In message . com, jim
writes

There are several reasons for using 3 phase in industrial & high load
installations, amongst them being economy of generation and
distribution and better control of electrically driven machinery.
Downside, if it is one, is that single phase loads need to be equally
balanced between phases so far as possible, plus the higher voltage
between adjacent single phase fittings when on different phases.

IIRC there was once a 6ft distance between accessible_by_touch single
phase fittings requirement (IEE 14th Ed???) but that has long since
disappeared from the IEE regs.

Quite correct 14th. edition reg. A.20

*All socket outlets in any one room shall be connected to the same phase
(or pole of a 3-wire system).

Exemption. -In non-domestic premises, if it is clearly
impracticable to comply with regulation A. 20, more than one phase (or
pole) of the supply may be utilized provided that all socket outlets on
one phase (or pole) are grouped together and are not intermingled with
socket-outlets connected to a different phase (or pole) ; and provided
that in no circumstances may a socket-outlet be installed at a distance
less than 2m from any socket -outlet connected to a different phase (or
pole).*

regards


--
Tim Lamb