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Boiler size

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daileyhome
daileyhome Member Posts: 3
in Gas Heating
I am replacing boiler in 50 year old classic 2 story colonial home suburban Philadelphia. baseboard. total square ft 3200. old boiler installed 1981 is 166K BTU. My heat loss calculations are coming up with about 90K. this is consistent with my reading that most homes have over sized boilers but I'm hesitant to accept my calculation. Is 90K in the ballpark for my house as described?

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  • Leon82
    Leon82 Member Posts: 684
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    How did you calculate it? The slant fin app can be 15 to 20 percent over the actual.
  • EzzyT
    EzzyT Member Posts: 1,295
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    We replaced a boiler a couple of months ago with about the same square footage and that heatloss came out to be 63,000 BTU's and that was using the slant/fin app.
    E-Travis Mechanical LLC
    Etravismechanical@gmail.com
    201-887-8856
  • SWEI
    SWEI Member Posts: 7,356
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    28 BTUs per square foot. Entirely possible with 2x4 walls and single pane aluminum sliders. Slab on grade?
  • John Mills_5
    John Mills_5 Member Posts: 951
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    How many feet of baseboard?
  • daileyhome
    daileyhome Member Posts: 3
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    240 ft of baseboard. Craw space. I caclculated using instructions on Weil McLain site and then a spreadsheet model from another results were close.
  • Zman
    Zman Member Posts: 7,569
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    daileyhome said:

    I am replacing boiler in 50 year old classic 2 story colonial home suburban Philadelphia. baseboard. total square ft 3200. old boiler installed 1981 is 166K BTU. My heat loss calculations are coming up with about 90K. this is consistent with my reading that most homes have over sized boilers but I'm hesitant to accept my calculation. Is 90K in the ballpark for my house as described?

    You certainly are in the ballpark. Perhaps a little high.
    It is great that you have so many feet of radiator.
    You only need to get 375 BTU/ft out of the baseboards which means you only have to run about 150 degree water on the coldest day.
    A Mod/com boiler with outdoor reset would be ideal for you.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    SWEIHatterasguy
  • daileyhome
    daileyhome Member Posts: 3
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    thanks much for advice and recommendation. i'm thinking simple old fashion cast iron. avoid extra cost and complex maintenance and repairs. initially considering Weil Mclain CGa 7 based on old boiler but calculations are telling me go down to as low as CGa 5. Appreciate any further thoughts and comments.
  • SWEI
    SWEI Member Posts: 7,356
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    Outdoor reset will make a big difference in both comfort and efficiency. If it were my job, and you insisted on a CI boiler, and assuming the heat loss figure was actually correct, I'd spec a CGa-4 with a 4-way Taco iSeries-R valve. It's quite probable the heat loss is less than that, or could easily be made so with some simple envelope upgrades. CGa-3 then.
    Rich_49
  • Rich_49
    Rich_49 Member Posts: 2,766
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    All Mod Cons do not require complex annual maintenance and don't cost all that much more . This was made for homes just like yours . Later when you need a water heater also you can fit a 40 plate heat exchanger and one circ and be done .

    http://www.htproducts.com/pioneer.html
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833

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