What size wiring for Central A/C compressor?

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On 3/4/2013 12:50 PM, The Daring Dufas wrote: ...

...
Far more likely they apply the correct section of Code for the purpose at hand.
It would be far better to reference the specific Code in question or even the controlling jurisdiction which would likely lead to being able to find the relevant Codes in play. I strongly suspect if that were done it would be found that the installation under discussion is compliant there as well.
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On Mon, 04 Mar 2013 12:50:54 -0600, The Daring Dufas

I have been a certified, state licensed electrical inspector for about 20 years.
Florida and we follow the NEC state wide, unaltered, except for requiring bonding of steel studs.
I said before, this is a common question on the inspector tests and if you say 8ga on a 40a breaker for a motor circuit like this, you got that one wrong. Maybe your inspectors are not certified and it is just the mayor's nephew who learned his trade from the Time Life electrical wiring for dummies book.
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On 3/4/2013 2:15 PM, snipped-for-privacy@aol.com wrote:

That's what they want around here with a disconnect at the condensing unit. I've always gone by the breaker size required by the label on the unit and sized the wiring for the breaker and that's what the inspectors want. If you were the inspector at the site, I would do what you demanded. It can't be simpler than that. Of course, different insulation types handle different currents. I don't argue with the inspector and do what their department requires. The inspectors around here would reject a 40 amp breaker on #10 copper 60°C NM/UF cable. Higher temp rated wire insulation would be different. NEC Table 310-16. I would put a 40amp breaker on #10 copper if it has 90°C rated THHN/THWN/XHHW insulation. O_o
TDD
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On Mar 4, 3:15 pm, snipped-for-privacy@aol.com wrote:

It's also possible that he's basing his experience on what's required by what he's used and had passed. Of course if you use 8 gauge where a minimum of 12 gauge or 10 gauge is required, it passes because it meets code. And the inspector isn't likely to say, BTW did you know that 12 was sufficient? So, he goes on thinking that 8 gauge is what is required for it to pass.
Obviously there hasn't been any discussion with an inspector about the issue, otherwise he'd be able to give us the code section that the position is based on. He refuses to recognize that the code treats breaker requirements for general purpose branch circuits differently than it does for motors, AC eqpt, etc.
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On Mar 4, 1:50 pm, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:

When you can give us the section of the NEC where you can conclude that there is something wrong with Mikepier's installation, under ANY interpretation, then we can discuss differing interpretations. If an inspector is going to fail it, then he should be able to tell you that per NEC section X.Y, it's not allowed.
This isn't the first time this issue has come up. And the result is usually the same. You have some people thinking that the same rules for lights and receptacles under the NEC also apply to motors and AC equipment. They don't. I would hope that someone who installs that eqpt would understand the distinction.
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On 3/4/2013 3:27 PM, snipped-for-privacy@optonline.net wrote:

If you'll look at NEC Table 310-16 you will see the amp rating for wire size. It changes depending on the insulation on the wire. Every 40 amp circuit I've ever installed in a home using 60°C NM/UF cable has been #8 copper. If I install a 40 amp circuit in conduit using 90°C THHN/THWN insulated wire I'll use #10 copper. I don't usually run conduit in a home. The last 4 ton AC condensing unit I installed used #14 THHN/THWN copper in conduit. It was a 3ø unit that called for a 15 amp breaker. I have to install what I know the inspector will pass and the inspectors do look at the temperature rating of the wire and check if the circuit breaker is HACR rated if it's hooked to an AC condensing unit. I don't argue with the inspectors, you can if you wish. O_o
TDD
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On Mar 4, 5:55 pm, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:

And if you look at that table, it shows that 12 gauge is OK for up to 25 amps. The nameplate on the AC eqpt Mike has says the minimum circuit ampacity is 24.4 amps. Therefore, 12 gauge meets the minimum requirement and is permitted.
The problem comes when you then try to tie the breaker to be installed for that AC eqpt with the wire size and treat it like it was a water heater, or a receptacle circuit. It is not. The eqpt manufacturer's rating governs and it says that a breaker of 40A max is permitted.

15 amp breaker for a 4 ton AC? That ain't right.
I

It's not an issue of arguing with the inspectors. It's what the NEC says disagrees with what you say. And if an inspector fails something, he should be willing to tell you what part of the code it failed and why, without getting into an argument. Any inspector should know that motors are treated differently than resistive loads.
Just do some googling. This whole issue has come up many times. Some homeowner or inspector raises the issue of the breaker for an AC being larger than would normally be permitted for a light circuit, etc. that uses a given wire gauge. Or some home inspector flags it. Then a lot of discussion follows and the folks most knowledgable about the actual issues and code say it's perfectly normal. In this case, you have gfretw, an actual electrical inspector, telling you how it works and that what Mike has is code compliant.
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On 3/4/2013 6:12 PM, snipped-for-privacy@optonline.net wrote:

Did you look at the notes from the table? They are at the bottom of the table and will show what I use and what the inspectors go by. You will see a little note reference next to the 25 amp figure. ^_^
TDD

It is a 240 volt three phase unit and 15 amps 3ø power is what it calls for. It has run without a problem for 10 years in three different locations. I installed it at a pizza place which has moved twice after I installed at their first location. I also use test equipment to check the current draw and phase rotation on all three phase equipment. ^_^
TDD

If gfretw was the inspector in charge I would do what he said but I have to go by what the inspectors here and now require. I also go by the manufacturers requirements unless they clash with the inspector who has final say. The city here actually has stricter guidelines in some areas than the NEC. Here, they want the circuit and wire gauge to match no matter what the load is with the only difference being that HACR rated breakers be used on AC and refrigeration units. Understand that the temperature rating of the insulation also determines the amp carrying specification of the wiring for both copper and aluminum. ^_^
TDD
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On Mon, 04 Mar 2013 20:36:50 -0600, The Daring Dufas

Absolutely. That note takes you to 240.4(D) which references 240.4(G)
G) Over current Protection for Specific Conductor Applications. Over current protection for the specific conductors shall be permitted to be provided as referenced in Table 240.4(G).
which references 440 part III & IV and 430 part III, IV, V, VI & VII where we get this permission for larger OC devices and the ability to use 310.16 at the listed rating.
Like I said, you need to read the whole code, not just the first thing you see.
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On 3/4/2013 10:06 PM, snipped-for-privacy@aol.com wrote:

I'll defer to you on it then but I'll continue to install what I know will pass inspection not what I think I can get away with. ^_^
TDD
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On Mon, 04 Mar 2013 22:21:55 -0600, The Daring Dufas

Whatever you need to do. You are just oversizing wire but as long as you keep getting the bid, rock on.
You probably should have the conversation tho. I am curious how your inspectors can ignore that label.
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On 3/5/2013 12:12 AM, snipped-for-privacy@aol.com wrote:

I remember one who would not pass a job unless the HACR sticker was on the breaker for the AC. It didn't matter what the paperwork from the manufacturer stated. O_o
TDD
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The Daring Dufas wrote:

I replaced my 3-ton a/c unit after its 12-year old predecessor croaked as a result of Hurricane Yikes*. The chap who replaced it said I could also swap out the 40-amp breaker with a 30-amp one inasmuch as more modern units, mine included, were more efficient and drew less power. Makes sense since the original a/c unit was a builder model from the 1960's. The compressor unit, no doubt, had been replaced, maybe more than once, before I bought the house. But nobody every fiddled with changing the circuit breaker.
---------------- * The fellow who did the work is a Guatamalan off-the-books a/c technician. Evidently he is part of a co-national underground network of repair people in that he knew a guy who obtains and reconditions a/c units, some from insurance companies after house fires. Anyway, the unit he chose was a two-year old Trane, and the unit has been working swell for the past four years. The whole business, compressor unit, installation, vacuuming, and recharge cost $750.
One point is this: If you can find ONE immigrant tradesman, you've got access, probably, to lots of others (roofers, sewer replacement, concrete work, etc.). No, they're not bonded, insured, and so forth, but the proof is in the pudding. If the job works, you're good. Besides, I know where Lewis, the guy who did the work, lives - next door to my son - and Lewis knows I have a gun.
Feel free to disagree, but this technique works for me.
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On 3/5/2013 2:45 PM, HeyBub wrote:

Whatever works. I try to avoid government involvement in business whenever I can because it tends to increase the cost of everything but at the same time I'll do quality work and not slipshod crap which gives folks a reason to complain to a government puke. ^_^
TDD
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What about the outside disconnect? It is just simply a "pull-out" type disconnect, no fuses, just solid copper buss bars. I don't see any rating for it. How do I know it's rating? Or are all these type of disconnects just a standard rating?
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On 3/5/2013 7:20 PM, Mikepier wrote:

I personally don't like the pull out disconnects because they can corrode from mishandling and pranksters can make off with the pull out. I use the Square D dummy breaker in a rain proof box. It looks like a standard Square D QO breaker but with no over current protection and a real circuit breaker will actually snap-in in its place. ^_^
http://preview.tinyurl.com/afjtpkh
http://preview.tinyurl.com/bav4wkr
TDD
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The Daring Dufas wrote:

As for pranksters, my disconnect has a a padlock, the key to which is kept in the main circuit-breaker box (which also has a padlock).
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On 3/6/2013 6:38 AM, HeyBub wrote:

Trust no one. ^_^
TDD
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The Daring Dufas wrote:

I trust YOU -- To give what you believe to be the straight skinney on this newsgroup.
Who know, if we ever met in person, I might even loan you a tool...
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On 3/7/2013 7:27 AM, HeyBub wrote:

I can appreciate that. I remember a famous man saying something to the effect, "Experience is a fool's best teacher." Believe me, I can admit to being a fool on more than one occasion but I survived it and learned from it. Years ago, I trained in martial arts and got knocked on my butt numerous times but I learned from it to the point that my instructors couldn't get through my coverup and I could block kicks and punches. Of course now, a couple of five year old kids could take me. ^_^
TDD
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