branch circuit design - Electrician Talk - Professional Electrical Contractors Forum

toolman001 · 06-29-2008, 10:02 PM

Hi Guys I am quoting a job on a golf coarse where we have 35 electric carts.
The branch circuits will run down two walls with a total of 18 110V 15Amp
circuits on each wall, the panel will be a 400Amp three phase. The max draw per cart charger will be 9.5 Amps, and a request by the manufacturer that each cart is on a septate 15 Amp circuit.The building is 80 feet long and 40 feet wide. my question is the best way to run the EMT to provide most wire per run and not derate my wire ampacity.
Thanks

480sparky · 06-29-2008, 10:05 PM

If you go with MWBCs, you can put 9 circuits (3 blacks, 3 reds, 3 blues and 3 whites) into one conduit and will hae a 20a breaker. If you've got 18 receps, that's only two pipe runs.

toolman001 · 06-30-2008, 08:20 PM

Thank You for your help I had ad idea that would be the best way to solve the problem. If my calculations are correct using #14 THHN will still give me the required ampacity of 9.5A. This web site is a great resource. Thanks to all who are there to help.
Toolman001 (just an old fat boy who got use to being shocked)

480sparky · 06-30-2008, 08:40 PM

Quote:

Originally Posted by toolman001

Thank You for your help I had ad idea that would be the best way to solve the problem. If my calculations are correct using #14 THHN will still give me the required ampacity of 9.5A. This web site is a great resource. Thanks to all who are there to help.
Toolman001 (just an old fat boy who got use to being shocked)

Um, how do you plan on protecting (read: over-current device) those 9.5a #14 conductors?

toolman001 · 06-30-2008, 09:10 PM

I hope I CAN USE 15A breaker

waco · 06-30-2008, 09:18 PM

I'd run #12 and use 20 amp breakers just to avoid the voltage drop over that distance. The additional cost is negligible.

toolman001 · 06-30-2008, 10:03 PM

I can see using # 12 wire the runs, they will not exceed 100' however the manufacture request each branch circuit be on 15 Amp breaker
Thanks Toolman001

480sparky · 06-30-2008, 10:31 PM

Quote:

Originally Posted by toolman001

I hope I CAN USE 15A breaker

If your calculated ampacity is 9.5 amps, they must be protected with an overcurrent device not exceeding 9.5 amps.

Recalculate using 12s and see if you can then use a 15a breaker. Also, break down the conduit into two, and separate the circuits out. That will help.

If nothing else, pulling 18 circuits into one conduit will be an exercise in futility. You'll spend more time keeping them all straight than it's worth.