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  • Silvia & multiple coffees

    Try hard as I might I just havent been able to master making multiple coffees with Silvia. The second coffee always turns out terrible - ie a very fast pour. We are usually drinking milk coffees so until recently I have been making each milk drink individually (there are two of us - so basically pull shot, steam milk, flush, pull shot, steam milk). We like a double shot in our coffees.

    Recently I was tuning in my new grinder (a Compak K3 Elite thanks to Chris at Talk Coffee), and was just pulling shots, and discovered that once I had the grind right, I could make very repeatable shots.

    So I changed my technique to pull two shots and then steam enough milk for two coffees which is working very nicely. But I guess I will come unstuck again, should a third person decide to join us for coffee!!! ;D

    So I can only conclude that as it is a problem after I have steamed, that its the whole temperature surfing issue with Silvia, and that its still quite hot inside, and I need to flush longer than what I am between coffees - in the past I have probably been flushing 60ml through! Lately I have tried flushing sufficient through to get the temperature indication on the PID controller down below 108 deg - which is what it is set at.

    Just wondering how other people get around this issue.

  • #2
    Re: Silvia & multiple coffees

    Myrtle, my silv isnt PIDd so i dont have your luxury.
    but i definately only steam after the 2nd/3rd shot which ever that may be.
    Basically i flush the group/GH (after each shot) until the boiler light flicks back on then i have my prescribed time (30-40 seconds.. whatever) to get ready to pull the next shot.
    agreed you need to go through some water to get there..

    Comment


    • #3
      Re: Silvia & multiple coffees

      Hi Myrtle,

      Basically, when you set your PID Controller up to control around a setpoint, in your case 108C.... The various setup functions will be more or less optimised for the particular scenario you used during the Autotune period, if your controller has this feature.

      It may be that you will have to change one or more of your setup parameters slightly to accommodate the different operating scenario you are now using. Also, it is a good idea to "Reset" your controller after steaming or any other operation that has resulted in a significant step change away from the nominal setpoint. This can be accomplished by simply turning the power Off briefly, for 5-10 seconds and then turn back On again. Id try the "Reset" manoeuvre first as this is the simplest thing to do, and just see how that goes.

      Cheers,
      Mal.

      Comment


      • #4
        Re: Silvia & multiple coffees

        Originally posted by Mal link=1170806138/0#2 date=1170824311
        It may be that you will have to change one or more of your setup parameters slightly to accommodate the different operating scenario you are now using. Also, it is a good idea to "Reset" your controller after steaming or any other operation that has resulted in a significant step change away from the nominal setpoint.
        Actually, that brings up a few interesting questions that I never got around to asking about the whole PID silvia thing. Most people seem to put their probe on the top of the boiler, where the tstats are. If you switch into steam mode, doesnt the whole boiler and group assembly heat up, which will make successive shots hotter? If the probe sits at the top of the boiler, how can it take into account the extra heat stored in the group head? For that matter, wont successive shots overheat?

        Of course, thats all grossly simplified because I have ignored the magnitude of the heating effect entirely. I know that when I backflushed my silvia several times in a row, the group would heat to the point that the water coming out was boiling and spitting. But how bad is the overheat effect for successive shots, or for pulling shots after steaming?

        Cheers,

        Luca

        Comment


        • #5
          Re: Silvia & multiple coffees

          There is no perfect location for the sensor on a PIDd Silvia. I prefer the top of the boiler because it is the hottest spot. If you control this temp then you can be assured of not overheating. If you attempted to use a sensor in the group for control, you would quickly overheat the boiler and blow the 165C tstat.

          The group temperature plays a major part in brew temperature. Unfortunately, with the sensor located on the top of the boiler, the group temp can only be controlled indirectly.

          The PID can usually handle easily the disruption caused by steaming. It will find its way back to SV pretty quickly without resetting anything. But it takes the group several minutes to cool back down to its normal temp after steaming - even though the temp at the top of the boiler has been back under control for some time.

          We use a temperature sensor permanently mounted to the group on our Silvia. With this it is pretty easy to tell when a combination of flushing and waiting has restored order. Shots pulled before the group has settled back in to its steady state temp will run a few degrees hot.

          So, what to do? Like Myrtle suggests, you can pull 2 shots consecutively (a "cleaning" flush in between will help stabilize the group temp). Or you can pull a shot, steam, then flush/wait until the group is back to normal (probably 10 minutes without flushing, 5 minutes with a few flushes).

          Any single boiler machine is going to have this shortcoming. Im not aware that the Silvia is any better or worse than others in this regard.

          Jim

          Comment


          • #6
            Re: Silvia & multiple coffees

            Lets not lose sight of the fact that as Jim says, the Silvia is a single boiler machine designed for one or two shots or milk drinks.

            It was never meant to keep brewing shot after shot after shot like a commercial or even a one-group heat exchanger machine.

            If it has a PID -- or doesnt---it makes no sense to brew/steam/brew/steam, or, as some people do, steam/brew.

            The critical thing is to pull the shot when everything is in a steady state temperature. Boiler, water, group, metal frame, everything.

            A PID will facilitate that with ease.

            Raising the temperature to around 160º --THATS RIGHT--for steaming., will throw everything way out, so its much preferable to brew first, then steam.

            --Robusto

            Comment


            • #7
              Re: Silvia & multiple coffees

              Yep,

              The thing is with any simple, single loop PID Controller, it isnt possible to model the thermodynamics of the Boiler, be it a Silvia, a Mokita or what ever you like. These controllers are essentially very basic in their design and only intended for very simple control, albeit very well for most applications that involve relatively slow rated disturbances to the PV. Single Boiler Espresso Machines dont really fall into that ballpark while a shot or shots are being pulled since this event significantly disrupts the thermo-stability of the system to beyond that which a simple PID Controller can manage adequately..... because of the lack of thermo-modelling capability or feed-forward technology.

              For most situations this isnt a big deal however as a routine is soon established that makes allowances for these shortcomings, and shot to shot thermo-stability is very reasonable. With my Mokita for example, once the system had attained thermo-equilibrium, it was possible to pull shots within a cycle time of 2 - 2½ minutes that provided for shot to shot temperature stability within a +/- 1.0C envelope.... nothing really wrong with that for most situations. The problem arises though when you complete a Milk Stretching Cycle and need to get back to the Brew Cycle within as short a time as possible.

              Because of the way that most of these Single Loop Controllers are designed, it is impossible for them to account for the existing thermal energy stored within the group and other attached heat tanks within the immediate proximity. The only way to overcome this within as short a time as possible, is to flush cooling water through the group and PF until the PV temperature is falling at a rate similar to that when a shot is being pulled and at a threshold that will allow quick recovery back to the nominal Brew Setpoint. It is at this threshold that the most benefit can be gained by Resetting the Controller as described above, thereby re-establishing the controller operational parameters to the scenario optimised for Brew Water Temperature stability.

              All this sounds a bit long winded for what is essentially a simple procedure for resetting the Controller back to its normal operating envelope, but it is worthwhile to understand what is going on so as to get the best out your particular system and minimise any waiting periods while the Controller cycles back and forth trying to attain its previous point of equilibrium .

              Cheers,
              Mal.

              Comment


              • #8
                Re: Silvia & multiple coffees

                Mal -

                I agree with your analysis of the situation, up to a point

                The problem that I have observed is not so much that the PID has trouble in re-stabilizing the temp at the sensor (in this case at the top of the boiler). The heat stored in the element definitely poses some challenges, but with a suitable choice of P, I, D parameters this can be mostly overcome.

                IMHO, the "problem" is that re-establishing steady control at the sensor location does not result in thermal equilibrium of the entire system (in particular the group). Even instantaneous, perfect recovery by the controller (using a reset, optimised tuning, or even magic) will not result in the group being brought back into equilibrium right away.

                Apologies for beating this to death - it is really a pretty insignificant point.

                The observations made by several on this thread are the important points: steaming messes up the thermal equilibrium of a single boiler machine to the extent that any reasonable control scheme is going to require a little bit of time to bring about complete system equilibrium again. Even simple PID control will make a big improvement, but will not completely change the nature of a single boiler machine.

                Jim


                Comment


                • #9
                  Re: Silvia & multiple coffees

                  Absolutely.

                  The one big advantage is being able to do a stand-up start to brewing a coffee. Walk up to the machine, and its ready. No surfing, flushing.

                  But once youre done the shot, and start thinking about some more.... thats another ballpark.

                  --Robusto

                  Comment


                  • #10
                    Re: Silvia & multiple coffees

                    Originally posted by robusto link=1170806138/0#5 date=1170840895
                    Lets not lose sight of the fact that as Jim says, the Silvia is a single boiler machine designed for one or two shots or milk drinks.

                    It was never meant to keep brewing shot after shot after shot like a commercial or even a one-group heat exchanger machine.  

                    If it has a PID -- or doesnt---it makes no sense to brew/steam/brew/steam, or, as some people do, steam/brew.

                    The critical thing is to pull the shot when everything is in a steady state temperature. Boiler, water, group, metal frame, everything.

                    A PID will facilitate that with ease.

                    Raising the temperature to around 160º --THATS RIGHT--for steaming., will throw everything way out, so  its much preferable to brew first, then steam.

                    --Robusto
                    Id second that- with the botticelli (soon to get PID) if I was making say, four milk drinks, Id brew the 2 sets of two, monitoring the temp (I have a thermocouple on the top of the boiler) then Id use my large jug to steam milk at between 135 and 140 C.
                    Works well
                    Brett

                    Comment


                    • #11
                      Re: Silvia & multiple coffees

                      Thanks for the discussion all.

                      I think sometimes we all need to be reminded of this ...

                      The critical thing is to pull the shot when everything is in a steady state temperature. Boiler, water, group, metal frame, everything.
                      Today I made my two shots as per normal and steamed the milk just how we like it. I had a few beans left over, so after I had enjoyed my great coffee, I decided to pull a third shot. No surprise it came out fantastic, just like the first two .... proving yet again - good things come to those who wait!

                      Comment


                      • #12
                        Re: Silvia & multiple coffees

                        after steaming milk if the coffe is great and I want another my process is pretty simple. flush the machine untill the themastat comes on, wait to reheat and flush again, grind and dose meanwhile flushing in preperation for a temp surf, then pull shot. I have found that the first two flushes of water will hiss out (at a guess that indicates the group/water to be over 100) the third must get it pretty close because the coffee is pretty consistent from the first to the second.

                        Comment


                        • #13
                          Re: Silvia & multiple coffees

                          Hi again All,

                          With the original issue being described relating to switching from a Steam Mode back to a Brew Mode......

                          The point I was trying to make is that there is a method using the basic PID Controllers that most of us use, which allows for reasonably quick recovery from "Steam" mode back to "Brew" mode and a Brew Equilibrium using a very simple method, that of "Resetting" the Controller as described above. If you are fortunate enough to own a Controller with more sophisticated (smarter) functions available, then it is possible that a Resetting manoeuvre is not required to switch back and forth between Steam/Brew modes..... The key points of the procedure being, from above....
                          The only way to overcome this within as short a time as possible, is to flush cooling water through the group and PF until the PV temperature is falling at a rate similar to that when a shot is being pulled and at a threshold that will allow quick recovery back to the nominal Brew Setpoint. It is at this threshold that the most benefit can be gained by Resetting the Controller as described above
                          Had been using this procedure with the Mokita for quite some time and after initial testing to verify that the Group/Boiler has achieved Brew Temperature Equilibrium, it was possible to pull a shot with the Brew Water Temperature on top of the puck measured with a small bead t/c that averaged 93C +/- 1.0C after a delay of only two minutes from stretching 500-600ml of milk.

                          Cheers,
                          Mal.
                          P.S.
                          I have a strong background in Process Control and various Servo Control Systems going back several decades and the information above was provided to assist those members who may have been experiencing similar issues to those originally described, and who may benefit from knowing about a simple shortcut to circumnavigate the usual waiting periods.

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