Voltage Drop

[jotw]

How do you adjust impedance for paralleled conductors?

 

[bob]

If you are just using the resistance, divide R by the number of parallel phase conductors. In you case it is 2.

 

[kingpb]

How do you adjust impedance for paralleled conductors?

Check post #4.

Also, don't switch cables at the pull box.

I doubt 2 runs of aluminum are going to be cheaper than 1 run of copper.

 

[kingpb]

Using Southwire VD calculator:

2 conductors per phase utilizing a #600 Aluminum conductor will limit the voltage drop to 2.70% or less when supplying 400.0 amps for 600 feet on a 480 volt system.

2 conductors per phase utilizing a #500 Aluminum conductor will limit the voltage drop to 3.02% or less when supplying 400.0 amps for 600 feet on a 480 volt system.

2 conductors per phase utilizing a #350 Aluminum conductor will limit the voltage drop to 3.85% or less when supplying 400.0 amps for 600 feet on a 480 volt system.

1 conductors per phase utilizing a #1000 Aluminum conductor will limit the voltage drop to 3.24% or less when supplying 320.0 amps for 600 feet on a 480 volt system.

I wouldn't get stuck on the 3%. It's only a guideline, also, the max. current in the cable is 320A not 400A, assuming your using a 400A that is not 100% rated.