Size of my Feeder runs, and voltage drop.

[Bob Cornett]

Hello,
I have three fedder runs from a 4000-amp MDP.
1- 800-amp, 480v, 1000 feet away, it is run in EMT.
1- 600 amp " 480v, 1000 feet away.
1- 400 amp " 480v, 1000 feet away.

with my math I have
800 amp 3 runs of 600KCM. and a 1/0 ground.
600 amp 2 runs of 600KCM. and a #1 ground.
400 amp 2 runs of 350KCM.and a #3 ground.


Am I correct or have i missed something?

 

[infinity]

What current value are you using in your calculation?

Welcome to the Forum.

 

[jaggedben]

Hello,
I have three fedder runs from a 4000-amp MDP.
1- 800-amp, 480v, 1000 feet away, it is run in EMT.
1- 600 amp " 480v, 1000 feet away.
1- 400 amp " 480v, 1000 feet away.

with my math I have
800 amp 3 runs of 600KCM. and a 1/0 ground.
600 amp 2 runs of 600KCM. and a #1 ground.
400 amp 2 runs of 350KCM.and a #3 ground.


Am I correct or have i missed something?

You missed telling us what is the maximum percentage voltage drop you consider acceptable.

 

[Bob Cornett]

3% voltage drop,
VD=ixr

 

[Bob Cornett]

the calculated load at the panel on the 800 amp is 550 amps.
600 amp is 440
and the 400 amp load is 310 amps.

 

[Knightryder12]

My quick calcs are this:
800a - 3 sets of 400 cu = 1.79%vd
600a - 2 sets 350 cu = 2.45%vd
400a - 2 sets of 4/0 cu = 2.85%vd

This is using the loads that you gave. So the only one that needs to be upsized is the 400a feeder from 3/0 to 4/0.