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Temp Controllers Cooling to below Set Point

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  • Temp Controllers Cooling to below Set Point

    I have a wall panel with Love TS2 controllers for my tank jackets, and some standalone Johnson A421 ABG-02 controllers. Every time during fermentation, they will kick on at 1F above my setpoint like usual, but will not stop cooling until the fermentor is about 3-4 degrees cooler.

    For example, if my setpoint is at 68F on the controller and the temp reaches 69F, the controller will start cooling and continue to do so until the tank is at 66F.

    Trying to stop this system from stalling fermentations, if anyone knows any workarounds. I've tries all sorts of different settings in the advanced settings, and both the company they were bought from and the manufacturer have been no help.

  • #2
    It is not clear from your comments whether the temperature controller is working correctly of not. Is the controller actually shutting off the coolant supply solenoid at the correct temperature and it is simply over shooting? Or is the temperature controller simply not shutting off when the measured temperature is as required?

    So - a couple of thoughts

    Firstly, if your controller is shutting the supply control solenoid, but the temperature continues to drop, this is almost certainly because of the residual "coolth" in the glycol (or other coolant). The first option is to simply raise the temperature of the coolant. The coolant only needs to be a couple of degrees cooler than the minimum temperature required, e.g. minimum beer temperature = Zero C, coolant minus one or minus two. It may be that the coolant supply rate is simply too great, and there is too much being supplied for accurate control, in which case you could restrict the flow of coolant into the FV so the overall temperature is not as cold, and the rate of cooling is slower, so reducing the overshoot.

    Secondly, is the temperature probe in the right position so you are actually measuring the temperature of the bulk of the fermenting wort? Is it appropriate to the position of the cooling panels. Use of the mash tun extended thermometer might give pointers to the consistency of the temperature throughout the FV.
    dick

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    • #3
      IT seems to be working properly in regards to cutting on at the correct point. I see the indicator light for "solenoid on" even after the temperature reads my original set point, so I believe the controllers are just continuing to let glycol flow.

      Good point about the flow rate, I'll have to play around with that as well as experiment with raising the glycol temp. As far as I can tell my temperature probes are reading accurately and are positioned well in the FV.

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      • #4
        Have you witnessed on the panel what temperature the valve closes? If it closes as soon as the temp hits your target, then the above response that there is too much residual cooling in the jackets would be correct. If you have manual ball valves on the back of your fermenters to control indivudual jackets, try cracking them so that they are barely open, or installing flow reducers for each tank after your bulk supply line. Having glycol that is too cold could also be a culprit (as mentioned above.)
        Peter Landman | Brewmaster | Seabright Brewery | Santa Cruz, CA

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        • #5
          Have you checked the temperature differential? This is the number that determines when the controller actually opens/closes the relays. For instance, if your setpoint is 68, set to cooling, and your diff. is 2 degrees, you get exactly what you describe. It's working properly, just not set right.

          The Johnson A421 does this a little differently. It has a minimum and maximum temp, but it amounts to the same thing.

          In both cases, also be sure the temp. controllers are set to cooling, not heating.

          And/or, as Dick wrote, your glycol is too cold. For some reason, everyone seems to want to set their glycol temp far too low. 26-28F is fine, and is about where your glycol chiller is designed to work. Too cold wastes lots of energy and causes numerous problems, such as icing inside the ferm--which will make temperature control highly problematic.
          Last edited by TGTimm; 11-16-2017, 11:48 AM.
          Timm Turrentine

          Brewerywright,
          Terminal Gravity Brewing,
          Enterprise. Oregon.

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          • #6
            +1 with Timm.

            Its very likely if your controller output light is on down past the set temperature that the differential is set too far apart. Keep in mind though, you don't want to set them too close together either. Then your controller will be continuously switching on and off causing it to burn out the relay much quicker. I believe the Johnsons have a short cycle prevention in them, if I remember correctly.

            Also as Dick and Timm said, flow rate and chiller temperature can play a big part.

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            • #7
              The Johnson controllers have an Anti-Short-Cycle Delay. Setting it to around 2 or 3 seconds seems to be about right for cooling.

              An "intelligent" controller, one that uses a PID formula, will also help keep your ferm at the right temp. These keep track of cooling time and rate to predict when to ask for cooling and maintain a constant temp much better than "dumb" controllers like the Johnsons. We use the Fuji PX series.
              Timm Turrentine

              Brewerywright,
              Terminal Gravity Brewing,
              Enterprise. Oregon.

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