3 phase service calculation

[treyp3]

I have a 120/208 3 phase service for 6 apartments and 1 house panel. I did an optional calc on the units 1200 sq ft, nothing fancy, and came up with a 125a service. Now comes my question. How do I get my main feeder size. I added all of my apartments and a 100a house panel with NO deductions because I believe that is what 220.84(c) 1-5 tell me to do for a table 220.84. When I add all these up I get 217,684va. I divided by 208 and then 1.732. That gives me 604. Because the apartments and house panel are using only two legs I have 4-5 panels between any two legs, so I applied the 45% from table 220.86 and came up with 272a. I would love any feedback!

 

[david luchini]

You should take the total load of the 6 apartments (as directed in 220.84(C) 1 thru 5) and the apply a 44% demand factor (for 6 units) from the table.

The house loads should be calculated separately and then added to the demand load for the dwelling units.

 

[treyp3]

How is this?
1488 sq ft appartmen
lighting, 1488x3va= 4,464va
2 appliance= 3,000va
refridgerator= 1,500va
microwave= 1,500va
garbage disp= 1,000va
dish washer= 1,500va
heat= 6,240va
dryer= 5,000va
range= 10,000va
@ 100% = 34,204va

34204va x 12 units= 410,448va
410440va/208v= 1,973.3a
1973.3a/1.732= 1,139.31a
1,139.31 x 41%(12 units)= 467.12a
467a + 1-100a house panel= 567a