Brew pressure regulation of plumbed-in espresso machine with rotary pump

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markk100

#1: Post by markk100 »

Good morning all,

Last night I plumbed my Brewtus IV-R with a friend, and I'll say it was quite a fun time, and even turned out a little better than I had anticipated. Home projects rarely seem to happen that way. What a joy it is to never have to worry about water supply.

In any event, my question lies around the in-line pressure regulator (the last in the chain before the Brewtus), and how it affects the brew pressure. I noticed that as I was operating the lever, so we could set the regulator, when he adjusted the regulator to the desired level (it currently sits at 27.5), the brew pressure gauge moved with it.

So, at 27.5 psi in, I am reading a smidge over 8 (it was set at 8 on the button from WLL), but I noticed it read higher when the regulator was set higher, and as we dialed it down to 27.5, the brew pressure dropped along with it.

Note: No pf was engaged, so it could have been an erroneous reading to begin with.

My question is, if there is a direct correlation between the two, instead of opening the Brewtus up and adjusting the brew pressure adjustment screw, can I simply raise the in-line pressure to say 32.5 psi, to get me to 9 bars whilst brewing?

Thanks!

Mark

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HB
Admin

#2: Post by HB »

markk100 wrote:...if there is a direct correlation between the two, instead of opening the Brewtus up and adjusting the brew pressure adjustment screw, can I simply raise the in-line pressure to say 32.5 psi, to get me to 9 bars whilst brewing?
Yes, assuming the inlet pressure is a reasonable preinfusion pressure range (say 3 bar). As you noted, a rotary pump increases the inlet pressure, assuming it has a simple bypass valve. There are "balanced" bypass valves that regulate the output pressure, within reason, to a given setpoint independent of the inlet pressure.

For the benefit of those following along and the sake of completeness, here's a related excerpt from How to adjust brew pressure of rotary pump espresso machine?
HB wrote:Assuming it's like Procon rotary pumps, you should find a pressure adjusting screw similar to the one shown below:

Image
From Procon exploded view; also see Adjusting espresso machine's rotary pump brew pressure?

Counter-clockwise = more water passes from outlet to inlet through the bypass valve = lower pressure. Clockwise = less water passes from outlet to inlet = higher pressure. Also keep in mind that your inlet pressure should be regulated to ~25 PSI.
Dan Kehn

markk100

#3: Post by markk100 »

Hello Dan,

Thanks for the note!

Okay, so I'm going to outline a course of action that I've thought out pursuant to your post. I wanted to get a thumbs up/thumbs down on my approach to ensure I understand everything correctly, as I'm fairly ignorant as to the specific inner workings/parts of my machine (outside of course of where everything is and how things work in a general sense).

So, here's what I would propose doing, with the ultimate goal of achieving 9 bars of pressure at time of brewing:

1. Engage back flush disc into group head
2. Engage lever
3. Adjust in-line pressure regulator until brew pressure stabilizes at 9 bars
4. Test pre-infusion to ensure it stabilizes around 3 bars

My guess is if I can get the above to check out, without exceeding an in-let pressure of 32ish, I'm good?

Thanks again,

Mark

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RapidCoffee
Team HB

#4: Post by RapidCoffee »

markk100 wrote:So, here's what I would propose doing, with the ultimate goal of achieving 9 bars of pressure at time of brewing:

1. Engage back flush disc into group head
2. Engage lever
3. Adjust in-line pressure regulator until brew pressure stabilizes at 9 bars
4. Test pre-infusion to ensure it stabilizes around 3 bars

My guess is if I can get the above to check out, without exceeding an in-let pressure of 32ish, I'm good?
Don't shy away from adjusting pressure on the rotary pump. It's very easy, literally just turning a screw.

Also note that 3 bar = 43.5 psi, so you will have to go higher than 32 psi on inlet pressure to achieve 3 bar preinfusion pressure.
John

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HB
Admin

#5: Post by HB »

RapidCoffee wrote:...you will have to go higher than 32 psi on inlet pressure to achieve 3 bar preinfusion pressure.
Not to put too fine a point on it, but the E61 group design already handles preinfusion pressure via its expansion chamber. Assuming the rotary pump is correctly adjusted to deliver 9 bar once the expansion chamber is full, the inlet pressure technically doesn't matter. Excluding espresso machines that use inlet pressure for preinfusion (e.g., program feature on some La Spaziale models), I believe vendors and manufacturers recommend lower inlet pressure to reduce the risk of solenoid valve bypass leading to drip drip drip from the grouphead. That's good advice, but is separate from the preinfusion question, which doesn't apply to an E61 / rotary pump combination.

For those who want more detail, see Is there a purpose for the E61 middle brew lever position? and E61 Group Espresso Machine: Is its reputation justified?
Dan Kehn

markk100

#6: Post by markk100 »

John/Dan,

Thanks for the respective notes...

I now realize again why it is I put in a regulator to begin with, to mitigate that pressure blowing the bypass valve and creating a potential water leak 'issue'.

Okay, so I'm gathering I'm probably safer dialing back the inlet pressure to 25 and just adjusting the brew pressure internal to the machine to garner desired results. That is, by the way, what I had intended to do all along then realized I might have a much simpler solution, as in a 15 second solution that didn't require popping my machine open. I recognize that neither are difficult, but surely one would be easier than the other.

Nevertheless, I got a good education today, so thank you!

Cheers,

Mark

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RapidCoffee
Team HB

#7: Post by RapidCoffee »

HB wrote:Not to put too fine a point on it, but the E61 group design already handles preinfusion pressure via its expansion chamber.
Dan is right, and I've corrected my post. 25 psi seems to be the most commonly recommended inlet pressure. Start with that, and adjust the brew pressure on the rotary pump to get ~9 bar.
John

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cannonfodder
Team HB

#8: Post by cannonfodder »

Also keep in mind most regulators have a range. If you have high water pressure you will need a regulator rated for it.
Dave Stephens