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Gold Line C30 Differential Controller Question

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  • Gold Line C30 Differential Controller Question

    Greetings from Vermont,
    I have two recycled Grumann 4’ x 8’ flat plate collectors with a newly installed recycled Heliodyne 119 gallon storage tank controlled by a GL30 controller in auto mode
    Filled the tank from our gravity feed spring 3 days ago with the starting temp at 50 degrees F. and with it running 2 sunny days
    we are at 115 degrees in the tank. Last night at 8:30 pm, with the sun set for over an hour I noticed he circulators still running?
    My question is , which way to turn the settings on the differential control? The values go from 12 to 24 degrees., assuming these are the
    differences in the temps at the collector sensor at top and the tank sensor at the bottom. Thinking the sensors should have shut down the pumps sooner?
    Thanks in advance for any input.


  • #2
    The GL 30 has a set differential of 4 degrees. The dial you are talking about is the pump on setting ( Collector vs. storage temp. differential). Check the resistance of your sensors to make sure they are reading the correct temps, also check to make sure you have the wiring on the correct terminals ( collector and storage).

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    • #3
      What should the resistance reading be on the sensors?
      Turns out my C30 is an old Independent Energy model from the mid 1970’s
      with only one internal temp adjustment.
      Thanks for the preset 4 degree difference info.

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      • #4
        Originally posted by LuminosityVermont View Post
        What should the resistance reading be on the sensors?
        ......
        Try Googling 10k thermistor. If I remember from the one I used in the 1970;s that is what was used and there are charts, You can check with a known temperature. like boiling water
        9 kW solar. Driving EVs since 2012

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        • #5
          Originally posted by LuminosityVermont View Post
          What should the resistance reading be on the sensors?
          Turns out my C30 is an old Independent Energy model from the mid 1970’s
          with only one internal temp adjustment.
          Thanks for the preset 4 degree difference info.
          Save yourself some trouble and buy a new controller too old to mess with.

          Comment


          • #6
            The controller is working fine. I just upgraded my tank from 80 to 119 gallons.
            Thinking that accounts for the longer circulator cycles.
            I have a 3 speed Grundfoss pump on the glycol side and went from medium to fast speed to compensate.
            My C30 manual states pumps on at a 20 degree difference and off at a 5 degree difference.
            Thanks all for your input !

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            • #7
              Problem solved by removing the thermistor sensor from the bottom of the tank and clamping it to the hot out at the top of the tank.
              This brought the temperature differential within range of the C30 controller and the circulators are now cycling on and off at demand as they should.
              Happy as heck. The new larger capacity tank was too much for my 2 panels to satisfy with the sensor at the bottom with the cold water dip tube so close.
              Thanks again for your inputs.

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              • #8
                Originally posted by LuminosityVermont View Post
                Problem solved by removing the thermistor sensor from the bottom of the tank and clamping it to the hot out at the top of the tank.
                This brought the temperature differential within range of the C30 controller and the circulators are now cycling on and off at demand as they should.
                Happy as heck. The new larger capacity tank was too much for my 2 panels to satisfy with the sensor at the bottom with the cold water dip tube so close.
                Thanks again for your inputs.
                That sure seems like a strange placement for a tank sensor.
                The way I learned it, the tank sensor wants to be at the tank outlet to the collectors, whichis usually or ought to be about the point where the water in the tank is close to the coldest.
                Do you understand the logic behind differential controllers ?
                Similar to Lucman's comment, is it possible you could have the tank and collector sensors somehow switched ? Or, one or both is/are somehow defective ?
                I'd also check the sensor wiring runs.
                Whatever the outcome, if you don't already know this, sensors need to be insulated to give the most accurate temperatures to the controller, both in about equal amounts. If If one sensor is insulated and one isn't, it'll screw up the temps the controller thinks it's working to. Was the old tank sensor insulated and the new one not ?
                The tank size shouldn't affect the operation of a controller.

                Take what you want of the above. Scrap the rest.

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                • #9
                  I do understand how the controller operates and my sensors are wired correctly.
                  My old 1975 C30 is fixed differential at 20 degrees + on and 5 degrees off.
                  I just increased the size of my storage tank from originally 80 gallons that are connected to two 4 x 8 foot flat plate collectors.
                  I replaced the tank with a Heliodyne 112 gallon tank that was off of a system that was connected to two larger 4 x 10 foot collectors.
                  I was thinking that the larger tank was sized to those larger collectors and my circulators were working overtime to try to make up the difference.
                  I will check the insulation on the collector sensor as the snow and ice may have effected it over the years.

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                  • #10
                    Originally posted by LuminosityVermont View Post
                    I do understand how the controller operates and my sensors are wired correctly.
                    My old 1975 C30 is fixed differential at 20 degrees + on and 5 degrees off.
                    I just increased the size of my storage tank from originally 80 gallons that are connected to two 4 x 8 foot flat plate collectors.
                    I replaced the tank with a Heliodyne 112 gallon tank that was off of a system that was connected to two larger 4 x 10 foot collectors.
                    I was thinking that the larger tank was sized to those larger collectors and my circulators were working overtime to try to make up the difference.
                    I will check the insulation on the collector sensor as the snow and ice may have effected it over the years.
                    The 10K sensors are pretty robust but they do fail occasionally. Insulation, even if it's closed cell foam, needs inspection/testing 1X/awhile. As much insulation as possible at equal levels (and as water tight as possible for outdoor applications) helps ensure the voltage the sensors are sending is a close representation of the temps. of the water at the sensors.

                    Also, it's good practice to try and have the same insulation level on both sensors. Reason: If not, the sensor with the lower insulation level will think the temp. it's sensing is lower than it actually is. That will screw up the perceived temp. differential the controller thinks it's seeing.

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                    • #11
                      Thanks J.P.M. I will have to check the insulation and chart Ohm values on the roof sensor.
                      I’ve paid it no mind in the last 15 year.s of trouble free operation.

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