Getting ready to upgrade

UPmqt Posted By UPmqt, Oct 8, 2018 at 11:28 AM

  1. Highbeam

    Highbeam
    Minister of Fire 2.
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    Dec 28, 2006
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    As treehouse used it, batch burning a pellet boiler just means running the boiler at high output (or most efficient output) level constantly to reheat his storage. Then shutting off until the storage cools. That is different than modulating pellet boiler output to try and match the heat load which varies and is less efficient.
     
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  2. Sparky978

    Sparky978
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    Jan 18, 2015
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    So how does he run his PB at 100% output constantly? I would think that it would start to modulate at some point. Unless he actually watches it and when it starts to modulate he sends it into burn out mode.
     
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  3. maple1

    maple1
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    Sep 15, 2011
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    'Then shutting off until the storage cools'
     
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  4. nhtreehouse

    nhtreehouse
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    Feb 11, 2017
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    Hi @Sparky978 ,

    I have the Windhager set to maximum boiler setpoint, which I believe is 176::F. I have a conventional Thermovar, a LK823 setup, much like you would setup any wood boiler hooked up to storage. Plumbing is really straightforward. I've got mine piped with 1" copper, and run an alpha on the lowest constant speed setting. Mine runs about 7 gpm at 14 degrees ::DTT.

    I turn on the pellet boiler when the top of the tank reaches close to the ODR target, which obviously fluctuates with the outdoor temp. Once the boiler fires, I keep it on until the return temperature of the pellet boiler reaches 160::F.

    The boiler's output temperature isn't the 176 number but rather determined by the flow rate and the regulating temperature of the Thermovar. I see the Windhager settle in at around 160-162 for a burn. Towards the end of the burn, the boiler temp does rise as the return temperature rises. But it happens quickly, as the boiler is putting energy into your storage and moving the thermocline down.

    I've got a 150 (15kW or 51kBTU/hr) unit and about 120 gallons of storage. My run times are around 2.5 hours on average.

    I don't know if a image would be helpful or not, here is the last complete burn:

    upload_2019-3-10_14-9-22.png

    bT = boiler temp (ya know, the hot side)
    LKAB = Boiler Return (ya know, the cold side)
    LKA = The "A" port on the LK valve, coming from the bottom of storage.
    pBR = crappy beer, or if you're a hipster, it's the pellet boiler return. This sensor is over in the tank several feet of piping away.

    The system which logs the data only logs when the boiler is being called to heat the tank. Those extraneous lines are the graphing software trying to connect the dots from the last full burn to the next.

    Anyways, it works really well. Super reliable and I've had no issues with it. In the biomass sticky there are some control systems like this described. I'm certainly not the first to do this.
     
  5. nhtreehouse

    nhtreehouse
    Member 2.
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    Feb 11, 2017
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    Loc:
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    Oh, and I should have said ... because the boiler never reaches the setpoint, it runs wide open at 100%. It may modulate a little at the very end of the burn as the return temp increases, and the thermovar opens. But if it does, it only modulates for a few minutes as that pellet boiler return temp is really moving fast.
     
  6. Sparky978

    Sparky978
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    Jan 18, 2015
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    Thank you
    Now I have a better understanding of how your system works. Very helpful.
     
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