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    Boiler Correct Size (26 Posts)

  • thumbiman thumbiman @ 7:11 PM
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    Boiler Correct Size

    Hi Guys,

    New to the forum. I have a question. I have a 1400 square foot ranch home with an additional 800 square foot finished basement. My plumber recently installed a 175,000 BTU burnham hot water boiler for my home. I think he may have put in an way oversized boiler. Can you tell me what you may think might be the average size for my home? I have all brand new windows and recently re-sided my home with insulation and wrapping. Thanks...
  • Steve Whitbeck Steve Whitbeck @ 7:34 PM
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    boiler size

    It all depends on everything - the amount of windows, doors, insulation R values. age of house, updates to all of the above.
    If this was an average 20 - 30 year old house I would think 100,000 should be plenty. 80,000 could even be enough in a lot of cases.
    Nothing against plumbers but if they don't specialize in hydronics  they shouldn't be installing boilers.
  • BarryNY BarryNY @ 7:35 PM
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    do a heat loss calc...

    I'm NO expert but just went through a new install myself. Did a lot of research and got smart fast. You should do a heat loss calc - there is a cool one you can use with a smart phone from slant fin.
    You are definitely over sized. I have a 2,700 sq ft ranch with a 1,000 sq ft finished bsmt (but i keep the bsmt at 60 degrees). I just got a Buderus WS-4 which some may say is over sized for me at 95,000 net btu but I bought it to accommodate a potential 600 sq ft upstairs addition. i came off a 1984 125k weil mclain. you should bring that installer back and have it swapped out.
  • Aaron_in_Maine Aaron_in_Maine @ 7:50 PM
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    Way to big

    That is way to big. I have a 1975 cape 2x4 construction 1300sqft. In Maine and my heat loss is 48,000btu. Get that installer back before it's too late.
  • Steve Whitbeck Steve Whitbeck @ 7:54 PM
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    Is it also heating your domestic hot water for baths and showers?
  • thumbiman thumbiman @ 10:41 PM
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    My boiler has a separate zone for an indirect
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    no one can say for sure without an accurate heat loss calculation but your boiler is probably double the size it needs to be.
  • R Mannino R Mannino @ 9:59 PM
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    you don't know what your talking me!
  • Chris Chris @ 10:07 PM
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    Way Over Sized

    I have 1800 sqft. 1968 construction, R11 Walls, updated windows. Design for 0 degrees. Heat Loss is just a tad over 36,000...Been doing heat losses and designs for 25 years and if your home had that bad of an infiltration rate you have bigger problems then an over sized boiler.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • R Mannino R Mannino @ 10:11 PM
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    I'd Say Your

    wrong Chris, but then I might not know what I was talking about.
    Thanks for backing me up Chris! You can email me too!
  • JohnNY JohnNY @ 10:23 PM
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    Way too big...

    ...unless the house is actually a flea market tent.

    I'm not a big fan of rules-of-thumb, but here in my part of the country, NYC, heat loss generally works out to be about 30-35 BTUs per square foot of living space.

    In Manhattan and much of Brooklyn, where typical homes are attached on two sides, that heat loss often comes out to about 19-25 BTUs per square foot.

    Another rule of thumb is *cubic* footage times 4.

    So, If we assume you've got 9.5' ceiling heights in your 1400 square foot home, we get 1400 x 9.5 x 4 = 53,200 BTUs output.

    35 BTUs x 1400 = 49,000 BTUs.

    So, again, unless your home's heat loss is equivalent to a single-ply burlap tent, or you live in the North Pole, your boiler is way oversized.
  • Gordy Gordy @ 10:36 PM
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    To many unknowns

    To make assumptions based on the information provided. OP might live in an area with a -30 design day with a home that's like a submarine with screen doors, new windows or not new siding house wrap or not. 2200 sf heated space or not. Maybe has an indirect with high demand, or an HX heating a pool.
    This post was edited by an admin on January 19, 2014 10:40 PM.
  • thumbiman thumbiman @ 10:41 PM
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    I do have a separate zone for an indirect
  • thumbiman thumbiman @ 11:00 PM
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    Recommendation for a Heat Loss Person

    Looking for a good plumber to come over to do a heat loss. Live on Long Island. Any recommendation or contacts? Thanks guys...
  • R Mannino R Mannino @ 7:51 AM
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  • thumbiman thumbiman @ 4:12 PM
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    How much extra for a 40 gal indirect


    How much extra BTUs would you guess for a 40 gallon indirect? Thx...
  • Robert O'Brien Robert O'Brien @ 4:18 PM
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    The answer to that would be zero
  • Add on for indirect.

    I think most of the professionals on The Wall agree that you don't add anything to the boiler sizing for an indirect.  I don't.
    Often wrong, never in doubt.
  • Steve Whitbeck Steve Whitbeck @ 6:44 PM
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    It all depends on how the indirect is piped and wired in.
    If it is a zone but doesn't have priority then You will need at least 40,000 extra BTU's
    If it is wired and piped with priority then no extra BTU's are needed ( how I do it )
    R Mannino - If you are the installer then explain why You installed such a huge boiler.
    I have a HTP 199,000 heating a 8000 square foot 2 story house and it does indirect also.
  • Le John Le John @ 2:37 PM
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    Holy Molly..... 8000 square feet

    I'd love to see the boiler room of that house.
    This post was edited by an admin on January 22, 2014 2:38 PM.
  • R Mannino R Mannino @ 6:58 PM
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    I Don't Think

    I ever installed a boiler that large ever.

    The OP is located on Long Island I seriously doubt his heat loss is above 50,000 BTU/ HR on a design day.
  • Steve Whitbeck Steve Whitbeck @ 7:46 PM
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    R Mannino

    WOW - that is a small one for me.
    I do commercial also. ( A LOT of church's )
    I tend to remove one BIG boiler and install multiple smaller ( 399,000) boilers staged together.
    Lowest savings I have seen is 33%
    Highest was 66%
  • SWEI SWEI @ 1:30 PM
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    Multiple 399's

    Never worked NY, but in most jurisdictions anything over 400k puts you in a different box for licensing, inspections, and safeties.  The combination of that plus the staging and redundancy usually makes multiple 399's a slam dunk.
  • R Mannino R Mannino @ 7:58 PM
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    I'm A Residential

    guy, most homes we do range between 1500 and 3000 sq. ft.. We usually pull out an old oversized clunker and install the smallest oil boiler we can get our hands on. Our customers report a savings of around 25 to 30 percent usually, sometimes more.
  • Steve Whitbeck Steve Whitbeck @ 10:03 PM
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    Don't pass up the bigger job when it comes your way

    Makes you feel good to know that You did a good thing for the customer.
  • Steve Whitbeck Steve Whitbeck @ 10:03 PM
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    double post

    This post was edited by an admin on January 20, 2014 10:04 PM.
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