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  1. #14
    Join Date
    Jun 2014
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    Dover, DE
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    Quote Originally Posted by Photobug View Post
    I got another bid today to install a 95% efficiency 80k btu Trane furnace into my crawl space, for significanlty less than my last bid. The guy seemed knowledgeable and professional and was recommended by someone I knew.

    The furnace will go into my crawl space, freeing up space in the pantry. The combustion intake and exhaust will be plumbed through the crawl space sill. He suggested spliting the return air for the furnace between coming from upstairs and the main floor.


    Any suggestions on this setup or Trane Furnaces?
    But how did he determine that you need 80k BTU worth of heat?
    “I haven’t failed. I’ve just found 10,000 ways that won’t work.” - Thomas Edison

    “It’s not whether you get knocked down, it’s whether you get up.” - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  2. #15
    Join Date
    Sep 2019
    Location
    Jackson, Wyoming
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    Thread Starter
    Quote Originally Posted by rider77 View Post
    But how did he determine that you need 80k BTU worth of heat?
    I think he based it on my previous heater. I think my situation is somewhat unique in a few ways. I have had two HVAC guys come to look at my home and neither did any sort of calculations before choosing furnace size. I don't know if the guys do that locally at least not the contractors I have contacted recently. What makes my home unique is

    Even though forced air is only downstairs it is designed to radiate to the upstairs rooms. I have a large open stairwell. During the day, baseboards are turned off and the furnace heats the whole house. The baseboards only heat the room doors are closed at night.

    Downstairs height is 8 feet, upstairs rooms have vaulted ceilings that range from 6 feet to 15 feet in the hallway.

    I think the house is insulated very efficiently. The outside temp has ranged between 30 and 12 degrees f for the last 48 hours and a 1500W space heater has kept the whole house at 67 degrees, I added a second heater it is now 70 degrees in the house.

    My home sits at the base of a 1700 foot ridgeline that keeps sun off the home till about 10am in winter, so very little solar heating in the coldest part of the year.

    I have gone around and taken on the measurements of my windows and will plug them into a heat need calculator to see what I get but not sure how to factor in my goal in the furnace heating the upstairs some also.Name:  20191010_121905.jpg
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  3. #16
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Your not in a unique situation. Unfortunately it’s become the norm.

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
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    9,495
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    Quote Originally Posted by Photobug View Post

    I think he based it on my previous heater.
    I think my situation is somewhat unique in a few ways.

    I have had two HVAC guys come to look at my home and
    neither did any sort of calculations before choosing furnace size.

    Downstairs height is 8 feet, upstairs rooms have
    vaulted ceilings that range from 6 feet to 15 feet in the hallway.

    I think the house is insulated very efficiently.

    The outside temp has ranged between 30'F and 12'F for the last 48 hours
    and a 1500W space heater has kept the whole house at 67'F,
    I added a second heater it is now 70'F in the house.
    Temperature ____________ 70'F
    AVERAGE Outdoor TEMP. = 21'F
    _______________ __ DT = 49'F

    I am trying to make sense of the above stated heating data.

    2 * 1500 Watts = 10,236 BTU/HR

    Design Temp = -10'F .:. DT = 80'F
    One might presume the Design Heating Losses =
    _________________ 80 / 49 * 10,236 = 16,712. BTU/HR at -10'F
    __________________ __ __ That's definitely NOT a True, COMPLETE assessment IMO.

    _ DEFINITELY UNIQUE : BEST BUILT 2,700 SQ FOOT HOUSE IN NORTH AMERICA.

    ((( ((( ((( ((( ((( ((( ((( __ ??? ___ ))) ))) ))) ))) ))) ))) )))

    AN 80,000 BTU/HR Furnace is a bit oversized.
    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

  5. #18
    Join Date
    Jun 2014
    Location
    Dover, DE
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    If 10,000 BTU worth of electric heat keeps the house at 70*, please explain how it’s a good idea to install 80,000 BTU worth of gas heat.
    “I haven’t failed. I’ve just found 10,000 ways that won’t work.” - Thomas Edison

    “It’s not whether you get knocked down, it’s whether you get up.” - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  6. #19
    Join Date
    Sep 2019
    Location
    Jackson, Wyoming
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    Thread Starter
    Quote Originally Posted by dan sw fl View Post

    _ DEFINITELY UNIQUE : BEST BUILT 2,700 SQ FOOT HOUSE IN NORTH AMERICA.

    ((( ((( ((( ((( ((( ((( ((( __ ??? ___ ))) ))) ))) ))) ))) ))) )))

    AN 80,000 BTU/HR Furnace is a bit oversized.
    You are right not a true valid analysis. Especially because without the furnace working and with only my wife and I living here we close off the doors to a large part of the rooms upstairs, so the house is only about heating 50% of the house.

    I crunched the numbers of windows and added it to the online calculator. The closest city to me was Cody Wyoming but this is the coldest part of the state. I had to go to Kalispell Mt to find similar temps, although Kalispell is a few degrees warmer but I figure about as close as I could get. It looks like about 50,000 Btus would heat the whole house. Because we are in the shade of the mountain for most of the winter rounding up to 60k btus is likely not a bad idea.Name:  Screen Shot 2019-10-11 at 8.34.11 AM.jpg
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