Multi Family dwelling units load calculation

[rowelelectrical]

HI,

Im doing a load calculation for a unit in a multifamily dwelling building. My question is, if i use the calculation method on 280.82 which is the first 10KVa and 40% remainder on loads for calculating the units main service, and when i have the total loads for each unit using this method of calculation, is it still right to use table 220.84 for calculating the building's service knowing i have used the 10KVA and 40% remainder on calculating the service for each unit? the building has 15 units so I have to use 40%.

Appreciate all you advise.

Thanks,

 

[david luchini]

It depends. You mention the first 10kVA plus 40% of the remainder of loads from 220.82. But you don't mention the Heating or Air-Conditioning loads from 220.82. If your units don't have electric space heating or air-conditioning, then you cannot use 220.84.

If your units do have air-conditioning or electric space heating, then yes, you can use 220.82 to calculate the load for each individual unit and 220.84 to calculate the load for the multiple units. However, you do not use the values calculated in 220.82 to apply the demand factor in 220.84. You start with 100% of the loads listed in 220.84(C), and then apply the demand factor. I couldn't tell from you're question if this is what you are asking.

 

[charlie b]

From the wording of your question, I am not sure whether you are calculating the feeder to a single unit, the service to the entire set of units, or both. But let us be clear about one thing. When you calculate a unit, you apply the demand factors to the loads within that unit. When you calculate the entire service, you look at the total loads in all fifteen units, and apply the demand factors to the entire set. You don't get to use the 40% factor twice for the service.

 

[rowelelectrical]

@ david.

Thanks, that helped a lot and yes we have air-conditioning and electric space heating.

 

[rowelelectrical]

# charlie.

Thanks. Noted.

 

[dana1028]

@ david.

Thanks, that helped a lot and yes we have air-conditioning and electric space heating.

Nothing was said about this so I will add - to use 220.84 each unit must also be equipped with electric cooking equipment [220.84(A)(2) - see exception].

 

[david luchini]

Nothing was said about this so I will add - to use 220.84 each unit must also be equipped with electric cooking equipment [220.84(A)(2) - see exception].

I disagree. The exception allows the units to not have electric cooking equipment, but
the calculation of 220.84 must include 8kW for electric cooking anyway.