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  1. #1
    Join Date
    Jun 2005
    Posts
    40

    Question

    Have a new Bryant Furnace 355AAV042060 with the evolution control In our home in Minnesota. The furnace was installed just shy of three months ago. We were aliitle disappointed in our December gas bill in that it didn't show usage going done much from our previous furnace, a 1990 Lennox G16 (80% efficiency at best).

    I am hoping the pros (and others) here can evaluate the furnace's performance. Also, your comments on how we are using the furnace, and how that maybe why we are not realizing the expected efficiency gains would also be appreciated.

    We have used the following setback schedule:
    72 degrees (5:45 am to 7:45 am)
    63 degrees (7:45 am to 4:45 pm}
    72 degrees (4:45 pm to 10:45 pm)
    65 degrees (10:45 pm to 5:45 am)

    Here is the run cycle data:

    Cycle Counts:
    Low Heat: 1107
    High Heat: 132

    Run times hours:
    Low Cycle: 466
    High Cycle: 238

    What do you think? Is this performance typical? Are we losing efficiency by using to large of setbacks? Any other thoughts?

    Thanks for your input.

  2. #2
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    17,918
    Are you useing a two stage thermostat?
    Behind the ostensible government sits enthroned an invisible government owing no allegiance and acknowledging no responsibility to the people.

    Theodore Roosevelt

  3. #3
    Join Date
    Jun 2005
    Posts
    40

    Yes

    we have the evolution tstat SYSTXBBUID01.

  4. #4
    Join Date
    Dec 2005
    Location
    Cleveland, OH
    Posts
    2,234
    It seems like your temperature swings are too big. You're dropping 9 and then heating back up. We usually recommend no more than a 6 swing in temps.

    Good? Bad? I'm the guy with the gun.

  5. #5
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    In comparing your gas usage, how do this year's outside temperatures compare to last years? Search for a local university atmospherics lab and see if they have local temp data. It would be great if they had actual heating degree-day measurements for this year and last year by month. You could probably use monthly average temperature if you can't find anything else.

    I also assume you're comparing units of gas (MCF or CCF) and not dollars of gas. Do you have other gas appliances that could be stealing your savings (like kids who are now taking longer showers, or more clothes drying)?

    I don't know what a 355 series is, but is it 95%, 90% or 80%? The Evolution control can give you a lot of control and more comfort, but I'm not so sure I'd expect this system to be much less expensive to run than your older system. Hopefully, you weren't expecting more than a 10% savings.

  6. #6
    Join Date
    Jan 2006
    Posts
    69
    Try your natural gas supplier's web site. You will have to compare degree days to figure this out. I was able to go to the Shell Natural Gas website where they had a link to the degree day figures for each month, current and past years for the Atlanta region. I think if you went to this site you could find your region as well. This is a great site, along with degree days it has highs, lows, record highs and lows, snowfall etc... Your supplier will probably have a link to a site since their phones are ringing off the hook with complaints about gas bills.

  7. #7
    Join Date
    Jun 2005
    Posts
    40
    I have compared heating degree days between last and this year. The are virtually the same. I have also discounted for the price differences.

    The result is the same conclusion. Despite now having a new furnace rated at 94% efficiency versus our old less than 80% efficiency furnace, our gas usage is only slighly less. All other factors (eg. appliance, kids usage etc.) are virtually the same between last year and this year.

    Hence, the reason for my original post with furnace setback and run cycle info. I would expect more than a 4.5% drop in gas useage. Any other thoughts from the info provided?

    P.S. I have adjusted the setback to a 6 degree difference as suggested above.

  8. #8
    Join Date
    Jan 2006
    Posts
    69
    Unless your t-stat setting is the same as last year I don't think you could compare accurately. Most likely you are saving 10 to 15%, cipher again. Virtually the same - is there a 5% difference, you are not looking for much.

  9. #9
    Join Date
    Aug 2002
    Location
    Westlake, Ohio
    Posts
    2,470
    Your 2-stage furnace was designed to make you more comfortable not save money. The time you are spending in 1st stage is using more fuel than you old furnace. Check the temperatures of the air coming out of the registers. Should be getting 115 degrees to 125 degrees assuming some duct loss. The furnace can be adjusted by a certified combustion analyst and give you more savings.
    captain CO

  10. #10
    Join Date
    Oct 2005
    Posts
    26

    Sure your bill wasn't estimated?

    Our utility company will often estimate usage based on previous and while it says on the bill it is estimated it is in very small print. If heating degree days and usage were close to identical, this it is a definite possibility your usage was an estimate.

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