Air Conditioner Wire Sizing

[jtttat]

Please help me size an aluminum wire for an air conditioner w/a max fuse - HACR circuit breaker of 50amps.

Peers have suggested I could use a #8 AL since the minimum circuit ampacity was less than 40amps.

I remember reading sometime ago of a situation where a 30amp circuit breaker was used on #14 THHN serving a motor load.

My review of: 440-2. Definitions. Branch-Circuit Selection Current hasn't helped. I am assuming the residential market utilizes hermetic refrigerant motor compressors.

Your assistance is greatly appreciated.

Jeff

 

[tonyyaroch]

Re: Air Conditioner Wire Sizing

What is the min. circuit ampacity? use 310.16 to find out what size wire to use(using MIN Ckt ampacity and 75 degree column)), and then use a 50 amp breaker,in your case. (Max breaker size) This is all we do to figure air conditioners at are company. (440.32)

[ November 09, 2004, 08:34 PM: Message edited by: tonyyaroch ]

 

[electricman2]

Re: Air Conditioner Wire Sizing

If the MCA is 40A and terminations are rated for 75c conductors, then 8AWG AL with 75c insulation is fine.

 

[kiloamp7]

Re: Air Conditioner Wire Sizing

One nice thing about modern HVAC equipment with hermetic motors is that "they" have already done the Art. 440 calculations for you.

Minimum ckt. ampacity, & maximum O/C protection is on the nameplate. This is an example where, frequently, on a motor ckt., the OCPD can be greater than the wire.