radiant heating from a buffer tank

Discussion in 'Radiant Heating and Cooling' started by englishjd, Apr 15, 2014.

  1. englishjd

    englishjd New Member

    i recently installed a 5 ton bosch water to air geothermal system with a desuperheater hooked up to a buffer tank. i was wondering if it would be possible to hook up a completely separate radiant floor heating system that would only circulate thru the buffer tank. my idea was to use an aquastat or something similar to not allow the pump to kick on if the buffer tank temp is too low so that i would only be supplementing with the radiant floor heating when the buffer tank is warm enough to help out. I would only have two zones for the radiant which would prob be around 650 sq. ft to circulate thru. Would this set up be possible or would the radiant system lower the buffer tank temp to low too quickly such that the system would never run? Also what sort of buffer tank temps would i need to notice any difference when using the radiant floor heating? Right now my buffer tank has gotten up to around 100 F the couple of different times i have measured it. thanks
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Edit - I just re-read and believe I misunderstood your layout. It is not a potable system you have your DSH hooked to. So yes, maybe. Just kind of a low but output for the costs.

    Original reply left for context:

    TLDR - not much point.

    IFF you have a heat exchanger separating the potable water from your glycol-infused radiant floor water. So now that is two pumps required. Or a new indirect tank.

    And, having gone to battle (as the guy signing off on a similar situation) with a client despite my warnings about:
    - no control over radiant temperatures
    - growth in potable water
    - stagnant potable water
    - not enough capacity
    - etc.

    The only code, for my area, that actually could stop this from happening is one related to "dual-usage water heaters" being required for this output. So basically the manufacturer needs to state the equipment can be used for both purposes. That is in my region though (Canada).
    Last edited: Apr 15, 2014
  3. englishjd

    englishjd New Member

    what i have right now is a standard water to air geothermal with a 50 gallon buffer tank hooked up to my hot water heater. what i was wondering is if the buffer tank reached a certain temp say 100 F, i could turn on a seperate pump during the winter time (central illinois) and run it thru a completely seperate system for radiant floor heating, so that the geothermal could still operate as normal but whenever it heated up the buffer tank, it would allow the radiant floor heating to be able to kick on. the water would run out of the buffer tank thru a loop under the floor and then back to the buffer tank, so that all i am really doing is circulating the water in the buffer tank. but i am worried that my buffer tank would cool to fast to ever really see any pay back for hooking up this kind of system, because it is only heated by the desuperheater. hopefully i have cleared things up a little.
  4. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Your DSH has perhaps 5KBTU to offer through DSH. What is the load of the two rooms? Is there even enough? Will it truly have an impact on your space heating that out weighs the penalty to your DHW cost?
    As Chris points out, I wouldn't do it without a seperate heat exchanger to keep potable water safe.
  5. TeggyBrandon

    TeggyBrandon New Member

    I design with buffer tanks often. First off it help reduce short cycling of a boiler when the system is multi, and possibly micro zoned. Keep in mind only on a design day will a properly sized boiler run long, or possibly non stop. Mild days or shoulder seasons may present small loads on a boiler. This can, and often does, lead to short in efficient boiler cycles. Sometimes bring on condensation issues in the flue piping system, along the way. Another advantage is the ability to store your recently converted thermal BTUs in a well insulated "thermos bottle" as opposed to a often thinly insulated boiler HX. Use a modern well insulate tank with very low standby loss to harbor those BTU's until they are called to duty. There are times when I use buffer tanks even on modulating burner heat sources. https://www.homeair.org/best-radiant-floor-heaters/ has great and informational reviews about radiant heating system .
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    When is resurrected this 3 1/2 year old thread, did you realize they were talking about a buffer tank for a desuperheater setup? Anyway, welcome to the forum!

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