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  • PID on a HX machine?

    I see that Bezzera make a HX machine with a PID.  Can anyone explain to me how that works?  

    Does the PID monitor the boiler temperature - which is usually the steam temp in a HX, right?  

    How then is the group head temp regulated if there isnt a pressurestat?

    Ive done a search of old threads for the last year but couldnt come up with an answer - although some people mentioned in passing that a PID wouldnt really be necessary on a HX machine?

    Yours in confusion,

    Sniff  

  • #2
    Re: PID on a HX machine?


    Originally posted by 08160E0315160D0C620 link=1275439729/0#0 date=1275439729
    I see that Bezzera make a HX machine with a PID.Can anyone explain to me how that works?

    Does the PID monitor the boiler temperature - which is usually the steam temp in a HX, right?

    How then is the group head temp regulated if there isnt a pressurestat?

    Ive done a search of old threads for the last year but couldnt come up with an answer - although some people mentioned in passing that a PID wouldnt really be necessary on a HX machine?

    Yours in confusion
    I believe you are referring to the Bezzera BZ 07 with PID

    I am almost certain that all the BZ 07 models have an adjustable heating element inside or before the brew head in addition to the boiler element

    KK

    Comment


    • #3
      Re: PID on a HX machine?

      I wouldnt have thought that there was a great need for a PID in an HX machine.

      Take the silvia for example. These machines are great with PIDs because brew temp is controlled as they dont have the stability of a big HX machine and with a small boiler its steam is more regular because there isnt that wide gap of the thermostat.

      Neither of those advantages are present in a PID HX machine. The boiler is big enough that it can take up the slack from the pressurestat gap and the thermosyphon design will keep the brew temp approximately stable as the group head temperature would stay the same as the boiler temp changes.

      I think the only advantage of a PID is that you can easily change the boiler temperature and therefore the brew and steam temperature albeit simultaneously. The other downside of an HX PIDd is that it takes time before the boiler temp change translates into brew temp change.

      Comment


      • #4
        Re: PID on a HX machine?

        hehehe....

        for those people that cant handle the truth, the display on a PID machine tells them what they want to see according to what they have set, not what really is happening. Atleast for some machines.....

        They are another example of the tail wagging the dog ie the clients pushing the market to get manufacturers to give them what they want, even though they dont know anything about what they are specifying.

        Apologies as usual, for being so up front with the truth.

        Rgerdz,
        Attilio
        very first CS site sponsor

        Comment


        • #5
          Re: PID on a HX machine?

          Originally posted by 06322533281F032F26262525400 link=1275439729/3#3 date=1275444933
          hehehe....

          for those people that cant handle the truth, the display on a PID machine tells them what they want to see according to what they have set, not what really is happening.

          They are another example of the tail wagging the dog ie the clients telling manufacturers what they want, even though they dont know anything about what they are specifying.

          Apoliogoes as usual, for being so blunt with the truth.

          Rgerdz,
          Attilio
          very first CS site sponsor
          I agree..

          MARKETING and BLING...

          Some have a place for very specific needs..

          BUT great bling.. Get the ones with the blue leds

          Comment


          • #6
            Re: PID on a HX machine?

            Aaargh!

            Attilio, AM, stop speaking in tongues!

            If the PID is controlling the steam boiler, then how is the brew temp controlled without a pressurestat? Is there some sort of thermostat that controls the grouphead temp then? :-?

            Sniff
            PS Attilio, is the sale still on?

            Comment


            • #7
              Re: PID on a HX machine?

              Sniff the pressurestat does exactly the same thing as a thermostat or PID.  Pretty sure that the pressure/temp relationship would be linear so they both achieve the same thing albeit a different way.

              As we all know the max temp of water at atmospheric pressure is 100. Under pressure the boiling point or max temp is higher so thats how a pressure stat works.

              Comment


              • #8
                Re: PID on a HX machine?

                Originally posted by 647A626F797A61600E0 link=1275439729/5#5 date=1275445471
                Aaargh!

                Attilio, AM, stop speaking in tongues!  

                If the PID is controlling the steam boiler, then how is the brew temp controlled without a pressurestat?  Is there some sort of thermostat that controls the grouphead temp then?  
                We dont speak in tongues! .. We use KISS.

                How ever for a quick explanation..

                http://en.wikipedia.org/wiki/PID_controller

                Then look at you machine and how it all works and al the physics involved.. Ie A single boiler Vs HX etc etc Then try and decide how to wire up the PID to gain some improvement.

                In a single boiler.. Some improvement.  For many, reading a value has lots of emotional satisfaction..  OOOhhh Arr  look 93.2156C am I not good.

                Further more trying to manage heat layers and the thermal properties between the Boiler / HX and Group is a balancing act..  Once ya get it set up.. Great... After that; unless ya into lots of tweaking and ya taste buds are trained.. WHO cares.. BRAGGING RIGHTS.

                Oh... Now where did ya place the PID sensors.. What is their accuracy..  Opps a big rush and lots of steam and hot water required...

                The PID can not control or manage any of that..  That is Elements and thermal mass..  Once stable.. Some tweaks..

                OH... 93.2156C  What ... An Audit.. Thats what the display says..  OH.. Turn that pot / cal factor.  Oooo Cool; now it reads 63.5C  :-?  So how come my coffee tastes the same  : : :

                Comment


                • #9
                  Re: PID on a HX machine?

                  Well as far as I can work out there doesnt seem to be much point in a PID on a HX. If the brew water is being heated through the coil in the steam boiler then the PID would presumably always be set to the higher temperature for the steam and to have any effect on the brew temp would mean lowering the PID to the brew temp level and then raising again to steam which sort of seems to avoid the benefit of a HX in that you can steam and brew at the same time...so effectively youre turning your HX into a single boiler?

                  Comment


                  • #10
                    Re: PID on a HX machine?

                    There was a great explanation on this on HomeBarista forum a while back - google it

                    Comment


                    • #11
                      Re: PID on a HX machine?

                      Not sure if you understand the concept too well. If an HX machine was at normal brew boiler temp then the water coming out of the head would be far lower than ideal.

                      Cold fresh brew water is heated instantly through the coil of pipes in the boiler when the brew button is pressed and the pump turns on. This is quite crude and temps would fluctuate dramatically depending on temp of the cold brew water going etc(for example if I leave my machine on the water in the tank will be quite warm so if i topped up the tank with fresh cold water that would then affect the temp of the brew water after going through the heat exchanger) The stability in an HX machine comes from the large amount of brass. HX machines have what is called a thermosyphon and this pumps water from the boiler through the group head etc. The temperature of the group assembly essentially remains stable. If you wanted to then adjust the brew temp independent to the the steam/boiler you would alter the flow of water in the thermosyphon. This is a mod that some of our sponsors do but it is not something you would change from week to week. Since the brew temp stability is dependent on the temp of the group etc so when you make a change to the boiler temp you have to wait long enough for the thermosyphon to bring the group up to temp or down to temp.

                      Since a dual boiler machine has a brew boiler and the brew water is a constant temp unlike my example of above with cold vs warm tank water, that is one less variable and therefore better stability because of that.

                      I hope that helps and after that rant I hope Im right but that is how I understand it.

                      Comment


                      • #12
                        Re: PID on a HX machine?

                        Great post Attilio..... [smiley=tekst-toppie.gif]

                        To back up what Attilio has said, in an HX espresso machine it is almost bordering on ludicrous to suggest that boiler temperature should be controlled by a PID Controller. It just makes absolutely no sense at all.

                        The Primary purpose of the Boiler in a HX machine is to supply good quality Steam at preferred volumes and rate of delivery. The Brew Water Temperature is controlled, not by the temperature of the water in the Boiler so much but by the design of the Heat Exchanger system, the Group and how the water is delivered from the Boiler to the Group.

                        A standard Pressurestat in a so-called Prosumer machine, will maintain Boiler Pressure at +/- 0.05Bar. This equates to a Temperature range from nominal of +/- 0.8C or expressed in another way, a peak temperature of 1.6C above the nominal setting. This is NOT the range of temperature variation reflected in the Brew Water as this is totally dependent on the HX system design as a whole. If you were to substitute the Pressurestat for a PID Controller, sure, you would be able to control the Boiler Water Temperature to a much tighter band but the only place youre going to see this (if it is at all possible) is in the Temperature of the Steam being delivered, not the Brew Water.

                        If you want to attain the sense of having absolute control over the Brew Water Temperature, then you need to to start thinking decent quality Dual Boiler machines with one of the Boilers dedicated to the Brew Water. Alternatively, buy a Silvia, Quaha/Imat/Nemox/Lelit style of machine and dedicate this to pulling espresso only.

                        HX espresso machines with PID Boiler Control is an absolute furphy but, if you like looking at bright LEDs and pushing buttons, then go for it..... :

                        Mal.

                        Comment


                        • #13
                          Re: PID on a HX machine?

                          Snip from the Bezzera Italy web site
                          http://www.bezzera.it/home_ing.html

                          PID SYSTEM: on BZ07
                          PID temperature control system, replaces traditional pressure switch, shows the boiler temperature on a display, the temperature can be adjusted by the user in a range from 85C ° to 100C °.

                          KK

                          Comment


                          • #14
                            Re: PID on a HX machine?

                            Originally posted by 56727B7B78784256726E70721D0 link=1275439729/12#12 date=1275481075
                            Snip from the Bezzera Italy web site
                            http://www.bezzera.it/home_ing.html

                            PID SYSTEM: on BZ07
                            PID temperature control system, replaces traditional pressure switch, shows the boiler temperature on a display, the temperature can be adjusted by the user in a range from 85C ° to 100C °.

                            KK
                            If the unit is installed and totally replaces a manual  / bellows system; there are some gains...

                            It should not be called a PID... Marketing and pandering to some section of the market..

                            Does my DCM have a PID controller NO..  

                            Does it perform the same if not better functions YES..

                            Because the PID is -  A generic control loop feedback mechanism; that is mass produced to allow others to use..

                            A high end system will / should have its own dedicated control loop feedback mechanism that should outperform any Generic system..  


                            A little like...  many after market car products... Perform a function and when used on a car that is 20years old... Makes big difference..

                            But like many after market products... Would I want the genuine ABS breaking system on my BMW or SABB or a cheep Chinese copy..

                            For the old EH.. The copy will do fine and may well add something..  With my new car... I want the system that is tailored to my car..


                            OH... And I do not want 101 lights all over the place..  People say to me.. The DCM should have a digital readout.. NOT required....

                            BLING that is confusing / misleading and not required..

                            But the masses love it and the marketing eat up the advertising dollars and real functionality and development, is stifled.

                            Comment


                            • #15
                              Re: PID on a HX machine?

                              Originally posted by 524C54594F4C5756380 link=1275439729/8#8 date=1275457916
                              Well as far as I can work out there doesnt seem to be much point in a PID on a HX
                              Apart from the lack of real benifits mentioned here relating to temperature there is a couple of side benifits to having a PID/SSR (solid state relay) on a machine.

                              Silence when not in use so no clicking on and off (much as some may like this to say their machine is on), no points to get earwigs under or burnout and generally easy user adjustment of the Temp from the outside of the machine while a PStat is normally covers off to get to it.

                              More marketing bling than anything else I reckon. :

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