HVAC - AWG - Question

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hardworker

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What awg size supply conductor would you recommend for an airhandler w/heat element that has minimum circuit ampacity of 84, maximum breaker ampacity of 60+60, and the supply run is 50 ft. Also what awg for the ground?

What awg size supply conductor would you recommend for the heat pump condenser that has minimum circuit ampacity of 24.6 maximum breaker ampacity of 40, and the supply run is 60 ft. Also what awg for the ground?
 
What type conductor ? (NM, SE, THHN, etc).

As an "installer" what size would you use ?

Lets see if we agree :D
 
THHN is the type.

I would use awg #6 on the heat/air handler and awg #8 on the condenser, but HVAC and code sometimes changes things.

Help me out.
 
hardworker said:
THHN is the type.

I would use awg #6 on the heat/air handler and awg #8 on the condenser, but HVAC and code sometimes changes things.

Help me out.
Click to expand...

Are you installing ONE circuit to the air handler to handle the 84 MCA ?

If I were installing the wiring for the condenser using THHN/THWN, I would probably use a #10 although under the '08 Code a #12 be compliant
 
The air handler is equipped with two 60amp double pole breakers, that control the air handler and the heating element. I will be running two 240 circuits.
 
There is no individual specification. I called tech support and they say it is 84. They did not have a break down. It has two 60 amp double pole breakers. It seems to me to be more or less even, based on the 60+60. The heating element is 20kilowatt.
 
Without the mfg specs showing the ratings as OTT2 mentions, the unit would not pass inspection here (Violation Art 424).
Without that info upfront, using THHN, the safe route would be (2) #6s, BUT for a 20 kw unit the calculated load would be > 100 amps** and depending on how the loads are separated a #6 might not be large enough. (With THHN probably O.K., with NM or SE, questionable)

** 20 kw would be 84 amps without applying the mandatory 25% or adding in the blower load.
 
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I traced the wiring from the two 60 amp breakers. Breaker A feeds 10k of heat and breaker B feeds 10k of heat plus 3 amps from 1/2 hp blower motor.
 
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hardworker said:
I traced the wiring from the two 60 amp breakers. Breaker A feeds 10k of heat and breaker B feeds 10k of heat plus 3 amps from 1/2 hp blower motor.
Click to expand...

As long as you are using THHN and the unit does not require 60? terminations, you should be o.k with (2) #6s. NM or SE, likely not.
 
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