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Correct boiler sizing

Mothra
Mothra Member Posts: 16
Hi, i'm looking to purchase a high efficiency boiler for my home. I have done some heat loss calculations using the link below. Attached are my heat losses per room/area. The only thing that it doesn't include, is that i'm going to run pex in the basement slab, roughly 2500 sq ft. to heat my basement. My contractor came up with his calculation of 158kbtu/hr, but that seems a little high to me. I'm not trying to say i'm right or he's wrong by any means, i just want to make sure that i'm sizing my boiler correctly, since i will be responsible for purchasing it alone. After doing my research on this site, i'm probably looking at a Lochinvar or TT. The house is in NW Ohio, going through some renovations, but when i'm finished, everything should be spray foamed insulated, at least on the outside walls. Thank you!

http://www.usboiler.net/heat-loss-calculator.html

Comments

  • Ironman
    Ironman Member Posts: 6,555
    There are no dimensions on your drawings, therefore, it's not possible to confirm their accuracy.

    What program did you use? We would also need the construction data for each exposed wall, floor, ceiling, Windows and doors.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mothra
    Mothra Member Posts: 16
    edited September 2017
    Sorry about that! I will work on providing specific room dimensions as soon as i can. I do know that the addition will be 1056, the first floor is 1312, and the upstairs 1192 square feet, respectively. A total of 3560 of area above grade and roughly 2500 below. I had used the usboiler.net website for my room specific calculations in the attached drawings in the first post. Thank you!
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited September 2017
    ^ You never replied to the followup post on the other heating forum where you were offered help:

    https://terrylove.com/forums/index.php?threads/boiler-question.71655/
  • gschallert
    gschallert Member Posts: 170
    NY_Rob said:

    ^ You never replied to the followup post on the other heating forum where you were offered help:

    https://terrylove.com/forums/index.php?threads/boiler-question.71655/

    Perhaps the OP hasn't been back and doesn't know someone finally responded (three days after the OP posted) - even if they were notified of a response via email it might have hit their spam folder. And honestly, does it really matter in this topic on this site since the OP has responded?
  • NY_Rob
    NY_Rob Member Posts: 1,370
    ^ A lot of good advise was offered at the other site, if the OP did no know about now he/she does....
  • Ironman
    Ironman Member Posts: 6,555
    Mothra said:

    Sorry about that! I will work on providing specific room dimensions as soon as i can. I do know that the addition will be 1056, the first floor is 1312, and the upstairs 1192 square feet, respectively. A total of 3560 of area above grade and roughly 2500 below. I had used the usboiler.net website for my room specific calculations in the attached drawings in the first post. Thank you!

    You need to do a SCIENTIFIC load calc based upon ACCA manual J. Those simplified on line calculators are not scientific and always over-size the boiler - often severely.

    SlantFin has a free app that you can download that is reliable.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Rich_49
  • Mothra
    Mothra Member Posts: 16
    Thank you for the comments. i was unaware of the comment on the other site, i responded back. Thank for for the advice on the Manual J. I went through cool calc, i'm just waiting on an email verification before i can get started there.
  • Mothra
    Mothra Member Posts: 16
    I used the slant-fin app and it came back at a design temp of 70 degrees to need roughly 93kBTU/hr... which is way under what my contractor said. I didn't take into account the hallway and stairwell space, as well as the basement. I have read that sometimes you multiply this number by 1.4, for a conservative approach. Should i do this and run with that final btu/hr number?

    Thanks!


  • Ironman
    Ironman Member Posts: 6,555
    No, I'd run the basement through the app and see what you get.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    GordyCanucker