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ceb58

ceb58

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Raeford, NC
Help a brain dead fellow out. I will be installing some electronic devises at a correctional facility. These devises are mounted on poles around the outside of the facility ( 4 poles ). Each devise must have a dedicated 120v circuit and has a load of 4 amps. Here is the problem. By the voltage drop calculations 2 of those circuits ( 460ft, 560ft ) must be # 6 THHN and the other 2 ( 1640 ft, 1740ft )must be #3 THHN due to the distance from a UPS panel inside of the prison to the devises. I think I can land the #6 on a SP 30 but unsure of the #3. Only other option is to put a short pig tail on the wire and land on 20 amp SP breaker.
No way to do transformers on the yard.
 
At the panel you probably could go as high as a #8 on a 20A breaker. Get a butt splice with set screws or a Polaris connector and splice the larger wire on. That short of a piece you could even just use #12. I don't know about your devices but you may have to splice down there too.
 
4 Amps of current draw causing that much of a VD to require #6??? Methinks you calculated something wrong. At 600ft I get a 6.75% drop using #12 wire. 6.75% drop is 112VAC at the device. On the longer one I get 7.6% drop using #8, so still over 110V.

Is it that sensitive? Most devices are +-10% and many things are actually designed for 115V when used on a 120V circuit. Check your specs and calcs again.
 
Jraef said:
4 Amps of current draw causing that much of a VD to require #6??? Methinks you calculated something wrong. At 600ft I get a 6.75% drop using #12 wire. 6.75% drop is 112VAC at the device. On the longer one I get 7.6% drop using #8, so still over 110V.

Is it that sensitive? Most devices are +-10% and many things are actually designed for 115V when used on a 120V circuit. Check your specs and calcs again.
Click to expand...

I used the voltage drop calculator from Mikes home page allowing for only a 3% voltage drop.
 
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