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solarbeam Member Posts: 7
My solar collector can collect an  an average of 150,000 to 200,000 btus a day,with 160F- 180F water. This hot water is stored in a 360 gallon tank. What is the best location to inject this hot water into my oil fired boiler, which has a 80 gallon storage tank of its own? I was going to inject the hot water into the boiler system return manifold, and was wondering where the return to the solar tank should come from? I am installing a circulator pump to move this water, and an aquastat to only allow solar injection above a set temperature.


  • hot_rod
    hot_rod Member Posts: 20,725
    depends on your piping

    if possible do not run the solar heated water thru the boiler. It just becomes a cooling tower and you lose some thermal energy to stack and jacket loss. If your boiler has a tankless coil for DHW, you may need to keep it warmed with solar?

    Either inject the solar directly to the load or the additional storage tank. Depending on your heating distribution temperature requirements, you may need to mix the temperature down, like for radiant floors.

    Here is one conceptual drawing, that used 3 way zone valves to divert the energy to different tanks and loads.

    Also a link to a idronics that has a few other piping and control options.


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • solarbeam
    solarbeam Member Posts: 7

    If you have 180F solar heated water available, and your boiler is set to 150F, why not inject any solar heated water in excess of 150F into the boiler returns? I was only asking is it better to inject in the returns or supply?
  • Simply Rad
    Simply Rad Member Posts: 176
    Solar injection

    I think in order to get the most of of solar you need to utilize the lowest temperatures.  I think the best injection location is on the radiant return on the load side of the hydronic separator.  These are the lowest temperatures in the system and therefore you are getting the most out of the solar harvest.    
    Jeffrey Campbell
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