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Old 08-11-2011, 08:33 AM   #1
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Geothermal single stage vs two stage

I'm replacing my 30-year old Geothermal system with a new one. I have four quotes, all of them telling me the house duct-work, etc. was designed well and efficient. One issue is the house is over 4,000 sq ft and the current system has only one zone, which will be fixed to two zones with the new system.
Three of the HVAC guys tell me I should do a 2 stage system - save energy, etc. The fourth is suggesting a single stage for a few reasons: He has replaced a lot more compressors on two stage units than single stage units (even saying his mfg rep says the same thing), the zones will still have over 2,000 sq ft each, the house is brown, open to sun with a lot of windows, etc. so the system will still need to crank 100% most of the time when it's on anyway. It's also less expensive - though not by much so that's not an issue. My issue is that the guy suggesting the single stage has been helping with my current system for years - I trust him, etc. He says he's taken everything about my house into account and would suggest the single stage. That said, he's OK to install the two-stage if that's what I want.
Thoughts from anyone in the business?


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Old 08-11-2011, 04:49 PM   #2
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I would trust him. 2 stage compressors are a lot more complicated ( have a solenoid operated slider valve which can stick) than a single stage and obviously whatever brand he is selling is having design problems with their setup. Usually the compressors are trouble free and have a 10 yr warranty so it sounds to me like some aspect of their geo unit is causing compressor problems and if that is the case better to trust him. A 2 stage unit may dehumidify slightly better in a very high humidity climate and not worth it in others.


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Old 08-11-2011, 05:25 PM   #3
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4000 sqft is a lot of home for one a/c unit. Have you looked into having a load calculation performed?
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Old 08-13-2011, 09:22 AM   #4
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Geo single vs. two stage

Thanks. I'm still thinking about it, but leaning to the two stage because of the dehumidification issue plus the long warranty on the compressors.
FYI - Three of the guys quoting did the heat/load calculation and agreed the 6-ton geo system is good for my house. That's what's here currently and it's served us well, especially given it's 30 years old!
Thanks for the replies,
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