There are 2 multifamily buildings let's say A and B(59 and 14 units respectevely)in the same lot or developing area, both buildings are electrically separated with independent services, (1200A, 120/208V 3 Phase, and 600A 120/208v 3 phase respectevely). The developer wants to add a built-in microwave of 1600 watts, and a 9.8 kw range per unit that makes building A 1600A service, but utility has a limit of 1200A for a pole mounted transformer and there is no space for ground mounted transformer. I told the owner to use counter microwaves (already included in my kitchen circuits) and 8kw range to keep our load to 1200A.

My project manager has a crazy question but I want to make sure it is not a good practice. Here I go:

In order to keep 1200 A service in Building A, can I feed both house panels (Building A and B house panels) from the 600A (Building B) service?

Can anybody tell me a code that states if this is allow?

Thanks.

No, you cannot do that. One service to a structure.

And how do you figure installing those appliances will require a service upgrade?
Did you do a new load calculation? Just changing from an 8kW range to a 9.8kW does not change the demand load at all.

Shouldn't a qualified electrician know all this?

Hi Stanfortyman,

My original calculations were without a built in microwave (fixed appliance) and 8 kw range. Now it is a 1600 w fixed microwave and 9.8 kw range per unit. If you multiply this by 59 units the overall service for building B will increase not too much but enough to be over 1200A. I am usinng NEC 220.84 calculation method with a demand factor of 24%.

Thanks

For any range 12kW or under you use 8kW as the demand figure.