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VBM Domobar Junior brew pressure too high?

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  • #16
    I've read about temp gauges that you can install on an e61 group head, I assume that would give you a fairly accurate reading of the water passing through the grouphead and slightly just over a puk?

    Or do you just need a scace device?

    Comment


    • roosterben
      roosterben commented
      Editing a comment
      There are E61 temperature sensors and they are usually within 2 degrees of the temperature at the puck. I used one for a few months. If you Google "Coffee Sensor" you will find a few options, I don't think any sponsors are selling them and it might be easier to order one from overseas.

    • lancruiser
      lancruiser commented
      Editing a comment
      There is a forum member selling a e61 group head thermometer.

      https://coffeesnobs.com.au/forum/mar...up-thermometer

  • #17
    So I guess something like this would work?

    https://alternativebrewing.com.au/pr...d-thermometer/

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    • #18
      I have similar. They are accurate for the position tested, and consistent. So I guess once you work out the offset, they work well.
      certainly made my cuppa better

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      • #19
        Originally posted by anthonypiccolo View Post
        In terms of measuring temperature, is this the kind of multimeter which could work? https://www.jaycar.com.au/cat-iii-mu...ature/p/QM1323

        How do I actually use this?

        Also, I know it's not a good solution, but how can I use my milk jug thermometer in the mean time?
        A cheap and reasonably reliable way of doing it without a scace is to use a thermometer with a thermocouple lead. A good option is the TM-902C on ebay, it's about $20. It's not as accurate as a higher end device so it's not what you'd use to set up a machine professionally however for home use and basic troubleshooting, it's going to do fine. It responds fast which is what you want.

        Prepare your portafilter as if to make a shot then run the thermocouple over the edge of the basket and position it on top of the middle of the puck. Lock the portafilter in and begin extraction. If the group seal is soft, there should only be minimal leakage around where the lead enters the basket. This shouldn't affect the results too adversely. If the seal is hard, it may leak more which could skew the results.

        The temperature you want to look for is a few seconds after the machine reaches full pressure.

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        • #20
          So I installed a coffee sensor on my machine, first extraction was about 89 degrees at the group on the sensor, before this it was sitting at around 86 or so degrees.

          Is this not hot enough? Should be 92-94 degrees at the group? Is there an easy way for me to increase the temperature on the machine? Could this be what is causing espresso to have a distinct sour taste?

          Comment


          • ev
            ev commented
            Editing a comment
            Be sure to let your machine fully warm up before adjusting the pressurestat (increased boiler pressure = higher brew temps). I find that my Domobar Super needs to be running for ages before temps hit the 90's. Let it sit for a couple of hours, flush some water through the group & watch the temp gauge. I flush mine until the temp rises to 93-94 deg & stop it when it stabilises.

        • #21
          How do I adjust the pressurestat though?

          And you leave your machine running for a few hours before you make coffee all the time? Or specifically for instances when you want to adjust the temperature?

          And is extracting at 89 degrees at the group too low? Should be 92-94 right?

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          • ev
            ev commented
            Editing a comment
            I never switch my machine off, only for servicing or holidays.

            The group temp sensor is only an indicator as it's not actually at the puck. It'll help you understand the behaviour of your machine. I get good shots even though the gauge drops to 89-90 after a long cooling flush. Your machine will most likely behave differently. Before you assume that it's too cool, let it run for longer to ensure it has actually reached a good working temp. If after a couple of hours, a flush doesn't bring the temp up into the 90's, then consider adjusting the pressurestat. I can't advise you on how to do this because I don't know what pressurestat you're running. I have my Sirai PStat set to 1.2 bar which seems to be the sweet spot for brew temp & good steaming.

        • #22
          Boiler pressure seems to drop to 0.9 then it goes up to 1.2 BAR, machine has been on for almost 2 hours and the group temperature is 87.3 degrees which I assume wouldn't be able to get to the sweet spot of 92-94 degrees when extracting at this point. So I'm assuming turn the pressurestat to raise the temp and get it above that 1.2 BAR? I assume somewhere around 1.5 BAR?

          And I was just going to adjust the pressurestat here;

          Comment


          • ev
            ev commented
            Editing a comment
            If the temp doesn't increase as you run more water through, you may have no choice but to increase the pressure. Yes, that hole at the top is most likely the pressuretat. I wouldn't go too far though. Try 1.3 bar & retest. For safety, best to switch off power before adjusting.

        • #23
          I actually just ran a cooling flush for around 15 seconds, the temp went just over 90c, then while I was extracting it was around ~89c at the group, so clearly never able to get higher. I mean surely I shouldn't have to flush for a minute or something before every coffee right?

          Comment


          • ev
            ev commented
            Editing a comment
            That's really not too bad. Bump up the pressure slightly & have another go. My gut feeling is that your coffee has been sour because you haven't been letting your machine warm up fully.

        • #24
          I've adjusted to 1.3 BAR for the boiler pressure now, was getting up to 1.2 BAR.

          Someone in the thread previously they needed to get it to 1.5 to brew coffee at 92-94C though.

          How long will it take for the temperature to have a noticeable change in the grouphead? I mean, should I keep adjusting the pressurestat up until the grouphead temp sits at around 92C when extracting a shot? Will it always be higher or lower at the puck?

          Comment


          • ev
            ev commented
            Editing a comment
            Why not just stop at 1.3 & see how your coffee tastes over the next few days? 1.3 is bar is pretty high. Why stress boiler components unnecessarily? Maybe some experts can chime in & offer some professional advice on the subject.

        • #25
          Originally posted by anthonypiccolo View Post
          I've adjusted to 1.3 BAR for the boiler pressure now, was getting up to 1.2 BAR.

          Someone in the thread previously they needed to get it to 1.5 to brew coffee at 92-94C though.

          How long will it take for the temperature to have a noticeable change in the grouphead? I mean, should I keep adjusting the pressurestat up until the grouphead temp sits at around 92C when extracting a shot? Will it always be higher or lower at the puck?
          Adjust a max of 0.2 bar at a time, allow the machine to idle for at least 30 minutes then take another measurement.

          The boiler safety valve is rated at 1.5 bar so you'll know if you're nearing the limit if it starts to hiss. I would not recommend running it over 1.3-1.4 bar though.

          The last machine I did was indicating 1.5 bar boiler pressure but the safety valve wasn't leaking at all and the boiler temperature did not represent 1.5 bar pressure. The gauges aren't always accurate. 1.5 bar should be 127C yet the indicated 1.5 bar was giving 120C (1 bar).

          If you're still unable to at least hit 93C during extraction with the machine indicating 1.3-1.4 bar, I'd hesitate pushing it further without monitoring boiler temperature. Going beyond pressure adjustments will be thermosyphon restrictor modification.

          Regarding heat up times, ​​​​​​​I expect an E61 equipped HX machine to be fully heated and ready for use after a maximum of 40 minutes. If it takes longer than that, it's not working properly.
          Other opinions may differ but that's what I think is reasonable to expect for home use.

          Comment


          • #26
            New Zealand variety (maybe a different restrictor in the thermosyphon?) I have a thermometer installed through the front of the group head so in the flow just above the Puck. The machine comes up to temperature and that reads about 96deg at idle. I take that to approximate the group temperature when just sitting there. A brief flush during which the temp rises to about 99 deg... About 2-3 seconds. Prep then extract for 25 seconds and the thermometer shows a brief rise to 97 deg or so settling to about 95deg during the extraction. Afterwards it settles at about 93 and slowly rises back to 95-96 deg over 15-20 minutes. This is with the boiler pressurestat set to peak at 1.2 bar. The coffee is good.

            Comment


            • #27
              Originally posted by GaryM View Post
              New Zealand variety (maybe a different restrictor in the thermosyphon?) I have a thermometer installed through the front of the group head so in the flow just above the Puck. The machine comes up to temperature and that reads about 96deg at idle. I take that to approximate the group temperature when just sitting there. A brief flush during which the temp rises to about 99 deg... About 2-3 seconds. Prep then extract for 25 seconds and the thermometer shows a brief rise to 97 deg or so settling to about 95deg during the extraction. Afterwards it settles at about 93 and slowly rises back to 95-96 deg over 15-20 minutes. This is with the boiler pressurestat set to peak at 1.2 bar. The coffee is good.
              Mine definitely doesn't get that high, got to about 89 degrees after leaving the machine on for an hour or so, then got it to about 91 degrees after flushing for 6-8 seconds. After I brewed the shot, still had a distinctive sour taste. Doesn't matter what I do with my dial in / brew ratio. The boiler pressure is now about 1.3 and the brew pressure is around 9.5 BAR or so, thinking of lowering it closer to 9 to see if that makes any difference.

              I just don't understand what is causing this. The coffee is horribly sour...

              Comment


              • ev
                ev commented
                Editing a comment
                Are you sure that the coffee you're using is ok?

            • #28
              From Square One roaster here in Melbourne. Has tasted like this since I first bought it fresh. Have had this issue with all other reputable coffee, Small Batch, Proud Mary, Industry Bean etc

              Maybe it’s my grinder? I’m using the Vario which I had to recalibrate recently and I can hear the burrs touch at 2Q which is what it is supposed to be. Maybe the grind isn’t consistent though? I have noticed that vibration seems to move the dial. For example, I can have it set to 1G, then the next time I go to make a coffee I’ll notice it’s at 1E. I’m not sure, perhaps I could try with another grinder to rule that out as it’s probably not the machine at this point right?

              Comment


              • ev
                ev commented
                Editing a comment
                I doubt your grinder will be the culprit. Are you new to espresso making? Is it possible that your technique is off & causing excessive channelling?
                The perfect technique can take years to master. I've had my VBM for 16 years & only just stumbled on a technique to reduce channelling! We're always learning. Once you're confident that your dose, grind, distribution & tamping are all perfect (correct flow rate without channelling), then start investigating faulty equipment.

            • #29
              Originally posted by anthonypiccolo View Post
              Mine definitely doesn't get that high, got to about 89 degrees after leaving the machine on for an hour or so, then got it to about 91 degrees after flushing for 6-8 seconds. After I brewed the shot, still had a distinctive sour taste. Doesn't matter what I do with my dial in / brew ratio. The boiler pressure is now about 1.3 and the brew pressure is around 9.5 BAR or so, thinking of lowering it closer to 9 to see if that makes any difference. I just don't understand what is causing this. The coffee is horribly sour...
              Time to get it looked at.

              Comment


              • #30
                One thing that I have noticed, which I don't think used to occur on this machine years ago, is that when I use some espresso cleaner (Caffeto) and a blind filter. There is so much pressure to the point where theportafilter is stuck. I try and wait for the brew. pressure gauge to go down so I can get the portafilter out but as soon as. I pull the lever it goes up to almost 10 BAR so quickly. When this happened. beforeit basically exploded and even gasket and shower screen popped out.

                When doing a backflush clean, I've also noticed that hardly any coffee or the Caffeto product is flushed through the drain of the. group. In fact, I remember when I did this years ago I would see some coffee residue and the Caffeto product and would keep backflushing until it was essentially clear water. Now almost nothing comes through, including water.

                Could that be a potential issue here?

                Comment

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