On 24 Oct, 22:19, "The Medway Handyman"
wrote:
Working for a regular customer in an industrial unit today & he asked me to
check why a 230v socket wasn't working. Socket tester showed no live but
all wires were properly in place. No mcb tripped on the panel.

Found another socket on an adjacent wall not working either, but sockets in
between them work fine.

/snip//

The most likely explanation is that the fuse (or perhaps a contactor)
on one of the phases has blown (or tripped), though there's other
possibilities.

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.

However there is one other important reason for using 3 phase derived
lighting (ie lighting shared between phases over one area) when
rotating electrical machinery is in use and that is to avoid the
strobe effect of a motor appearing to be standing still when in fact
it is going at full tilt. It is in the back of my head that it is or
was a legal requirement under one or other of the Factories Acts or
similar, but cannot vouch for it.

Flourescent tubes, including CFLs, flicker much more than ordinary
GLS, so is this a looming problem if CFLs become common place?

Lastly, whilst 3 phase is rare in homes in the UK unless used for
storage heaters, it is far more common on the continent.

BTW you need a waste transport licence (around £340 for 3 years from
Environment Agency IIRC) for even thinking about taking away
virtuially anything from a job site where you've been working. Even
your Mars bar wrapper is deemed scrap by the Blairite shock
troops ;-) And yes, even the filaments in the scrap flourescent
tubes;-)))

HTH