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  1. #1
    Join Date
    Sep 2012
    Posts
    2

    sizing question for btu on new furnace

    Hey Everyone,

    I got a couple quotes and different opinions on sizing for new furnaces. I am replacing 2x25 year old 90,000 btu lennox furnaces.

    I am looking at 2 95% efficient furnaces with ECM motors.
    My house has the upstairs which is 850 sq ft, the main is 950 sq ft

    one furnace runs the upstairs the other runs the main floor and 2 vents in the basement. (not need much heat down there)

    one quote said a armstrong air 90,000 for main floor and a 70,000 for upper.

    the other quote said 2x 60,000 goodman furnaces. and told me a 90,000 is way to much for the size of the house.

    Can anyone chime in and let me know what they feel would be good sizing for the 95% efficiency furnaces for the sizes of my house.

    Cheers,

    djrocketodd

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,700
    90,000 sounds grossly over sized for a house of your size.
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  3. #3
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    180,000 on 1800 sqft a bit much. Resizing both will probably require more then just replacing the units. Should be able to handle that space with much less but it's really not that easy to get there from here.

  4. #4
    Join Date
    Apr 2006
    Location
    Barrie Ontario
    Posts
    318
    Do you live in Alaska with paper walls. I've done 1800 sq feet with one 60,000 furnace in northern central Ontario do you self a favor and get a heat loss calc done on your house

  5. #5
    Join Date
    Feb 2012
    Location
    Toronto Canada
    Posts
    1,090
    Where is this house located. ???

    Sounds very very over sized to me

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,884
    In our cold climate for a house of that size we would have 1 70,000 BTU furnace typical construction. So I can't imagine meeting anywhere near what those dealers are suggesting.

    Find a good dealer who will do a heat loss calculation.

    Sent from my HTC VLE_U using Tapatalk 2

  7. #7
    Join Date
    Sep 2012
    Posts
    2
    I live in Calgary Alberta, so it does get a little cold and the house was built in 1986. I want to keep the split of main and upstairs separate since there is no zoning in the house. Thanks for the input, i felt 90k was a bit overkill as well.

  8. #8
    Join Date
    Jan 2008
    Posts
    1,955
    2 - 40,000 btu units sound just about right.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  9. #9
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,145
    Quote Originally Posted by 2old2rock View Post
    2 - 40,000 btu units sound just about right.
    +1

  10. #10
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,628
    Might even want to go to the next level and get a pair of 2 stage 40-45,000 furnaces. There's not much cost difference and quite a bit more comfort. The upstairs unit will probably never go to high fire.

  11. #11
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by martyinlincoln View Post
    Might even want to go to the next level and get a pair of 2 stage 40-45,000 furnaces. There's not much cost difference and quite a bit more comfort. The upstairs unit will probably never go to high fire.
    Ya. What he said.

  12. #12
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,233
    Quote Originally Posted by 2old2rock View Post
    2 - 40,000 btu units sound just about right.
    Ditto
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  13. #13
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,696
    Love Calgary, awesome town.

    Quote Originally Posted by martyinlincoln View Post
    pair of 2 stage 40-45,000 furnaces.
    x3. Nice suggestion.

    Look for turn-down to 20-24k. Then the equipment will only be over sized 20% of the time instead of 90%.

    Get a load calc and blower door. Please share cfm50 number, and make sure they use that leakage in the calc.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

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