3 phase calculations

[robert1234]

I have a 208/120, 3 phase service , i haven't done this in a while but when calculating the total Amps on a branch circuit. For example a Dryer that is using phase A & B do I get the total watts(VA) and divide it by simple 208 or do i use P = 1.732×V(line-line)×I(line-line) formula?

 

[Ingenieur]

for 2 legs no sqrt3 (1.732)
just like 120/240/1

 

[kingpb]

I have a 208/120, 3 phase service , i haven't done this in a while but when calculating the total Amps on a branch circuit. For example a Dryer that is using phase A & B do I get the total watts(VA) and divide it by simple 208 or do i use P = 1.732×V(line-line)×I(line-line) formula?

There are 2 answers to your post. Yes, you always want to calculate KVA, then divide by voltage to get current. However, as stated in previous post you only use your formula for 3-phase loads and drop the 1.732 (sqrt 3) single phase loads.