Announcement

Collapse
No announcement yet.

TAMING THE SAN MARINO!, Need some help please

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • TAMING THE SAN MARINO!, Need some help please

    Hey coffee folk,
    I have recently acquired a San Marino Lisa, and after playing around with the machine and reading a fistful of coffee forums, its seems these badboys have a pretty sketchy reputation.....
    well so far I've managed to get some killer coffee out of it, with the aid of a couple nights servicing with brother in law, a few seals and a bottomless portafilter...
    then just had to surf the temp for a couple hours to find a sweet spot..
    from what i can tell it has everything available to make great coffee, one big hot steam tank,plenty of pressure and enough steam to give away.
    I understand its temperature issues, but what do people expect when you have a brass group head bolted onto a copper boiler?, I am however committed to making this machine user friendly and consistent...

    What i am asking from any techs or backyarder whose played with these machines or who know how more automated machines operate is where do they regulate temperature?,
    you obviously cant regulate it running through a heat exchanger in the boiler, do i modify the end of the water/boiler circuit just before it enters the grouphead?
    and how do you keep a constant temperature do you need a second tank that cycles between the main one to keep the temp?, or introduce another temperature before the grouphead?...
    i also want to set up a low pressure pre infusion but this seems a bit easier than the temperature issue...
    any advice or help would be much appreciated,.

    I already proved this machine is capable of greatness, its just on a sliding scale, so please no comments about swapping it for another machine thats just a cop out... im very partial to this one and i will make it work

    everyone deserves a great coffee

  • #2
    As you've already discovered, the biggest issue with the San Marino design is temperature stability at the group.

    You've got the group bolted directly to the thermal mass of the boiler which is sitting about 30 degrees hotter than the ideal brew temperature. The heat exchanger in this case is a tube in the boiler onto which the group bolts.

    As such, the brewing water will ALWAYS be too hot as it's just been sitting in the heat exchanger, and there is no thermosyphon system to cool it. Once cold water starts being fed into the HX, the system works pretty well.

    Of course you can redesign the hydraulic circuit and add a discrete boiler that takes water from the hx tube and feeds it back into the group, but it sounds like alot of mucking around for potentially little gain.

    A few practical things you can try:

    Add a section of teflon tube to the injector pipe that delivers cold water into the heat exchanger. The outlet to the group is a longer pipe that feeds from lower in the HX, so by injecting cold water further into the HX you reduce the amount of overheated water at the start of the shot.

    Program one of the touchpad buttons to flush the group for long enough for the steam to disappear and hit it before locking in the coffee.

    Add a restrictor to the solenoid to slow down the water delivery, aim for 100 mls in 20 seconds - should be about 0.7mm for the jet. This will help stabilise the shot temperature as well.

    Obviously it would be pretty handy to have access to a scace device to see the effect of the changes you make.

    Originally posted by rond79@hotmail.com View Post

    I already proved this machine is capable of greatness, its just on a sliding scale, so please no comments about swapping it for another machine thats just a cop out... im very partial to this one and i will make it work
    Mate, I hate to break it to you but San Marinos have their reputation for a reason. It's pretty hard to compensate for the inherent problems in having a group bolted directly to a steam boiler, and no thermosyphon to circulate excess heat out of the HX.

    You will always need a cooling flush unless you can control the temperature of the water post-heat exchanger, but there are way more suitable machines out there to modify in that way if that's what you're looking for.

    My advice is to make a few simple changes to the HX inlet pipe, restrictor, set the boiler pressure correctly and flush religiously. I modified a client's SM Lisa for him and he's very happy with it.
    Last edited by coffee_machinist; 4 April 2013, 11:30 PM.

    Comment


    • #3
      Originally posted by coffee_machinist View Post
      As you've already discovered, the biggest issue with the San Marino design is temperature stability at the group.

      You've got the group bolted directly to the thermal mass of the boiler which is sitting about 30 degrees hotter than the ideal brew temperature. The heat exchanger in this case is a tube in the boiler onto which the group bolts.

      As such, the brewing water will ALWAYS be too hot as it's just been sitting in the heat exchanger, and there is no thermosyphon system to cool it. Once cold water starts being fed into the HX, the system works pretty well............

      ........Mate, I hate to break it to you but San Marinos have their reputation for a reason. It's pretty hard to compensate for the inherent problems in having a group bolted directly to a steam boiler, and no thermosyphon to circulate excess heat out of the HX.

      You will always need a cooling flush unless you can control the temperature of the water post-heat exchanger, but there are way more suitable machines out there to modify in that way if that's what you're looking for........
      My take on this would be....dont waste your time. As per quote "...there are way more suitable machines out there to modify in that way if that's what you're looking for..."

      Comment


      • #4
        Thanks heaps for providing a couple of suggestions, ill def be giving those a shot!,
        Ill let u know how I fair with mods and outcome

        Comment

        Working...
        X