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Firing rate confusion

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Hey, all the numbers work now..

Thanks Ken. Looks like I have 102,844 BTU available at 82.5% efficiency. Which nicely covers my 95,677 BTU needs (radiation + 1.33 pickup).

jim

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  • Jim Franklin
    Jim Franklin Member Posts: 170
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    I have a Dunkirk 3ES1.35 which has an input of 189,000, output 156,000 BTU at 1.35 gph. If oil has 190,000 BTU/gal, why isn't the firing rate close to 1 gph?

    The current nozzle in there is a .75, but running at 140 psi, so do I really have 1.4 * .75 = 1.05 gph firing rate? If so, how do I calc the BTUs available to me?

    My oil co was out today looking at my poorly piped header and their conclusion for the slow heating was that I'm way underfired. I have 299' of radiation and this system is rated for 488 at that 1.35 gph, so I need to find out how close I am with the current firing rate.

    thanks,
    jim
  • maine ken_4
    maine ken_4 Member Posts: 2
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    oil only has roughly 140k btu per gallon.

    .75 @ 140psi = .89gph @ 140k btu per gallon = firing rate of 124,600 btu/hr.
  • Steamhead (in transit)
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  • Jim Franklin
    Jim Franklin Member Posts: 170
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    Insulated, not yet, working on the header rebuild. I know that's attributing significantly to the slow progression to the mains.

    Venting - I think so. 1.4 cf of mains into 2 Gorton #1s is plenty by my numbers. Would you agree?

    jim
  • Steamhead (in transit)
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    At 3 ounces

    that would work fine. You can always add more if needed. Lately I've been sizing main vents at 1 ounce though, it affords more of a differential between venting the mains and venting the radiators.

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  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
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    Efficiency not 82%

    Sold Dunkirk and I do not believe that boiler is designed to operate that low of input at all. Regardless, you will be lucky to be operating at 50% efficiency at that firing rate. Forget the 82% because the actual firing efficiency of oil can only reach about 74% to 75% if fired perfectly which would be about 4% O2 or 12% CO2.
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