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  1. #1

    Hmm Help!! Single vs Two stage Gas

    I can't seem to get a straight answer on this q and I've researched on Line forever so I'm putting it out here:

    I am looking into replacing a 35 yo gas furnace/AC with an a new 80% AFUE model furnace and 13 or higher SEER AC for a 1200+ sf TH in Maryland. The 2 offers I'm in a hair-pulling contest over are:

    1: a Carrier 58CTA 2-stage (with new Honeywell Thermostat) and with a Comfort-13 AC unit and
    2: a Trane XR80 Single Stage with an XLI-14 AC unit

    The price difference between the 2 systems is only $125 but my predicament is, is worth going to a 2 stage or will the cost savings not really be realized as the 2 stage will run longer using more electric than the single stage using more gas.
    Thanks.

  2. #2
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    Not sure on those two options but I would go with the 2 stage. If set up with a 2 stage thermostat it will save gas and give you better comfort. Running on low tage on a mild day the unit will run longer and heat those rooms that may be more uncomfortable better. Also only running on say 60% of your total load you will save in utilities. Are any of these variable speed? This would make you even more comfortable.

    Make sure the unit is sized properly. This is very important.
    Its a good Life!

  3. #3
    Join Date
    Sep 2007
    Location
    South
    Posts
    85
    I think you have it wrong, I believe this is a 2 stage gas heat vs single stage gas heat, check it and make sure, if it is what I'm telling you a 2 stage gas will be recommended, the second stage will kick in only if needed (very cold days).
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    - Steven Wright

  4. #4
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    You expressed concern about the electric usage with a 2-stage furnace. I do not know what percent of your energy bill it will be, but if you upgrade to a variable speed (VS) furnace I believe the electric portion will be substantially lower. As far as I know the gas consumption is the same. I have such a furnace, in my case the American Standard Freedom 80. There is a Trane model which is nearly identical. I am a homeowner in S.Texas and appreciate the advanced technical qualities of this furnace.

    It is possible someone more knowledgeable than I will demonstrate that the electricity savings of a VS furnace will be inconsequential. But among other benefits it will make your AC more efficient and greatly improve humidity removal in cooling season. You can read pros praise VS for cooling airflow over and over on this board. I do hope you get a quote on that and it fits within your budget.

    If one of the quotes is from a better installer, it will be best to go with him no matter which brand he sells. People ask about brands all the time but often don't realize brand quality is only a tiebreaker, it is install quality which matters most.

    Hope this helps -- Pstu

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,330
    80% ?

    I didn't know Maryland has low gas rates.



    2 Stage is for comfort, not saving money on your heating bill.
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  6. #6
    Join Date
    Oct 2006
    Location
    Lower Burrell, PA
    Posts
    79
    Why is it that 2 stage wont save money on gas?

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,330
    Quote Originally Posted by tabyhvac View Post
    Why is it that 2 stage wont save money on gas?
    An 80% furnace isn't going to become 85% efficient because its in first stage. It will still be 80% at best.

    If the house needs 16,000 BTU's at 40* OD temp. An 80%er will use 20 CF of NG at 1000BTU per CF weather its single or 2 stage furnace. But the longer run cycle of a 2 stage will allow a humidifier time to put humidity in the air.
    They also tend to help eliminate the cool draft feeling from short cycles.


    Same with a 90%. It isn't more efficient in first stage. Just runs longer, to give better comfort.
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  8. #8
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,305
    As said two stage is for COMFORT.

    However, You may see a saving if your current furnace is oversized or going from an old 30+ years old to a 95%. But if you are putting a 90% two stage next to a 90% single stage, gas savings will not be there..

  9. #9
    I often compare a 2 stage unit to a 4bbl carb. Now, does it really save money. I think the jury's still out. I think it takes X amount of BTU's to heat a space (regaurless of how fast). With that said, I agree that a 2 stage will give you a more constant temp (less spikes and valleys). It will also run more often (on the lower stage) in order to achive this.

  10. #10
    Join Date
    Sep 2007
    Posts
    21
    Hi, I just had a new system installed about a month ago and researched the same question. For the two stage, check that you have more than 4 wires running to your thermostat. If not, is it easy to run more wires to the thermostat? The 2-stage runs best with a 2-stage thermostat and most of these tstats need more than 4 wires.

    With a 2-stage tstat, it will manage when the 2nd stage comes on depending on conditions. With a single stage tstat, the furnace automatically switches to the 2nd stage after 10 minutes.

    There are tstat options for 4 wires or less but they are more expensive. The Honeywell Vision Pro IAQ can run 2-stages with just 3 wires. There are also wireless tstats. I also saw something called faststat (google faststat).

    Unfortunately, I went with the 2 stage furnace without realizing this. Currently I have a single stage tstat running my furnace.

  11. #11
    Join Date
    May 2002
    Location
    MEDIA PA
    Posts
    1,383

    2 Stage

    is purly a comfort thing ' My unit has 4 stages 2 HP 2 gas It always on and confort lever is great

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