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Old 08-29-2009, 12:05 PM   #1
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Rewiring air conditioning compressors


I am currently looking for some advice on running new wiring to my air condition compressors.

I have 2 airconditioning systems in my home. A 1.5 ton compressor and a 2.5 ton compressor. These two compressors are both wired to the same 50 amp breaker w/ 8 guage wire.

I am upgrading the 1.5 ton unit to 2.5 tons and am going to move the wiring from the exhisting conduit on the exterior of the house to romax run through the walls and the crawls space.

So my question is will 8 guage wire w/ the 50 amp breaker be okay after I upgrade from the 1.5 ton to 2.5 compressor?

Any help would be appreciated. Thanks.
Jeff

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Old 08-29-2009, 12:32 PM   #2
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Rewiring air conditioning compressors


You need to know the min circuit ampacity for both A/C condensers. Add them both up to get min wire and breaker size. Then provide over current proctection for each, out at the conderser units.

The A/C name plate will give you min ciruit amps and Max fuse.

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Old 08-29-2009, 12:40 PM   #3
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Rewiring air conditioning compressors


Better to run each on its own branch circuit IMO. Is that what your planning? . It would help if you could give us the load data off the nameplates...specifically minimum ampacity and max breaker.
Also agree with post before this...just saw it. fusible disconnects yes.
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Old 08-29-2009, 12:49 PM   #4
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Yes, each compressor has it's own branch circuit.

My HVAC contractor has installed my new furnace, coils, and ductwork, b/ has not placed the new condensor yet. I will have to get w/ him for the load data on the new unit. The other condensor that is staying, has minimum of 20.4 and max. of 35.

Thank you.
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Old 08-29-2009, 01:04 PM   #5
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Rewiring air conditioning compressors


Quote:
Originally Posted by jmwilson@usg View Post
Yes, each compressor has it's own branch circuit.

My HVAC contractor has installed my new furnace, coils, and ductwork, b/ has not placed the new condensor yet. I will have to get w/ him for the load data on the new unit. The other condensor that is staying, has minimum of 20.4 and max. of 35.

Thank you.

#12 (25 amps) will be fine on 35 amp breaker... you are allowed to have larger breaker on smaller wire for A/C. Can explain if you want. I would try a 30 amp breaker first as 35's are supply house inventory not big box,
If you ever think you will upsize that unit install 10 awg.

Using the #8 for the bigger unit will work but the 50 amp breaker is going to be to big I think. Probably is going to be a 40 or 45.
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Old 08-29-2009, 01:10 PM   #6
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Rewiring air conditioning compressors


Sorry I thought you were upgrading to bigger than 2.5 on the new unit I see your existing one is still a 2.5 and your adding a 2.5 from a 1.5. So likely same for the new one as the existing one but wait for the unit to arrive. #8 is going to be plenty big though. The 50 breaker is going to be too big.
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Old 08-29-2009, 01:32 PM   #7
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Rewiring air conditioning compressors


Stubbie,

Thanks for that info.

I was hoping that I might be able to get away with running #10 wire, as it is easier to work with, I've already got it, oh, and it's cheaper. I guess it's moot until I get the ampacity info from the new condensor.

Thanks.
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Old 08-29-2009, 01:35 PM   #8
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Rewiring air conditioning compressors


You also need to comply with NEC 210.63 which requires a 120 volt gfci receptacle outlet 15 or 20 amp within 25 feet of the AC compressor and on the same level. This a maintenance outlet. A good way to comply is with a combination disconnect that has this outlet pre-installed along with the A/c disconnect. It will require a 120 volt branch circuit separate from the a/c. If you already have this outlet and it is within 25 feet of both units you are fine.

Looks like this or similar depending on maker if your interested

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Old 08-29-2009, 03:22 PM   #9
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Quote:
Originally Posted by jmwilson@usg View Post
I am currently looking for some advice on running new wiring to my air condition compressors.

I have 2 airconditioning systems in my home. A 1.5 ton compressor and a 2.5 ton compressor. These two compressors are both wired to the same 50 amp breaker w/ 8 guage wire.

I am upgrading the 1.5 ton unit to 2.5 tons and am going to move the wiring from the exhisting conduit on the exterior of the house to romax run through the walls and the crawls space.

So my question is will 8 guage wire w/ the 50 amp breaker be okay after I upgrade from the 1.5 ton to 2.5 compressor?

Any help would be appreciated. Thanks.
Jeff

Note that #8 awg romex is not rated for 50a, you would be best off using 8-8-8 SE (service entrance) cable to handle the 50A, from the main panel to the sub-panel at the condensers.
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Old 09-02-2009, 12:31 PM   #10
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Rewiring air conditioning compressors


There is seldom any contact between the people that do HVAC work & a homes electrical needs. In my case an inspector pointed out that the breaker values had not been changed in 45 years despite their replacement with modern more efficient units.

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