three phase problem - supply/motors/board?

[telectrix]

could even be main switch or MCB breaking down on 1 phase under load.

 

[snowhead]

There is a fault on the incoming cable or distribution fuse outside of your building.
As others have said contact the DNO.

Forget the 240, all that matters is the phase to phase voltage.
Who was using the test meter?
Check one reading isn't 240mV

 

[Darkwood]

I take it the OP turn the main switch off when testing the supply... any three phase loads connected will give feed back that may lead to confusing test results i.e.... if a motor was still inline or a coil on a contactor you would register voltage on a phase that has been cut.

 

[Knobhead]

Best advice
Get an electrician in that doesn’t spout the proverbial!

 

[GLENNSPARK]

Best advice
Get an electrician in that doesn’t spout the proverbial!

well im flattered ...i really am....
now....the O/P can go through the series of tests....
alternativley
see post #7

 

[Knobhead]

well im flattered ...i really am....
now....the O/P can go through the series of tests....
alternativley
see post #7

???what???

 

[yorvac]

Many thanks for all help.

All those who said the problem is external to my building, looks like you were right. I came in this morning and everything was working. The reading across L1-L3 is back to 425v so obviously there was a phase down somewhere.

Thanks again.

 

[44ALLAN]

Aye some clever fellas on here mate