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High Efficiency Steam Boilers

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Polycarp
Polycarp Member Posts: 135
I'm trying to get a handle on the efficiency levels that are available for steam boilers.  I know that steam boilers typically come in at lower numbers than the high-efficiency hot water boilers since a condensing unit really doesn't do them much good.  So, what would be considered a "high efficiency" steam boiler?  Would you find a difference below 300 kBtu/h as opposed to above 300 kBtu/h?  Would you find a difference between gas and oil?



Thanks in advance

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  • Steamhead
    Steamhead Member Posts: 16,935
    edited May 2010
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    The most efficient residential steamer

    is the Burnham MegaSteam. Presently it's only offered as an oil-fired unit, though Burnham knows we want a gas version too.



    For gas, the Smith G8 or Slant/Fin Intrepid are the boilers to have. These can be fitted with oil or power gas burners.



    Most people only look at AFUE ratings, but a boiler's thermal efficiency (BTU in to BTU out) is just as important. For example, a certain atmospheric gas steam boiler has an input of 112,500 BTU per hour and a DOE output of 90,000, and a Net rating of 281 square feet EDR. Its DOE is 80% of its input. The Smith G8 has an input of 105,000 and a DOE of 91,000, so its DOE is 86% of its input. Its Net rating is 283 square feet. So even if they both had the same AFUE, the Smith is more efficient because it uses less gas to support slightly more radiation.



    Not surprisingly, gas utilities love the above-mentioned atmospheric boiler.



    In larger sizes, features such as power gas burners and variable firing are big energy savers.



    Tell us more about your project and we can be more specific.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Dave in QCA
    Dave in QCA Member Posts: 1,787
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    Most efficient small commerical Steam Boiler

    Steamhead,

    I'd like to know your thoughts regarding efficiency and life cycle cost on gas fired steam boilers in the 500-700 MBTU range.  I notice that Weil-Mclain has a Model 88 that boasts 85.6% thermal efficiency.  I wonder about its initial cost and reliability comparied to atmopheric boilers, and whether in the long run, it is a money saver. 

    Are there other boilers out there that are comparable to this model?

    I look forward to your insight.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • ttekushan_3
    ttekushan_3 Member Posts: 960
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    Large scale steamers

    I'd also like your take on the Smith 28HE. Its numbers are in the 85% range. I've gotten quite a bit of positive feedback about these.
    terry
  • Steamhead
    Steamhead Member Posts: 16,935
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    Our experience with W-M 88 boilers

    is limited to servicing them- they seem to do as well as anything out there efficiency-wise. We have installed the smaller 80 series on larger residential Vapor systems, and they work well.



    I'd stay away from the Smith 28, or 28A, or 28HE or whatever they're calling it this year. That series has had problems with leaking sections. I don't really know why this is, since the Smith 19 series appears well-made (at least the ones we've seen, we haven't seen many in this area) as well as their 8 series units which we install on residential gas-fired steam as the "G-8".  But there it is.



    90%+ efficiency has been done on steam, but not in this country. Amazing, isn't it?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
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