# 120/208 3 phase to condo and apartment buildings



## jar546 (Jul 10, 2013)

Honest question that I don't know.

What, in most cases is the single, largest factor for deciding to run 120/208 3 phase instead of 120/240 single phase to an apartment building or condo setup?

I am especially curious when the house panel does not run much other than lighting and other small common area circuits.


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## raider1 (Jul 10, 2013)

By running a 3 phase service to those buildings you can install a smaller service then if you used a single phase service. That is the biggest factor I have seen for the decision to run a 120/208 3 phase service instead of a 120/240 single phase service.

So for example I have a calculated load of 200 Kva for simplicity sake.

200,000 divided by 240 would result in a single phase service of 833.333 amps or more likely a 1,000 amp service.

200,000 divided by 208*1.732 (Square root of 3) would result in a 3 phase service size of 555.555 or more likely a 600 amp service.

Chris


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## jar546 (Jul 10, 2013)

I was confused by this because some POCOs charge significantly more for 3 phase services and in this case I did not know if the reduction in service size paid for the additional costs of a 3 phase service.  About 2 years ago we had a lot of permits to convert 3 phase services back to single where they did not have any equipment that needed 3 phase.

Thanks for the clarification.


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