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Thread: Oscar Version 1 - Changing flow pressure from the group head?

  1. #1
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    Oscar Version 1 - Changing flow pressure from the group head?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi,

    I am new to the home espresso scene, and have recently purchased a 2nd hand NS Oscar and also picked up a 2nd Hand Mazzer grinder.

    I have played around a bit with timings, grind size and setting up the machine right (i.e. start up procedure: Purge the group and steam wand)

    One thing I can't do is pull consistent shots, i.e. To get the same results of coffee, time, yield.

    I am aiming for 16-18g coffee (seems to be the basket size I have) : 25-30 seconds : 30g yield

    Sometimes the Yield might be higher than the last one even though I've used the same grind, technique, and vice versa.

    I have varying results, with the coffee coming out too fast and too slow.

    Though I am aware my technique could be an issue, I also think the way/flow of water from the group may be affecting it.

    Here are two videos, showing different types of flow from my Machine.

    (1) . Pressure seems to high?
    https://photos.app.goo.gl/2LvW9watiqjpBtjL9


    (2) . Pressure seems normal (this occurs after running the group for some time, and also after letting some steam out of the steam valve)
    https://photos.app.goo.gl/ew8SqmstZWwv29pd6


    Could anyone confirm that the difference in these flows would make a difference to the coffee? I've found that with (1) the coffee gushes out more, though that could be a result of my technique too.

    More importantly, does (1) suggest anything is wrong with the machine, parts ? Is there a way to avoid it with the machine setup procedure.

    After running the group for 10-20 Seconds, and letting off some steam from the valve, I can get the flow to appear in (2).

    Any help/idea are appreciated - cheers!

  2. #2
    Senior Member Jackster's Avatar
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    I have a Musica, very similar machine... I was also having consistency issues. A portafilter pressure gauge confirmed low pressure and also inconsistent pressure.
    Then I flow checked it, and it was also low and inconsistent flows.

    A new pump fixed it...

    Check your main pump flow. It should be putting out around 300ml in 30sec. Test with your shower screens removed (you may as well clean them while youre there.
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  3. #3
    Senior Member Jackster's Avatar
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    Your screens look blocked as the water is spraying about a lot.
    It's actually a bit of a dragon, might pay to lower your boiler pressure a little. Or maybe it has no gicleurs fitted.
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  4. #4
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    Thanks Jackster. I will look to test the flow rate, removing the screen. I think I want to upgrade with a new group gasket and shower screen anyway, seems like a good use if $30 so might as well do it all at once.

    Consistency has improved since i posted this thread, with no alterations to hardware, so i think the issue might have been largely due to my technique with tamping.

    The seller i got it from said they replaced the pump.

    More recently I'm getting a dripping problem. The leaks start after turning ghr machine on, and untill it basically cools down. This became more of a problem after backflushing , so maybe that put undue pressure through all the fittings... anyway so i plan to take the housing off to iID where the leaks are occurring. Another issue that has got more attention than the inconsistency.

    But I'll check about lowering the boiler pessure - how does one go about doing that? I've heard about the giggluers, are they a must have?

    Cheers

  5. #5
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    Where is the leak coming from? Is it dripping to under the machine at all? I recently bought an oscar aswell and have done a few fixes so far on it. One was a leak aswell

  6. #6
    Senior Member Jackster's Avatar
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    Giggleurs are restrictors for the group head. They are used to tune the brew water temperature. If you are always bleeding off the steam from the group before loading your portafilter, then you might do with some giggleurs.
    I had my group head off my Musica, so I added them. Yours has same group as mine, so they are available.
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  7. #7
    Mal Dimal's Avatar
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    Quote Originally Posted by Jackster View Post
    Giggleurs are restrictors for the group head. They are used to tune the brew water temperature. If you are always bleeding off the steam from the group before loading your portafilter, then you might do with some giggleurs.
    I had my group head off my Musica, so I added them. Yours has same group as mine, so they are available.
    That would be "gicleur"...

    Mal.
    Jackster likes this.

  8. #8
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    Yes dripping under the machine at two points that I can see, one near the back right leg of the machine and the other (which drips less) near the front left of the machine, about where the drip tray starts. I am going to take off the housing and see exactly what's dripping, assuming it's a fitting or something that can be easily fixed (fingers crossed)

  9. #9
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    Sounds like what mine was doing, does it have a large puddle of water under the drip tray? Mine was leaking from the left hand fitting on the group head, running down the a copper pipe to behind the drip tray, filling that spot and then running towards the back of the machine.

  10. #10
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    Haven't found the source of the leaks

    Quote Originally Posted by Howze View Post
    Sounds like what mine was doing, does it have a large puddle of water under the drip tray? Mine was leaking from the left hand fitting on the group head, running down the a copper pipe to behind the drip tray, filling that spot and then running towards the back of the machine.
    So I just inspected with the top cover off, to see if I could find the source of the leaks. I didn't find them but I did find that the safety valve on top of the boiler spits a little during the initial heat up phase. I also noticed a lot of oxidisation (green stuff!) all over the boiler and some of the copper pipes.

    The leaking is occurring, but it must be on the bottom parts/fittings that are not visible with only the top cover off. I checked the left hand fitting on the group and that seems to be sound with no leaks.

    Here are a set of pictures showing the internals: https://photos.app.goo.gl/breD3mqjgefpXtvcA

    To identify the source of the the leaks, I probably need to take the bottom off and turn it on again to see if I can see it occurring. I assume it's not safe to have the machine on when it is not upright?
    I might need to try it on a transparent surface so I can look underneath or take the side body parts off as well so I can see everything.

    Any ideas here?

    Here's a rundown of how the issue occurs:
    1) Turn on
    2) After 5 Mins, the safety valve starts to spit a little
    3) After 5 more minutes, the valve stops
    4) Still no leaking from bottom
    5) 20 minutes passed, dripping in drip tray starts (slowly, 1 drop every 3-4 seconds)
    6) . another 5-10 minutes, can start to see water drip from the right back leg area
    7) . Dripping gets worse, and can see if dripping at 3 points from the base
    8) . Turn off machine, and take the Water Tank out to eliminate that from the equation
    9) Dripping continues for a little while (5 minutes or so)
    10) Still warm, but no dripping happening

  11. #11
    Senior Member Jackster's Avatar
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    Ah, yep... Thanks Mal

    I was looking at a website that was linked to on here, some bloody expensive machine, however there was a tech page about their use of the gicleurs, and the tech/history of the thermocycle heated group.
    Bloody good read, even had insights for those that do understand the system.
    Suggested that the dual boiler was a cop out, and nothing romantic about it at all.
    Dimal likes this.

  12. #12
    Super Moderator Javaphile's Avatar
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    Quote Originally Posted by BuddingBarista View Post
    So I just inspected with the top cover off, to see if I could find the source of the leaks. I didn't find them but I did find that the safety valve on top of the boiler spits a little during the initial heat up phase.
    What you're seeing is the anti-vacuum valve doing it's job (Opens when the machine is turned off as the boiler cools down and closes when the machine is turned on and the boiler heats up.), not the safety valve leaking. As long as it only spits while the boiler is heating up such behavior completely normal. When it doesn't spit on start-up is when you should start worrying about it.

    The vertical silver part on the top of the boiler that's spitting is the anti-vacuum valve. The horizontal brass part next to it with no connection on one end is the over-pressure safety valve.


    Java "Sometimes spitting is a good thing!" phile
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  13. #13
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    Thanks for the explanation Javaphile I like that little spitting thing then - it seems it is responsible for the temperature regulation too, as without it you are required to open the steam valve during heat up phase as perthis link (https://www.elektros.it/it/en/tips_t...tml#paragrafo8) - Step 3
    "3) Turn on the machine, leaving opened the valve knob (clockwise). This is not necessary if you have the antivacum valve. "

    Good to know what is doing that now

  14. #14
    Super Moderator Javaphile's Avatar
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    Nah, the anti-vac valve has nothing to do with regulating the temperature in the boiler. It is there to prevent false pressure by making sure the air in the boiler is supersaturated as well as to prevent the boiler from collapsing in on itself as it cools down.


    Java "No vacuum" phile
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  15. #15
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    So to loop back to what i was asking about at the start of this thread - pressure/inconsistency etc. After some opening up and looking around, I found the pressurestat is set to 1.4Bar. Today a tech came around and looked inside for the leak, and nothing could be identified. He said it's most likely the way I've been inserting the drip tray (so basically the problem is me). As if you push it in at a horizontal angle enough you will end up pushing the overflow tubes (that would usually go in the drip tray) behind the drip tray, and then water will head toward the back of the machine.

    He took the shower screen off for me while there and cleaned it out/soaked with some detergent. So the 'dragon like' flow was fixed from that - yay

    Hopefully the dripping/leak problem is fixed by using the drip tray properly. the difference between when I've usually been getting the problem and his inspection was that he opened the steam valve after 10 or so minutes to start testing and looking for leaks.

    We also played with the grind setting and used some fresh beans (Pablo and Rusty) to make some real good coffee - pointing out the amount of Crema I should be looking for and getting with the fresh beans.

    So now back to the daily routine, with fresh beans!

    Thanks for all the contributions and ideas folks
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  16. #16
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    Glad it's coming allong well for you. I really should get my boiler pressure tested but I just set mine to just below boiling point coming out of the group head.

  17. #17
    Senior Member level3ninja's Avatar
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    Gotta love a happy ending!

    Just in case the tech didn't mention it, the amount of crema can vary bean to bean. It should be consistent if you're using the same bean, and you can sometimes tell something is off if the crema changes. Crema itself doesn't taste good, it just looks pretty, so if you find a bean you like that doesn't produce much crema don't worry, enjoy!
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  18. #18
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    I checked my main pump flow today with the shower screens removed and found it gives about 350ml in 30 sec. So A little higher than what you've said it should do, it is a fairly new pump (less than 6 months old) - Here is a video, it also shows some 'dragon breathing' like steam coming out of the group until it regulates to a regular water flow after about 5 seconds... https://photos.app.goo.gl/SDBGSPkD1cyKA6fN8 . Also, has anyone had any experience where the pump noise changes significantly? It used to sound a bit louder and now has gone to a muffled type noise, it actually changes between the two occasionally, sounds like something might be blocked



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