Was wondering...when calculating lighting and other loads given in real power (kw), should these kw figures be converted to kva to be "pure"?
Assuming a .9 pf for fluorescent light fixtures, one should technically divide the kw by .9 to get kva. It might not add much but for large loads it looks like it will increase the load enough to consider the next higher OCPD and wire size.
Thankfully for motor loads you can get the FLA from the tables in section 430, and multiply by the voltage to get VA directly. If given watts instead, I'd be inclined to convert with a .8 pf or whatever was appropriate.
Most EEs seem to keep this stuff simple either because they forgot about these relationships, don't care, or are ignorant (mostly non EE graduates...designers). It's sad that MEP Electrical Engineering has been reduced to just knowing the NEC and Ohm's law...and knowing about sqrt(3) for 3 phase power.
Watts and KVA are interchangeable to most, yet you cannot even begin to pass the PE exam if you don't understand these relationships WELL.
Edited by audioaddict, 07 June 2010 - 09:53 PM.