Sizing parallel conductors

[packerbacker]

I am looking to run 400 amps, single phase underground through pvc sch. 80, about 350' on a dairy farm. I have failed to find a sizing chart for parallel circuits in NEC. I am aware of 310.15 b 16, is it a simple as dividing by 2 for parallel runs? Also is there a direct burial cable that is listed to be used for this application that I can run parallel?

 

[pjholguin]

The short answer is None, Yes and Yes.
As for direct burial cable, yes there are several direct burial cables available. You will need to check for the types from the NEC or the manufacturer... I don't have a NEC handbook with me at this time. One important requirement is to bundle the direct burial cables. I am really not a proponent of direct burial cables...I have seen way too many failures. JMHO

I am looking to run 400 amps, single phase underground through pvc sch. 80, about 350' on a dairy farm. I have failed to find a sizing chart for parallel circuits in NEC. I am aware of 310.15 b 16, is it a simple as dividing by 2 for parallel runs? Also is there a direct burial cable that is listed to be used for this application that I can run parallel?

 

[augie47]

I am looking to run 400 amps, single phase underground through pvc sch. 80, about 350' on a dairy farm. I have failed to find a sizing chart for parallel circuits in NEC. I am aware of 310.15 b 16, is it a simple as dividing by 2 for parallel runs? Also is there a direct burial cable that is listed to be used for this application that I can run parallel?

You have to keep 310.15(B)(3)(a) in mind when you have 4 or more current-carrying conductors, although if your insulation allows you to use the 90? rating ( such as THWN-2) this may not be an issue.
In you situation, for optimum performance voltage drop may be the bigger issue in selecting your conductor.

 

[don_resqcapt19]

If you are running directly burial cables in parallel, you have to make sure you can comply with 250.122(F). Often compliance with that section will require a custom cable, or the use of a cable with one more full size conductor than you need for the circuit.