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  • VBM Domobar Super temperature variability

    I use my VBM only 2 to 3 times a day and notice that the group-head temperature seems to stabilise at greatly varying temperatures, sometimes barely hot sometimes boiling.  I installed a Eric Svendson digitherm to see what was going on and indeed it shows a huge variation.  BTW, this is a real nifty device, see the pic.  The boiler pressure oscillates nicely around 1 bar so it would seem the pressurestat is OK.  Im going to give it a good descale, as soon as I get some descaler.  Any other ideas?


  • #2
    Re: VBM Domobar Super temperature variability

    what you are seeing is thermosyphon stall. It happens when there is an air or vapor gap in the heat exchanger and the convection current cannot overcome it. It is most often caused by doind a short group. Some of the water in the HX flash boils and causes a "gap" in the water. The preventitive measure is, as can be assumed, that when you do a group flush, make it for at least three or four seconds.

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    • #3
      Re: VBM Domobar Super temperature variability

      Thanks, Im sure thats part of it.  I have been doing small cleaning flushes.  However, that would account for the low temperatures.  What would cause the group to get to 100C as it does sometimes?

      Comment


      • #4
        Re: VBM Domobar Super temperature variability

        Hi Bob,

        How old is your machine?

        Was it an ECA import?

        Cheers

        Chris

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        • #5
          Re: VBM Domobar Super temperature variability

          Originally posted by 63565B5C68745851515252370 link=1327895468/3#3 date=1327918663
          Hi Bob,

          How old is your machine?

          Was it an ECA import?

          Cheers

          Chris
          A few years old now. I bought it at Sobonis at Pymble so it may well be an ECA import.

          Comment


          • #6
            Re: VBM Domobar Super temperature variability

            Hi Bob,
            Did you get an answer on the high temp?
            I have the VBM Super Electronica 2009 model with Erics temp as well and my std temp is around 210f if I leave on for a while. I can reduce the temp with back flush and other means and currently I brew at startinging temp 203f but keen to have std temp a bit lower.
            Pressure is between .9 and 1.1 bar with brew pressure showing 9.8 bar which as I understand means actual pressure at the group head is 8.8
            Keen to hear what options I have.
            Thx Rusty

            Comment


            • #7
              Re: VBM Domobar Super temperature variability

              Originally posted by 577A5056515C250 link=1327895468/5#5 date=1328873307
              Hi Bob,
              Did you get an answer on the high temp?
              I have the VBM Super Electronica 2009 model with Erics temp as well and my std temp is around 210f if I leave on for a while. I can reduce the temp with back flush and other means and currently I brew at startinging temp 203f but keen to have std temp a bit lower.
              Pressure is between .9 and 1.1 bar with brew pressure showing 9.8 bar which as I understand means actual pressure at the group head is 8.8
              Keen to hear what options I have.
              Thx Rusty
              Short answer, "No".  Im still playing with it.  The temperature occasionally sores to 100C, the water boils in the group head forming a vapour lock forms which shuts down the thermosiphon and the group head temp plummets to the 80s.  I have now set the boiler pressure to around 0.7bar.  This seems to help but I need more time to confirm it.  I suspect the 1bar recommendation is if you are pulling shots all day.  I rarely pull more than two at a time.  However, there is always the chance my gauge is inaccurate.

              I descaled the machine.  That certainly got some gunk out but didnt do anything for the overheating.

              I have a group head pressure gauge and find I need about 11bar on the dial to get 9bar at the group head with a double shot basket.

              Comment


              • #8
                Re: VBM Domobar Super temperature variability

                Sounds like its minus the ECA spec thermosyphon restrictor. Assuming its an ECA import, your supplying dealer will be able to fit one. There was a mob selling these some 5 years ago in Australia. The older machines are of different spec. and run hot.

                Comment


                • #9
                  Re: VBM Domobar Super temperature variability

                  Originally posted by 7144494E7A664A43434040250 link=1327895468/7#7 date=1328934771
                  Sounds like its minus the ECA spec thermosyphon restrictor. Assuming its an ECA import, your supplying dealer will be able to fit one. There was a mob selling these some 5 years ago in Australia. The older machines are of different spec. and run hot.
                  I had a look and couldnt see anything that looks like a flow restrictor, so where do I get one? Id like to install it myself. However, one has to ask why this has become such a problem only after a few years of reasonably satisfactory operation. I suspect something else is faulty or needs maintenance. Any ideas?

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                  • #10
                    Re: VBM Domobar Super temperature variability

                    OK, so I put the VBM in to ECA for a long overdue service.  It came back looking like a new machine.  I mentioned the flow restrictor issue but neither the storeman nor the tech new what I was talking about so I let it go.  Unfortunately the overheating is still there.  Ive got it to stabilise somewhat by setting the boiler pressure to just under 0.8bar.  This gives me a brew temp in the low 90s.

                    A warning to all E61 HX users not to install Erics thermometer.  It is a wonderful piece of kit but what it does is tell you how poorly these machines are regulated.  I defy anyone to pull a shot at a consistent 92°.  Sure if you are really careful and employ a long flush and wait technique you might be able to average 92° but average is not the same as consistent.  Also, I dont think it acceptable that one should have to use long flushes to get a decent shot out of a machine this expensive.

                    Before Im bombarded with derision, I would like to qualify my comments by saying that I have no doubt HX machines work great in a heavy use environment where each shot stabilises the next but for the home user that might pull just a few shots irregularly during the day, the HX just doesnt do the job.  Im thinking PID machines might be the way to go.

                    Comment


                    • #11
                      Re: VBM Domobar Super temperature variability

                      I am sorry Bob, but I have to disagree with you.

                      Scace II traces prove that these (ECA imports) can and do run beautifully- and consistently.

                      The original importers of VBM delivered a totally different configuration- with domestic pressurestats and smaller boilers. They were hot running dogs.

                      Personally, I dont place too much trust in a meat thermometer jammed into a group as it has little to do with what occurs at the puck.  :-?

                      As youre in Sydney, I suggest you speak with Charlie, Renzo or Dennis (Jetblack, Di Bartoli or cuppacoffee respectively). A Scace calibration together with the installation of appropriate thermosyphon restriction will deliver you a totally changed beast.

                      Bottom line is that there are a myriad of brilliant HX machines out in the field and when well designed and calibrated appropriately for the Australian market, they are excellent.

                      Chris

                      Comment


                      • #12
                        Re: VBM Domobar Super temperature variability

                        I have a VBM Domobar SS, bought through Chris/Dennis. The only time I have heat issues are when I leave the thing running for hours on end without making a brew. When this is the case, I run a long flush (until the water coming out of the grouphead is no longer flash boiling) at which point I start my grind/tamp routine.

                        This gives me a pretty decent result on a regular basis.

                        Grant

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                        • #13
                          Re: VBM Domobar Super temperature variability

                          I dont recall ever seeing my VBM Domobar SL flash boiling.

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                          • #14
                            Re: VBM Domobar Super temperature variability

                            Originally posted by 6B5E5354607C5059595A5A3F0 link=1327895468/10#10 date=1331422697
                            Personally, I dont place too much trust in a meat thermometer jammed into a group as it has little to do with what occurs at the puck.  :-?
                            It is a well-designed add-on and it really works. Can be used to easily create a consistency in the temperature of the extraction and costs a LOT less that a Scace which can be used to set an OPV or a pressurestat but will NOT give feedback in actual use. They are two different tools that are designed to do two different jobs.

                            Comment


                            • #15
                              Re: VBM Domobar Super temperature variability

                              If a bloke grabs a trout upstream, I dont neccessarily assume Ill get one 3 ponds down.

                              Whilst the meat thermometer will measure water temperature, its not at the puck and to presuppose that hot means a hot extraction is by nature an extrapolation. Theyre damn good when shoved up the rear end of a chook though.

                              Ill back my Scace as a more accurate approximation. As for the OP, a bead probe at the puck would be well worth a try. My diagnosis and recommendations stand.

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