Multi-Family Dwelling Unit 220.84

[Npstewart]

Hello Everyone.

I have used 220.84 many times in the past however I have only applied it to a single meter center.

My situation is this. I have one Main MDP feeding 8 meter centers. Each of the meter centers is feeding approximately 8 dwelling units. I just want to make sure it is permissable to use 220.84 once on the individual meter centers, and then re-apply the demand factor to the MDP.

Hypothetical Example:
Each dwelling unit has a connected load of 24kW.

Meter center Main. 24kW * 8 Units = 192,000 * 0.43 (220.84) = 82,600 @ 208-3 is 229 Amps. I would use a 400A.

MDP Sizing: 192,000 * 8 meter centers = 1,536,000 * 0.23 (220.84) = 353,280 total watts @ 208-3 is 982A. I would use a 1000A breaker with this.

Does this sound correct?

PS> If you wondering why I am using 208-3 instead of 208-1 its because the meter centers are 3phase in and single phase out.

Thanks!!!!

 

[charlie b]

When I first read the question, I thought you might be double-dipping on the demand factors. But you are not. I agree with your numbers. However, for the main service, you need to account for "house loads" separately. Any office space, corridors, maintenance shack, outdoor lighting, swimming pool, or other loads that are not associated with any specific dwelling unit would add to the 982 amp total.

 

[Npstewart]

Its funny, when I originally wrote that I told myself that I cannot double dip on the demand factors. After I finished I went back and realized that I accidentally double dipped so I had to re-write it. Its extremely easy to take the demand factor twice without even realizing it.

Thanks for your reply Charlie, much appreciated!