Multifamily Dwelling Calculation and OCPD

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Dub-A-Dub

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Johnson City,TN
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I'm working on 14-units that are housed inside a bigger complex. Each dwelling unit is showing around 111 Amps, using 220.82, and I'm going to install a 125A ML 120/240 1-ph panel in each. I'd like to install a 3-phase panel to serve sub-feed each apartment panel from. The complex has multiple services coming in at 120/208 3-ph. When I use 220.84 to size the feeder to my new main panelboard I'm getting ~360A (111*14*208 = 323kVA --> 323kVA * 0.40 = 129.3kVA --> 129.3kVA / 208V /1.732 = ~360A).

My question is this...I've calculated the feeder based on 220.84 of the NEC, do I now need to multiply by 125% for the conductors and OCPD or can I just round it up to a 400A panel and feeder?
 
125% factor does not need added to final result of any of those art 220 calculations, it is already included if necessary within the calculation.

You must have at least 360 amp conductor and since 400 is the next size up overcurrent device you can use it, over 800 amps you would need the conductor to be have ampacity equal or greater than the overcurrent device.
 
Dub-A-Dub said:
I'm working on 14-units that are housed inside a bigger complex. Each dwelling unit is showing around 111 Amps, using 220.82, and I'm going to install a 125A ML 120/240 1-ph panel in each. I'd like to install a 3-phase panel to serve sub-feed each apartment panel from. The complex has multiple services coming in at 120/208 3-ph. When I use 220.84 to size the feeder to my new main panelboard I'm getting ~360A (111*14*208 = 323kVA --> 323kVA * 0.40 = 129.3kVA --> 129.3kVA / 208V /1.732 = ~360A).
Click to expand...

You can't use the 220.82 result in the 220.84 calculation. You have to use the connected load.
 
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