Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

goldline GL-30

islandboy Member Posts: 1
I stumbled upon this website & hope you can help. I have a solar water system using a Goldline GL-30. It came with the house I have lived in since 2001. Never received any instructions on how to adjust it. I have noticed recently on cloudy days, my water temp is pretty average but the temp gauge on my water heater is about 100-110. So, when taking a shower, I have to crank up the hot to almost full. I have also noticed that the "Solar Collection" Indicator on my GL-30 rarely lights up which I believe activates the circulation pump. It would seem that the circulation pump should work more often to keep warmer water in lines. I am not sure where the "differential control" on the GL-30 should be set. My environment: I live in Maui, Hawaii where the average outdoor temp is around 85. We do get passing clouds from our trade winds but it only seems to be a problem water temp wise during our rainy season (Nov.-Feb.) when it can be quite cloudy. I have my water heater timer set for 3:00 AM - 10:15 AM and again from 5:00 PM - 10:00 PM, Mon. - Sun. Can you tell me where my differential control should be set?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    edited November 2016
    You have a basic differential temperature controller. The differential is for ON. The off differential is fixed at 5 degrees F if memory serves me correctly. You can perform a few quick checks to see if the control is still functional.

    The first would be to disconnect one wire on the Storage sensor. This should cause the control to turn on the solar pump. Now, connect the two wires going to the sensor together on the control side. This should cause the controller to turn the solar storage pump off.

    Reconnect these wires and now short the two solar collector wires together. This should cause the controller to turn the pump on. If it fails any of these gross checks, the control is most probably bad. If it passes these tests, then it is an indication that the control is OK, but the sensors may be bad. I believe these sensors are a 10 K ohm sensor at 70 degrees F.

    I also believe there was a TANK high limit adjustment. If you are not sure if you have a safety temperating device someplace in this system to avoid extremely hot discharge temperatures, then I'd suggest setting the TANK HIGH limit setting fro around 130 to 140 degrees F.

    It would be very helpful if you can get us some close up pictures of the controller and far back pictures of the system it is connected to.

    There are numerous manufacturers of differential controllers, but they will require replacement of the storage and solar sensors.

    EDIT: Forgot to mention that a longtime industry expert named John Klima is still able to rebuild these controllers, completely. Also an excellent resource for the sensors.


    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • SWEI
    SWEI Member Posts: 7,356
    When it hit the market, the GL-30 was a revolutionary product. Most of them lived long lives and provided good service.

    Modern solar thermal controls are available at similar cost and add important safety features which the GL-30 lacks. I would strongly recommend replacing the controller with a low-end offering from someone like Caleffi, Steca, or Resol.
  • hot_rod
    hot_rod Member Posts: 19,935
    I second the opinion to upgrade. The new digital controls offer so much more control, along with data logging and online interface ability.

    Just having a large digital display of the temperature conditions is helpful to dial in the best performance.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,079
    Hello: This control uses 10K ohm sensors. They can drift with time and quit working correctly. Also, sensor wires don't hold up well to sunlight, mice or birds. I'd disconnect the sensors, dip only the copper part of them both into a glass of water, and read continuity with an ohm meter. They should have nearly identical readings. For your environment, where freezing is not going to happen, this simple control might be all you need. If the control itself turns out to be bad, I would look to upgrade. Putting your solar control on a surge suppressor might not hurt either!

    Yours, Larry
  • hot_rod
    hot_rod Member Posts: 19,935
    Along with Larrys suggestion, adding surge protection on the collector sensor, either on the roof or at the control is also a good idea
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • H20_Heat
    H20_Heat Member Posts: 1
    The differential that is adjustable on the GL-30 refers to the temperature difference between the solar panels and the holding tank. Where I work, we normally set the differential at 12. That means the solar panels will have to be 12 degrees hotter than the holding tank temperature before the circulating pump will come on. The controller does have the turn off differential factory set at 4 degrees above the tank temperature. The sensors are 10k ohm at 77 degrees and like one of the previous posters said, the sensor wire at the panels is susceptible to damage from sunlight.
    Unless you are looking to do lots of fancy things with the control, the GL-30 is a simple, inexpensive controller that will take care of most systems with minimal problems.