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  • OPV + rotary pump pressure valve

    Posted by coffeegeek on March 31, 2022 at 7:08 pm

    What is the correct procedure to adjust the pressure of an 2-3 group HX machine? They have both the pressure adjust screw on the rotary pump and the common over-pressure valve? I always insert my modified portafilter with a manometer and adjust the pump until it ready 9-10 bar. But then you have the OPV. Which I never really adjusted.

    fixbear replied 1 year, 11 months ago 2 Members · 4 Replies
  • 4 Replies
  • fixbear

    Member
    April 1, 2022 at 3:03 pm

    It all depends on the machine your working on. And what OPV your talking about. A brewing OPV is 15 bar normally. But a boiler relief valve will be a bit more. To set one of those, you need a hand pump and a calibration gauge fixture.

  • coffeegeek

    Member
    April 2, 2022 at 9:11 am

    Sorry, I meant expansion valve. Looks like this:

    https://www.cafeparts.com/Expansion-Valve/Product_Manu/14198/Cimbali/415-928-000

    Many are set at 12 bars from the factory.

    My first thought was to adjust the pump quite high (at least higher than 12 bars). Then choke the group with my manometer portafilter. Then adjust the expansion valve to approx. 10.5 bars (I heard this is good). Then lower the pump back to 9.5-10 bars (optimal brew pressure is 9 bars).

    Or am I doing it wrong?

  • fixbear

    Member
    April 2, 2022 at 7:25 pm

    That would work for that one.

  • fixbear

    Member
    April 4, 2022 at 1:41 pm

    BTW, the OPV is something you should never have to adjust. That’s why they stake to setting after calibration. It’s purpose is to prevent rupture of the heat exchanger from expantion of the water when heated. Depending on the make and model of the HX, it’s normally in the 15 bar range. Well above the brewing pressure. If it is showing signs of leaking, replace it instead. It usually means that the valve seat has damage or foreign material in it.

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