Sizing service

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john Tiano

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We have 65 apartments with individual panels - each has a demand of 15.9KW
max. We would like to know what size service in amps do we need for a three-phase 208/120volt system. We are having a disagreement with our designer.
 
All I can say, given the limited information you have given us so far, is that the answer is not 65 times 15.9. Or at least it need not be that high. You have to do a service calculation that looks at the entire facility, adds up all the loads, and takes advantage of all the available demand factors.

For example, if each individual dwelling unit has only three fastened-in-place appliances, then you can't take advantage of 220.53, when you calculate the individual unit's feeder load. However, the building as a whole will have 65 times 3 such appliances, so you can use a demand factor of 75 % for these items.

Good luck with this one. We may be able to help a bit more, if you can tell us the nature of the disagreement with the designers.

Welcome to the forum.
 
service

service

the plans call for 800amp 3phase 208/120 volt service: each apartment has a range (8100watts), two appliances ( 1500watts each), PTAC (max 2930 watts) Din.rm Liv.rm calculatons of (1620 watts) Bedroom (1800 watts) lighting (550 watts) bathroom (1500 watts)
All common areas have a seperate service. These are small residental rental units for seniors (over 55) with hydronic heat.
 
Using article 220, try to size this yourself and let us know what you come up with. With no more information the designers service looks in the ball park to me.

Roger
 
john Tiano said:
the plans call for 800amp 3phase 208/120 volt service: each apartment has a range (8100watts), two appliances ( 1500watts each), PTAC (max 2930 watts) Din.rm Liv.rm calculatons of (1620 watts) Bedroom (1800 watts) lighting (550 watts) bathroom (1500 watts)
All common areas have a seperate service. These are small residental rental units for seniors (over 55) with hydronic heat.
Click to expand...
Keep in mind that most 240v-rated loads will require even less power at 208v.
 
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