Residential AC condenser conductors

[wrobotronic]

Would someone be so kind as to direct me to the article which states #12 conductors can be used on a 25A breaker if feeding a residential AC condenser unit.

The book is bouncing me all over the place, which is fine lol, but I just can't seem to put my finger on this allowance.

I started in 240.4g.. But the way I'm reading 440, on 25A a #10 would still be required. I'm clearly missing something somewhere.

thank you all.

 

[david luchini]

Would someone be so kind as to direct me to the article which states #12 conductors can be used on a 25A breaker if feeding a residential AC condenser unit.

The book is bouncing me all over the place, which is fine lol, but I just can't seem to put my finger on this allowance.

I started in 240.4g.. But the way I'm reading 440, on 25A a #10 would still be required. I'm clearly missing something somewhere.

thank you all.

440 is the correct place. Part III gives you maximum overcurrent protection size, and Part IV gives you minimum branch circuit conductor ampacity.

For example, if 440 Part IV said you need a conductor with an ampacity of at least 22 and Part III says your OCPD can't be greater than 25A, then #12 and a 25A c/b meets the requirements.

 

[infinity]

You can only use the #12 conductors at 25 amps if you're not using NM, UF or some other cables that have a 60° C limitation. If you want to use the 75° C rating for #12 you would need to use raceways and wire or MC cable.

 

[GoldDigger]

You can only use the #12 conductors at 25 amps if you're not using NM, UF or some other cables that have a 60° C limitation. If you want to use the 75° C rating for #12 you would need to use raceways and wire or MC cable.

Not that it necessarily matters in this case, but the NM or whatever would only have to have the MCA amperage after adjustment, not the full 25A.

 

[Dennis Alwon]

The reason you can use a higher overcurrent protective device for a/c units is that the units have overload protection built in. The overload protection protects the #12 while the overcurrent protective device protects against short circuit and ground faults. On older a/c units we would often install a 30 amp breaker because those units were nameplated with max overcurrent protective device at 30 amps-- sometimes even higher.

The new units max overcurrent protective device seems to be closer to actual FLA.

 

[ActionDave]

...The book is bouncing me all over the place, which is fine lol, but I just can't seem to put my finger on this allowance.

I started in 240.4g.. But the way I'm reading 440, on 25A a #10 would still be required. I'm clearly missing something somewhere.

240.4(D) lets you wave the small conductor rule in Table 310.15(B)(16), unless you are using romex, per 334.80 as infinity said.