There is an outside Air Conditioning compressor for Central Air. The name plate running Amps says 19amps. 30 amp breaker at the Panel. Even though the code says #12 is good for 25 amps, the unit should be wired in #10 wire, right? Is there an exception in the 440 section of the code? As far as I know #12's limit is 20 amps. No exceptions? Thanks - Good Day
If the "19 Amps" is labeled as the "minimum circuit ampacity" or words to that effect. Grab a hold of your hat. You could use #14. (per 310.16, 60 degree column). There was a question on the inspectors test about a 1hp motor on a 120v circuit where the right answer was "40a breaker, 14 ga wire". Strange sounding things happen around motors and HVAC units. The exception is in 240.4(G) (2008 code or in 240.4(D)ex in earlier versions).
I seen 240.4(D)(5), saying 12 AWG Copper - 20 amperes. I thought I had to go with that? Is 240.4(G) only refer to Overcurrent Protection, so I would have to go to a #10? Could I leave #12's? The Electrician already wired the unit with 12's.
#194369 - 05/26/1004:04 PMRe: Conductor Size for AC compressor
240.4(D) Small Conductors. Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied.
so the whole issue is about overcurrent protection.
#194370 - 05/26/1004:06 PMRe: Conductor Size for AC compressor