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PIDing a heat exchanger machine

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  • PIDing a heat exchanger machine

    Hi there,

    Just a question for the skilled and knowledgeable. I am tinkering with PID'ing my heat exchanger machine (Astoria CKX) to get more thermostability during the extraction. Since the heat exchanger type, is it a waste of time?

    If it has been done before, is there any guides out there.


  • #2
    Its a waste of time for that reason, a pressure swing for example between 1 and 1.2 bar (gauge pressure) only equates to around 4deg temperature change in the boiler, the change in the brew water will be a little less and then buffered by the thermal mass of group

    Its been done before and can be done the same way as piding a single boiler, bezzera even makes the BZ07 with a pid

    To get a stable brew temperature from HX machine requires a combination of 1. boiler pressure + good HX design for sufficient brew temp through to the end of the shot, and 2. idle group temp control (thermosyphon restrictors) for correct temp at the start of the shot


    • #3
      Yeah. Just wanted to confirm my thoughts and what I was reading in on Should I PID my Heat Exchanger? - Knockbox •

      Their application is more on shot recovery than brew stability?


      • #4
        How much pressure swing do you have?

        The machine in that thread is different to yours with the HX section of the boiler connected directly to the grouphead, it would overheat

        There are reasons to pid, no more clang/ping from the pressurestat for example


        • #5
          Thank Jim.

          I think the CKX tends to run hot while idling thus requires a flush before use. I am going to attach a probe to the grouphead to detect the change in temp during flush. As for boiler pressure and design, I am not too sure about the CKX design and adjustments.

          No boiler pressure reading available... only steaming pressure gauge...


          • #6
            Originally posted by coffeeboy83 View Post
            No boiler pressure reading available... only steaming pressure gauge...
            Errr ? ... Steaming pressure IS boiler pressure !


            • #7
              Ah... yes. indeed.... opps

              is that adjustment dependent on the pressurestat? (how do you adjust that?)


              • #8
                The CKX group might be a candidate for an active heating conversion, I've just made one for a commercial Bezzera. Basically a small brass block with built-in PID controlled heaters gets bolted on between the group and solenoid, providing precise temperature control of the group. This is complimented by a thermosyphon restrictor to lower the group's initial idle temp. and allow the PID to fine tune it.

                Some domestic Bezzeras have actively heated groups as standard (that's where I got the idea), but they are using thermostat control at present.
                Attached Files


                • #9
                  Hi Coffee machinist, I have been admiring your work. Some questions came to mind,

                  1) Why do you think it is a candidate for active heating conversion? Is it because of the availability of room within the machine chassis to install such a device?
                  2) The CKX is not a standard E61 grouphead, does it have a thermosyphon restrictor? <--- just read your website
                  Answer is NO! CKX does not have a thermosyphon restrictor




                  • #10
                    Hi Andy, thanks.

                    To answer your questions,

                    1) You need a decent flat surface under the group where the solenoid bolts on, as the heat is transferred to the group via conduction across the brass. The larger the flat surface, the more efficient it is. The bezzera group is up to temperature from cold in a matter of minutes, with 200W heaters.

                    2) Correct. The only reason to add a restrictor in this case is to make sure the group isn't running too hot in the first place, as the heater can only, well, heat.


                    • #11
                      Nice idea cm, how many watts?

                      Looks like the same config would work on the ckx


                      • #12
                        1) The internals of a CKX has been well documented in this forum thanks to LaceHim and A_M see:

                        Seem like there is alot of potential room for the heater to go onto?

                        2) I assume then the boiler pressure has to be brought down to accommodate this drop in temperature? Does this mean a new pressurestat or adjustment possible with the stock pressurestat?


                        • #13
                          Jim... might need your PID kit afterall. Maybe a double PID on the cards?

                          1) for the grouphead heating element
                          2) for the boiler and disable pressurestat?