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Thread: Rocket Giotto Premium - Air bubbles when flushing group head.

  1. #1
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    Rocket Giotto Premium - Air bubbles when flushing group head.

    Cafelat Coffee Tamper and Accessories
    Hi guys,

    I've been having this issue recently (at least from what I can remember) where if I do a full flush (i.e., lever not in pre-infuse position but full) the flow of water is not consistent and it bubbles at the shower screen. Hard to describe. Essentially it doesn't flush with a few streams of water flowing, it bubbles and comes down in one big stream of water....

    Will go home and give the machine a backflush with detergent and see if there's something happening.

    Anyone experience the same issue or know what the problem is?

    Cheers,
    Ron

  2. #2
    Senior Member saoye's Avatar
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    Is it bubbling due to temperature at the group being hot? After a few seconds does the bubbles go away and you're left with a more consistant stream? The E61 group head does tend to run hot which is why you need to do the cooling flush to bring it back down to the correct brew temperature.

  3. #3
    Site Sponsor Talk_Coffee's Avatar
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    Yes- this is known as a cooling flush and is required in all unmodified Giotto Premium machines.

    Our thermostability upgrade overcame the need for the flush.

    Cheers

    Chris

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    Correct me if I'm wrong Ron, but do you mean:
    Not flash boiling where there is a audible gurgle and splashing of boiling water from the group, but after that stops (if it's there at all) you get one solid stream of water from the middle of the group (instead of a few smaller streams), but at the very top of the one solid stream there is an air bubble that's attached to the shower screen, drops down about 1-2cm an just sits there, and then the one solid stream forms below it?
    If so I get the same thing every now and again on my Isomac. Don't know anything about it though!

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    Nah the only time there's an "audible gurgle and splashing of boiling water" is when the lever is in pre-infuse position. Then it does what you're describing (which is accurate to what I'm experiencing as well). I find that purging 250ml of water will get the group head "working" normally. Going to the states for 6 months, so I'll get a thermo stability upgrade when I return (this is suppose to fix it).

  6. #6
    Site Sponsor Talk_Coffee's Avatar
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    Hmm....

    There is no preinfuse position on a vibe pump operated machine and what you actually do is void the thermosyphon- which will lead to stability issues and potential thermosyphon stall. This would likely cause the symptoms you describe as you are not using your machine correctly.

    Get a clean flow of water and then leave your machine to sit idle for 30 min iCoffee. Then raise the lever fully and report back on what you observe.

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    Oh dear. That doesn't sound too good. I mentioned that in my opening post I had a laugh. Anyway it's when the lever naturally goes falls into position (half way up). I'll redo it and let you know, but there's a possibility that it will start to steam/gargle (from memory).

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    Ok, so I tested out the following scenarios:

    1. Turning on machine from cold. Flushing (handle fully turned on) just as pressure is ready and machine is warm (not hot to the touch). This produces a smooth flow of water and looks as it should.

    2. When the machine was heated up (too hot to touch group head) I ran a flush and it started to bubble and gargle (i flushed it till it stopped doing that and I got a clean flow of water). Waited 30 min and raised the lever full, it started to bubble and gargle again (my assumption is the group head gets too hot).

    When the machine is hot and I pull the level half way (which is what I thought was "pre-infuse") the group head steams and lets a small amount of water out, then it just continues to steam. (though I've never done this for very long only a few seconds).

    Is there an issue?

  9. #9
    caffeinated lemoo's Avatar
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    pretty much sounds like its getting too hot

    like chris said, a thermostability upgrade should suss it out

  10. #10
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    Quote Originally Posted by iCoffee View Post
    ..........2. When the machine was heated up (too hot to touch group head) I ran a flush and it started to bubble and gargle (i flushed it till it stopped doing that and I got a clean flow of water). Waited 30 min and raised the lever full, it started to bubble and gargle again (my assumption is the group head gets too hot).

    When the machine is hot and I pull the level half way (which is what I thought was "pre-infuse") the group head steams and lets a small amount of water out, then it just continues to steam. (though I've never done this for very long only a few seconds).

    Is there an issue?
    Yes and no. If you are leaving the machine on for long periods when it is actually NOT IN USE but still switched on, then you shouldnt / neednt. HX machines are designed and built to run continualy (in a commercial situation). In home use you / we dont run them continually and they cant help overheat. That is not the machine's fault. In order to counter that, some importers, agents and manufacturers purposely modify their models to run a bit cooler. But the easiest fix is still not to leave a HX machine ON when it is NOT IN USE. If you know you are not going to want to use it for a while, switch it off and switch back on later. Otherwise you are simply wearing it out as it cycles on/off while it is doing nothing, wearing out internal management components. And of course if it is an older model machine that pre dates these cooling (thermostability) mods, you can have its set up modified as Chris mentioned above.

    As the person that pioneered the practice of doing these kinds of modifications here, I can recommend doing it however you then need to consider that when you have an occasional dnner party with many coffees being drawn off the machine, you could end up overcooling when drawing lots of coffee off. But of course that is not a common occurence with most machines in a home use situation seeing perhaps no more than between 2 and 6 cups being run off in a sitting and then being switched off til later.

    WRT the last part of your post (placing the lever in the mid way posi).............DONT DO THAT. You are allowing water to expand out of the heat exchanger without the pump being activated to replenish it. That causes your groups gurgling & steaming problems when you next go to make a coffee ie, the operator caused the problem. These groups already do a pre-infusion as part of their normal designed function when the lever is moved from fully off to fully on.........

    As an aside......the "general care and use tips" that I place in the carton with each sale of my own BFC Diadema Junior machines, includes a bit of blurb about NOT placing the group lever in the mid way position.

    Hope that helps.

    Attilio
    very first CS site sponsor and of course,
    BBP
    Last edited by Fresh_Coffee; 19th July 2012 at 04:55 PM.

  11. #11
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    Thankns fresh! Appreciate it. So I have caused gurgling of the group head?! Is there a way to rectify this? Should I take the machine in for a repair or some sort?

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