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  • Giotto Pressure cycle for steam

    Hi all,

    As ACT temperatures have dropped latey, the Minister for Finance has been requesting hot chocolates to ward off the chills, with a shot of Baileys too! I digress...

    Anywho, I have noticed that while texturing milk, with the pressure guage at 1.2 bar, the guage will drop to lower than 0.7 bar before the pump kicks in, about 40 seconds. Im trying to texture a 2/3 filled 600ml jug and about the same time the temperature gets to 60 degrees, there is a hint of a screech beginning and the swirl slows down. I get the impression its about to run out of oomph.

    Without a jug, from 1.2 bar, tap open full, 40 seconds to drop to 0.7 bar, a pump cycle, mabye 3 seconds worth, impressive twin streams of dry steam clearly visible. Another 40 seconds, about 0.4 bar, another quick pump cycle, steam is no longer visible, wouldnt move coffee grinds off a tea spoon.

    My question for experienced Giotto owners is, does yours behave the same, machine that is? What is the "normal" pressure drop before the pump kicks in? Is there a minimum? Im not really concerned about the pressure guage, its only an indication. My concern is that the Silvia can beat the pants off it.

    Boris

  • #2
    Re: Giotto Pressure cycle for steam

    Originally posted by Boris link=1175907475/0#0 date=1175907475
    Without a jug, from 1.2 bar, tap open full, 40 seconds to drop to 0.7 bar, a pump cycle, mabye 3 seconds worth, impressive twin streams of dry steam clearly visible. Another 40 seconds, about 0.4 bar, another quick pump cycle, steam is no longer visible, wouldnt move coffee grinds off a tea spoon.
    Thats an interesting observation Boris that prompted me to check mine...
    No jug starting from 1.1bar, tap fully open drops to .9 immediately, then at 60 sec a 2-3 sec pump cycle and still heaps of steam until we get to about 90 sec, then like yours drops down progressively and quickly to .4bar and stays there

    Comment


    • #3
      Re: Giotto Pressure cycle for steam

      The pump cant be looking at pressure for when to run , this would lead to the possability of no water but full pressure, not good on any pressurised steam system, BANG.

      The pump has to be level controlled, anything else would be dangerous.

      The pump is putting relatively cool water into the boiler, so cooling the remaining water, reducing steam production by the amount of heat required to raise the "new" water to the boiling point for the pressure.
      As the element is putting a finite amount of heat energy into the system, this produces a finite amount of steam, this amount of energy is set by the amount of "stored" energy in the system and the ability of the power source to supply energy to the element without overload, 240 volt/10 amp, 110 volt/ 15 amp.
      This is expressed as the wattage of the element, 2400 watts from 240 volts at 10 amps, but only 1650 watts from 110 volts at 15 amps
      This is why the euopean machines dont work well in the US, not enough energy comeing in. :-[

      Any addition of cool water reduces the steam produced by the amount of sensible heat energy required to raise this water to boiling, reducing the heat energy availble to be consumed as latent heat to fuel the phase change of water to steam, this equates to reduced steam production.
      The only work around that I can think of is to only allow the pump to top up the steam boiler when it is at full pressure, so there is no influx of cool water when steam is required, and so no reduction of the amount of steam being produced.

      This could be potentually dangerous, like in the situation of the steam wand being left open, lowering the pressure and so not allowing the pump to top up but at the same time using boiler water.
      This would lead to the water level dropping enough to allow the element to be exposed allowing it to over heat.
      The system as it stands will run the pump, topping up the boiler, until the water runs out, then the low water cut out will shut the system down, much safer.

      A larger wattage element would require a 15 amp power point, so while we are better off than the yanks, it is fixed when it comes to energy out of the system.

      You only get out what has been put in.

      I just had a thought, is your Giotto an old one?
      If it is then it has a smaller boiler, and so less stored energy in the form of heat in the water, the new Giotto premium has now got a larger boiler, and so can produce more steam from the "Stored" energy in the increased volume of water in the boiler.

      Sounds like a good excuse to upgrade to me :

      Comment


      • #4
        Re: Giotto Pressure cycle for steam

        Just to compare I tried similar onmy Expobar.

        No jug starting from 1.2bar, tap fully open drops to .9 immediately, then at 25 sec a 1 sec pump cycle and still heaps of steam but pressure dropping to .8, at 50 seconds a 1/2 second pump.
        Stopped at 60 sec, pressure about .7

        - 1.8L boiler
        - 1300W heating element

        Comment


        • #5
          Re: Giotto Pressure cycle for steam

          Hi Andy G - some interesting comments. Bottom line is I have never run out of steam, so no problemo, and I do have a giotto premium which is only a couple of months old.

          TG - Im not sure if Expobar owners are allowed to post here ;D Jokes aside, why did you stop at 60sec? Your machine seems comparable at that point. Take her to the limit TG!

          I feel like Scotty from the starship enterprise ;D

          Comment


          • #6
            Re: Giotto Pressure cycle for steam

            You answered the question Dennis.
            Seemed so close that I couldnt be bothered going any longer.


            P.S. My Expobar sits nicely in this category thank you very much. (Bloody ECM Snobs)

            Comment


            • #7
              Re: Giotto Pressure cycle for steam

              Originally posted by Thundergod link=1175907475/0#5 date=1175942602
              You answered the question Dennis.
              Seemed so close that I couldnt be bothered going any longer.

              P.S. My Expobar sits nicely in this category thank you very much. (Bloody ECM Snobs)
              Thank goodness my new glasses arrived this week - what a great idea for a t-shirt..."Im an ECM Snob"

              Comment


              • #8
                Re: Giotto Pressure cycle for steam

                Bling on its own does not a great coffee make...... Lets leave the machine snobbery for another forum shall we,

                Mal.

                Comment


                • #9
                  Re: Giotto Pressure cycle for steam

                  Well so far the concensus is that my Giotto (yes its a new type) is performing the same as others. :-?

                  Id be interested to hear from anyone with a Expobar Minore II. Ill assume that as they have a seperate boiler, there is no preformance loss.

                  Any chance we can have a comment from the guru of ECM? Id love to see the design intent / quoted capability. Ill be in Italy later in the year, might swing by if were close enough. ;D

                  Boris

                  P.S. Thundergod, I would like to order a XL T shirt please!! "Im an ECM Snob" Love it. ;D

                  Comment


                  • #10
                    Re: Giotto Pressure cycle for steam

                    Originally posted by Boris link=1175907475/0#8 date=1175988697
                    Well so far the concensus is that my Giotto (yes its a new type) is performing the same as others.  :-?

                    Id be interested to hear from anyone with a Expobar Minore II. Ill assume that as they have a seperate boiler, there is no preformance loss.

                    Any chance we can have a comment from the guru of ECM? Id love to see the design intent / quoted capability. Ill be in Italy later in the year, might swing by if were close enough. ;D

                    Boris

                    P.S. Thundergod, I would like to order a XL T shirt please!! "Im an ECM Snob" Love it. ;D
                    Seems to me, that each machine is capable of turning out two milky drinks and doing that pretty consistently. The bottom line is not really how much steam, more can it keep up with you- i.e recovery time. Try making 10 and see what happens...Ultimately, steam comes out of a 1.8L boiler which contains a HX- in both machines. Performance would be similar when the pressurestat is set identically- BUT I suspect the Giotto would have a slight edge as it has a larger element (1300W) than the Minore which has 2 x 1200W. Neither is a commercial machine and neither can be expected to keep up with one....

                    2mcm

                    Comment


                    • #11
                      Re: Giotto Pressure cycle for steam

                      Im pretty sure recovery time is more than adequate.
                      It would just be a matter of how you made the drinks.
                      Shot, steam, shot steam or whatever.

                      I havent tried it but with two PFs with double baskets I reckon I could make four coffees in a minute and texture enough milk in a large jug for those and by the time Id cleaned, refilled and tamped the PFs it would be ready for another go.

                      As it is though the machine more than adequately keeps up with me.

                      The only thing Ive noticed recently that would slow it down is drawing 400 mls from the tap for two mugs of tea.
                      In which case they would be done last if required.

                      Comment


                      • #12
                        Re: Giotto Pressure cycle for steam

                        Yep,

                        Prosumer machines dont have the boiler volume or heater power to steam forever....

                        There is a HUGE thermal capacity difference between a 17 L boiler of water at 125C and a couple of litres at the same temp..... Add enough water to replace that given off as steam.... and the temp of the 17L barely drops..... but for the 2 L you have just added a significant percentage of cold water- which reduces the temperature very significantly.....

                        Then you have a 4Kw heater restoring the temp (the couple of degrees needed) in the commercial compared to 1.3Kw to make a much larger increase in temperature with the prosumer.....

                        A prosumer, (as Thundergod said above) is really designed for shot / steam...... allow recovery whilst grinding then shot / steam again...... and that will work really well....

                        If you want to texture half the milk in the dairy in one sitting - then you need a full commercial (and allocate the space and be prepared to pay the power bill to use it)

                        Comment


                        • #13
                          Re: Giotto Pressure cycle for steam

                          Had people over tonight and made 8 milk coffees, a hot chocolate and two teas.

                          I couldnt be bothered setting up my 2nd PF with another double basket to push (test) the machine so just split the shots for two coffees at once and steamed milk then did two more until I was done followed by the hot chocolate.
                          Then poured the water for the teas and as expected the boiler refill dropped the pressure to billy-o.

                          By then I was sweating but the machine didnt bat an eyelid.

                          While everyone enjoyed their drinks I backflushed, refilled the reservoir and cleaned the bench - all done.

                          As JavaB said, shot / steam works really well.
                          It doesnt actually need grinding time to recover.
                          Empty / clean PF + dose tamp time is more than enough if it hasnt already recovered by the time Ive poured the milk.
                          Ive never actually noticed any need to recover whilst making multiple coffees.

                          Comment


                          • #14
                            Re: Giotto Pressure cycle for steam

                            Originally posted by Thundergod link=1175907475/0#10 date=1176003781

                            As it is though the machine more than adequately keeps up with me.
                            In my case its more a matter of me keeping up with the machine than the other way round

                            Comment


                            • #15
                              Re: Giotto Pressure cycle for steam

                              My machine had its first test yesterday - knocked out 10 milk coffees without any fuss at all. Like TG, it was me working up the sweat.

                              Very happy with the end result.

                              Comment

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