available, which I imagine it isn't!

Kind Regards, John

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You're right it isn't avaible but it should be for those occasions when it's used for DC.

SUNRAY said:

You're right it isn't avaible but it should be for those occasions when it's used for DC.

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As far as I can make out (per BS 7671), even with DC, blue/black T+E would have no use, and blue/grey T+E would only be appropriate for positive-earthed 2-wire DC systems.

Kind Regards, John

SUNRAY said:

This was originally installed when it was commonplace to retain phase colours throughout 3ph installations [whether required in the regs or not], there are no indivudual switches, just the one to control the main contactor. If there was a 3 pole switch controlling ccts 1,2 & 3 [say] then I would not hesitate it a 3ph cct.

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Thats sort of looking at it upside down, if its a three phase lighting circuit you need to have switching device to break all three phases together, this can be a 3ph breaker, or if its on SP breakers or fuses, then a seaparte isolator downstream. 559.6.2.3

As to whether it is three phase or not. How many neutrals are there? I'd say if each leg has a separate neutral, and you could take them out individually, work on them, test them etc then you just have three single phase circuits. And I could move them onto 1R 2R and 3R if I wanted and I;d have o troubles with overloaded or shared neutrals, I bviously couldn't split up a three phase circuit this way.

It was never actually permitted for single phase cicuits other than submains to be wired in the phase colour, although as you say it was very common and was specified on many jobs

Adam_151 said:

As to whether it is three phase or not. How many neutrals are there? I'd say if each leg has a separate neutral, and you could take them out individually, work on them, test them etc then you just have three single phase circuits.

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That's surely what SUNRAY was talking about, isn't it? - and, as you say, three separate single phase circuits (just like in my house) If there are three phases and one neutral (or no neutral) in a circuit, then there surely can't be any argument that such is anything other than a 3-phase circuit? As I said, I would think that the distinction should be based on whether or not 'the circuit' could, or could not, supply a 3-phase load (with or without a neutral) - which none of the circuits (distribution or final) in my house could.

Kind Regards, John

Adam_151 said:

It was never actually permitted for single phase cicuits other than submains to be wired in the phase colour

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I've lost count how many times I've had to point that out here, although National Rules elsewhere do permit it.