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Controls for solar hydronic, overheat and freeze protection


I'm having a solar system made by Globe Solar installed(roof mounted integrated tank and evacuated tube) and have a question about controls.  The solar feeds a gas fired tank used for DHW and a hydronic slab, all open direct with no heat exchangers.  Can I use my existing circulator and some combo of controller/valves to circulate the solar lineset for freeze protection and to dump heat to the gas fired tank and slab in the summer?

Thanks for any ideas,



  • hot_rod
    hot_rod Member Posts: 18,268
    known as a ICS

    integrated collector storage. These are very common in warm climates due to freezing concerns. I don't see any data on how much energy is needed to keep them from freezing in cold, severe climates.

    Even with 3-4" of insulation a tank with 120- 140F water will lose a bit of energy when mounted outside in winter time temperatures, maybe below 0F at times in your area?

    The testimonials note they work fine and "didn't even freeze" but no numbers to qualify that. One freeze up and related water damage could offset the cost difference between a glycol or drainback system, perhaps?

    I'd like to see one of those systems datalogged, included the energy needed to prevent freezing, especially if gas or oil fired HW is part of the freeze protection.

    Most all of the electronic Solar controllers have freeze protection settings.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Randy Baerg
    Randy Baerg Member Posts: 26
    solar control

    Yes you can, depending on your piping. You could use a tekmar 157 control to do variable speed through the panel to optimize output and then bring on a Heat Dump pump (piped in parallel) to operate when the tank and panel got too hot. This would be set up in a Mode 3 application.

    There is optional freeze protection but should only be considered for locations where the outdoor air rarely falls below 35°F, otherwise consider glycol or drainback system.

    Check out the Data Brochure D157 and the application brochure A157 for more information on this product. I believe A157 page 4 is  an example. www.tekmarcontrols.com

    You would use standard wet rotor circulators for the two pumps.
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