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  • #16
    Thank you for additional info.

    I don't want to high-jack the thread but I'm in same situation and wondering can RTD be controlled with on/off controller (as I can see on ebay RTD's are always PID controlled), and I am wondering is it really necessary to use PID for single solenoid/motorized valve (without additional devices like pumps etc.)?

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    • #17
      PIDs are a type of temperature controller that use a duty cycle or proportional output to more precisely control temperature than standard hysteresis controllers. To be exact, PID is actually the algorithm that those temp controllers use. You would need a proportional valve to use it on a fermenter. Most people do not use PIDs on their fermenters because we are usually happy to maintain fermenting beer within +/- 1 degree. Proportional valves add some complexity and cost to your glycol setup.

      You most often see PIDs being used to control temperature with electric heating elements, where a duty cycle is employed on a SSR to simulate proportional power on a heating element by rapidly turning it on/off.

      RTD is just a type of temperature sensor. There are a lot of different temperature controllers that can use an RTD sensor. Check the specs before buying.

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      • #18
        Originally posted by UnFermentable View Post
        Again, in my limited knowledge, a PID is generally more accurate at maintaining a set temperature than an on/off with hysteresis. Also, I don't think you can program ramp/soak into a temperature controller with hysteresis, but I could be wrong. I forgot about the contact, which is definitely a good idea to include, but I am fairly certain I don't have one on my pub setup. It controls 24V red-hats and have not had to replace anything in 5+ years.

        I don't know that you would actually save anything from having the main chiller pump only kick on when calling for chilling, but it probably depends on the size of your cellar and chiller. We generally have at least one tank cooling at all times anyways. I would have concerns of the relay or contact failing due to constant switching. The VFD setup is interesting but again your dependent on no failures in the pressure transducer. In my general experience (both in and out of brewery) sensors fail a lot more often than working components such as elements, pumps, valves, ect. I often subscribe to the KISS method.
        [ATTACH]58416[/ATTACH]
        From my experience, pids generally have to be tuned to do so more accurately and the conditions have to be the same as when it was tuned for it to work better. Normally they turn the heating and cooling on and off multiple times in a relatively short period of time to work better then hysteresis so they are not used directly with refrigeration compressors and such unless they are programmed to work with delays which make them operate like a hysteresis controller. (think Johnson or stc1000) But some pids have an Hysteresis mode built in so they can be used as such as well.

        Yes there are at least a few hysteresis controllers with program/ramping capability. I use program and ramping with brucontrol and hysteresis temp controllers just and I did with STC1000+ units with alphaomegas custom firmware to allow the multiple temp schedules.

        I am currently only using such a system at the homebrewing level with #4 12 gallon stainless conicals so I honestly dont know if the large systems benefit from running the pump constantly or not. depending on the amount of piping and distance I could see it working better but in a smaller system its a waste and just burns the pump out faster. (I do believe it would be more reliable not running the pump constantly myself)

        I have am designing my setup for our nano now and in the beginning we are just going to have one or two of our conicals for lager use running off a chiller I have that has both heat and cooling capabilities built in as it was designed with a built in tube to control temps on the fly like a rims.. jury still out on how effective it will be for this type of use. The rest of our conicals are going in a temp controlled room for ales.

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        • #19
          Originally posted by darko View Post
          Thank you for additional info.

          I don't want to high-jack the thread but I'm in same situation and wondering can RTD be controlled with on/off controller (as I can see on ebay RTD's are always PID controlled), and I am wondering is it really necessary to use PID for single solenoid/motorized valve (without additional devices like pumps etc.)?
          As mentioned RTDs are a type of temp sensor like a PT100 which is a commonly used RTD sensor used with a lot of pids and homebrewing electric rigs. Their accuracy is better than thermisters but this is generally not needed for fermenter temp monitoring.

          Some devices such as many hysteresis controllers and BCS controllers wont work with rtds either.

          I used a simple $9 stc1000 temp controller for each one of my fermenters for about a year and it worked fine. the cooling relay turned on the dual relay for the valve and main chiller pump and the heating relay was connected to silicone heating strips attached to the outside walls of the fermenter. this worked great and maintained temps fine on a homebrewing scale. I went to the brucontrol software mainly because I already had it for my hot side brewery control and it allowed a lot more flexibility as well as graphs and fermentation temp schedules that were easier to program using the same template. plus I could use just about any type of temp sensor so I reused the stc thermister type I had in the conicals already. I also wanted the ability to be able to monitor and check on things remotely.

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          • #20
            Originally posted by augiedoggy View Post
            From my experience, pids generally have to be tuned to do so more accurately and the conditions have to be the same as when it was tuned for it to work better. Normally they turn the heating and cooling on and off multiple times in a relatively short period of time to work better then hysteresis so they are not used directly with refrigeration compressors and such unless they are programmed to work with delays which make them operate like a hysteresis controller. (think Johnson or stc1000) But some pids have an Hysteresis mode built in so they can be used as such as well.

            Yes there are at least a few hysteresis controllers with program/ramping capability. I use program and ramping with brucontrol and hysteresis temp controllers just and I did with STC1000+ units with alphaomegas custom firmware to allow the multiple temp schedules.

            I am currently only using such a system at the homebrewing level with #4 12 gallon stainless conicals so I honestly dont know if the large systems benefit from running the pump constantly or not. depending on the amount of piping and distance I could see it working better but in a smaller system its a waste and just burns the pump out faster. (I do believe it would be more reliable not running the pump constantly myself)

            I have am designing my setup for our nano now and in the beginning we are just going to have one or two of our conicals for lager use running off a chiller I have that has both heat and cooling capabilities built in as it was designed with a built in tube to control temps on the fly like a rims.. jury still out on how effective it will be for this type of use. The rest of our conicals are going in a temp controlled room for ales.
            Almost all the quality PIDs now days offer auto tuning features (although I don't find this feature to be needed personally). While you can apparently use some temperature controllers to create a ramp/soak profile, it seems you need additions such as the BruControl? I too have used STC-1000 on my homebrew setups, but would never use them in the brewery. They just seem less accurate and capable than the PXR4's I use in the brewery. Could be the PID, could be your BCS controller difference, could be other parts of the setup. Seems like a BCS could be quite useful (especially if wanting wifi/ethernet connectivity), but it looks as if you are also tying a bunch of controllers through a single unit. So it seems as though a failure of the BCS would risk more than one tank? I'm not saying there is anything wrong with any of these for any given brewery. I just prefer a single unit to each tank so I can replace one unit if/when it breaks without risking my entire cellar. I also prefer the durability and linear response of an RTD (in industrial applications). I'll take the pure metals over a ceramic/polymer type construction of a typical thermistor. Industry standard would most certainly lean towards PIDs with RTDs.

            To Claponsies point, you actually don't need proportional valves to make use of the better functions of a PID. The PID will switch off and on for shorter periods as it reaches closer to the set point, allowing you to reach temp without as much likelihood of over/undershoot. I am fairly certain a temperature controller will just maintain on/off until the hysterisis point is reached, often causing over/under variations. In any event, proportioning valves are also becoming much more prevalent in the industry. Many places are seeing the advantages of proportional ball valves as opposed to the old solenoids. Belimos seem to be the current trend.

            It is a common misconception that a pump motor will burn out faster by running continuously, but that is not actually the case. They are much more like a light bulb. A light bulb can stay lit a very long time if left on, the heating and cooling of the metal element is what eventually causes failure. The most stress motors see (in the form of heat) is at shutdown and startup with up to 90% of electric motors failing on startup. Motors will usually burn up windings based on increased resistance, often due to bearing failure. Voltage changes can also lead to more heat. If you keep properly lubricated bearings and regulated voltage, an electrical motor will run a very long time.

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