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  1. #1

    Two Stage vs Modulating Gas Furnaces

    I am trying to decide between 2 different gas furnaces manufactured by Trane. The 2 models I am looking at are the XV 95 (two stage) and the XC95(modulating). Are there any energy savings by going with the XC 95 or is it simply for comfort?

  2. #2
    Join Date
    Mar 2003
    Posts
    7,326
    either would be a good choice, but the modulating would give you better comfort, if you can tell the difference. a lot depends on the home, the residents, etc. there may be some potential energy savings, but it would be tough to measure unless you had two exact same structures.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,591
    The mod is no more efficient then the 2 stage. It will however provide better comfort.
    And may give you a slightly lower heating bill, if it makes you feel more comfortable at a lower temp setting.
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  4. #4
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,186
    The mod will be more quiet most of the year as it will only fire as hi as it needs to to maintain set temp.

    If you get the mod make sure you get the TCONT900 thermostat with it, it gives better control over the modulation than just a regular stat and also will do humidification and dehumidification if you have humidifier and a/c.

  5. #5

    Furnace Size?

    Thanks everyone for your responses regarding the Two Stage vs Modulating. One more question: The Manual J Calculation that was done on my house showed that the upper end of my need would be 76,000 btu/hr. If I get an 80,000 btu/hr furnace with 95% AFUE, that would give me exactly 76,000 btu/hr. Would I be better off going with a 100,000 btu/hr (95%) modulating furnace rather than an 80,000 btu/hr (95%) to cover in case I need more than the 76,000 btu/hr. My rationale is that this would cover me if I needed more than the 76,000 btu/hr and since the furnace would be modulating it would only use what it needed so it should cost me much (if any) more to operate than the 80,000 btu/hr unit.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,591
    Nope.

    If you do that. Then there is little to no use getting the mod.

    Better off adding insulation to your attic, or doing something else to reduce your heat loss.

    More likely then not. Your actual heat loss will be lower then the load calc says by a few hundred to a couple thousand BTUs.
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  7. #7
    Join Date
    Aug 2009
    Posts
    1,127
    Just to add to beenthere's post: for well over 95 percent of the year, picking the exact match for very coldest day of the year will mean that you are effectively oversized most of the year. Thus the right size furnace (or a little undersized) will be the best match, giving you the best comfort most of the year. If it turns out that it can't keep up on the coldest days, some home improvement should enable it to keep up.

    I suspect manual J assumes average heat loss due to duct leakage. Just tightening that up can give you an extra margin of safety.

  8. #8
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by commerce48 View Post
    picking the exact match for very coldest day of the year will mean that you are effectively oversized most of the year
    so would you have the customer with a cold house on the coldest day, news flash, it don't work like that

    Thus the right size furnace (or a little undersized) will be the best match
    yes, you continue to spew this garbage over the net, your wrong!
    if you can't put the right sized furnace in, you got problems, and as usual your everyday answer of undersizing is not correct

    If it turns out that it can't keep up on the coldest days, some home improvement should enable it to keep up
    ya, and if it turns out a customer with an undersized heater can't sleep at his house cause it's too cold, and home improovments are too expensive or don't work, then what

    i now see why your not in the a/c trade mr. commerce

    and i just hope 99% of your post go ignored by home owners



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