Results 1 to 14 of 14
Like Tree3Likes
  • 1 Post By jammar
  • 2 Post By coffee_machinist

Thread: La mazocco gs3 pressure drop at rest

  1. #1
    Junior Member
    Join Date
    Feb 2011
    Posts
    12

    La mazocco gs3 pressure drop at rest

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi guys
    Long time first time!
    I have the above machine and made the mistake of turning off the machine for 6 months leaving the boilers full of water.
    It has been a long and slow process getting the machine back on track.
    When the machine was switched back on, it's performance dropped over a few weeks.
    In short I have replaced the
    pump (as the old was only producing 6 bar)
    Pump check valve
    Numerous orings and seals throughout the unit where leaks occurred. (Head, top and bottom only, vac breaker, steam wand)
    The final problem I have not been able to sort.
    Run the pump, up to pressure 9 bar
    Switch off
    And the pressure gauge starts to drop
    After 90 seconds 5 bar
    10 minutes down to 1 or 2 bar.
    I have replaced the pump check valve, no water appears to be going into the drip tray.
    As soon as I start the pump it's up to pressure within 2 seconds.
    Where is the gauge taking it's reading from and could I be losing pressure there.
    Any feedback would be appreciated
    Thanks

  2. #2
    Site Sponsor coffee_machinist's Avatar
    Join Date
    Jun 2011
    Posts
    683
    So 9 bar pressure can be maintained into a blind filter when the pump is running? If so, the logical answer is the check valve. It could also be the brew boiler expansion valve or any number of other seals, its probably a very slow leak, only needs to lose a few mls to drop in pressure dramatically.

  3. #3
    Site Sponsor coffee_machinist's Avatar
    Join Date
    Jun 2011
    Posts
    683
    Or, leaky heat exchanger or any number of other parts in the brew boiler circuit

  4. #4
    TOK
    TOK is offline
    Senior Member
    Join Date
    Apr 2013
    Posts
    697
    Great answers from CM particularly regarding the heat exchanger. Its not common but it can happen.

    All you can do is trace the whole circuit patiently from start to finish and see if you can unearth something.

    With regard to:
    Quote Originally Posted by jammar View Post
    ....made the mistake of turning off the machine for 6 months leaving the boilers full of water...Any feedback would be appreciated. Thanks
    What makes you think it would be any different if you had drained the water? That could even have made it worse although if it was worse, the problem may be easier / more obvious to trace.
    Last edited by TOK; 29th June 2014 at 07:21 PM.

  5. #5
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    Hi coffee_machinist
    Thanks so much for the reply
    Yes the pump holds the selected pressure on the blank. (9.25bar on the blank and 9bar on the poor)
    I originally cleaned the pump check valve (salt, vinegar and hot water) and have now replaced with a new one.
    The expansion valve is set to 12 bar and vents into the drip tray, I have had paper towel in the tray and it has stayed dry
    I have been over the internals and no leaks can be found, so my problem is an internal one.
    The gauge raises from 2 bar to 9 the instant the tea button is pushed, and takes about 2 to 3 seconds when the lever if activated, and drops at the same rate as described above.
    I now feel the issue is after the pump and prior to the boiler
    I note there is a check valve (part number B.2.008) Page 23 and 24 on link http://www.lamarzoccousa.com/wp-cont..._V2.3COLOR.pdf
    This appears to be from the steam boiler
    Can the thermostatic valve body (number 12, page 46, above link) be a possible problem?
    It appears the water is pre heated from the steam boiler any thoughts here?
    Thanks again for looking into this problem for me.
    saroadie likes this.

  6. #6
    Site Sponsor coffee_machinist's Avatar
    Join Date
    Jun 2011
    Posts
    683
    There are a few check valves it seems. The function of the inlet manifold/mixer is to bleed a variable amount of cold water straight from the pump outlet into the feed to the hot water solenoid. Logically the solenoid is after the mixing has occurred so this necessitates another check valve to prevent cold water from the manifold flowing back into the steam boiler - this could be your problem, if you have replaced the check valve on the outlet side of the pump body only.

  7. #7
    Senior Member
    Join Date
    Mar 2012
    Posts
    1,275
    Run the pump, up to pressure 9 bar
    Switch off
    And the pressure gauge starts to drop
    After 90 seconds 5 bar
    10 minutes down to 1 or 2 bar.
    Out of curiosity, did you also do this check before the long shut down ? ..IE do you know if it is a "new" problem ?

  8. #8
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    Hi guys
    Thanks all for the input,
    TOK, I feel that the water that was left inside the machine caused some scaling, once the machine was restarted this scale has been like a cancer through the machine. Little gremlins have been affecting the performance over the first 2 months of restart up.
    Blend52, in short the gauge on the boiler ranged from 9 to 12 bar, only dropping when perfusion on the paddle was applied.
    My next mission is take the above advise, I feel the check valve from the inlet manifold and boiler may be suspect, allowing the back pressure to equalise into the steam boiler. Hence the drop to 1 to 2 bar, but not loosing any water temp!
    Any other ideas and response please feel free to comment, this may take a couple of days for my reply as my job is getting in the way of this conquest!
    On a positive note I have loved getting a better understanding of the working of an amazing piece of machinery!

  9. #9
    TOK
    TOK is offline
    Senior Member
    Join Date
    Apr 2013
    Posts
    697
    Quote Originally Posted by jammar View Post
    Hi guys
    Thanks all for the input,
    TOK, I feel that the water that was left inside the machine caused some scaling, once the machine was restarted this scale has been like a cancer through the machine. Little gremlins have been affecting the performance over the first 2 months of restart up.
    ..................
    Any other ideas and response please feel free to comment, this may take a couple of days for my reply as my job is getting in the way of this conquest!
    On a positive note I have loved getting a better understanding of the working of an amazing piece of machinery!
    Hi jammar,

    scale forms when water is subjected to heat. I am not sure you will get a build up of scale while the machine is cold, so would tend to think that if there is a scale ***problem***, the majority of it had most probably already happened before the machine was laid up (in which case it would have manifested whether the machine was laid up with water in or not).

    I sincerely hope you solve your problem but note it may not necessarily be scale related....and even if it is, that doesnt mean your machine is "full" of scale or that anything was caused by laying up the machine with water in it etc....

    Hope that helps

  10. #10
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    TOK, A possibility as I have not had the head off prior to the problem,
    I have just cleaned the check valve and there was a slight hope, but problems still occurring, held pressure for a few seconds, still a possibility that check valve has a internal fault.

  11. #11
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    With check valve appearing to be ok
    The next plan of attack is the thermostatic valve body or as above the heat exchanger.
    Any advise on testing checking these
    Thanks for all the input

  12. #12
    Site Sponsor coffee_machinist's Avatar
    Join Date
    Jun 2011
    Posts
    683
    Okay so we have established that water is not visibly leaking inside the machine or from the group, or into the drip tray. If it's not going back into the reservoir (unlikely if you've replaced the pump end check valve) then that leaves the steam boiler. Inlets and outlets into the steam boiler that could be the problem are: cold water inlet (solenoid and check valve from t piece on mixer valve>flow meter pipe), hot water outlet (steam boiler>check valve>mixer valve), heat exchanger.

    I am inferring from what you've said that the machine's not plumbed in. If you plumb it in, leave it turned off and pressurise up to mains, clearly the defective seal will allow flow through and by removing pipes one by one you should be able to track it down.
    jammar and TOK like this.

  13. #13
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    Thanks for the above info, I have spent the evening going over and understanding the hydraulic flow. I am starting to understand what you have been telling me. I will go over the system over the next few days, I have found 3 more check valves in the subject area.
    Feeling that the check valve on the thermostatic valve body may be suspect, allowing back flow from the boiler through the thermostatic valve body back into the steam boiler.
    Once I have satisfied the check valve inspections, I will work on how to hook it to mains pressure, I am not sure if the mains pressure will show if there is a check valve problem as both boiler will equalise?
    I'll keep you posted!
    Last edited by jammar; 1st July 2014 at 08:08 PM.

  14. #14
    Junior Member
    Join Date
    Feb 2011
    Posts
    12
    Hi guys, just a follow up on my works.
    All the information supplied above has helped me identify the problems with the system
    I removed the other 5 check valves in the system, 2 of them were stuck in the open position. Inlet on the hot water mixer and inlet on the heat exchange mixer.
    I cleaned them all and have found some success.
    The system now runs at 9 bar and when heating rises up to 13.5 bar (quick adjustment of the expansion valve) now holds 12 bar at rest for a few hours . Then drops to 6 bar.
    I feel this is because the check valves are worn/damaged and not holding pressure.
    I am going to replace the following parts just for piece of mind.
    All the check valves and copper washers.
    Both thermostatic bodies and associated pin and orings.
    Mix valve gigleur on the thermostatic body, from the heat exchanger.
    That way I know I have addressed the problem area,
    Once the parts arrive I will clean the temperature probes And will inspect the heat exchanger.
    Thanks all for your input and any feedback in much appreciated.
    Jammar.



Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •