Results 1 to 6 of 6
  1. #1
    Join Date
    Jul 2012
    Location
    Iowa
    Posts
    6

    a/c failed, time to upgrade furnace too?

    hi,

    I've got a 1997 carrier weathermaker 58TUA speed / 2 stage furnace and a
    2.5 TXA030 a/c unit. Compressor failed on condensor.

    So.. had couple of companies out already.

    Plenum above furnace where a/c coil is is 16"
    Return air duct on side of furnace seems undersized for all
    the return air going into it.

    I understand that a/c and furnace dont need to be replaced together.
    I dont need more than 14 SEER given that I use it about 1/4 time in
    summer. So no need to replace both to get higher SEER for a/c.

    Would you replace the furnace and a/c now? I'm considering buying
    the manual J program Hvac-calc and running some figures as I
    may build out a room. Contractors have little interest in doing it,
    I think I can input all the data at least (I'm an engineer).

    Replace furnace and a/c together now? Any ideas on life left in the
    furnace, motor has been already replaced.

    Thanks for any advice

  2. #2
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,275
    How much are your summer electric bills?

  3. #3
    Join Date
    Jul 2012
    Location
    Iowa
    Posts
    6
    Low in the summer $150 july/aug

  4. #4
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,665
    I would replace the furnace with a 95% efficienct furnace

  5. #5
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    I'd also replace the furnace. At 15 years old there's not a lot of time left before you're dealing with a very expensive repair or two.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by restar View Post
    Low in the summer $150 july/aug
    Having a load calculation done may not be a bad idea. At $150 ($100 for cooling only I'm guessing, $50 for "base load"), you may be closer to 2 tons than 2.5 tons, especially in yoru climate and with the hotter weather. If it's been maintining 75F in the late afternoon when it's be in the mid 90's and above, it's definitely not undersized.

    For example, I'm right at 3.5-4 tons and and am projecting a $240 bill so about $190 for cooling with an average of about 14 SEER between both systems. But obvisouly every home is a little different.

    You might as well replace the furnace and go vairable speed, 2 stage and 95%+. You'll spend 3/4 of the labor just to change the coil, you might as well swap out the furnace then, otherwise you have to remove the coil all over again when you do change your furnace.

    THe load calculation should verify your furnace size too. You don't oversize just because it's 2 stage. In northern Iowa I think design temperature is around -2 to -5F so at those temps and lower it should be running almost continously in high stage and almost continously in low stagebelow about 10F.
    Last edited by motoguy128; 07-23-2012 at 08:55 AM.

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