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Bezzera Duo DE Dual Boiler

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  • #31
    Adjusting the steam and water wands ON position is easy. Just turn the wand on in the position that it holds on by itself. While clicked on, you can rotate it to any position you like; up, down, or sideways. The Duo wands are far superior to the ECM wands in my own experience and humble opinion.

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    • quester
      quester commented
      Editing a comment
      Thanks Mike. I wasn't so bothered by the locking direction but, rather, the lever not locking in position. As you say, it's quite cool that you can easily rotate the lever, in the locked position, to change the direction it locks in.
      The adjustment of the locking sensitivity, and changing locking direction, is shown in this Whole Latte L Youtube clip: https://www.youtube.com/watch?v=UoDRdSXV06U at about the 18 min mark in the Youtube entitled: Review: Bezzera Matrix and Duo Internal Components

    • quester
      quester commented
      Editing a comment
      Just an update on my steam lever, which wasn't locking in at 12 o'clock. Discovered, this morning, that the lever was locking in properly.... at 1 o'clock. Followed Mike's advice here, locked it in at 1 and rotated anticlockwise to 12. Done. Thank goodness I didn't need to fiddle with the valve!

  • #32
    The grippiness of the group gasket is because it's a big fat soft O-ring rather than the conventional square-cross-section group gasket. The o-ring is great because it compresses to make the seal with only a fraction of the handle force. I found if you insert the portafilter too tightly, it gets grippy. I am now more delicate with my insertions!!!!

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    • #33
      Just wondering whether anyone has run a Scace pressure gauge over the Bezzera Duo DE? I'm wondering how close was the correlation between the displayed pressure and that measured at the portafilter?
      The Duo DE comes preset to around10.5Bar - don't know why. I have set my pressure to 8.5Bar but the digital gauge is quite coarse and reads in half a bar increments. So it flicks between 9bar with prewetting, comes back to 8.5Bar and, if I have the grind a little wrong, it will go down to 8 Bar.

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      • #34
        Hi Quwsyer. I made my own portafilter pressure gauge. While the Duo pressure gauge moves around a bit but averaging 8 bar, my portafilter gauge measured spot on 8 bar. Click image for larger version

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        • #35
          Click image for larger version

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          • #36
            I can't fathom why the Duo gauge jumps around while the gauge on the portafilter is steady. It might be because the analogue passive gauge has a slow lag time constant by virtue of the viscous oil. The electronics in the Duo might be measuring instantaneous pressures with no smoothing. Or the pressure transducer might be 'noisy'. Further investigation needed!!

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            • #37
              OMG! this guy is Good! Thank you Mike. That is really informative and what a great innovation. Your own Scace! Very reassuring measurements too. Next stop will be how the temperature at the puck compares to the displayed setting. I have my temp set to the text book 94 degrees. Not having a place for a grouphead thermometer is a bit of a tease (compared to the E61) though the shower screen gasket seems flexible enough to sneak a thermocouple wire in. My difficulty with that is that my Fluke's thermocouple reads approx 4 degrees out. So much for buying quality.
              In the meantime, I can't get over the great steam pressure in this machine and the quick warm up time. It really is a joy.

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              • level3ninja
                level3ninja commented
                Editing a comment
                That's just a pressure gauge, not a Scace device.

            • #38
              Hi Quester,

              I did a few tests to confirm group head temp. I took the top off the machine and saw that the thermocouple that senses temperature for the BZ PID is located at the back of the group head assembly where it attaches to the front panel of the machine. The head heating element is 120W. O measured 0.5A into the head. I also noted that the indication on the LCD that the boiler is heating (the little red bar) follows the boiler heater only, not the head heater. That's ok.

              I placed a tiny thermocouple up tight behind the group head but in front of the lights. Stuck it in with some bluetac and compared the indication on the LCD panel vs my Fluke. The results were spot on. So I'm comfortable that the measured temp is much the same as the indicated temperature.

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              • #39
                I was initially concerned that the placement of the internal thermocouple was not right. The placement of the sensor behind the head heating element is about the same distance as the grouphead is in front of the heating element. So it's in fact an excellent replica of the head temp.

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                • #40
                  Hi level3ninja,

                  You are right that it's just a pressure gauge and not a Scace. A Scace is an identical glycerin-filled gauge combined with a thermocouple. I measure temperature separately with a range of thermocouples and meters. If one wants to measure (maximum) pump pressure with a blanking basket then my set-up is fine. If I wanted to simulate the resistance of an 18gm double-shot coffee puck, I could add a bleed-off tap in between the portafilter and the gauge and set it to a bleed-off of say 45mls in 20 seconds. For me, I think that's not necessary given the rotary pump regulation is strong when comparing the (infinite) resistance of the blanking basket to the lower (but still high) resistance of the coffee puck. It seems to me that the Scace is very nice but very expensive for what it is. cheers Mike

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                  • #41
                    Hi Quester,

                    Hope you're enjoying your Duo. I noticed that the Duo does not have a pressure sensor on the steam boiler or steam circuit. I checked the exploded view of the Duo Parts Diagram (available on the Barazi website) and confirmed that no pressure sensor is present. (Of course the coffee boiler/group does have its own pressure sensor). The steam boiler, as we know reheats under the control of the temperature PID ie the boiler temperature is a surrogate for boiler pressure. So the indicated steam pressure on the LCD is calculated, not measured as far as I can see. The relationship between temperature and pressure in a boiler (of fixed volume) is essentially linear. The line of best fit to describe the relationship that Bezzera probably used (in the firmware) is something like Pressure = 0.0587 * Temperature - 5.87 for Temperatures between 100C and 130C. This relationship is typical and essentially the same for any water/steam boiler (assuming the water level is equivalent to about 50% water volume/50% steam volume). So does this matter? While an analogue physical pressure gauge is measuring actual pressure and the Duo is not, it makes no difference to the actual available steam. As we know the Duo has great steam, but maybe we don't know the real pressure at the time we're using it. It would be worthwhile making a quick comparison to say an ECM Syncronika to see if the PID temperature equates to a similar pressure as is indicated on the Duo. cheers Mike

                    Comment


                    • #42
                      Originally posted by mikef View Post
                      The relationship between temperature and pressure in a boiler (of fixed volume) is essentially linear.
                      The relationship between temperature and pressure in a saturated steam boiler is independent of the volume of the boiler.

                      Where volume matters is in how much steam will be available and how much steam can be produced in what period of time.

                      Originally posted by mikef View Post
                      While an analogue physical pressure gauge is measuring actual pressure and the Duo is not...we don't know the real pressure at the time we're using it.
                      If the Duo is using the measured boiler temp in its calculation you know the actual boiler pressure.


                      Java "Science is fun!" phile
                      Toys! I must have new toys!!!

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                      • #43
                        Originally posted by Javaphile View Post
                        The relationship between temperature and pressure in a saturated steam boiler is independent of the volume of the boiler.
                        Incorrect. If the boiler is not of fixed volume and can expand with pressure the relationship is no longer linear and does depend on the boiler volume, that’s why Mike specified “of fixed volume”.

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                        • #44
                          Hi Javaphile. Thanks for your comment. My fluid dynamics are very rusty. Yes the boiler is saturated.

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                          • #45
                            Originally posted by Blackfish View Post

                            Incorrect. If the boiler is not of fixed volume and can expand with pressure the relationship is no longer linear and does depend on the boiler volume, that’s why Mike specified “of fixed volume”.
                            Whether the boiler expands or not doesn't matter to the relationship between temperature and pressure. If you know the temperature in the boiler than you also know the pressure no matter how large or small the boiler is.

                            You are heating the water to a set temperature. If the boiler expands increasing its volume then the temperature and pressure will drop triggering the heating circuit to kick in to get the boiler back up to temp. This will continue until the system reaches stasis, ie the boiler stops expanding, or the boiler explodes.


                            Java "Great expanding boilers Batman!" phile
                            Toys! I must have new toys!!!

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