High Temperature to Low Tempature Connection

[Dale Hayes]

At a control panel the electrical load for a heating unit is 16Amps. The maximum ambient temperature inside the control panel is "under" 55C. After all derating, the wire size on the "line side" of a control contactor inside the control panel will be 12Ga.THWN-2 90C.

The "load side" of the contactor is connected to a heating unit several feet away, but because of the higher ambient temperature at the terminal enclosure of the heating unit, 6Ga. THWN-2 wire is being used for connections there.

Considerations have been taken regarding the 75C terminations.

I have experience with junction boxes where high temperature wire and low temperature wire are switched out due to different ambient temperatures at the control panel and the heating unit.

Is there any special considerations needed on an application such as this where "because of different ambient temperatures" at the control panel and the heating unit a switch from a 2Ga. wire to a 12Ga. wire is made at the contactor?

 

[petersonra]

I am pretty sure there is no problem doing what you are planning to do as far as the wire size.

I would point out the UL listed control panels (UL508a) have a maximum ambient temperature rating of 40 degC so you cannot install such a panel in a location where the ambient temperature exceeds that.