feeder current calc for 120/240

[dataca]

Hi all,

Suppose I have a 120/240 VAC source (single phase/ 3 wire), and a connected load of: 2 KVA for L1 & 3 KVA for L2.

To size each feeder (L1, L2), I calculate the currents I:

• 
  [*=1]IL1 = 2 KVA/ voltage
  
  [*=1]IL2 =3 KVA/ voltage

My question is, do I divide by 120v or 240v?

How would my current change if I added one 0.75 KVA 240V load? This has been confusing me. Thanks for your time.

 

[Smart $]

Well you technically can't calculate line current from a kVA value unless you know what the other side of the circuit is connected to.

If the L1 and L2 loads are connected line to neutral, then you divide the kVA by 120V.

The 240V 0.75kVA load would add half of the kVA to each of the lines at 120V.