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Old 10-07-2012, 12:22 AM   #1
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Central air wiring question


The old aluminum wiring for my A/C is oxidized and I'd like to replace it. Based on the info on the tag, I should be able to use a 30A breaker with 12 gauge or larger wire, correct?

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Old 10-07-2012, 12:55 AM   #2
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Central air wiring question


No. size for your min breaker

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Old 10-07-2012, 03:10 AM   #3
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The OP is correct, that's the code. And for short distances there's no down side for #12 wire. For longer distances, esp. through hot attics, there is power lost as heat from the resistance in the wire. Upgrade the wire a little and you can recoup your investment with lower bills. By the way, aluminum is a perfectly good conductor. A wire brush, some Noalox grease and a torque screwdriver will make for efficient long lasting connections.

Last edited by Glennsparky; 10-07-2012 at 03:27 AM.
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Old 10-07-2012, 03:55 AM   #4
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No. size for your min breaker
Totally incorrect. #12 on a 30A breaker is just fine in this application. In fact, I'm pretty sure #14 would be allowed since it is actually rated 20A (25A for 90C) but, like #12, is subject to a special maximum breaker size for most types of circuits - but not this one.
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Old 10-07-2012, 05:08 AM   #5
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12 is fine. Myself I would use a 10, but code allows 12.
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Old 10-07-2012, 07:56 AM   #6
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Upgrade the wire a little and you can recoup your investment with lower bills.


What are you talking about, if this was true he should be wiring it with #6 or #4 to save even more money.
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Old 10-07-2012, 08:26 AM   #7
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if this was true he should be wiring it with #6 or #4 to save even more money.
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Old 10-07-2012, 09:00 AM   #8
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12 is fine. Myself I would use a 10, but code allows 12.
Thank you. I do plan on using 10ga.
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Old 10-07-2012, 09:03 AM   #9
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Originally Posted by Glennsparky View Post
The OP is correct, that's the code. And for short distances there's no down side for #12 wire. For longer distances, esp. through hot attics, there is power lost as heat from the resistance in the wire. Upgrade the wire a little and you can recoup your investment with lower bills. By the way, aluminum is a perfectly good conductor. A wire brush, some Noalox grease and a torque screwdriver will make for efficient long lasting connections.
Thanks for your input. True, aluminum is fine, but since I have the copper, I'd like to just replace it.
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Old 10-07-2012, 10:57 AM   #10
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If you use a fused disconnect it has to be #10 to the disco, then #12 to the unit. Non fused can be #12 from the panel all the way.
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Old 10-07-2012, 05:32 PM   #11
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I got it done with 10-2 to the fused disconnect and kept the 8ga whip that was already there.

Thank you everyone.
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Old 10-07-2012, 06:27 PM   #12
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Depending on what code cycle you are on, you could use #14 AWG. and a 30 amp breaker.
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Old 10-07-2012, 06:28 PM   #13
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12 is fine. Myself I would use a 10, but code allows 12.
Why would you use 10 AWG? It serves no purpose.
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Old 10-07-2012, 06:47 PM   #14
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Why would you use 10 AWG? It serves no purpose.

No idea how long his run is. but less voltage drop on those hot days when the compressor has to start. Also, don't have to run a new wire down the road if he adds on and needs to increase the size of the A/C to something that has a min cir amp of 25.

No real cost difference between 10 and 12.
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Old 10-07-2012, 06:49 PM   #15
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No real cost difference between 10 and 12.
yes, there is... I personally would wire the unit with 14 AWG.

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