I have a three phase supply,is it more economical to use each phase and neutral to supply a domestic situation I.e. kitchen off the red phase and neutral, ground floor power and lighting off the yellow phase and neutral, first and
second floor power and lighting off the blue phase and neutral?

 

It depends on the load. Low power devices are best run on single phase power but high power devices like stoves and dryers have to run either dual phase or three phase. They can't run single because the current would be too high.

 

I have a three phase supply,is it more economical to use each phase and neutral to supply a domestic situation I.e. kitchen off the red phase and neutral, ground floor power and lighting off the yellow phase and neutral, first and
second floor power and lighting off the blue phase and neutral?

If you have a 3 Phase supply, the right way to do the wiring is to distribute the load on each phase equally - as far as possible. You need to study what loads are "on" most of the time and work out the load distribution.

You also need to know the "worst case imbalance" situation when you have all the loading on a single phase and the neutral wire will carry the same current as your loaded phase. In a perfect balance, the neutral current is 0.

What did you mean by "economical" in your post? Cost of wire? Or cost of Energy consumed?

Ramesh

 

In a domestic situation, a kilowatt hour is billed as a kilowatt hour, no matter which phase you use. Everybody is concentrating on phase balance because that's about the only mistake you can create.

 

It's possible if everything runs from 1 phase that your wiring will have greater current, and greater resistive losses in your wiring.

If you run from 3 phases instead than each phase will onlyhave 1/3 of the current and the resistive losses will be much less.

However in a domestic wiring situation the resistive losses of properly installed wiring will be very low, so it won't matter much at all.

One real benefit of running 3 circuits from 3 phases is when you get a power blackout on one or two phases. You will still have some power points working. I lived on a street where it was common for 2 phases to go down sometimnes at night, you could look down the street in the dark and see about 1/3 of the houses (randomly) still had lighting and power. Unfortunately I only had 1 phase at it was one of the bad 2.