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  1. #1
    Join Date
    Jul 2019
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    26
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    Where to find blower tables?

    I currently have a bryant 340aav036080 furnace, and am in the process of deciding if it needs to be replaced or not. I have done a manual j calculation and it appears that the BTU (80,000... 72,000 actual) is just barely enough for my needs. I am adding a couple of conditioned spaces, and converting the basement to be fully conditioned. I am going to redo the calculations, as I am not 100% sure I got this right. The problem I am running into is that I am not sure if I will have enough available CFM for the new design. According to the manual I have looked up online the maximum CFM is 1190 on this unit. I am thinking that I may just replace the furnace entirely, as its pushing 20 years old anyway. I live in a very cold climate, design temp -10 for my area. House is 120 years old, about 2,000 sq. ft. including unfinished basement. Also 2 story. I am ok with the basement being a little cooler, 60 instead of 70, but I do use it in the winter. Not sure if I should start trying to see if I can design something based on this current furnace, or look to replace it all. Like I said, it seems like the CFM output is just a little too light for my needs. Thoughts?

  2. #2
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,924
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    If you're adding load you better check the duct design.
    You can just rob peter to pay paul.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  3. #3
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
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    Basements get a separate unit!

    Where is this "Design" -10°F ? (Zip Code Works)

  4. #4
    Join Date
    Jul 2019
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    Thread Starter
    Quote Originally Posted by dandyme View Post
    If you're adding load you better check the duct design.
    You can just rob peter to pay paul.
    Yes, I am not just tapping off other lines for the added areas. I am completely reworking the entire duct system. I am also adding returns to just about every room as well.

  5. #5
    Join Date
    Jul 2019
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    26
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Basements get a separate unit!

    Where is this "Design" -10°F ? (Zip Code Works)
    What do you mean by a separate unit? I hope you're not refering to a seperate furnace just for the basement. I am assuming you are talking about a separate manual j calculation just for the basement since I am planning on it being 10 degrees cooler, then adding the 2 BTU totals together?

    And as for the design temp, I guess to be completely accurate I should say that the closest place to me listed on their chart for winter design temps is -8 degrees. But I live a little bit away from there, and comparing the average temps between the place listed and where I live, it is always significantly colder here due to elevation changes and other factors (I am not an expert in weather....) It is in the Upper Peninsula of Michigan.

    As for the blower tables, do they exist anywhere that I would be able to see them?

  6. #6
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
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    Basements have a different heat load loss then the rest of the structure so need a separate heat source.

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Remember the house is seeing below freezing temps the basement 55*

  8. #8
    Join Date
    Jul 2019
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Basements have a different heat load loss then the rest of the structure so need a separate heat source.
    I have never hear of anyone around here running a separate furnace just for the basement. Can't I just run less ductwork to supply less air?

  9. #9
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
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    Quote Originally Posted by Jebusfreek666 View Post
    I have never hear of anyone around here running a separate furnace just for the basement. Can't I just run less ductwork to supply less air?
    Unfortunately the heat exchanger is designed for a certain amount. Go too low and you can damage the Equipment.

  10. #10
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    9,969
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    FIRST - BLOWER DOOR TEST


    SEAL IT. ... ... ... WHAT IS A.C.H. Natural ?
    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

  11. #11
    Join Date
    Jul 2019
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    26
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    Thread Starter
    Quote Originally Posted by dan sw fl View Post

    FIRST - BLOWER DOOR TEST


    SEAL IT. ... ... ... WHAT IS A.C.H. Natural ?
    Not an option in my area. Very small, very rural area. No one around here offers those services.

  12. #12
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    9,969
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    Quote Originally Posted by Jebusfreek666 View Post
    Not an option in my area. Very small, very rural area. No one around here offers those services.
    http://www.michiganblowerdoor.com/business-directory

    120 Year Old
    Residence

    Difficult -to- IMPOSSIBLE to perform an accurate Heat loss calculation
    without knowing the leakage rate.
    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 2019
    Posts
    26
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    Thread Starter
    Quote Originally Posted by dan sw fl View Post
    http://www.michiganblowerdoor.com/business-directory

    120 Year Old
    Residence

    Difficult -to- IMPOSSIBLE to perform an accurate Heat loss calculation
    without knowing the leakage rate.
    I have already looked into it. Trust me. All those companies on the link you supplied are in the lower peninsula. I'm in a remote area in the upper peninsula. The closes one listed is about 6 hours away, one way.

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