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  1. #1
    Join Date
    Sep 2008
    Posts
    11

    Furnace in the attic: 80% or 90%?

    I'm installing a 2 furnace system and am hoping someone can clear up whether it is appropriate to install a 90+ furnace in an attic, or if you should stick with a 80% unit for this application.

    I understand that the proplem relates to freezing due to condensation, but have received 2 conflicting opinions from the pros who have bid my job - 2 in each camp.

    Thanks!

  2. #2
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,406
    First thing we need to know is where you live (so we will know the weather). Freezing condensation would not be much of a problem in, say, Houston TX. But in Maine it would be a serious problem...
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  3. #3
    Join Date
    Jan 2004
    Location
    Northen West By God Virginia
    Posts
    72
    Install a 80% and heat pump have the best of both worlds

  4. #4
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,904
    In areas where there is no risk of freezing, heatpumps are the way to go and high efficiency furnaces probably never pay off.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  5. #5
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    here in jersey a company i worked for but a few 90% in attics and every one had frozen condensate line that year when a real severe and long cold front came through.


    I would because of that never recommend one for an attic install where it can get extreemly cold or if freeze potentail is there

    80% and no worries the differance isnt worth the chance

  6. #6
    Join Date
    Sep 2008
    Posts
    11

    Furnace in attic

    Sorry about that - I'm in Pennsylvania.

  7. #7
    Join Date
    Feb 2004
    Location
    chicago suburbs
    Posts
    4,422
    condensing furnaces have condensation traps. they freeze and the furnace won't run...how will you keep the trap from freezing when it's really cold?
    FILL OUT YOUR PROFILE!!

  8. #8
    Join Date
    Sep 2008
    Posts
    11
    The reason that I'm asking the question is that I don't know whether the condensation trap would freeze in the attic, and 2 of 4 fairly large, longstanding, and well-receommended HVAC companies in my area tell me to use a 90+ in the attic.

    If the trap is likely to freeze and create problems, then I will obviously choose an 80% furnace for this application.

  9. #9
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,406
    Quote Originally Posted by cdetar View Post
    Sorry about that - I'm in Pennsylvania.
    While I am in GA, we get marginally cold enough here that a 90% furnace in the attic has to be carefully insulated or it will 'freeze up' and quit heating. I have a lot of them out there. A little careful attention to things, and it will work... but PA is too cold IMO.

    I would follow the advise in this thread to either use an 80% furnace, or set up dual fuel with an 80% furnace.

    THX for posting your location. That does make a difference.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  10. #10
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,754
    we have been putting 90% furnaces in nj attics since the 1980's, never had one freeze.



    like everyone says, the install is the most important part of the system.

  11. #11
    Join Date
    Dec 2002
    Posts
    77
    I've seen heat tape kits for the condensate trap to keep it from freezing. I'd be curious to know if anyone has experience with these.

  12. #12
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    Quote Originally Posted by t527ed View Post
    we have been putting 90% furnaces in nj attics since the 1980's, never had one freeze.



    like everyone says, the install is the most important part of the system.
    Hear what he say, hear what he say....

  13. #13
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,754
    Quote Originally Posted by mlrman View Post
    I've seen heat tape kits for the condensate trap to keep it from freezing. I'd be curious to know if anyone has experience with these.

    they work......

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