litungping
New member
I am having trouble figuring out the calculation on a warehouse space that is fed with a 225 main,120/208 3 ph 4 wire panel. They want 70kw of hid lighting.
I use the formula W/ V x pf =A
70kw/ 208 x 1.732 (360.256) = 194.3a p/phase
1st- why do we divide by 208 & not 120v? (the ballast are 120v/1,000w )
2nd - if I de-rate to 80% of the main (225) I come up with 60kw & 167a p/ph. using above formula.
3rd- art 220.18(b)-Maximum loads: states to go off rated amps of ballast, if so we are talking 9.5a at 120v. If I go by this article than I can only install 55kw
and also I am having trouble finding where in the code it says how many neutral conductors are required. Is it 1 p/ 3ph, I thought 2008 code required neutrals for every hot? there also are existing loads I will have to account for.
and one last thing...... I had another Jw tell me I can add a 100a sub panel if I need additional ckts and that this would not affect the loading of the 225a panel, that just sounds wrong to me, but at this point my head is spinning.
thanks for the help
I use the formula W/ V x pf =A
70kw/ 208 x 1.732 (360.256) = 194.3a p/phase
1st- why do we divide by 208 & not 120v? (the ballast are 120v/1,000w )
2nd - if I de-rate to 80% of the main (225) I come up with 60kw & 167a p/ph. using above formula.
3rd- art 220.18(b)-Maximum loads: states to go off rated amps of ballast, if so we are talking 9.5a at 120v. If I go by this article than I can only install 55kw
and also I am having trouble finding where in the code it says how many neutral conductors are required. Is it 1 p/ 3ph, I thought 2008 code required neutrals for every hot? there also are existing loads I will have to account for.
and one last thing...... I had another Jw tell me I can add a 100a sub panel if I need additional ckts and that this would not affect the loading of the 225a panel, that just sounds wrong to me, but at this point my head is spinning.
thanks for the help