Design questtion for water well

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R@rpe

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I am wanting to feed two well pumps from a 480V 3-phase service using one feeder.
The pumps are both 5 HP and will be run continuously. The first pump will be located 1350 feet from the service and the second pump will be an additional 300 feet away.
My design is to run a #3 conductors protected on a 30 amp breaker from the service to a j-box at the first pump then to a fusible disconnect (20 amp fuse) and from the j-box to the second pump feeding directly into a second disconnect.
Is this the most cost effective design?
 
A GE THQL is rated 8-3 for a 35 amp breaker -your right, I need to increase the breaker size to 35 amp. The 30 amp ranges 14-8. Thanks
 
V drop

V drop

I just did a computer-simulated V drop calculation (SKM) out of curiosity.

It looks like the only restriction you would have is that both pumps don't start together, in which case you could have about 17% V drop during startup. Even that may not be a problem. (The Fire Pump section of the NEC limits the startup V drop to 15%.) And your running Vdrop is less than 3%.

But even if the pumps are independent there's probably a low probability that the 2 could start exactly together - so even that may not be a problem.

John M
 
mayanees said:
I just did a computer-simulated V drop calculation (SKM) out of curiosity.
Click to expand...

My calculator matches your results.
Underground PVC conduit provides no significant VD improvement.

If 480v minimum is measured at the service, the same load on #6cu, in PVC delivers under 5% VD total, and motor-rated voltage with an interlock delay at the first pump disconnect, preventing simultaneous spin ups from blowing that 30A breaker. The only issue would be interrupting the 2nd well pump for a second or two each time the 1st one spins up.
 
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