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Buffer tank

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I installed a buffer tank to work with a HTP Elite FT boiler. I would like to use all the "stored" heat in the buffer tank before the boiler fires to recover the buffer tank. I spoke with HTP and were no help. I'm sure it could be done, I just can't figure it out. My idea is to have any zone run off the buffer and when tank temp drops below outdoor reset, the boiler will fire and heat the tank up again. Thanks in advance.
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  • hot_rod
    hot_rod Member Posts: 22,144
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    Got a diagram on how you piped it? How large of a tank. What is the heat load of the space? Multiple zones?

    Also will you use an outdoor reset control for the load side?

    This journal has all the data you need to size, pipe and wire systems. There are numerous way to control these systems, I prefer delta T controls that watch the tank and the source temperatures and make the decision.

    Spend the evening reading through it and bring us more info.

    You are headed towards a somewhat complex system to pipe and control depending on you goals and experience.

    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Wellness
    Wellness Member Posts: 141
    edited September 2017
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    As HotRod said, what you are trying to accomplish can be very complex. What complicated things for me was the required outdoor reset, which can trigger a boiler firing before the heated water in the buffer tank is depleted. Another issue is assigning a wide enough thermostat setpoint deadband to cope with the temperature fluctuations of the buffer tank supply water going into the radiators of each space you are trying to heat. As manufacturers automate things by measuring water temps at the boiler output instead of external storage devices like buffer tanks, third-party or aftermarket custom controls become more difficult to deploy effectively.
  • reedevery
    reedevery Member, Email Confirmation Posts: 3
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    I have a Buderus G115B28 oil boiler piped with an 80 gallon buffer tank, Tekmar 256 outdoor reset with probe in the buffer tank. I used a Grundfos Alpha pump and have a mix of baseboard, panel rads and radiant. My differential is set for 20 degrees so I extract all of the heat from the tank before my boiler fires. I used roughly 150-200 gallons of oil each year so far. Very happy with how it works.
    Derheatmeister