Derating Conductors HVAC Equipment Temperature Rating

[kyleapec]

The engineer has sized the conductors per 60 degree column unless noted otherwise all the way from the switchgear. I am of the opinion that we can run 90 degree to the JB next to the VAVs or whatever equipment it is and only the flexible whip into the equipment would need to be sized according to the rating of the equipment. They are fixated on 310.15(B)(16) and 110.14(C), but I don't think it needs to be all the way back am I correct or am I missing a code somewhere.

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[david luchini]

They are fixated on 310.15(B)(16) and 110.14(C).

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310.15(B)(16) and 110.14(C) apply to the entire circuit. Can you provide an example of what you are trying to do?

 

[Dennis Alwon]

You can run 90° wire all the way for a circuit but the engineer may be saying he wants you to use the 60C column when selecting the overcurrent protective device.

 

[kyleapec]

I just thought it might save the owner money, we are in a VE process, and after I went over the conductor sizing the Engineer had on the panel schedules they seemed larger than usual. The engineer than told me that unless the equipment says otherwise you are to assume 60 degrees, which I did not know so I learned something. There are junction boxes next to the VAV's, I thought we could satisfy the rating of the equipment by just over-sizing the section from the junction box to the VAV instead of applying the 60 degree rating to the entire circuit, but if david is saying 110.14(C) has to apply to the entire circuit I guess not. I typically just run what the engineer tells me to , but based on the short distance the large size of the wire jumped out to me. Great song in your signature by the way dennis, I prefer the bob dylan reference myself.

 

[infinity]

I just thought it might save the owner money, we are in a VE process, and after I went over the conductor sizing the Engineer had on the panel schedules they seemed larger than usual. The engineer than told me that unless the equipment says otherwise you are to assume 60 degrees, which I did not know so I learned something. There are junction boxes next to the VAV's, I thought we could satisfy the rating of the equipment by just over-sizing the section from the junction box to the VAV instead of applying the 60 degree rating to the entire circuit, but if david is saying 110.14(C) has to apply to the entire circuit I guess not. I typically just run what the engineer tells me to , but based on the short distance the large size of the wire jumped out to me. Great song in your signature by the way dennis, I prefer the bob dylan reference myself.

That is only true when the conductors are 100 amps or less, #14 AWG through #1 AWG. Look at 110.14(C).