Aug 31, 2012 12:50 pm
What does NEC say about parallel PV feeder cables?
I'm installing 14 290W Suntech PV panels 200' from the equipment room. The panels will be wired as seven series-pairs, and all seven pairs will connect to a common point inside a Midnight combiner box.
Due to the distance, I'm using individual #2 type XLP-UF aluminum wires from the PV array to the Outback load center in the house.
Sadly, due to the fact that the wire is aluminum, the power loss through the #2 wires will be 10% -- too high for me.
So I want to use TWO #2 wires in parallel for each feeder (two for positive and two for negative), to cut the resistance and the power loss in half.
Can someone tell me if the code allows this? When I asked Outback tech support, I was told that I can't use parallel wires (and that I need a combiner box, which told me he probably was confused).
All I want to do is to connect TWO wires to the combiner box's positive TBB and TWO wires to the negative TBB, then connect the other ends each pair to the same positive and negative TBBs inside the load center in the house. According to the aluminum wire table, this gives me the same resistance as 2/0 wire.
NOTE: The aluminum ampacity table shows that ONE #2 wire is large enough for the 53 amps of current my PV array can produce, so I'm not trying to parallel the wires to handle more current -- only to reduce power loss in the cables.
Thanks in advance for any definitive information.