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Old 06-11-2010, 12:08 PM   #1
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?? about AC sizing

I had a tech out yesterday because my outside unit stopped working. The motor was shot. As soon as the tech say the unit he said he was surprised it lasted as long as it did. 10 years. I have a 2600 sq ft home and the outdoor is a 3 ton unit. He told me in my area that the rule of thumb is 700 per sq ft of living space. Which gives me a 3. 71 ton. And I live in the Kansas City Ks. area. From what I have read, there shouldn't be a rule of thumb. The system has to be matched specifically to the house. Can't a system that is too large be just as inefficient? Now I now this is a builders grade ac and furnace that I have. And he said that the unit is good for up to 85 degree weather. Anything over that and the unit is working too hard to cool the house. It sounds like doom and gloom to me.


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Old 06-11-2010, 01:33 PM   #2
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Is it the compressor which is shot? or the fan motor with the blade? Lots of builders grade units only have 5 yr warranty on compressors and if it burnt out then it is VERY expensive to clean out and replace the compressor. Do a proper heat load calculation for a few bucks:Load Calculator
and shop around for a few reputable long term contractors as this guy is sounding a bit "less than knowledgeable" and qualified IMO. You should get a second opinion and not trust the first guy as it may be something simple as a bad capacitor. Don't tell the 2nd guy what the first said. Some companies will waive the service call fee if you buy the unit from them so a 2nd opinion is a good idea.


"Cut it twice and it is still too short".

Last edited by yuri; 06-11-2010 at 01:37 PM.
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Old 06-11-2010, 02:17 PM   #3
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My samples say 3/4ths last more than 15 years.
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Old 06-11-2010, 02:22 PM   #4
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yea the first guy wanted to do a rebuild. New motor, fan blades, capacitor and a hard start kit. A service contract for the rest of this year, for the low low price of $800. This was the service guys suggestion as what I should do to make this thing last another few years. Well I asked if he could just replace the fan motor. He told me he didn't price any of that out and would have to price just that out and find someone to do it. He didn't call back. I called another guy who replaced the motor and tested out the dual run capacitor and it checked out fine. $200. The house is cool again.
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Old 06-11-2010, 05:13 PM   #5
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How does your A/C cool when its above 85 outside?

Rules of thumb are often dumb.
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