Air compressor

S

sesllc

Member
Location
Nc
Occupation
Electrical
Having a debate,
A new replacement air compressor motor is rated at 20.3amps. Existing wiring is a 12 thhn on a 20amp breaker....can the 12 thhn be placed on a 25amp breaker? Or does the wiring also need to be upgraded to 10 thhn?
The breaker terminals are rated for 75°c, the pressure switch terminal ratings are unknown.

The ampacity chart rates 12 thhn for 25amps but then refers to 240.4(d) which then refers to 430 for motors.

Which method is acceptable?

Thanks!
 
240.4(G) allows the #12 on the 25 amp breaker. (You may actually need a larger breaker)
 
fastline said:
Residence? Overall, I would not be worried about #12 other than code compliance unless there are some extremes.
Click to expand...
Its a commercial building, but the compressor is just a residential grade oil bath upright compressor
 
sesllc said:
Its a commercial building, but the compressor is just a residential grade oil bath upright compressor
Click to expand...
Those residential type compressors rarely run their ratings so IMO a 25A circuit is fine. If that was a real motor with say a 2 stage, maybe bump it to a full 30A circuit just for no hassles. I prefer breakers on the edge, which can save the compressor on a bad day.
 
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