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Very efficient boiler(heat king)

george_42 Member Posts: 98
Years ago a good friend of mine used to make boilers in his shop.They were smaller but very similar to bethlehem dynatherm,in that they were horizontal tube multipass boiles with water jacket over most of the boiler.They would run 180 to 200 degrees but the stack temp was only about 230 t0 250 degrees. I Put one in my home replacing a weil mcclaine cast iron . The cast iron would use about 1600 gal of oil per heating season and the heat king cut that down to about 1000 per season.I ran that for about 10 years till I sold that home and that was 20 years ago. I don1t know if it is still there or not. I have alwas said the true rating on a boiler can only be checked with stack temp as they all have about the same temp going into them at the burner.


  • Big Ed_4
    Big Ed_4 Member Posts: 1,779
    The problem with stack temperatures falling below 350-400 the flue gasses will condense which causes other problems ..
    I have enough experience to know , that I dont know it all
  • hot_rod
    hot_rod Member Posts: 15,066
    The efficiency would be the number of gallons of oil burned, based against the number of BTUs out the other end :)
    Stack temperature, even a combustion analysis only tells you burn efficiency, not fire to actual heat output.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • george_42
    george_42 Member Posts: 98
    dropping my oil consumption from 1600 gal to 100 gal over ten year period is a good measure also
    EBEBRATT-Ed Member Posts: 10,371
    Rule of thumb is the stack temp must be 100 degrees over the boiler water (or steam temp)
  • Zman
    Zman Member Posts: 7,009
    edited December 2020
    I think this speaks more to how inefficient the old boiler was. The boiler that used 1,000 gallons was, at best, 88% efficient. That would make the original boiler approx. 55% efficient given the same heating load. That's not out of the question for an oversized, poorly tuned boiler
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SuperTech
    SuperTech Member Posts: 1,691
    I would be really concerned about condensation in the chimney, if there is one, from such low stack temperature.  Is this boiler vented through a traditional chimney or is it using a sidewall power venter?
  • george_42
    george_42 Member Posts: 98
    It was in conventional chimney with induced draft, never had condensation problems in the 10 years or so I lived there