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bezzera bz07 .... pid ..... if its HX, what does it control ????

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  • bezzera bz07 .... pid ..... if its HX, what does it control ????

    doing a bit of reading, and am puzzled by a dumb question that those wiser then me would have an answer to.
    Bezzera bz07 comes as a hx pressurstat version, and a pid version. What does the pid set the tempearture to ?
    If it sets the boiler temp then at 93c to pull a good shot, I should not be able to steam. Is this pid version a single boiler machine, or dual boiler machine ? Or does it use the pid to set the boiler temp, eg 110c so that it steams, and they depend on the element in the group head for temp of the brew head. ????

  • #2
    Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

    Originally posted by 7A7D6C6C7D6A796C7077757D180 link=1303774158/0#0 date=1303774158
    doing a bit of reading, and am puzzled by a dumb question that those wiser then me would have an answer to.
    Bezzera bz07 comes as a hx pressurstat  version, and a pid version. What does the pid set the tempearture to ?
    If it sets the boiler temp then at 93c to pull a good shot, I should not be able to steam. Is this pid version a single boiler machine, or dual boiler machine ? Or does it use the pid to set the boiler temp, eg 110c  so that it steams, and they depend on the element in the group head for temp of the brew head. ????
    Hello better,

    Have a read over http://coffeesnobs.com.au/YaBB.pl?num=1303098386/19#19 which should answer your question re the PID

    You seem also to be confused by the difference between single boiler and HX. Home Barista has a good explanation http://www.home-barista.com/espresso-machines/espresso-machines-101-t368.html

    The only note Id add is that the reference/s to cooling flush are out of date for current machines.

    Hope that helps

    C

    Comment


    • #3
      Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

      If its an hx and uses a PID, then its simply going to set the temp around 130deg. Probably the only advantage of a PID is easy adjustments if you need to, and a smaller deadband (the temp difference between when the element is turned on and when its turned off).

      You should probably read up on what a heat exchanger (hx) machine is

      Comment


      • #4
        Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

        Wish Id thought of that :P

        Comment


        • #5
          Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

          I understand how a heat exchanger works (have stripped and rebuilt boiler on my S27), I know how a pid works (digital temperature control instead of dependent upon a pressurestat and the temp of boiling water being above 100c water as pressure increases, I own a pressure cooker).

          BUT it is the Bezzera BZ07 with PID I was specific on, I pressume its a HX machine, one boiler with a heat exchanger becasue they have 3 machines in the range and I know the semi-auto and auto are single boiler with a heat exchanger, so would the pid read 93c (no steam, but I can make coffee) or 130c (steam), and what is the PID on THIS SPECIFIC machine measuring, boiler temp, group head temp, or water into the group head temp ???.

          hmmm keep saving for the duetto or expobar.

          It seems a bit of a waste to have a PID on a HX machine, but makes absolute sense on a dual boiler where you want the brew boiler at 93c, and the steam boiler at 130c

          Comment


          • #6
            Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

            Hi betterathome

            I wondered about this same issue some time ago, the thread is here:

            http://coffeesnobs.com.au/YaBB.pl?num=1275439729

            The short answer is above in your thread, basically the PID will reduce the deadband.

            The actual PID display I think is set to display the temp at the brew head, so the actual boiler temp will be much higher to allow for steaming. I think this is called offset.

            Cheers

            Sniff

            Comment


            • #7
              Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

              Reading sniffs post, I am wondering if the temp is measured at the group head, or is it measured in the boiler and an offset applied to estimate the brew temp.
              Just curious

              Comment


              • #8
                Re: bezzera bz07 .... pid ..... if its HX, what does it control ????


                Id say measured at the boiler and then offset to show the estimated temp at the brew head.

                Comment


                • #9
                  Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                  Originally posted by 425C44495F5C4746280 link=1303774158/7#7 date=1303874321
                  Id say measured at the boiler and then offset to show the estimated temp at the brew head.
                  ....and with a HX machine using restrictors, that can be a veritable can of worms. Izzo provide raw data from the boiler thermocouple.

                  Comment


                  • #10
                    Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                    Originally posted by 21263737263122372B2C2E26430 link=1303774158/0#0 date=1303774158
                    doing a bit of reading, and am puzzled by a dumb question that those wiser then me would have an answer to.
                    Bezzera bz07 comes as a hx pressurstat  version, and a pid version. What does the pid set the tempearture to ?
                    If it sets the boiler temp then at 93c to pull a good shot, I should not be able to steam. Is this pid version a single boiler machine, or dual boiler machine ? Or does it use the pid to set the boiler temp, eg 110c  so that it steams, and they depend on the element in the group head for temp of the brew head. ????
                    The best advise to give you is call the importer
                    Barazi its a free call
                    http://coffeesnobs.com.au/YaBB.pl?num=1163931729

                    I am sure the BZ07 with PID is measured at the boiler
                    You should confirm it with Barazi

                    However I will explain the 3 relationships between pressure, temperature & steam very simply for all

                    A coffee machine is essentially a pressure vessel (boiler) with an air gap above to hold steam

                    Steam can & is produced at low temperatures and stored in the air gap of the vessel

                    A home test
                    " Try boiling some water on the stove top and one can observe that it steams long before its boiling albeit at a lower rate
                    This is more evident when steaming vegetables in a closed steamer pot " at a very low heat

                    The pressure vessel is also an efficiency vessel by collecting all steam produced and storing it for use

                    The available steam and the length it can be used is governed by how large the boiler is and how much steam is stored in the air gap

                    Hope that helps

                    Now does anybody want me to explain how a HX works

                    KK

                    Comment


                    • #11
                      Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                      Originally posted by 4A6E676764645E4A6E726C6E010 link=1303774158/9#9 date=1303880261
                      Now does anybody want me to explain how a HX works
                      Well, as you appear to be on a roll, then sure, why not. ;D

                      Comment


                      • #12
                        Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                        A heat exchange by definition is a transfer of heat from one vessel to another to attain equilibrium of both

                        In espresso machines the heat exchanger is located inside of the boiler
                        One design of an exchanger is constructed as a spiral of pipe that holds a set amount of water that the manufacturer has determined to work for the model. This water is fed directly from the tank

                        This sealed spiral of pipe is independent of the boiler
                        The boiler element heats the water and a heat exchange has already started

                        Home Test or see a cooking demo

                        See a heat exchange in action when you see a demonstration of chocolate being melted in a double boiler

                        KK

                        Comment


                        • #13
                          Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                          After much good input into this thread, I took the advise of one of the contributors and called barazi, who were most helpful.
                          It seems its a simple HX machine (single boiler, but with heat exchanger). The PID uses an "offset", so probably not worth the extra $300 (more bling than zing), especially since its an electronically heated group head.
                          So to get the temperature the PID reads on this machine, you need to be pulling the perfect shot as its thermodynamic engineering is still based around a HX and the assocaited flow rate of cold water, via the HX being heated to the preffered temperature (90-96c depending on skill, or 93c for the Australian purists with the exact skill of grind and tamper)

                          Comment


                          • #14
                            Re: bezzera bz07 .... pid ..... if its HX, what does it control ????

                            Good thing that you found an answer which worked for you better...

                            As all have stated, a PID in a HX machine simply takes on the role of the pressurestat to set boiler temperature and therefore pressure. It can be considered a solid state, small deadband pressurestat and thats it.

                            What happens at the group of a HX machine will be dependent on how the group is heated, but ultimately only small changes to temperature will be possible. With an electrically heated group, it makes even less sense to me than a PIDed e-61, however I guess it was incorporated in response to "market forces". I suspect these forces originate due to incomplete understanding of purchasers.

                            Nevertheless, PID or no PID, if its a good machine it will do the job well- and thats what we are here for

                            C

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