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Rocket Giotto V2 - expansion valve outlet dripping: how much is ok?

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  • TC
    replied
    All V2 (at least the Aussie ones) have insulated boilers.

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  • colombiasmoothbean
    replied
    Thanks all!

    This is fixed for now. I adjusted the pump pressure, the exp valve outlet stopped running at just under 10 bar, to 9 bar. Of course I can't be sure if the gauge reads correctly. After Christmas I'll take the panels off and check the OPV to see why it lets go at that pressure, adjust it and see what happens.

    Reading various posts I note that 9 bar is considered just about right. I just pulled a shot and it is fine. Is there any reason to go up/down from that?

    When I take things apart to check the OPV I should insulate the boiler (I assume it is not insulated). Any suggestions on preferred insulation material I should use?

    Thanks again, all!

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  • artman
    replied
    I had a similar thing on my Faema, it ended up being the pump bypass piston/adjuster being jammed inside the pump head, causing the pressure to go sky high and the OPV dumping all the excess water. Your brew pressure showing 10 bar is about right though, the OPV is normally set to 12, perhaps it is adjusted low? Or your gauge is not correct? You would need a known good pressure reading to start diagnosing. As mentioned above, its probably slightly too high brew pressure and/or slightly too low OPV setting.

    You could try unscrewing the OPV and making sure it is clean and the rubber seal intact (mine is just a spring loaded rubber stopper essentially). Then set your brew pressure to 12 bar, adjust the OPV until it just starts to drip, then set your brew pressure to 9 bar.

    Cheers

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  • TC
    replied
    Most likely the OPV (as distinct from pump bypass) or alternately the expansion valve needs looking at

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  • chonski
    replied
    When I was having the similar issue my reading suggested it was one of 2 things
    Either the brew pressure (adjusted on the rotary pump) was set too high forcing the opv on the expansion valve to open at ~12 bar

    Or there was something wrong with the opv itself and it was opening at a lower pressure or there was something blocking it from closing completely

    For me adjusting the brew pressure resolved the issue.

    Even if your gauge on the right isn't reading too high I guess you could adjust the brew pressure down temporarily to see if that makes a difference?

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  • colombiasmoothbean
    replied
    This is a plumbable Evo version with rotary pump. Brew pressure seems fine, just 1 bar and it does not trickle at all at that stage. The (over)flow starts when I pull a shot. The group pressure (if that is what the gauge shows) goes up during pre-infusion (is that the right term?) and then peaks at just over 10 bar during the shot. That is when the outlet starts flowing.

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  • chonski
    replied
    Could be something else as I am no expert, but is there any way you can verify the brew pressure at the group?

    I had this happen to me on an evo (relevant difference here being rotary vs vibe pump) and found that the brew pressure was too high
    Probably different to your situation though as mine was reading 10 - 10.5 bar on the gauge
    Adjusting the brew pressure down on the rotary pump reduced the flow to a trickle

    I'm not sure if it's the same for the vibe pump giotto, but I believe the expansion valve is set to open at ~12 bar to protect the boiler?

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  • Rocket Giotto V2 - expansion valve outlet dripping: how much is ok?

    The round drain outlet is dripping steadily when I pull a shot. Starts when the shot begins to flow. The pressure goes up to 8 bar when I open the lever, then to 9 bar when it flows. In terms of 'how much' I would say that for every 30ml of shot there is twice that coming from this outlet from the expansion valve. It is definitely not just dripping, but flows steadily. I have only started thinking about this when I last emptied the bucket that catches what comes from the drip tray. Is that normal? Can I check/adjust anything?

    Unfortunately there is no knowledgeable person around here in Cyprus so I have to wait until I get move back to Melbourne to get it properly looked at.
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