What size wiring for Central A/C compressor?

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On Mon, 04 Mar 2013 16:55:43 -0600, The Daring Dufas

You have to look at the whole code, in context, you can't just cherry pick one article and believe that is the way it works in every situation. When you are looking at an AC unit you start in 440 if you are sizing the breaker, not using the label.
440.22 Application and Selection. (A) Rating or Setting for Individual Motor-Compressor. The motor-compressor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. A protective device having a rating or setting not exceeding 175 percent of the motor-compressor rated-load current or branch-circuit selection current, whichever is greater, shall be permitted, provided that, where the protection specified is not sufficient for the starting current of the motor, the rating or setting shall be permitted to be increased but shall not exceed 225 percent of the motor rated-load current or branch-circuit selection current, whichever is greater.
12 ga wire has an ampacity of 25a in the 60c column so you can start with a 45a breaker and you might end up with a 60 if you use the round up rule at 225%. The label is actually rounding down to get to 40a.
The label is very unambiguous. It tells you can use 12ga wire and a 40a breaker. If an inspector is confused about that, he is incompetent. I am not saying there are not incompetent inspectors out there but at a certain point they need to be educated. That probably does not happen on an active job but you can send a letter to the state licensing authority asking for a ruling. Fix it for everyone, not just that job.
What is your jurisdiction? I may actually know someone there.
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On 3/4/2013 8:46 PM, snipped-for-privacy@aol.com wrote:

It's Birmingham in Jefferson County Alabamastan. I noted the 25 amp rating in the 60°C column too but I also read the notes at the bottom of the chart and those jive with what has always been told to me. The city code does differ a bit from NEC and that's what I've been told by the inspectors I've dealt with. Now in your experience are you also considering LRA of the compressor? Is that part of the 225% overload? O_o
TDD
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On Mon, 04 Mar 2013 22:12:47 -0600, The Daring Dufas

The 225% is the max O/C device based on FLA but usually 175% will be plenty. When you even start approaching that is after the compressor gets old and they put a hard start kit on it.
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On 3/5/2013 12:10 AM, snipped-for-privacy@aol.com wrote:

I've had hard start kits break the connecting rod on reciprocating compressors. You can tell by the sound made by the compressor which sounds like an electric blower motor running without a belt. ^_^
TDD
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On 3/4/2013 8:46 PM, snipped-for-privacy@aol.com wrote:

...

+about5
If the inspectors in this area are this bad, they're costing a lot of money over time for no reason (other than perhaps kickbacks from the local distributors???)
When first in TN years ago there was an incompetent so widely known that it was a standing joke. The locals put up w/ it and just bought innumerable pints of Old Turkey (from which you can imagine the joke).
I finally got fed up enough and being new to the area was willing to be the one who pulled his plug by documenting it and making the complaint. In the end, was _much_ "more better" all around...
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Some areas fo the counrty do not exectally follow the NEC. Unless you have a very good reason and can show the inspector where he is mistaken, it is best to just do as they say. If you ever get on their bad side, they will really look over your work and try to find a reason to make you redo something.
It doesn't mater about the gun and cuffs, but they can have the power cut off or not turned on in the first place.
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On 3/4/2013 12:09 PM, Ralph Mowery wrote:

I get along with the inspectors and since I know them and they know the quality of my work, they don't usually dig to deeply into it unless I insist in order to satisfy a customer who may have doubts. That is something they understand since they themselves worked in the field. In some places they actually have to use a stamp with their name and number for the department which can be seen inside breaker panel doors. ^_^
TDD
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wrote:

If you figure a SEER of 12, 3.5T (42,000BTU/HR) is 3.5kW or 14.5A. To get to 6.5A you'd have to have a SEER of 27! Something's not adding up here.
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Right.
It's pretty cold outside ! A couple of things. My memory is bad. The unit is in fact 2.5 tons. The installer quoted price for 3 ton unit !
Gsc130301a goodman. 13.7 minimum amp Max fuse amps 20 Compressor 9.7 amp 1.5 hp fan.
The reading have been stable last 2-3 summers. 6.5 amp draw. Could low r22 cause reduced reading ?
Im happy with the performance, low bills. I even drop the temp down to 68 degrees in summer nights.
Greg
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On 3/3/2013 7:22 PM, Mikepier wrote:

a new unit will require less amps.
10 ga on a 30 is all you need for what he has.
--
Steve Barker
remove the "not" from my address to email
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On Tuesday, March 19, 2013 at 10:57:02 PM UTC-5, Steve Barker wrote:

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On Sunday, March 3, 2013 at 7:22:54 PM UTC-6, Mikepier wrote:

well you will just have to upgrade
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On Fri, 27 May 2016 17:38:19 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Wrong, 10ga is plenty. There are different rules for motor loads
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On Friday, May 27, 2016 at 8:50:41 PM UTC-4, snipped-for-privacy@aol.com wrote:

IDK why this old thread had to be re-opened, the full thread with all the facts is here, but as you say, what's there is fine. The problem is that some people can't understand that motor load circuit breakers are sized differently and you can have a breaker that is larger than would be allowed for a lighting or water heater circuit that used the same size conductor.
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On Sunday, March 3, 2013 at 7:22:54 PM UTC-6, Mikepier wrote:

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On Sunday, March 3, 2013 at 7:22:54 PM UTC-6, Mikepier wrote:

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On Sunday, March 3, 2013 at 7:22:54 PM UTC-6, Mikepier wrote:

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