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Oil to Gas Conversion Efficiency

NumptyNumpty Member Posts: 3
Hi All,

We've just had our oil boiler converted to gas (Wayne P265F Combustion burner) and the efficiency of the boiler has now dropped from 82/83% to 78.7%. My understanding is that the efficiency should stay the same or possibly even increase. I am wrong about this and, if not, where does the fault for this drop in efficiency lie - the burner, the boiler (5 years old) or the person doing the install.

Any help would be gratefully appreciated.

Many thanks,



  • SteamheadSteamhead Member Posts: 11,373
    What make and model

    is the boiler?
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • NumptyNumpty Member Posts: 3
    Oil to Gas Conversion Efficiency

    A Columbia - although it's been suggested that it's a rebranded Utica. Only 5 or so years old (installed by the previous owner). 
  • Jamie HallJamie Hall Member Posts: 6,693
    Your 82 to 83 on oil was pretty good...

    pity the gas isn't up there.  It could be several things, but the places I would look first would be how accurately the new burner is matched to the boiler (BTU input, flame geometry, all that) and how well the new burner has been set up.

    Both of which really go back to the installer.

    But I suspect that if the old oil burner was reasonably well matched to the boiler, and set up properly, you may have trouble getting much better than what it was doing.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 2,470

    look up the efficiency of a new boiler fired on gas and fired on oil. you will find the gas efficiency is always a few percent lower.

    gas has water vapor that lowers its efficiency and its always lower than oil unless we are talking about a condensing application.

    you can have a lower cost fuel at  a lower efficiency or a higher cost fuel at increased efficiency.....but not both. your talking 4%-5%. Maybe the gas burner could be adjusted better or the firing rate adjusted to close the gap a little bit
  • JStarJStar Member Posts: 2,668

    Did they clean the boiler? Install the proper draft control? What were the combustion results?
    - Joe Starosielec
    [email protected]
  • rich11cooprich11coop Member Posts: 25

    You loose a couple of % points in efficiency BUT what is the % difference in the fuels being used?
  • FizzFizz Member Posts: 339
    Jamie is absolutely right!

    I converted a WM SGO6 in Dec 2011, using a Wayne P250AF.  According to the conversionc chart in the Wayne manual converstion was based on size of nozzle, which in the SGO6 was 1.75 GPH, and called for a firing rate of the gas gun of 140K BTU/gal of out-put which equated to 245K BTU/hr.  Now, our boiler is oversized for our connected load of 500 sf of edr as it is rated at so we originally fired to the connected load at about 157K, but the heat was slow in coming and not efficient.  So I looked at the WM SGO 5 the model below SGO6 and more closely rated to our connected load. It was rated for 542 SF of steam vs the SGO 6 rated at 654 SF; I then converted the nozzle rating of the SGO5 of  1.45GPH to BTU using the Wayne 140K multiplier and came up with 203K BTU rating.  Next I divided the 542 by 500(our connected load) and came with a 1.084 factor and divided it into 203K firing rate for the SGO5.  The result was a firing rate of 187K.  My installer re-drilled orifice to 186K.  By dumb-luck it's a perfect match.  We keep out thermostat at 72, and house is comfortably warm, and just got heating bill for last month, one of coldest in yrs, and bill was $371 vs old oil bill of 700-800!!!  What I"m saying is see what your boiler is rated, the size of nozzle and what Wayne reccommends, then do the math.  Good luck!
  • SteamheadSteamhead Member Posts: 11,373
    Which Columbia is it

    a CSFH/CSFE model?

    If so, that Wayne burner is not a good match for that boiler. It's not a flame-retention burner and cannot develop the static air pressure needed to fire these boilers.

    We've converted several of these with the Carlin EZ-Gas burner and we get combustion efficiencies in the 82-84% range.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • NumptyNumpty Member Posts: 3
    CSFE model

    Therefore, is the issue the combustion burner (the Wayne has a range of 65-200,000 BTUs rather than the 50-250,000 range of the Carlin) or the way it's been installed?

    If it's the former, I guess there's not much that can be done now; however, if it's the latter, can anything be done i.e. should I ask the person who installed it to come back and make some changes to improve the efficiency if possible?

    That said, the responses on this board seem to reflect mixed views, so I'm wondering if the drop in efficiency is not really anything to be overly concerned about. 

  • SteamheadSteamhead Member Posts: 11,373
    edited February 2014
    The issue with the Wayne burner

    is that it does not have the compact, controlled flame pattern of a flame-retention oil or gas burner.

    Back in the days when all we could get were the Midco E-series and the Wayne P-series burners, lower efficiency results were normal in modern smaller boilers since you had to add excess air to keep CO levels down. In a lot of cases the flame would strike the firebox or cast-iron, quenching the flame and causing high CO. Adding more combustion air would help but this reduced efficiency. Also, in some cases the burner fan could not move enough air thru the firing zone on a boiler with tighter flue passages.

    With flame-retention burners like the Carlin EZ-Gas, Midco EC and Riello, this is much less of a problem. So we don't use those Wayne P-series burners- there are much better choices.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
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