derating

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Can you be more specific as to your question? Derating conductors is a consideration of heat and its effect on the conductor.

But I guess the closest answer to your question as asked would be the load.

Roger
 
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Ok, I have 10 2.2amp 3 phase motors I have to wire, they are for zone pumps for radiant floor heat. Each pump has a motor starter and I want to mount all the motor starters on a board with a wireway acrosed the top of them then bring a 2" EMT from the panel into the wireway to the line side of the motor starters, then out of the starters back up into the wireway into another 2" EMT over to another wireway out of that wireway with mc into the pumps. My 2" emt pipes will have 31 #12 THHN's on a 15 amp breaker but are only drawing 2.2 amps of current on startup.If you only derate with the actual load and not the breaker size I will be fine.
 
I agree with you, although the inspector may not based on the actual wording of 310.15(B)(2)(a) and its table, of course you could use 10 amp breakers. :smile:

Roger
 
he may make me use 10 amp breakers even though I already have the 15's if he does I will have to change them no big deal.
 
I hope he uses common sense for his call so you don't have to change the breakers, good luck.

Roger
 
Show your inspector this section, and see if he/she will buy it. This rule is for control circuits, but in my opinion, it is no more unsafe that what you describe.

725.28 Number of Conductors in Cable Trays and Raceway, and Derating.
(A) Class 1 Circuit Conductors. Where only Class 1 circuit conductors are in a raceway, the number of conductors shall be determined in accordance with 300.17. The derating factors given in 310.15(B)(2)(a) shall apply only if such conductors carry continuous loads in excess of 10 percent of the ampacity of each conductor.
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