Voltage drop and derating combined ? 1

[batman2010]

hello all,

i am running feeders to (2) 3 phase , 480V, 75HP pumps. FLA for each pump is 96A and they are located at a distance of 176 feet from the panel.
according to code:

96A * 1.25 = 120 A, then adjusting for voltage drop gives me #1/0 wires

now do i need to add derating factor if i am running feeders to both pumps in one conduit OR it is either or (voltage drop or derating but not both)? meaning one will cancel the requirement for the other?
if i have to do adjustment for derating then i ll end up with #3/0 which is too large??

thank you,

 

[davidbeach]

Apply all deratings/adjustments independently and then use the largest conductor that any one requirement necessitates. Note that if you increase the size of the phase conductors for voltage drop you also have to increase the size of the grounding conductor proportionally.

So if your conductor sized for voltage drop without considering multiple conductors is large enough when you consider multiple conductors but not voltage drop then you're good to go.

 

[batman2010]

Thank you for the response, this makes sense now since counting for both makes the conductors too large.