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solar loop balancing

I have a solar tube system with a PAW pump station on it is a WILO 3 speed pump and a flow meter, my question is how do I determine the right flow rate to adjust the circulator to correspond to my system? I live in Northern New England with the circ on slowest speed this time of year I don't worry of overheating in the collector but in July maybe different. I am a master plumber.


  • hot rodhot rod Posts: 6,716
    edited March 2014
    what type of collector?

    and what type of controller?

    The collector manufacturer will tell you the required flow rate. It depends on the type and size of the collector and how many in the array.

    Flat plate style collectors generally 1- 1.5 gpm per collector.

    At you can look up your collector, if it was certified. They show the flow rate that they were tested at, to get their output rating.

    Most new controllers have a variable speed function, be sure the pump is running at 100% speed when you adjust the flowrate. Adjust it by first selecting the pump speed on the speed switch, use the balance valve to fine tune it to the appropriate flowrate

    Read the top of the spinning float until it floats to the top, then read the bottom of the float on the opposite scale.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • tube collector

    Thanks for the reply, Apricus AP-30 tube rack with 70 ft of 1/2" copper and 30 ft of 3/4" pump staion piping. I looked up the link you provided and if I read the chart right 1.27 gpm ?
  • hot rodhot rod Posts: 6,716
    From Apricus

    I doubt that you can dial in the flowrate with the meter in that pump station, that accurately, it's a pretty coarse scale.

    Shoot for somewhere between 1 and 1.5 GPM for that 30 tube array and youwill be fine.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Apricus

    Thanks again for the great information
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