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Open/closed system

I have a outdoor wood boiler which is an open system going to a new shop with infloor heat. It will be separated by a water to water heat exchanger because of elevation difference. There is a pump on the load side to move the water around but wasn't sure if I would need an expansion tank as well?


  • hot_rod
    hot_rod Member Posts: 21,858
    On the closed loop, pressurized side you will
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • fatalbert1
    fatalbert1 Member Posts: 3
    If an expansion tank isn't connected would the water temp and pressure build up from the pump cause a leak?
  • Jamie Hall
    Jamie Hall Member Posts: 22,918
    If you are speaking of the closed side -- the side with the infloor heat, I presume, it's not the pump that's your problem. In a closed system, the water will try to expand as it warms up. Unless that expansion has someplace to go -- an expansion tank, perhaps, or in an open system a vented tank -- the pressures resulting from the expansion can be amazingly high. If you have a pressure relief valve, hopefully it will open before you have a problem. Otherwise, the system will fail -- catastrophically -- at the weakest point in the pipe or fittings.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,726
    hot_rod said:

    On the closed loop, pressurized side you will

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