Adjusting espresso machine's rotary pump brew pressure?

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dawgcatching

#1: Post by dawgcatching »

Hi there,

How do I adjust the pump pressure on the Bric? I have a PF-mounted gauge handy. I assume I take the shell off (not sure how to do that either) and then, where is the pressure adjustment screw? To lessen the pressure, do I turn the screw in or out? Also, should I use an in-line pressure regulator? I notice the brewing water tends to pulse as the Flo-Jet is cycling. Thanks!

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Compass Coffee
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#2: Post by Compass Coffee »

Cover removal first take off the the top (cup warming area), 3 phillips screws. The body wrap is held on by one flathead screw on the outside back, two hex top inside front, then lift straight up. (has to 'ears' that slide out of slots bottom front) As you're facing the Bric', pump pressure regulator is on the left hand side just behind end of the boiler. The adjustment screw faces towards the front and upwards about 45 degrees from horizontal, right by the boiler, was a bit tricky to get at on mine but not too bad. Adjust in small increments.

Not using a Flojet so no suggestion there.
Mike McGinness, Head Bean (Owner/Roast Master)
http://www.CompassCoffeeRoasting.com

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barry

#3: Post by barry »

dawgcatching wrote: I notice the brewing water tends to pulse as the Flo-Jet is cycling.
get an accumulator

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malachi

#4: Post by malachi »

What Barry said.
"Taste is the only morality." -- John Ruskin

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HB
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#5: Post by HB »

What Barry and Chris said, to which I'll add a picture and link:

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Shurflo accumulator from espressoParts.com

Adjustments are performed at the pump screw as Mike describes (clockwise = higher brew pressure).
Dan Kehn

dawgcatching (original poster)

#6: Post by dawgcatching (original poster) »

Thanks for the tips! I will tear it apart tonight. Do you think the higher (12 BAR) pump pressure that I am running is causing some excess channeling? On my bottomless PF, I notice that the rim of the basket sees extraction about a second before the extraction seeps through the center of the basket. The extract appears as a 1cm-wide ring and then fills in across the entire basket. I am hoping that a bit lower brewing pressure will not force open the inherent weakness of the coffee/basket interface as much, and make for a more even extraction. What do you think?

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malachi

#7: Post by malachi »

12 BAR?!?!?!

Umm... that is really high.
suggest dropping to 8.5-10 BAR.
"Taste is the only morality." -- John Ruskin

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HB
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#8: Post by HB »

dawgcatching wrote:Do you think the higher (12 BAR) pump pressure that I am running is causing some excess channeling?
I raised the pressure to 11 bar to produce this beauty:

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System meltdown from Perfecting the Naked Extraction

Just the other week a group of locals and I were checking out the La Marzocco GB5 at Counter Culture Coffee's espresso lab. The shots were not coming together... they were marginally drinkable. Looking at the brew pressure, I see it's edged up to 10.5 bar. A quick reduction to 9 bar and magically we were back in the groove. So yes, it definitely makes for an easier extraction.
Dan Kehn

dawgcatching (original poster)

#9: Post by dawgcatching (original poster) »

I hooked up the pressure gauge attachment to the PF tonight to check the pump pressure (I was told that it was not adjusted at 1st-line). To my surprise, the gauge read 8.9 BAR. But, seal around the grouphead gasket wasn't great, and it was squirting water out, despite my best efforts at tightening it. Do you think that my pressure is close to 9 BAR, or am I losing 1-2 BAR with the bad seal? How the heck can I tell what the real pressure it, or can I somehow estimate it?

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HB
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#10: Post by HB »

dawgcatching wrote:Do you think that my pressure is close to 9 BAR, or am I losing 1-2 BAR with the bad seal? How the heck can I tell what the real pressure it, or can I somehow estimate it?
Given a rotary pump's high flow rate, some dribbling won't affect the displayed pressure reading. I cannot say if a "mini-geyser" would invalidate the reading entirely.
Dan Kehn