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#83073 - 01/08/03 06:24 PM Aircondition load
abode electric Offline
Junior Member

Registered: 01/08/03
Posts: 8
Can I install a 12-2 nmc cable to an AC that has a min circuit ampacity 22amp on a 30amp breaker. The AC draws about 17amps. The 22amps is at 125%.The name plate states the 22amp min circuit ampacity and a maxium 30 breaker.
2002 NEC
310.16 12cu 60c 25amps with*
*240.4d 12cu only 20amps unless permitted in 240.4e through 240.4g
240.g permitts AC article 440 parts III, VI
440.22a Rating or setting 175% branch circuit

[This message has been edited by abode electric (edited 01-08-2003).]

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#83074 - 01/08/03 07:00 PM Re: Aircondition load
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
i would run at least 10 gauge wire. 12 gauge is only good for 20 amps, also AC is considered a continous load and 80% rules apply here. Other things to consider are voltage drop and ambient temperatures which also mean derating. With these other factors you may even have to run #8s.

[This message has been edited by spyder (edited 01-08-2003).]

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#83075 - 01/08/03 08:04 PM Re: Aircondition load
abode electric Offline
Junior Member

Registered: 01/08/03
Posts: 8
Spyder,
(1)310-16 12cu 25amps
(2)240.40d allows higher than 20amps on 12cu
(3)AC isn't considered a continous load, it's a motor load, 125% of motor load. 17 amps X125%= 22 amps
(4)voltage drop and ambient temperatures are not factors here
I haven't found a reason why I can't do this. I know this may not be the best way but it complies with the code.

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#83076 - 01/08/03 09:04 PM Re: Aircondition load
Nick Offline
Member

Registered: 08/13/01
Posts: 603
Loc: Riverside, CA
The 15, 20 and thirty amp limitations on #14, #12 and #10 wire do not apply to motor and air conditioning loads. Per the sections Dan quoted #12 looks acceptable.

>

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#83077 - 01/09/03 03:58 AM Re: Aircondition load
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
Remember the code is just minimum standards, you can always do better.

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#83078 - 01/09/03 04:24 AM Re: Aircondition load
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
abode,

Your "code loop" seems valid, but as spyder said, the NEC is a minimum standard.
Considering voltage drop, especially during compressor start, (what's your LRA?) I'd run #10.



[This message has been edited by Redsy (edited 01-09-2003).]

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#83079 - 01/09/03 02:36 PM Re: Aircondition load
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
abode electric

You said voltage drop not a factor so the run must be short. Unless you got couple of hundred to do, how much are you going to save buy using #12. Plus anyone that goes into the panel after you is going to ask questions on this, I am thinking "Home inspectors" or the GC who thinks he knows that 30 amp breakers need #10s
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#83080 - 01/09/03 04:02 PM Re: Aircondition load
abode electric Offline
Junior Member

Registered: 01/08/03
Posts: 8
I wouldn't normally run a #12. The hvac guy didn't have his compressor on the job and told me it was a smaller unit. When it came to final inspections the inspector said I wasn't compling with the code. I knew the #12 I already ran meets code requirments of this unit. Why should I have to take that out and run a new one? There is sheetrock already in place.

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#83081 - 01/09/03 04:13 PM Re: Aircondition load
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Let's aproach this from another view.
THe local AHJ stated "non compliance".
Did he state a NEC Article??
We have to in NJ to make it a valid "Fail".

Now that I said that...
THe AHJ usually has the final word, unless you have an appeal process. If you do, then you have to "win" the Appeal. This usually takes time...(Time + Money)

You also probably will have future dealings with this AHJ, or other ones that he knows.
(Some AHJ's have good memories)

I'm not saying that AHJ's are vindictive if they "loose", but who knows.

The solution, in my humble opinion is to change the feeder. This way you can't really loose.

John
_________________________
John

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#83082 - 01/09/03 04:26 PM Re: Aircondition load
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
abode electric, In that case I would try to get the #12 passed, this keeps the GC happy.

If I could not, I would hope that I had some proof that the HVAC guy F***** up and I would back charge the repair or at least get something in return.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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