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Pressure issue with Flojet and Synesso

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  • Pressure issue with Flojet and Synesso

    Hey guys!

    So I'm trying to get a Synesso up and running in a mobile setup.

    I'm having a problem with the pressure staying stable throughout the shot.

    I'm using the Flojet Water Dispensing System, but it seems to be "pulsing" which is in turn making the pressure jump up and down.

    I can see it on the pressure gauge as it's moving around instead of staying stable at 9 bars.

    Currently the setup is as follows:

    Water Bottle--> Jetflow Water Dispenser --> Water Filter (3M highflo series)--> Synesso Pump

    So I'm wondering if you can see any obvious flaws in my setup, or have any tips to try and rectify the
    problem?

    The Jetflow is supposed to deliver a steady 40PSI but perhaps the water filter is causing an issue and needs to be moved in the chain?

    Another thing to note is the pipe from the Jetflow to the filter is rather long. Perhaps an issue there?

    Anyway, if anyone has any ideas I'd greatly appreciate it!

    Warm regards,
    Geoff

  • #2
    Hi Geoff,

    I'm afraid the short answer is the problem you are experiencing is insurmountable, it's a fundamental difference in the way peristaltic pumps (flojet) work compared to the rotary vane pump. The rotary pump will sit there spinning away at a constant rpm, and will deliver the desired pressure at the outlet side almost irrespective of the actual flow rate moving through the pump. When your groups are running unrestricted (ie. no coffee), the flow rate is quite quick so the flojet sees effectively 0 bar and is on constantly to try to build pressure at the outlet.

    When you place a restriction in the system, the pressure the flojet sees rises, until the point where the pressure switch kicks in and disengages. In this way the flojet is binary, it's either on or off. Unfortunately the kind of flow rate common to an espresso extraction is always going to make the flojet pulse on and off, as it is unable to deliver a constant low flow rate by nature of the pump mechanism and pressure switch. Plumbing changes will have little effect, as water is only very slightly compressible.

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    • #3
      Hypothetically you could get it to work by adding a bypass valve set to 30 PSI between the flojet and the rotary that bled back into the reservoir, and then switch the flojet power on only in series with the rotary. Sounds a bit convoluted though, not sure why you need a flojet in this application?

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      • #4
        A pressure accumulator may reduce the pulsating although not getting rid of it completely

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        • #5
          I suggest trying your arrangement with the pump pulling water through the filters instead of pushing the water; little to zero cost to try it. Originally I had my Shurflo pump set-up without an accumulator and aside from the pump cycling on/off more often it worked fine supplying water to my LI. Now I have the system set-up with a diaphragm type accumulator...no issue and the accumulator keeps the pump from waking me up when the system turns on at 5:00AM

          Water tank > filter(s) (1- 10" filter + 1-10" carbon filter in my array) > pump > accumulator > espresso machine.

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          • #6
            Using a flojet or similar to fill a boiler or water reservoir is entirely appropriate. Using one to simulate mains water feed to a rotary pump for espresso brewing, especially on multi-group machines, not so much.

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            • #7
              edit/delete...answered my own question

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              • #8
                Hey guys, thanks so much for the great insights and suggestions :-)

                They are very much in line with what Scott from Synesso and the guys are Bombora are suggesting (BTW these companies have amazing customer support!)

                I am going to try a kind of accumulator tank solution to see if it helps, although I agree that the Flojet is not ideal for this situation.

                Are there any more appropriate pumps that anyone would recommend that would work in a mobile situation, and play a bit nicer with the Synesso boost pump?

                I believe the Flojet pressure is also a little low (I think it does 45 PSI which is as low as you'd want to go with this particular setup).

                Thanks again for the great knowledge and if anyone has further ideas they would be very much appreciated!

                Have a great day,
                Geoff

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                • #9
                  What I did for my mobile setup for my GS3 was to throw the braided hose straight into a large water bottle of filtered water. I also had a spare bottle of filtered water ready if the first one ran out, which it didn't.

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