A/c

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Thank you Bob. I didn't have the actual numbers other that what was on the plans.

From talking to the guy my guess for doing this is to show how much he knows. If you get my drift.
 
cowboyjwc said:
I don't see this a lot, but I just had a long discussion with an engineer about sizing overcurrent for an A/C unit.

(Some of these numbers are made up so don't do the math)

Min Cir Ampacity = 22amps (which equates to #10 conductors)
Max Fuse or Hacr breaker = 30 (Fused disconnect on roof)

The problem was this.

He had those #10 conductors coming off of a 60 amp breaker saying that he can size the overcurrent 200% and the conductors 125%.

I say that all of the calculations have been done and the overcurrent device cannot be larger than 30 amps to protect the conductors. If he had a nonfused disconnect on the roof the largest size the overcurrent device could be is 30 amps per the nameplate.

Am I missing something?
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IMO your not missing anything. I think your answer is in your statement. If the disconnect was non fused he couldn't use the 60 amp breaker. Because the 30 amp fuses do comply with the nameplate he can use the 60 ahead of it. IMO.
 
We can only use the nameplate.If as in this example he had fused disconnect (why ?)and had a 30 amp fuse then there is no reason to use a 60 breaker.While #12 would be ok i view this two ways,first the run is short so using #10 wouldnt cost me much extra or second is run is long and i would not want voltage drop so get out #10 anyways.Your also helping the owner if later on he needs larger unit.I would refuse to install a 60 without a letter from him taking full liability and another from the inspector saying he is aware of the breaker size.If there is a fire it will be your insurance company first.Personally i would tell him NO
 
Problem is Jim that I'm the inspector and I ain't sign'n nothin. :grin:

The guy was so adement that I was the only plan checker to ever call him on it, that I started to doubt myself.

Thanks everyone. I was pretty sure I was right and you all just confirmed it.
 
Jim W in Tampa said:
While #12 would be ok i view this two ways,first the run is short so using #10 wouldnt cost me much extra or second is run is long and i would not want voltage drop so get out #10 anyways.
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Jim I agree with you-- I don't think I ever ran a #12 or smaller to an a/c unit. I usually upsize in case someone adds on an addition or whatever. My point was that it is legal-- that's all.
 
iwire said:
It is not 'legal' in this thread.

The 12 AWG can not be protected with the 60 amp breaker.
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Bob, we already made that point and John changed the thread by raising other issues which we are responding to. Why must you always attack everyone. Give it a rest will ya.
 
iwire said:
It is not 'legal' in this thread.

The 12 AWG can not be protected with the 60 amp breaker.
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Secondly, I never said it could be protected by a 60 amp breaker. Read my post I said you could use a #12 wire for a 22 amp a/c load-- I never mentioned the 60 amp breaker.
 
Captain Obvious asks - Why a 60 amp breaker? Is that the only breaker in town? Can't we get like, say, maybe, a 30? Or is that thinking to much outside of the box?
 
Dennis Alwon said:
Secondly, I never said it could be protected by a 60 amp breaker. Read my post I said you could use a #12 wire for a 22 amp a/c load-- I never mentioned the 60 amp breaker.
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But that is what this thread is about! :roll:
 
Dennis Alwon said:
Bob, we already made that point and John changed the thread by raising other issues which we are responding to.
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Really?

IMO you are the one that has continually changed the topic here, it seemed like you did not even read the first post.

Why must you always attack everyone.
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Dennis there is a difference between attacking someone and correcting someone or just making the issue clear. If you feel attacked you should ask yourself why you feel that way.

Give it a rest will ya.
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No, I will not 'give it a rest' if I feel someone is confusing the issue with their own agenda.
 
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cowboyjwc said:
I think he was trying to use Article 430 for his argument, but he didn't give me an exact code section.

He also used the old "this is only the second or third time anyone has questioned me on this."
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Then tell him you must be the second or 3rd guy to do his job.I would hope all the electricians out there did not follow his bad advise.We often see mistakes on prints and just fix them.
 
Jim W in Tampa said:
Then tell him you must be the second or 3rd guy to do his job.I would hope all the electricians out there did not follow his bad advise.We often see mistakes on prints and just fix them.
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Even a blind squirrel.......:smile:

Minuteman said:
Captain Obvious asks - Why a 60 amp breaker? Is that the only breaker in town? Can't we get like, say, maybe, a 30? Or is that thinking to much outside of the box?
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That was pretty much my thinking. Guess it's not his money.

wireman71 said:
So in this scenario could you use #10, 30amp HACR breaker and a non-fused disconnect? I'm thinking you could.
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Yes you could do that, and I even suggested that.
 
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