3 phase to single neutral problem

[Spark123]

The suppliers neutral being loose shouldn't cause your neutral conductor upstream to melt tho.
Is the neutral consuctor a smaller size than the phases?
Has that part of the neutral already suffered damage? Has it been loose?

 

[Space cat]

If the idea of all three supplies having been taken from a single phase is a bit far-fetched - and it is - then try this for size. Idea number two:

A wrongly wired transformer has left one of your three phases reversed. The upshot would be that, even with the three phases balanced, the neutral wire would have to carry twice the current of a phase wire.

You can check this by measuring the three phase-to-phase voltages. They should all be roughly equal at about 415 volts. If you find two of them are only 230 volts, you have one phase wired backwards.

 

[ban-all-sheds]

You can check this by measuring the three phase-to-phase voltages very carefully, as a 400V mistake can be very unpleasant.

 

[Spark123]

You might notice any single phase loads or lamps etc don't last very long if that is the case, usually only a few seconds

 

[RF Lighting]

I'm getting half tempted to have a drive down the road tomorrow just to see who has guessed right

 

[ColJack]

me too.. meet you there for lunch?

 

[bogoiler]

yorkshire eletric came out and say theres no resistance on the wire's in but voltge moved about abit just a few volts but he said thats normal house 248 volts on yellow phase workshop 235 volts on red phase , earth has 3 amp! so we no wiser has to the problem ,sparky tested house says it supplier they tested line and said its the house !!!!!!!!!

 

[Space cat]

earth has 3 amp!

That's a lot of earth leakage!

Measuring the phase voltages at each location won't tell you anything about the phase angles. Phase to phase measurements will.

NB: BAS is right. You're looking for 415 volts so take extra care. You don't want any short circuits either so make doubly sure that your meter is up to the job and that it's set to volts and not amps!