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VBM Domobar Piccolo thermostat

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  • VBM Domobar Piccolo thermostat

    Have been fixing up a Piccolo which I picked up recently.

    I have removed the boiler to fit a new heating element and after tightening and reconnecting everything I have been doing some testing. After quick test all functions are working normally with the exception maybe of steam mode. It does not seem to be turning off the element and I am not sure how long I am game to run it for but I need to know if the thermostat is faulty. I think either I have damaged the thermostat or it was already faulty and killed the old heating element. Much more familiar with HX machines and this thermostat is very odd.

    I know there is a thermal switch which will kill the element if it reaches 150 degrees but bit worried about killing the element or the machine.

    Couple of questions;
    1. It it normal for some steam moisture to escape from the thermostat boiler connection, particularly when in steam mode? I ask because when removing it from the boiler I did twist the thin wire around a bit and may have damaged it.

    2. How long should the steam mode take to run the element and turn off the lamp (with the machine warmed up with full temp for normal coffee mode)?

    Don't want to grab a new thermostat unless I have to.

  • #2
    Don't know if there are wiring differences between the older versions and the later ones. Did you only disconnect wiring on the Boiler or elsewhere as well?

    On my earlier one, the Active (Red) wire path to the heating element is always routed through the single 150 deg C thermostat mounted on top of the boiler. When the Steam switch is on, its a direct route so it acts as the steam thermostat. When powered on normally (Steam switch off), the Active (Red) wire path is first through the adjustable Bulb Capillary Thermostat, then through the 150 deg thermostat to the heating Element. (now acts to protect heating element if the capillary thermostat fails I suppose.)

    Earlier version of the Bulb Capillary Thermostat fits inside Thermowell mounted to Boiler (Thermal Paste required for better heat transfer) -

    Click image for larger version

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    Thermowell -

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    Later version of the Bulb Capillary Thermostat mounted directly onto boiler and has direct water contact -

    Click image for larger version

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    Question 1 - Not sure what you meant by this. Shouldn't be any moisture escape. Can you add an image of this. If the thin wire is the Thermostat Capillary tube then the main thing is that it has no sharp/tight kinks. It can be damaged causing it to leak and malfunction. If it's the earlier type inside the thermowell, it needs to be carefully pushed in until it bottoms out. If it's dried out inside the Thermowell, add some thermal paste to the bulb section which makes seating it smoother as well as having better heat transfer between the Thermowell and the Capillary Bulb. Sometimes the "spring" in the capillary tube can tend to lift the Bulb inside of the Thermowell. Adjust carefully so this doesn't happen. Keep the Capillary tube away from the "Hot" lines so you don't get heat transfer from these affecting the Capillary Thermostat.

    Question 2 - When the machine is fully up to Brew Temp, it only takes a minute or so (never measured) to come up to Steam Temp once the Steam button is turned on.

    You should use Thermal Paste between the 150 deg C thermostat and the top of the Boiler. The Thermostats are cheap enough to replace and probably better to do so on an older machine as there is no separate safety Thermostat.

    Vibiemme Thermostat 150°C 16A 250V - Part Desc. ELETGLDOM

    Click image for larger version

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    Last edited by CafeLotta; 21 February 2020, 05:44 PM.


    • #3
      Thanks CafeLotta!

      I only disconnected wiring to the boiler and water tank sensor plate, all other wires I left connected.

      Question 1 - My model must be the later version as it has the red wiring. I only removed the full sheath out of the boiler and didn't disconnect the thermostat bulb from the sheath etc. I am pretty sure I damaged it as when I change to steam mode with the higher boiler pressure steam is venting out of the sheath a bit like an anti-vac valve would release some steam. But in normal mode for running shots it is not venting and I can hear the element switch on/off normally. I will see if I can take a still shot when I do further testing tonight.

      Question 2 - I might take your advice and replace this item here as I don't want to blow up the boiler as I am not 100% sure the 150 degree thermostat is working properly. Or it could be due to the leak in the bulb or wire that the pressure won't get high enough to raise the temp to 150 degrees.

      Thanks for the info I was not sure how the pressure was set for steam so that makes sense that it switches to the 150 degree thermostat.


      • #4
        No worries. Does sound like the 150 deg C thermostat may be the culprit then. (Don't forget the Thermal Paste).

        Also if the Capillary tube is leaking you'll need to replace the whole Capillary Thermostat unit. When you say venting out of the sheath I'm still not sure where you mean?

        Check you're PM for some info re: parts.

        If you'd don't have a complete parts diagram, PM me an email address and I'll send you a downloaded PDF of the Vibiemme document.

        Originally posted by roosterben View Post
        "My model must be the later version as it has the red wiring.
        Just to clarify, "the red wiring" is actually a very small diameter liquid filled copper tube with a red outer protective sleeve (fairly sure these ones are liquid, not gas filled). If liquid is leaking out of the copper capillary tube the adjustable brew thermostat won't work correctly.
        Last edited by CafeLotta; 22 February 2020, 12:14 PM.


        • #5
          Thought I'd mention that if anyone's after a late model Vibiemme Piccolo and you can pick-up from around the Bondi NSW area, there's currently a late model used one for $800 on GumTree. I'd definetly have a look if I were local. Good value if it works OK.


          • #6
            Thanks CafeLotta got your PM.

            Yeah I will have to order some more parts I don't fancy blowing up the boiler. I am grabbing some pics now and will show you where it was leaking.


            • #7
              Here is a picture, when I switch to Steam mode the machine leaks some steam/water from this spot inside red circle in pic below.

              Click image for larger version

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              • #8
                Can't be 100% sure but to me it looks like it may be an earlier version boiler that has had a later version Capillary Thermostat installed. As the female thread is a different size for the newer version, it appears that a male to female adapter has been used for the new unit to mount into. Does your machine have the round red push-in buttons that light up? I believe the version which originally used the Thermowell had a 1/4" BSP female thread for the Thermowell. The new Capillary Bulb mount fitting is M12 thread I believe.

                Does the leak appear to be coming from the Capillary tube or from inside the male hex fitting the tube routes into? May just need more Teflon tape on the adapter fitting threads or possibly a missing seal/washer between the Capillary Bulb flange and the adapter fitting?

                Another slim possibility is mis-matching threads on the male/female adapter which the Capillary bulb mounting fitting screws into and the Boiler thread.

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                This is discussed in Post #90 of this thread. Even though it's on a Vibiemme Junior Dual boiler, I think the Brew boiler is somewhat similar to the Piccolo and Thread sizes may be the same -

                Last edited by CafeLotta; 24 February 2020, 10:19 AM. Reason: Info added


                • #9
                  CafeLotta: It is the version with the red push buttons that light up, I don't have decent picture of the front sorry. Not sure if it is leaking from the fitting or tube. Although logically it is probably the fitting as I can't image the tube would be venting steam/water or if it was then it would soon run out of moisture as it heats up. I will remove it the thermostat bulb assembly and separate the adapter and thermostat bulb and have a look. You could be right it might actually just need some plumbers tape and retightening, I haven't removed it yet as it is stuck fast pretty good but I will remove it and see what I can discover before I put in an order for more parts.


                  • #10
                    Here are a couple more pics;
                    Attached Files


                    • #11
                      Originally posted by roosterben View Post
                      CafeLotta: Not sure if it is leaking from the fitting or tube. Although logically it is probably the fitting as I can't image the tube would be venting steam/water or if it was then it would soon run out of moisture as it heats up. I will remove it the thermostat bulb assembly and separate the adapter and thermostat bulb and have a look.
                      I'd first concentrate on the seal between the small copper flange at the top of the thermostat bulb and the mating surface of the adapter fitting. If you can't tighten the Hex nut above the Bulb flange any tighter against the adapter then it may require a sealing washer of some description. If you're not seeing any leakage externally, the adapter to boiler thread connection and the adapter to Capillary Bulb nut threads are unlikely to be the source of the leakage. Try shining a torch inside the Bulb nut to see if you can spot where it is leaking.

                      The Red Button model you have would likely have originally had a Thermowell with the earlier version Capillary thermostat bulb sliding into it. Same model as mine.

                      Click image for larger version

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                      Original Thermowell and internal Capillary Bulb. (Stock Photo)
                      Last edited by CafeLotta; 25 February 2020, 09:33 AM. Reason: Photo added


                      • #12
                        CafeLotta you were on the money! I loosened all the boiler fittings, removed the thermostat assembly, then broke the seal between the two parts, the bulb and tube seemed sound so I applied heaps of plumbers tape and reassembled.

                        Finally did a full test today after letting everything dry out (due to loose nuts) and working perfect in normal and steam mode. No additional parts required after all.

                        Thanks for all the help on this thread, fun repair this was my first full boiler removal and 2nd/3rd heating element replacement.

                        Machine is now back to 100% and ready for a new owner.