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Boiler Correct Size

thumbimanthumbiman Member Posts: 8
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 WhitbeckSteve Whitbeck Member Posts: 669
    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.
  • BarryNYBarryNY Member Posts: 12
    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_MaineAaron_in_Maine Member Posts: 313
    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.
    Aaron Hamilton Heating
    [email protected]
  • Steve WhitbeckSteve Whitbeck Member Posts: 669

    Is it also heating your domestic hot water for baths and showers?
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 2,371

    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 ManninoR Mannino Member Posts: 422

    you don't know what your talking me!
  • ChrisChris Member Posts: 3,056
    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 ManninoR Mannino Member Posts: 422
    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!
  • JohnNYJohnNY Member Posts: 1,811
    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.
    For private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • GordyGordy Member Posts: 7,106
    edited January 2014
    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.
  • thumbimanthumbiman Member Posts: 8

    I do have a separate zone for an indirect
  • thumbimanthumbiman Member Posts: 8

    My boiler has a separate zone for an indirect
  • thumbimanthumbiman Member Posts: 8
    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...
  • thumbimanthumbiman Member Posts: 8
    How much extra for a 40 gal indirect


    How much extra BTUs would you guess for a 40 gallon indirect? Thx...
  • Robert O'BrienRobert O'Brien Member Posts: 2,935

    The answer to that would be zero
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • 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 WhitbeckSteve Whitbeck Member Posts: 669

    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.
  • R ManninoR Mannino Member Posts: 422
    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 WhitbeckSteve Whitbeck Member Posts: 669
    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%
  • R ManninoR Mannino Member Posts: 422
    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 WhitbeckSteve Whitbeck Member Posts: 669
    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 WhitbeckSteve Whitbeck Member Posts: 669
    edited January 2014
    double post

  • SWEISWEI Member Posts: 7,356
    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.
  • Le JohnLe John Member Posts: 50
    edited January 2014
    Holy Molly..... 8000 square feet

    I'd love to see the boiler room of that house.
  • SHGradeSHGrade Member Posts: 1
    2,700 sqr foot house, 250,000BTU, our guy says its a commercial unit, way more than we need.
  • ced48ced48 Member Posts: 383
    Way to big!
  • rick in Alaskarick in Alaska Member Posts: 623
    I put in a 175,00 btu boiler in a six plex apartment building that is 70"s vintage and only decent insulation. Oh yeah, also heating a 120 gallon indirect. been working fine now for over 15 years. So yeah, most likely, that boiler is grossly over sized.
    My house is 2400 feet of really well insulation, and if I remember right, was something like 42,000 btu. Also heating 60 gallon indirect.
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