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On demand lp boiler paired with outdoor woodstove

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Sasquatch
Sasquatch Member Posts: 7
Hooking up a heat plate exchanger to separate my on demand lp boiler with my pressurized wood boiler. Do i make a break in return line and force the return of lp boiler through the heat echanger? Or do i run one to supply and one to return side? A diagram would be sweet too!

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  • hot_rod
    hot_rod Member Posts: 22,476
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    What is the intention of the heat exchanger, if both heaters are pressurized?
    Tankless heaters are never a good idea as a substitute for a hydronic boiler.
    If piped primary secondary, or into a hydro sep, you can force them to do what the were not designed to do🤭
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Sasquatch
    Sasquatch Member Posts: 7
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    To separate the systems in case of another issue. Had a line blown last winter. Novice with boilers at best.  Just trying to save our family some money and was told heat exchanger and an aqustat is what i need to run properly. my lack of knowledge on boiler systems is funny to you? 
  • hot_rod
    hot_rod Member Posts: 22,476
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    Is the wood boiler outside?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hot_rod
    hot_rod Member Posts: 22,476
    edited December 2022
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    Depending on how the system is currently piped..
    You will end up with two separate systems. So two air purgers, two expansion tanks, two fill systems.

    If the wood boiler is outside, maybe a fill tank is best to avoid dumping a lot of water outside if it freeze and thaws.
    IF it is outside, glycol is an option since you will have a HX isolation.

    When you say LP on demand, makes me think the boiler is a tankless water heater?

    If that is the case I would do a primary secondary with a dedicated pump on that heater, sized correctly for the required flowrate.

    A third pump is the system pump, sized just for the heating load(s)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGross
  • Sasquatch
    Sasquatch Member Posts: 7
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    I can get some pics but its in the shop about 100ft from the house. Guy jerry rigged the system it did work. But on the first warm day stove was too hot and blew apart some pex in the cabin. On demand tankless boiler yes. Baseboard throughout the house
  • Ironman
    Ironman Member Posts: 7,399
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    If it’s an on demand tankless, it’s a water heater, not a boiler. It’s not designed, approved or controlled for space heating.

    As hot rod said, you may get it functional with an oversized pump and p/s piping, but it’s gonna have issues and a shortened life expectancy.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 22,476
    edited December 2022
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    A bit of a learning curve heating with wood boilers. Without a large buffer tank you will probably need a heat dump zone to prevent over heating and blowing Pex connections

    That, or build and maintain the firing carefully, trying to match the wood load to the heat that is required. That takes someone checking the fire throughout the day.



    At the wood boiler location a dump zone could be added to protect from over firing and power outages  that could also cause temperature over shoot.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,956
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    Please share some photos of the system in question along with the models of the boiler/water heater(s).