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Bypass . . . design & function questions

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by ISeeDeadBTUs, Nov 21, 2011.

  1. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    The RMND (Seton-clones) do NOT have a bypass designed in, or at least my GW doesn't. I am currently working on a redesign and want to incorporate a bypass. I am curious how yours are designed, and how you operate them.

    I envision the redesigned unit to completely bypass the HX when:

    1)The load door is open,and
    2)During idling aka the damper is closed

    Jimbo

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  2. Singed Eyebrows

    Singed Eyebrows New Member

    Joined:
    Jan 22, 2009
    Messages:
    1,420
    Loc:
    Midwest
    ISDBTU'S, I would keep the bypass opening at the very top of the chamber & as your boiler is natural draft I'd make the opening somewhere around 5"(My Atmos is about 3 1/2", induced fan though). I'm not sure how you will completely bypass the exchanger as an opening in back of it will still allow hot flue gas to go through at least the top. Unless you go through the side of the unit & the "wall" blocks the exchanger, I forgot the exact layout of the Seton. // My Atmos has a cast iron disc with an integral cast arm that is connected to a push/pull rod that goes to the front of the boiler, Randy
  3. PassionForFire&Water

    PassionForFire&Water Minister of Fire

    Joined:
    Jan 14, 2011
    Messages:
    570
    Loc:
    Billerica, MA
    You need a bypass during startup, to minimize condensation.
    it takes about 30 to 60 minutes to bring them up to temperature and in steady state mode,meaning flue gas temps are minimum 250 but mostly around 280 to 350F
    If you can not bypass the HX you will build up creosote with every cold start and if you don't burn continuosly at the end of every burn, when your temp drops below 250F
    You are basically quenching the fire below 250F
    Key is having a very clean combustion before the gasses hit the HX

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