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  1. #27
    Join Date
    Aug 2004
    Location
    Tyler TX
    Posts
    676
    I would agree with carnak on this, the longer run times and fewer start cycles would be more efficient. I would also consider for the same reason that the furnace would probably last longer due to less stress on the heat exchanger.
    HVAC Contractor, Tyler Texas.

  2. #28
    Join Date
    Apr 2002
    Posts
    11,808
    If it is a comfort issue then forget the two stage and get a rheem mod
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  3. #29
    Join Date
    Feb 2005
    Posts
    655
    The 75,000 is more than you need But so is the 50,000
    input on the two stage 80% of the time.
    Get my point?

  4. #30
    Join Date
    Feb 2005
    Posts
    655

    two speed

    Comfortmaker also makes two stage with two speed inducer and two stage gas valve, not modulating. (Model C9MPT050F12)

  5. #31
    Join Date
    Nov 2004
    Posts
    2,927
    maybe they say that for a reason.

    so people wont think that they should down size their furnace because it is "more efficient" two stage.
    Sometimes there are compounding complexities of multiple variables that are not intuitively obvious

  6. #32
    Join Date
    Apr 2002
    Posts
    11,808
    I think a lot of two stage out there hardly ever hi-fires.

    The furnaces seem to be over sized, some times intentionally to get enough air for AC.

    The two stage is like a safety net for oversizing.

    I guess my reason for saying this was the most common furnace sizes I sold in Canada were 60 & 75 MBH, and designing for close to 100F temperature differential.

    I see all kinds of posts in here on furnaces 100 & 125 MBH, in a much warmer climate.

    [Edited by Carnak on 10-22-2005 at 03:19 PM]
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

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