Big BTU vs small BTU ... which in upper, which in lower
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  1. #1
    Join Date
    Feb 2008
    Location
    Buffalo, NY
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    14

    Big BTU vs small BTU ... which in upper, which in lower

    I'm still fighting with an issue, but am looking for a long term resolution.

    In a double (we will be living in both upper and lower) how would you assign one 75K BTU and one 50K BTU furnace? It was 50k on bottom, 75K on top, but I'm thinking that we will not be heating the top all the time, mostly on weekends. It will only need to get to 68F. The 75K seems better suited for the bottom given poor insulation. It's about 1000 sq ft each, gas with hot air.

    Thanks.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,833
    You would do a heat loss calc and size to what the calculations say. Unless there is no insulation or all glass, I doubt 1000 sq ft needs 75K, certainly not the first floor with conditioned space above it.

  3. #3
    Join Date
    Jun 2007
    Location
    Wisconsin
    Posts
    35
    If you already own these units and don't want to do a heat loss calc., it would be logical to think of assigning the first floor the larger of the two regardless of insulation or windows. Heat rises.

  4. #4
    Join Date
    May 2007
    Location
    somewhere between heaven and hell
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    957
    Quote Originally Posted by gulliver View Post
    I'm still fighting with an issue, but am looking for a long term resolution.

    In a double (we will be living in both upper and lower) how would you assign one 75K BTU and one 50K BTU furnace? It was 50k on bottom, 75K on top, but I'm thinking that we will not be heating the top all the time, mostly on weekends. It will only need to get to 68F. The 75K seems better suited for the bottom given poor insulation. It's about 1000 sq ft each, gas with hot air.

    Thanks.
    Curious of what became of your other situation on your return air? Did anyone come out? If so what did they say?

  5. #5
    Join Date
    May 2007
    Location
    somewhere between heaven and hell
    Posts
    957
    I read your other thread sounds like you got nothin resolved. I myself would like to see pics of this but it is not necessary only if you want to.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,627
    At face value. It would make sense that the first floor should have the larger furnace.
    In reality, neither floor may need that size furnace.

    Money may be tight. But, since chances are you will have a hard time finding someone to doa load calc.
    You should do your own. Clink on the hvac calc link, pay the fee and do one.
    Then you'll know if neither or both floors need the larger furnace.
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  7. #7
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    After you move into this place and change two units into one big unit, your whole set of requirements changes. You'll have different air patterns, and a lot more heat being generated by lights, appliances, people, etc.

    You spent a whole day removing the 2nd floor furnace and installing it in the first floor, and that didn't solve your problem. I have to assume that you have no job and no social life. Call a contractor and get it done right, or keep screwing around with it until you get a gas leak, then your problems could be all over.

  8. #8
    Join Date
    Feb 2008
    Location
    Buffalo, NY
    Posts
    14
    Thanks for all the help!!!

    Sorry no pictures ... I love pictures, but I've been working on this as priority-one and don't have time.

    The contractor made matters worse by 10F, and quoted $2k for some easy return runs that anyone can do. I appreciate those who express concern, but I have an engineering background ... and technical job that pays far less than the $88/hr the contractor wanted. I know what I'm doing when I do it ... or I don't do it!

    If the answer for everything was "call a contractor", there would be no need for this forum

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