spur from three phase to single phase.

weston29 · Jul 21, 2009

Hello all, is it possible to supply a single phase socket 230v outlet via a fused spur from a three phase and neutral supply? It is a job i've come across whereby the 230 outlet needs replacing because its damaged (metal clad thing thats had a clout and is hanging off). The supply now is from the red phase of an adjacent three phase isolator and subsequent neutral. The customer nearly fainted when i said it may need its own seperate supply as it is a huge cable run which will cause major disruption to his workshop as the conduit run is buried behind all manner of machinery which looks impossible to move.

Had a look at the regs and cant seem to find anything on it?

Any ideas chaps please let me know.

xraytek · Jul 21, 2009

What about replacing the isolator with a small distribution board?

ryanryan · Jul 21, 2009

If the isolator only supplies the 230v SSO, why not disconnect the 2 phase at the db and isolater (remove if in conduit, or earth down if armoured)

weston29 · Jul 21, 2009

The isolator supplies a three phase welding socket which he also wants changing, so needs to keep the isolator in place.

Darkwood · Jul 21, 2009

Are you trying to say then that this isolator supplies both a 3ph welder socket and 1ph socket????? Only way you can rectify this is as mentioned above (if the supply is big enough) fit a board instead of the isolator and fuse down to the seperate outlets.

weston29 · Jul 21, 2009

I know, its a dodgy setup, am a little bit reluctant to tackle this guys "projects", think a non electrician who has "known a bit" has dabbled in the past. Was thinkin of a board in place but doubt he'll go for the price so will have to leave the 230v outlet i think.

Mr Mark Sparks · Jul 21, 2009

there is nothing wrong with it as long as all cables and sockets are fused correctly
its common in the motor trade to provide a socket on a ramp like this

Darkwood · Jul 21, 2009

Mr Mark Sparks said:
there is nothing wrong with it as long as all cables and sockets are fused correctly
its common in the motor trade to provide a socket on a ramp like this

Your above example is it seems a bad comparison as if the ramp has a socket on it it will be in the design when it asks for a certain supply size, and although we have a lack of info to type of fuse(s) and cable size it sounds like someone has tapped a 13amp 1ph socket of a 3ph welding socket.
Given thats hes already said the 3ph isolator is still needed for the welder socket it is highly likely that the socket has a heavy load so tapping a 13amp socket off a phase isnt good practice in this case.

boatnik1 · Jul 22, 2009

Be worth having a look at the welder in question. If it's an ordinary 440v transformer type welder then it's usual for them to run off only two live phases so only two phases need to be run through the isolator for the welder and the other phase & N could be run through a seperate switchfuse/rcb etc. for the socket. All properly labelled of course.

Darkwood · Jul 22, 2009

boatnik1 said:
Be worth having a look at the welder in question. If it's an ordinary 440v transformer type welder then it's usual for them to run off only two live phases so only two phases need to be run through the isolator for the welder and the other phase & N could be run through a seperate switchfuse/rcb etc. for the socket. All properly labelled of course.

With the welder been on a plug top and not a fixed installation it working on 2 phase cant be used to justify tapping the 1ph socket off as the customer may replace the welder etc or plug something else or run an extension whose phase wiring may be crossed.
The only way you can do as you suggested is to make the welder a fixed installation and lots of marking up.