Posted By: Electric Eagle

## A/C conductors and overcurrent - 12/16/03 04:00 AM

I need to see if you guys understand the allowable ampacities for air conditioners the way I'm reading it.

Here's the situation. Several moths ago we wired 2 A/C units on a roughin. The job wasn't huge, about 1500 sq ft per unit. So since nobody informed us diferent the units were prewired with 10awg CU. Today we go back to trim out and find a monster unit sitting by 1 disco. As it turns out they decided to use a large heat pump (the inside unit needs 100 amps by itself). The nameplate says min circuit ampacity 31.2, rlc 24, maximum OCP 55.

art 310.16 rates 10 awg thhn at 35 amps, you are allowed to go over 30 amp OCP for equipment such as AC units. According to art 440 I can put a breaker up to 175% of the rlc (24) or the branch circuit capacity (35) whichever is greater.

If I read and calculate correctly, The #10 wire is OK and we can use a 55 amp breaker on it if we need to, although I think a 35 or 40 will do the job. Correct?

Just tell me if this is safe and legal, not how you would want to do it. Trust me, we would have run a larger wire if we knew if was going to be this close. Thanks.

Here's the situation. Several moths ago we wired 2 A/C units on a roughin. The job wasn't huge, about 1500 sq ft per unit. So since nobody informed us diferent the units were prewired with 10awg CU. Today we go back to trim out and find a monster unit sitting by 1 disco. As it turns out they decided to use a large heat pump (the inside unit needs 100 amps by itself). The nameplate says min circuit ampacity 31.2, rlc 24, maximum OCP 55.

art 310.16 rates 10 awg thhn at 35 amps, you are allowed to go over 30 amp OCP for equipment such as AC units. According to art 440 I can put a breaker up to 175% of the rlc (24) or the branch circuit capacity (35) whichever is greater.

If I read and calculate correctly, The #10 wire is OK and we can use a 55 amp breaker on it if we need to, although I think a 35 or 40 will do the job. Correct?

Just tell me if this is safe and legal, not how you would want to do it. Trust me, we would have run a larger wire if we knew if was going to be this close. Thanks.