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Thread: pressure, single boilers, hx and preinfusion?

  1. #1
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    pressure, single boilers, hx and preinfusion?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Sorry for the confusing heading!
    Just thinking about why both the Boema and Bezzera seem to have the espresso coming out of the spouts quite quickly, yet both have that pressure build up hiss of preinfusion. The Botticelli and Quaha are both single boilers and therefore have no preinfusion, but with both there is quite a wait for the espresso to appear.
    Is this a pressure thing? On the Bott I set the pressure via the OPV to 9 bars and did the same (slightly less accurately) on the Quaha. The Bezzera says 9 bars on the gauge (ramps up from the 3.5 bars from the pressure reducing valve).
    Any thoughts?
    Brett

  2. #2
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    Re: pressure, single boilers, hx and preinfusion?

    Hmmm... I have also been wondering about why some machines pour out coffee faster then the other while both is on 9bars.

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    Re: pressure, single boilers, hx and preinfusion?

    well i think that the difference lies in the type of pump, vibe pump arnt very powerfuland deliver small volumes at 9 bar and as a result you get a slow ramp up in pressure which acts like pre-infusion. plz correct me if im wrong *;D

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    Re: pressure, single boilers, hx and preinfusion?

    Quote Originally Posted by Segrave link=1182419045/0#2 date=1182420708
    well i think that the difference lies in the type of pump, vibe pump arnt very powerful and as a result you get a slow ramp up in pressure which acts like pre-infusion. plz correct me if im wrong ;D
    Segrave,

    Yep, thats my thoughts also.... it is as much to do with volume delivered. A commercial rotary pump can deliver heaps of volume at 9 Bars (mine will supply both groups AND fill the boiler at the same time- and at 9 Bars).

    A vibe can supply 9 Bars.... but only at a low flow rate. So with the PF requiring quite a bit of water to fill the void between the coffee grains (and to be absorbed into the grains as well).... the rotary pump can get it filled and up to 9 Bars almost instantly.... even with pre-infusion.... The vibe will take a lot longer to fill the void and then get to 9 Bar and start extraction.

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    Re: pressure, single boilers, hx and preinfusion?

    I think youve hit the nail on the head, JavaB- may explains also why the quaha is slower again than the Botticelli.
    I started thinking about this when people were talking about how long it took the espresso to appear on their machines, as if slow was necessarily better. Also comparing single boiler times to hx preinfusion.
    Thanks
    Brett

  6. #6
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    Re: pressure, single boilers, hx and preinfusion?


    There are plenty of HX machines that dont have any pre-infusion. The thought is that they are less forgiving of preparation imperfections. Then there are different types of pre-infusion, such as the mechanical typre found in E61 groups or delaying the pump and using the mains pressure for pre-infusion. Some machines simply use small gicleurs to slow the ramp up, such as the common 0.6 mm jets used in La Marzocco machines.


  7. #7
    Senior Member robusto's Avatar
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    Re: pressure, single boilers, hx and preinfusion?

    Too long a wait for coffee to appear can also be the result of an over-packed basket or an overly-fine grind.

    --Robusto



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