# of Phases for Residential Service

[Designer69]

What determines whether you generally provide 1 or 3 phase service for an apartment building?

Is there a rule of thumb?

IE- a new 16 unit, 3 story apartment building.

Thanks

 

[zbang]

The PoCo and the planned load will drive a lot of the decision. It they already have 3-phase in front of the building you're more likely to get it (and maybe required to use it) than if the nearest 3-phase is half a mile a way. For your example building- electric air conditioning? electric or gas heat/cooking? Located in Montana or Texas?

 

[augie47]

That's the case here also. POCO & budget.
POCO can often give you options and cost of each option.

 

[kwired]

And if you are in a position where you can pick one way or the other -

the higher the total load the more likely you will pick three phase.

Total load of say 175kVA you probably need 800 amp service equipment if single phase, and that doesn't leave much for future additions.

Go with three phase and you only need 600 amp service equipment - not a lot more room for future additions but a little more then the 800 amp single phase.

Now if you installed 800 amp three phase gear it likely doesn't cost much more then the 800 amp single phase gear - in fact might be same thing in some instances just with one unused bus.

 

[Dennis Alwon]

If I had a 16 unit building I would figure the load with single phase and see if that is feasible for you and the power company.