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Thread: Adjusting the brew pressure (OPV) on Isomac Mondiale

  1. #1
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    Adjusting the brew pressure (OPV) on Isomac Mondiale

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    A few weeks I decided, after months of thinking about it that I would
    adjust the brew pressure from its approx 13 bar to a more respectable
    level. Although Id managed to get reasonably predictable, and usually
    quite good, results at this level, reading around here and elsewhere
    and observing the improvement KJM had achieved in adjusting his Silvia
    convinced me to give it a go. Even more so when I had the opportunity
    to borrow a manometer from KJM.

    Now for most machines there are at least at few hints on the web about
    adjustment specifics. For the Mondiale, not a sausage. Talking to
    various people had led to responses from "only an expert can do it" to
    "the Mondiale doesnt have an adjustable OPV" to "youll never get it
    back together again", so I thought Id write a brief report to put the
    mythology to rest and show that (as one would expect) it isnt that
    difficult after all.

    First of all I made some measurements. I removed the single spout from
    of our portafilters, and screwed on the manometer (with some plumbers
    tape). This showed readings about the same as on the Mondiales gauge
    (the manometer is in kg/cm2 so there is some difference). I made
    adjustments with the machine cold as much as possible.

    Below is a composite picture with four panels. The first shows just
    the top with two screws removed so that the cup warmer can be tilted
    back to give some internal access. At the right is a component with an
    orange top -- this is the pressurestat, which can be easily adjusted
    with no further dissection of the machine necessary. I adjusted so
    that it settles back to 1.1 bar (on the Mondiales gauge).

    The first picture also shows to small red arrows. These are screws
    that need to be removed to commence removing the casing of the
    Mondiale, which is its distinguishing feature and also what makes it a
    bit more difficult to get inside than other Isomac HX machines.

    There are also two screws at the front to be removed. *The second
    picture has more small red arrows indicating these. *To get at them, I
    removed the drip tray, unscrewed the front legs, and removed the
    ledges on which it rests (all shown in the picture). *I also removed
    four (I think) screws behind the machine (not shown). At this point,
    the sides spring apart and the outer casing can be removed.

    The third picture shows what things look like at this point. Shown
    tilting back is the platform that supports the water container (which
    I had of course removed before starting disassembly). On the right is
    a partial view of the removed casing, used as a support. And on the
    left is the important bit.

    The fourth picture is a closeup on the OPV itself, shown with another
    red arrow (by then I had figured out how to make the arrows somewhat
    bigger :)). To adjust it, I removed the tube, put a couple of white
    dots to measure how many turns, then rotated the inner barrel to
    adjust. Anticlockwise lowers the setting. To get it moving, I had to
    use a small pliers (with jaws padded) but it was then pretty smooth.

    Getting water into the machine at this point needs a little
    thought. One way is run the tubes into a separate container, and put a
    weight on the platform to keep the water level sensor depressed. I
    didnt do that, I carefully positioned the platform in a stable
    position and used the machines water container. *After a few
    iterations I finished with a reading of 9 bar (about one full turn).

    Getting the thing back together is the most difficult part of the
    exercise. The casing springs out quite a lot, and needs a careful
    balance of tension to get everything lined up properly. With two of
    us, it wasnt too difficult, but a touch tricky. No new four letter
    words needed :).

    Internally, the machine has a very similar layout of OPV etc to both
    the Isomac Tea and Zaffiro.

    Removed inactive link.....
    Mal.


    This wiki (which has an enormous amount of useful information,
    including an article on different types of OPV) is now member-only
    access; Ive emailed Dave to find out how to subscribe.

    As for results -- it was well worth the effort. Its much easier to
    make shots at finer grind, which gives crema with a finer structure
    and greater discrimination along the flavour spectrum (for want of a
    better way to put it).




    aaleks likes this.

  2. #2
    A_M
    A_M is offline
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    Re: Adjusting the brew pressure (OPV) on Isomac Mondiale

    Sorry..

    You mention a number of pics... But they are not available.

    In addition the wiki states..

    The Coffeetime Wiki is private and no longer available for public access!

    However I went there before reading the bottom of your post... Typical male I guess... RTFM when nothing else works.

    Would suggest you re position the link at the very bottom..

  3. #3
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    Re: Adjusting the brew pressure (OPV) on Isomac Mondiale

    Hi Hazbean,

    Nice description. Unfortunately the coffeetime website has been down for several days now and the access has been cut.

    I had similar exprience two months ago when after measuring the brewing head pressure I saw it at 12 bars. When I opened the machine my OPV had been stuck and I needed some descaling.

    After that it is hapilly sitting at 9.2 bars when brewing.

    Cheers,
    John

  4. #4
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    Re: Adjusting the brew pressure (OPV) on Isomac Mondiale

    AM, after a bit of puzzling I see your point, the post did get a bit
    long so the pictures were out of view. I was going to go back and
    remove the link and see if was possible to move the pics up, but
    I cant edit the post any more.

    John, yes it seems you are right about the site being inactive
    despite the invitation to join by email. I hope all is OK, Dave C
    seems to *been pretty energetic on the UK scene. Ive *also
    descaled the HX, all running smoothly now.

  5. #5
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    Re: Adjusting the brew pressure (OPV) on Isomac Mondiale

    Quote Originally Posted by 3A33283037333C520 link=1236582474/3#3 date=1236684878
    AM, after a bit of puzzling I see your point, the post did get a bit
    long so the pictures were out of view. I was going to go back and
    remove the link and see if was possible to move the pics up, but
    I cant edit the post any more.

    John, yes it seems you are right about the site being inactive
    despite the invitation to join by email. I hope all is OK, Dave C
    seems to *been pretty energetic on the UK scene. Ive *also
    descaled the HX, all running smoothly now.
    Dave C is back, I have just re-registered at the website. This is a great place with lots of resources and he is indeed very helpful man.

  6. #6
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    Re: Adjusting the brew pressure (OPV) on Isomac Mondiale

    Just updating this thread as the link that I put in my original
    post, which temporarily became inactive, is alive again:

    * *http://tinyurl.com/n5gour

  7. #7
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    I realise that this is an old thread, but it is so very helpful. I can show service guys tomorrow morning where the OPV is on Mondiale and that it is not normal to go up to 15 bar.

  8. #8
    TOK
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    Hi there.

    look going only on face value of your post, I would be tread carefully lest it insults your service tech and causes some unnecessary "heat".

    Any professional service tech who has never been inside a Mondial can nevertheless work out where the pressure bypass valve is immediately the body is removed, and let's remember that it can still be considered quite normal (depending on the manufacturer) to have a factory setting of 12 bar.....so while 15 bar is "out of adjustment", if you are thinking on the 8 to 10 bars often discussed in these forums, you may want to take in consideration that the original factory setting was probably 12 bars unless it is a relatively late model machine.

    You would need to establish politely with your service tech, what setting you want it readjusted to. I dont know anyone that would set it to 12 bars, but that is not the point...

    I guess its all in the method of delivery.....

    Take care.
    Dimal, coffee_machinist and TC like this.

  9. #9
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    Thanks for the advice TOK, I agree, there is no need for unnecessary "heat".
    I was little annoyed by straight out statement from the tech that the machine has no OPV and that I need to adjust the grind, and it's normal for these to go up to 15 bar. I actually noted that pressure build up also happend few times when the machine was not brewing. I would have appriciated honesty in saying that they don't know rather than the comments made.

    I'll see how the machine behaves when I get it back. But I get the feeling this will be best if I do it all myself Will be fun fixing it anyway, and excellent opportunity to learn something new

  10. #10
    TOK
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    Well, it would be normal for it to run at 12 bar if it is a machine of the era where that is where they were set to in the factory. 15 is a figure requiring rectification. Was the 15 bar measured with a calibrated instrument and therefore, how accurate is the figure?

    When you say that "...I noted that pressure build up also happend few times when the machine was not brewing....", do you mean water line pressure (your 15 bar while brewing, but normal for the water pressure gauge to fluctuate slowly when idling if it is a water reservoir - non plumbed- machine) OR steam pressure (boiler/steam pressure around 1.1 bar, also fluctuating from say 0.9 to say 1.2). Different things.

    You are taking the machine to the same techie that told you that stuff?

    Rhetorical questions not requiring an answer here.

    However speaking plainly. Either your techie doesnt have much experience or.....for some reason he doesnt want to do the job...

  11. #11
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    I dunno if I'd be trusting a technician who doesn't know where an OPV is or flat out says that an OPV doesn't exists on an expensive prosumer machine.

    What I've seen of Isomac brew pressure gauges, they're not always the most reliable sources of measurement. However, no matter the machine, you should never trust the gauge to calibrate the brew pressure by. It is always best to use a portafilter with an inbuilt pressure gauge. To fit an E61 group head, a Nuova Ricambi portafilter with gauge is only like $100 so there's no excuse for a service centre not to have one.

    You also should be within your rights to ask for a demonstration of the machine before handing over your money. If they seem averse to this or refuse then there's not a lot you can do but I wouldn't be taking it back there.
    For a machine of the Mondiale's price and quality, you should receive service that matches this.

  12. #12
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    Haven't logged in for ages and notice that one of ancient posts is getting some attention ...

    I can say that the OPV adjustment I did in 2009 has held rock solid ever since at pretty much where I want it -- now confirmed by a technician who does know what he's doing.

    aaleks, if you are in SA I can recommend a tech who will do a good job, having recently serviced my Mondiale.



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