Air conditioner circuit sizing

[crtemp]

Am I correct in sizing this with a 12-2 nm-b on a 30 amp circuit breaker?

 

[augie47]

If I read it correctly it shows MCA of 18, MOCP of 30, if so you are o.k.
(If it happens to say max fuse, a different story)

 

[crtemp]

Here is a better picture.

 

[Ponchik]

You are OK with your proposed idea.

 

[RLyons]

Excuse my ignorance but I just did a unit with the FLA of 18 amps and was instructed to upsize the wire to #10 because 18 amps is more than 80% of the 20 amp rating of 12-2. I'm not sure where the idea of 80% applies but I'm also seeing it being used on wire sizing for electric wall heaters.

 

[kwired]

Excuse my ignorance but I just did a unit with the FLA of 18 amps and was instructed to upsize the wire to #10 because 18 amps is more than 80% of the 20 amp rating of 12-2. I'm not sure where the idea of 80% applies but I'm also seeing it being used on wire sizing for electric wall heaters.

FLA or MCA of 18 amps?

FLA isn't normally a term used with air conditioning and refrigeration equipment to begin with, it is used with art 430 motors.

Keep in mind MCA already has 125% of the compressor or other largest motor factored into it.

ADD: the compressor RLA (near bottom of nameplate) is 13.5 and the condenser fan FLA is .90

13.5 x 1.25 = 16.875 + .90 = 17.775 they must have rounded that up to 18.0 for MCA.

 

[RLyons]

I just upsized the wire per PM's instruction and the label indicated FLA 18A, LRA Don't remember this number off hand and Min OCPD which was 30A this was on a 208V 1Phase condenser. I'll see if I can get a picture of the nameplate...

 

[kwired]

I just upsized the wire per PM's instruction and the label indicated FLA 18A, LRA Don't remember this number off hand and Min OCPD which was 30A this was on a 208V 1Phase condenser. I'll see if I can get a picture of the nameplate...

MCA is the number you need to pay attention to. And it already has 125% of largest load factored into it so you don't need to increase anything again. If MCA is under 20 then 12 AWG conductor is sufficient. If MCA is 25 or less you can still use 12 AWG conductor if it is allowed to be used at the 75 deg C ampacity (primarily if it is not NM cable it can be 12 AWG).

 

[infinity]

The OP did say NM cable, if you used MC cable you could use #14 conductors.

 

[iwire]

The OP did say NM cable, if you used MC cable you could use #14 conductors.

Yes, I was thinking the same thing, MC, AC pipe and wire all could be 14.