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  • #31
    Re: PID on a HX machine?

    The PID is on the boiler not the grouphead.

    The grouphead on this machine has two small elements (PART 33 below) inserted in the brass block instead of running thermosyphoned water like an E61 head. Like my Izzo groups you also get heat transfered from the hot boiler as the group is still bolted to it as well.

    While the boiler is at say 120 degrees the actual temp of the group will be below this due to being exposed to cooler air than the 120, getting this balance right is part art part science.

    With a thermosyphon loop on the E61 style you are using the temp differential in the boiler (hot water rises) to pass a small lot of water through a loop to add to the heating of the head.

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    • #32
      Re: PID on a HX machine?

      The BZ 07 does not have an E61 group head

      Heater element in the BZ 07 group head is to heat the metal part of the head to keep it at a constant temp

      There are 3 popular ways to heat up a group head that I am aware of & they are
      1 - Thermosyphon
      2 - Electric Element
      3 - Brass Bridge

      Not all machines are built the same and one should take the time to study the product before commenting on it with authority

      KK

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      • #33
        Re: PID on a HX machine?

        KISS

        Ya trying to manage temp control and relying on static non managed Air temp to do the cooling.

        Thus lots of smoke and mirrors and being reliant on conduction and convection as ya mediums..   True control is from both sides.. All this is focused on one approach..

        Side of a barn door.... But it is FIT for purpose..

        And what is in the cup is what matters...

        PS. I  have to control critical incubating blocks on clinical analysers and it has to be linear across a small area  and with in  1C....  It is neigh on impossible and requires continuous cycling of heating / cooling blocks and variable fan control for air flow...

        All the PID and HX stuff  etc is wide open and if people think its critical and can be rock stable... They need to start teaching and lecturing the Thermo dynamic classes in uni as to the new sciences etc....

        It is BUCKET temp control at best.

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        • #34
          Re: PID on a HX machine?

          KK - thanks for your post regarding the ways in which heads are typically heated and that the BZ07 is heated with an electrical element.

          What I would like to do is further clarify what the purpose of the PID controlled heat exchanger machine is. As stated by other esteemed colleagues, a PID on a single boiler machine such as a Rancilio Silvia is predominately focussed at improving the temperature stability. In the case of an HX machine such as the BZ07, the purpose the the PID is provide the flexibility to the user to change the temperature (ie. pressure) of the boiler (which will directly impact the temperature of the water during coffee extraction) to match different coffee blends, origins and roasts.

          By inference, increasing the temperature will increase steam availability while decreasing the temperature will decrease steam availability.

          If you require further clarification, We are only a phone call away on 1300 550 927.

          Chris
          Bezzera Australia

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          • #35
            Re: PID on a HX machine?

            If the PID was on the heaters in the grouphead I would think that this would reduce the need for cooling flushes as the group wouldnt overheat (or even change temp that much) as long as it could cool itself well enough (fins maybe) when the elements were off

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            • #36
              Re: PID on a HX machine?

              Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

              The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.

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              • #37
                Re: PID on a HX machine?

                Originally posted by 3136323D353F2A3A3D34530 link=1275439729/35#35 date=1275544428
                Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

                The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.
                Thanks BF..

                Provided that link and a few other; a few post previously....

                Done and dusted...

                Comment


                • #38
                  Re: PID on a HX machine?

                  Originally posted by 6364606F676D78686F66010 link=1275439729/35#35 date=1275544428
                  Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

                  The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.
                  You must be reading my mind....
                  Have just finished reading all articles AM mentioned
                  Thanks to both
                  This is all very interesting

                  Comment


                  • #39
                    Re: PID on a HX machine?

                    Originally posted by 6D6A6E616963766661680F0 link=1275439729/35#35 date=1275544428
                    My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.  
                    So the Izzo would love a PIDd element in the group to keep it warm enough when left idle on a cool day :P

                    Comment


                    • #40
                      Re: PID on a HX machine?

                      I wrote a small post last week on the workings of the Heat Exchanger System in a coffee machine

                      http://coffeesnobs.com.au/YaBB.pl?num=1274527580/14#14

                      KK

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                      • #41
                        Re: PID on a HX machine?

                        Originally posted by 110A0315161B620 link=1275439729/38#38 date=1275546396
                        PIDd element in the group to keep it warm enough when left idle on a cool day
                        Nope just wouldnt be the same with a digital display or buttons to make it go beep, manual shots, manual fill is what it is and how it will stay Just like a cooling flush a warming flush in my case is just getting to know the machine to get consistantly good results out of it. In my case it is just pull the lever down and run 100ml or so of water through each of the groups, even without this it still makes great shots but if I do it I get better shots again 8-)

                        sorry AM the thread was getting to long and I missed your link

                        Comment


                        • #42
                          Re: PID on a HX machine?

                          Originally posted by 4245414E464C59494E47200 link=1275439729/40#40 date=1275547816
                          sorry AM the thread was getting to long and I missed your link
                          NA it is t e h issue with auto correction and that many dont bother or may not understand, even after reading a good article or two...

                          I might do an A. and just leave it alone..

                          Comment


                          • #43
                            Re: PID on a HX machine?

                            I recall watching a Barista making changes to the boiler temp on an NS Aurelia which is of course an HX machine. She had a particular blend that she felt the temp needed to be different.

                            I think a PID would take the guess work out of it all. Unless you know your machine REALLY well and know EXACTLY how far to turn the screw on your PSTAT it could be a pain the the !@#$ making changes to the temp especially considering the delay as you would have to leave the machine to settle in to the new temp.

                            So to the OP I reckon the idea of a PID is as crazy as some have pointed out.

                            Comment


                            • #44
                              Re: PID on a HX machine?

                              Sorry....

                              Im not convinced that any of the "Pro" arguments for PID Controlled Boiler Water Temperature on a HX machine is worthwhile. Like I said above, my background is in electrical engineering, specifically in Control Systems, SCADA and Process Control - Knowledge and experience gained over several decades with systems that are several orders of magnitude more complex than the thermodynamics of a HX Espresso Machine.

                              No more posts from me....

                              Mal.

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                              • #45
                                Re: PID on a HX machine?

                                I think that we, as snobs, or at least, coffee geeks, look at the term "PID" technically and literally. To the ignorant masses, "PID" means digital temperature control, and not much more than that.
                                Kleenex vs. facial tissue
                                Crescent wrench vs. adjustable spanner
                                Q-tip vs. cotton swab
                                PID vs. digital thermostat
                                KY vs. water based lubricant
                                You get the idea.

                                I agree that there is little real benefit, if any, to be gained from adding a PID to a HX machine. It would add convenience of external adjustment of the temperature as well as adding the SSR to eliminate the contacts of most pressurestats (which can be done without the PID, of course).

                                A properly designed HX machine can perform very well, indeed, without the PID. As an example, the brew temperature curve of the Vibiemme Domobar Super is excellent without fancy temperature control of the boiler.

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