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Geo-thermal control idea's

Paul Rohrs_5
Paul Rohrs_5 Member Posts: 134
for the primary loop.

Steve & Brad,
Thanks for the advice, I think I will have him re-pipe the AHU directly off of the primary and I will suggest repiping the secondary RFH zones via a mix valve or if budget allows, proportional or injection mixing.



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  • Paul Rohrs_5
    Paul Rohrs_5 Member Posts: 134
    2nd set of eyes

    A salesmen at the supply house installed his own geo-thermal (closed loop) system and is running two zones of radiant floor heat and 1 zone of radiant with a hydro-coil. In summer, the fan coil will also be cooled with the geo.

    The salesman asked me how I would control it. Well, it's already piped. Ideally, I still would have given him a reset mix temp to the radiant heat zones and maybe used a tekmar 150 setpoint control to control the buffer tank via a differential. With the current piping set-up, and economy in mind, this is what I came up with.

    Any other ideas out there to incorporate all of the above?



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  • Brad White_63
    Brad White_63 Member Posts: 24

    What is the common temperature and is the air handler more than capable of using it? Thinking that maybe the air handler coil can tolerate an overall cooler water and still work while being sufficient for the RFH. Of course the RFH might overheat a tad as you suggest and a mix-down for the RFH is in order.

    Sort of nibbling at the edges, pushing the envelope (and running out of metaphors, apparently) but seeking the finite capability of the AHU coil (which defines your high temperature requirement) balanced with what might work at the RFH level also.

    If there is still a wide disparity, I see a mix-down as being the only practical solution.

    My $0.02

  • S Ebels
    S Ebels Member Posts: 2,322
    You could experiment

    Take the loop going to the AHU and make it primary secondary, dumping back into the primary side ahead of the RFH loops. Provided the AHU is running, the supply temp would be dropped going to the floor heat circuits. It would be relatively inexpensive to try it and fun to see how well it works. Other than that, you're going to have to mix the RFH side down via an injection loop or a mix valve.

    Let me guess....either he thought he knew everything because he is the salesman or else he was trying to save money......At least his mistake is above the floor so it can be fixed.
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    2nd and 3rd zones...

    As long as the floor tubing is sized properly, I like the A/H being first on its own set of tees and mixing down the 2nd two. This looks like a good setup for a couple of Taco iradiant 3 ways.

    The cost is minimal and like Steve said...all the pipings already there.(hopefully easily accessable). Let us know what you decide to do. Chris
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