Feeder size

[fisherelectric]

I have a customer who has put up a two story building to house his wife's sheep shearing/wool/ teaching others/store hobby. The load is small. Receptacles, lights, 2 mini-splits for HVAC. It has been wired with a 200amp service. Not a dwelling unit. He also wants to feed a nearby livestock barn for the sheep. A few lights and receptacles and 8 water trough heaters. I figure never more than max 150 amps for both. Probably much less.
The power co has a transformer approx 760' from the new building. He does not want to give them an easement through his property to set another transformer closer to the new building. He is also insisting he wants 400 amps run to this part of the property. The power co is willing to set a CT cab by existing transformer for us to feed from. His idea is to run 400 amps to the building and then from there another 260' to the barn.
My suggestion is going to be to run 300amps.
Question I have is:
Can I use a 300 amp service rated fused disconnect and parallel 2 sets 4/0 Al to the building? I figure about 3.67% VD with 150 amp load. But would 2 4/0s be compliant for 300 amps?

If he insists on 400 amp, would 3 sets 4/0 al be compliant?

 

[augie47]

Paralleling (2) 4/0AL would be compliant for a 360 amp load and could be protected at 400 amps. Acceptable voltage drop would be your and the customers decision.

 

[petersonra]

If you are right about the level of current actually required I'd be inclined to run the 400 amp circuit using the smallest conductors allowed for 400 amps and be done with it. On the other hand if the guy has money to spend do what he wants.

 

[fisherelectric]

Thanks for the replies. I guess I am a little confused about the ampacity of the feeder. I thought parallel 4/0 was only good for 400 amps in dwelling units. If not that makes this a lot easier.

 

[Smart $]

Thanks for the replies. I guess I am a little confused about the ampacity of the feeder. I thought parallel 4/0 was only good for 400 amps in dwelling units. If not that makes this a lot easier.

Gus (augie47) is saying parallel 4/0's are good for 360A (w/75°C-rated equipment and terminations) and can be protected with 400A-rated overcurrent protection device... provided your calculated load (w/continuous loads factored 125%) does not exceed 360A.

Who knows what Bob (petersonra) is eluding to. :blink:

 

[fisherelectric]

OK thanks for the replies

 

[Smart $]

Note parallel conduits or direct burial cables required. All in one requires derating, which will lower the ampacity to less than can be protected with a 400A OCPD.