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    A Mid(co) Summer Night's Dream (8 Posts)

  • MarkS MarkS @ 10:51 PM
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    A Mid(co) Summer Night's Dream

    It's been a few months since we converted to gas and installed the Midco LNB-500 modulating burner, and I wanted to provide an update. When the Steam Odyssey 2 thread ended in April, the system was performing well except for high stack temperatures. Over 40 or so spring heating cycles, the modulating controls did a good job of controlling the burner to maintain a steam pressure setpoint at the boiler, even though the controlling voltage was at the low end of the range (max 2.8 volts on a full scale of 2-10 volts). The burner has seen light duty over the summer producing DHW.

    In an attempt to mitigate the stack temperatures, the folks at Midco developed a new LNB-250 burner head that's rated for 50-250 MBH. The development rep and an engineer from Midco came out in mid-August to install and test the new head, which uses the same blower, valve train, and controls as the LNB-500. If nothing else the new head is better matched to the boiler's rating of 245 MBH. The new head is shorter (14" vs 28"), with the burner mesh centered in the firebox and has a smaller orifice plate at the inlet than the LNB-500.

    We ran tests with the firebox insulation installed, and another set of tests with it removed. While we unfortunately did not see a large drop in stack temperatures, removing the insulation did yield a 30 to 50 degF reduction in stack temps. At high fire we're seeing 800-850 degF at the boiler and 500-550 degF a foot from the chimney, so I'll be replacing the galvanized vent pipe between the boiler and chimney with something that's rated for 1000 degF continuous before the heating season sets in.

    Over the summer I added a few new features to the EcoSteam modulating controls. Each of the DHW, Preheat, and Heat On cycles now has an individual set of configurable parameters that define how the boiler is controlled during that cycle. The parameters include the initial output voltage, control strategy (fixed output voltage, pressure control, stack temp control), a control delay time, and setpoints for the steam pressure and stack temperature controllers. I've also added a "setpoint control" option in the outdoor reset model so I can bypass the math and simply run until the indoor temp hits the setpoint-minus-anticipator target.

    The website describing the EcoSteam boiler control project in detail has been updated with the recent changes. Here's the link: EcoSteam project
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
    This post was edited by an admin on September 1, 2013 11:00 PM.
  • SWEI SWEI @ 11:36 AM
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    LNB-250

    is really great news!  Fully modulating residential steam!

    I'm somewhat mystified by those stack temps and look forward to seeing what you learn.
  • JStar JStar @ 12:27 PM
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    Midco

    What were the temperatures at the lowest firing rate?
    - Joe Starosielec
    http://thatcherhvac
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    Guaranteed performance. Guaranteed energy savings.


    Serving all of NJ, NYC, Southern NY State, and eastern PA.

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    (Formerly "ecuacool")
  • MarkS MarkS @ 5:39 PM
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    Low fire temps

    At lowest fire (2 volts) I clocked 75 MBH on the gas meter, with temps 400 degF at the boiler and 195 degF at the chimney.
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
  • Steamhead Steamhead @ 7:07 PM
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    How about

    the excess air percentages? Too much excess air can jack up the stack temps. 
    "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.
  • MarkS MarkS @ 5:41 PM
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    Combustion analyzer results

    See attached pic for combustion results; two from the oil burner, then low/high fire on the gas burner. Efficiency numbers aren't great but the emissions are impressive. (I should add that the stack temps I listed in my first post are from a thermocouple, not an analyzer.)
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
    This post was edited by an admin on September 3, 2013 5:41 PM.
  • Steamhead Steamhead @ 10:24 PM
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    Just a thought

    I can usually get excess air down below 25% on an EZ-Gas or EC-200 without CO going up, assuming there are no air leaks into the boiler. Does the CO start rising when you reduce the air below where it is now?
    "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.
  • MarkS MarkS @ 5:22 PM
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    Adjustments

    On this burner the only real adjustment is on the Dungs regulator. I can borrow an analyzer but I'm not comfortable messing with the air/fuel mixture, so it'll have to wait until JStar or the Midco guys are out this way again to try it.
    Homeowner, Royersford PA | 1890 one-pipe steam system | 3009 sf | 3 floors | 14 radiators | Utica SFE5200S boiler
    NEW Midco LNB-250 Modulating Gas Burner | EcoSteam modulating controls | 70 to 300 MBH |
    607 sf EDR connected load | Operating pressure: 0.5 oz/in2
    Four main runs (insulated) totaling 135 ft in length | All Gorton vents on mains & rads |
    A Steam Odyssey | Odyssey 2 | A Steam Enthusiast's Outdoor Reset Control
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