Code reference on wiring methods

[WizzDizzle]

I've been requested to install two resistive heating units in one of our workshops. Along with this I was asked to do it a certain manner. This would consist of running both loads from panel to discos (multi circuit) in a common conduit. My question is can I downsize the conductors after the discos to feed the heaters. e.g. #4 awg between panel and disconnect(s) (which includes continuous load rating @ 125% and de-rating of 80% for multiple current carrying conductors in common raceway,) to #6 awg to feed from disco(s) to heaters (which still includes continuous load rating.) I don't feel like I'm in over my head this far, but i do recognize that I may be missing something. Any help would would be appreciated

 

[infinity]

The ampacity of the conductors needs to be derated when you exceed 3 CCC's in a raceway so this would apply to the common raceway between the panel and the disconnects. After the disconnects you would not need to apply the derating factors because there are no more than 3 CCC's in each individual raceway.,

 

[WizzDizzle]

Thank you for your reply. Your response was was my gut feeling on this issue. I strive to only make theoretical mistakes not physical mishaps, and sometimes one needs a sounding board to concrete an idea