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  1. #1
    Join Date
    Jun 2008
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    Need advice on HVAC replacement

    Hello all, and thanks for your help in advance.

    I have a mid-50s home in Memphis, TN. It faces west and most of the windows are on the west and east facing sides. The house has no insulation between the plaster walls, a vented crawl space, and approx 25 yr old blown insulation in the attic.

    I currently have a Carrier A/C unit that the contractors I've called estimate the age to be 30+ years old. It is so rusted that no one can read the serial or model numbers on it. It is likely the first unit installed on the house.

    All of the contractors have said that it's on its last leg, and I've had to call 3 times in the last 2 years to have the compressor 'unclogged' and recharged. I am being told parts will be almost impossible to find when the inevitable happens.

    I'm replacing it next week with a Coleman 14.5 SEER 3.5 T unit and evap coils. I expect to see some big savings on my utility bills.

    The 3 contractors that bid also recommended I go ahead and replace my gas furnace and air handler as well.

    The gas furnace is a Lennox 100000 BTU unit (is that right?), model GS18Q3. The date stamp is 1988, which makes the unit 20 years old. I haven't had any problems with it yet, but I am not happy with gas bills are running about $200/mo and that's keeping it on 68 when I'm home and setting it back to 65 during the day and at bedtime.

    Our winters are fairly short and relatively mild here, but it's not unusual to see several weeks of at/below freezing weather.

    My questions are this: Can anyone tell me what the AFUE of the Lennox GS18Q3 is?

    All three contractors bid on replacing it with an 80% AFUE 100000 BTU model and new air handler. I asked about a higher efficiency unit, and was told that namely because of the nature of the winters and my plans to stay in the house for another 5-7 years, I would not make up the cost difference.

    Based upon the AFUE of the current unit, can I expect to see a positive impact in my winter gas bill if I do replace it? Or should I just stick with what I've got and roll the dice for another 5-7 years and hope I don't have any problems?

    Thanks again for your help!


  2. #2
    Join Date
    Jan 2004
    Post Likes
    You might want to check into getting a heat pump instead of an A/C. It should be ale to heat your house for a lot less then your gas.
    Call your contractor on Monday, and find out the price difference.
    Its possible that you won't need to use gas for heat, until its 35* or colder outside.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Mar 2006
    The South
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    Here are my ideas about your situation.

    1. Because of your area/location and a relatively mild winter climate, it is a mistake not to leverage your inexpensive electric rate with a high eff heat pump system.

    2. With today's rising fossil fuel prices including nat gas, an 80% AFUE eff furnace is a dinosaur unless paired with a HP. And you should consider a var spd blower whether air handler or furnace.


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