ac units

[southernboys#2]

Hey guys on an ac unit if its marked for a min circuit ampacity of 30a is there any exception that would allow me to pull #12 wire and be protected by a 30a breaker? My boss tried to throw in a 10% percent rule to justify the 12 awg wire. I think he meant the 110% rule that applies to some motors but not those with a min nameplate rating. Could use some clarification

 

[ryan_618]

Re: ac units

12 AWG is a 30 amp conductor at 90 degrees, but 110.14(C) will not allow it. There is no exception you are going to be able to use.

 

[jimwalker]

Re: ac units

does name plate say min supply 30 or max breaker/fuse

 

[infinity]

Re: ac units

#12 THHN is only good for 25 amps so you're stuck if the MCA is 30 amps. You'll need to use #10 or larger.

 

[jimwalker]

Re: ac units

This is why it is smart to over size the wire on a rough.

 

[ryan_618]

Re: ac units

Originally posted by infinity:
#12 THHN is only good for 25 amps so you're stuck if the MCA is 30 amps. You'll need to use #10 or larger.

12 AWG THHN is good for 30 amps. The terminations, however, are not.

 

[electricman2]

Re: ac units

Splice a piece of 10 on each end.

 

[infinity]

Re: ac units

Originally posted by ryan_618:

Originally posted by infinity:
#12 THHN is only good for 25 amps so you're stuck if the MCA is 30 amps. You'll need to use #10 or larger.

12 AWG THHN is good for 30 amps. The terminations, however, are not.

Ryan is correct. I should have said that in the practical application the 25 amps would be used based on the termination limitations of 75 degrees. Thanks for the correction.

 

[ryan_618]

Re: ac units

Originally posted by electricman2:
Splice a piece of 10 on each end.

Remember to do that to the EGC as well to satisfy 250.122(B)