On 06/02/2021 23:14, Theo wrote:
While I was on the TLC website I was doing a thought experiment.

Twin and earth cable comes in a variety of sizes:
1, 1.5, 2.5, 4, 6, 10, 16 mm2.

But what if you want to wire three phase? TLC only have 1 and 1.5mm2 three
core and earth. Doncaster Cables also have 2.5mm2 but not larger. CEF
likewise. There's some three core in SWA but I assume that's primarily for
external use?

I understand that using three phase you can get 3x the power compared to
single phase - so a 32A radial would get you 7.3kW single phase or 22kW
three phase.

But how should you wire that? For a 32A single phase radial the TLC
calculator indicates it needs 6mm2. What cable do you use for three phase?

I suppose you could run a pair of 4/6/10mm2 T&E but that would seem
'surprising' - one of those pairs carries two phases instead of live and
neutral, and anyone who mixes up a phase for neutral may be in for a shock.
Plus the colour scheme is confusing (two brown and two blue, which phase is
which again? You can sleeve, but what if you mix up the cables?)

You could use SWA, but that's fairly unwieldy and pricey for an internal
installation.

So what's the 'proper' way to do it?

Thanks
Theo

IME at the domestic / light industrial level 3 phase is usually wired in
single core.