Caste Metal Light Switch

[SUNRAY]

I'm reminded of the instance when we were pre-purposing a 30A switch fuse in a mains room (fed off the busbar) which used to feed a 3ph compressor for something else, there was no neutral provided as the compressor being a true three phase load did not require one, but we now needed one. The installation was from the 70s, so Red, Yellow, Blue conductors in use. I supoose installing black for a neutral in 2016 wasn't strictly in accordance with 7671, but a using blue would have been insane!, can't even remember if I bothered to declare it as a deviation or not

I've had added several neutrals to 3ph circuits in very similar situations and also automatically use black, IMO it is not a deviation. I think it would easily come under the umbrella of H&S / EAWA act to use black.
The only other alternative would be replacing the old colour tails which would be a silly expense.

 

[SUNRAY]

The sleeving question came up on another electrical forum the majority sleeve as below:
View attachment 133231

I'd love to get away with working to that standard.

I would never mix new sleeving on old cables.

Although I have total sympathy with this statement it is not permitted by many consultants

For a single phase circuit connected to a 3 phase supply, the line conductors should be brown. It used to be common for single phase line conductors to be the phase colour when wiring in conduit and trunking but apparently no version of the regulations permits this. It does look cool though...

Whether it ever appeared in the regs it seems most schools I've worked in were wired this way, the real PITA being making alterations where a phase change is required.
I even remember buying flex in phase colours.