a/c mca and 3 hours

[caosesvida]

440.32 gives you 125% of motor compressor load for branch circuit conductor. This is where they get the minimum circuit ampacity. If the mca is 30 amps, the unit would be 24 amps and run #10. But if the unit mca was 31 you would have to go up to a #8? do I have this straight? 240-d sends you to 440. I read the #10 is good for 30 amps only in 240.4 d with the exception of e thru g, and in the 440 I don't see that they allow more than 30 amps on a #10 copper. thanks.

 

[bphgravity]

Re: a/c mca and 3 hours

No, you are not reading the sections properly. Under general installations, 240.4(D) tells us that small conductors have maximum overcurrent protection unless permitted in (E) through (G). Table 240.4(G) tells us to use Section 440 for sizing OCD for A/C equipment.

440.12(1) requires the disconnect to be at least 115% of the RLC, 440.22(A) permits the protective device be sized up to 175% of the RLC, and 440.32 requires the branch-circuit conductors to be sized not less than 125% of the RLC. None of these sections are dependent on each other.

 

[caosesvida]

Re: a/c mca and 3 hours

let me see if I have this straight, if 310-16 allows 35 amps but is restricted to 30 amps by 240, then #10 is only allowed 30 amps. If the mimimub circuit ampacity rated on the unit reads 30 amps I can go with #10 but if it reads 31 amps I need to go with #8. The maximum overcurret protection is a different story. This is with singel compressor only.