Combiner D/C Feeder

[Leonard O'Donovan]

I have a 190 amp Combiner D/C feeder to a re-combiner that travel 120 LF across a roof with 5 inch clearance off of surface. Area high temp is 100 F. The total run is 240 LF. I calculated (2) 3/0 THWN-2 and (1) # 6 THWN-2 ground. I do not think there is enough volume in conduit for cooling also may pose difficulty for wire pulls through LB' etc..

 

[Dennis Alwon]

I have a 190 amp Combiner D/C feeder to a re-combiner that travel 120 LF across a roof with 5 inch clearance off of surface. Area high temp is 100 F. The total run is 240 LF. I calculated (2) 3/0 THWN-2 and (1) # 6 THWN-2 ground. I do not think there is enough volume in conduit for cooling also may pose difficulty for wire pulls through LB' etc..

What is your question? What size and type conduit are you using?

 

[jaggedben]

The NEC does not care what size conduit you use with respect to cooling. As long as you meet the minimum physical space requirements for fill in Chapter 9 you are okay. If you want to go up a size or two to make the pull easier that is entirely up to you.

You have not been clear if the 190A is the actual amps or the calculated current required in Article 690.

If 190A is the calculated current, you still need to derate your conductors for temperature. You need to use 130F for the derate because of the 30deg rooftop adder for 3.5-12 inches. At .76 derate, 3/0 is not large enough; you need 4/0.

If 190A is the actual amps then you'll need an even larger conductor.