A/C CONDUCTOR SIZING

[volt102]

Re: A/C CONDUCTOR SIZING

If an ac is marked 19.9 min. circuit ampacity with a max. fuse size of 35 amps.

I could wire it with #12 copper.
Put a 35 amp breaker in the panel.

Thanks to 430.62(a)

 

[benaround]

Re: A/C CONDUCTOR SIZING

I hate it when these things end up unfinished,or still with issues like,is it a "feeder" or a "branch circuit"?

I know on the unit it says," Minimum CIRCUIT ampacity"
I've never seen minimum FEEDER ampacity!

Although some of the members are calling it a feeder and I hold much respect for their knowledge and depth,it goes hanging in my head as to what is right and that's how a lot of posts end. Ahhhhwwww shutup.

frank

 

[infinity]

Re: A/C CONDUCTOR SIZING

I could wire it with #12 copper.
Put a 35 amp breaker in the panel

You could save a few cents and use a #14 too.

I know on the unit it says," Minimum CIRCUIT ampacity"
I've never seen minimum FEEDER ampacity!

The problem arises when you look at 440.6(A) which uses term "the branch circuit conductors". These conductors are by the definition in article 100 as " the circuit condcutors between the final overcurrent device protecting the circuit and the outlet". If your final overcurrent device is a fuse at the fused disconnect adjacent to the unit I don't know how you get around the fact that by definition the conductors feeding the fused disconnect are now feeder conductors.

Article 100 Feeder: "all circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit over current device.


I know this sounds incorrect but I can't find any article(s) to prove it otherwise.


Trevor

[ August 03, 2005, 09:10 PM: Message edited by: infinity ]

 

[augie47]

Re: A/C CONDUCTOR SIZING

there are sooo may more learn-ed that me commenting, I somewaht hate to...but I never learned when to hush.
If we were to put a "pull-out", un-fused disconnect, or non-rated breaker at the unit to serve as a disconnecting means, then the wiring from the panel supplying the unit would be branch circuit wiring; correct?
In the areas I inspect we "choose" to look at the disconnecting means at the unit as just that, a disconnectimg means"--fusible or not...
perhaps not the letter of the law code wise, but sure solves a lot of arguments.

 

[vasparky27]

Re: A/C CONDUCTOR SIZING

is 125% MOP? sorry.... lost helper here need input.

 

[infinity]

Re: A/C CONDUCTOR SIZING

is 125% MOP? sorry.... lost helper here need input.

No, because on the namplate listing of the AC unit there is a minimum circuit ampacity (MCA). This already contains the 125% and has been specified by the manufacturer as part of it listing. This requirement is in Article 440. Branch circuit conductors are sized using the MCA and no further calculation is needed.

 

[volt101]

Re: A/C CONDUCTOR SIZING

Maybe I missed something here. The conductors from the breaker to the fuses are feeders. 440.6a tells you that you need to use the nameplate in determining disco,wire, etc. It does not tell you that # is the final outcome. 430.62(a) permits in this case, that the feeder's overcurrent protection and the ampacity of the wire can be the same size as the branch circuit.

Jim

 

[milwaukeesteve]

Re: A/C CONDUCTOR SIZING

volt 101 and volt 102 are correct.

430.62 states that for motor loads, the feeder shall be provided with a protective device having a rating not greater than the largest rating or setting of the branch circuit SCGF protection... then its says in brackets " [based on the maximum permitted value for the specific type of a protective devise in accordance with 430.52 , 440.22(A) for hermetic refrigerant motor compressors] "

 

[volt102]

Re: A/C CONDUCTOR SIZING

Sorry about the confusion,
Volt101 and Volt102 are both me, 101 is at my work on the city's computer, 102 is at home.
Jim

 

[jwelectric]

Re: A/C CONDUCTOR SIZING

Originally posted by volt102:
Sorry about the confusion,
Volt101 and Volt102 are both me, 101 is at my work on the city's computer, 102 is at home.
Jim

Well it hain't no wonder both of you are rite!

 

[volt102]

Re: A/C CONDUCTOR SIZING

Yeah, but it also implies that stupid is as stupid does, doesn't it?

 

[milwaukeesteve]

Re: A/C CONDUCTOR SIZING

I didn't want to insult two different people by assuming you were the same. If you weren't the same person, that might have been embarrassing.

Just don't argue both sides of an issue, now, because we no who you are. Both of you.