Voltage Drop percentage

[mtaylor]

I am running 2 sets of 400 XHHW for a 600A 1P 120/240v service.

http://i276.photobucket.com/albums/kk32/sirikin/windemere_new.jpg

Generator to Transfer switch = 141 ft
Transfer switch to three 200A disconnects on outside wall of structure = 174 ft

1. Would you calculate voltage drop over both lengths (174 + 141) or just one of the lengths.

2. What would the voltage drop percent be?

3. What percent voltage drop is acceptable for an application like this one?

Thanks!

 

[charlie b]

You are going to lose voltage over the entire length of the conductors between the source and the load. So calculate the VD for all 315 feet. I did a quick estimate, assuming the load current was 600 amps (you gave me no other information to use as a basis). I got a result just under 7 volts, or just under 3%. It is generally held that a VD of 5% to the end of the branch circuits will give acceptable performance. But you didn't give us any information on the length or nature of the branch circuits, so I can't say for certain if this will be a good design.