Flow control: Can a machine's brew pressure gauge be used instead of a grouphead one?

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boren

#1: Post by boren »

I have a grouphead thermometer that I like and don't want to remove. If I install a flow control device, can I use the built in brew pressure gauge to adjust pressure in the grouphead during extraction?

Thanks!

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Jeff
Team HB

#2: Post by Jeff »

No, you're on the wrong side of all the restrictions.

boren (original poster)

#3: Post by boren (original poster) »

You mean the boiler pressure gauge will be unaffected by any changes to flow?

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Jeff
Team HB

#4: Post by Jeff »

Pretty much, yes.

Assuming the pump can keep up, it will be measuring close to OPV or bypass valve pressure all the time.

Bluenoser

#5: Post by Bluenoser »

The downside of the flow mod on HX machines.. you could install flow meter and then measure pressure for various rotations and mark somehow.. then reinstall thermometer.. not ideal.. and not sure if pressure changes for different beans or other varying parameters. I think the BDB does actually measure the group pressure.. but it is one of the rare ones that do.. Too bad because I find the pressure gauge on these machines mostly useless except when I want to set the OPV.. But Breville shows it is possible.

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HB
Admin

#6: Post by HB »

boren wrote:...can I use the boiler brew pressure gauge to adjust pressure in the grouphead during extraction?
Not without tapping into the brew chamber directly. That's what mohninme did in Lelit Mara - HX Profiler Conversion:



AndyH followed suit in Izzo Alex E61 HX Profiler Conversion mod. In theory, you could cap off the existing gauge tee and reuse the existing brew pressure gauge for flow control monitoring.
Dan Kehn

Pressino

#7: Post by Pressino »

boren wrote:I have a grouphead thermometer that I like and don't want to remove. If I install a flow control device, can I use the boiler pressure gauge to adjust pressure in the grouphead during extraction?

Thanks!
The boiler pressure gauge usually reads from 0 to 3 bar, so it wouldn't be suitable for measuring brew pressure, even if you could install one at the brew chamber.

The best solution for HX e61 machines would be to install a dual reading temp/pressure gauge with the appropriate ranges in the access hole (which is used for maching access during e61 group head manufacture and then closed with a bolt---fortunately for those who want to do things like add temperature and pressure gauges...). There are some dual reading gauges that could be adapted to fit.

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HB
Admin

#8: Post by HB »

You're right Pressino about E61 HXs, but to avoid confusion, allow me to mention that the OP's profile lists a Quickmill Alexia EVO, which is a single boiler with only a brew pressure gauge. FWIW, I refer to an espresso machine gauge as either a steam pressure or brew pressure gauge instead of an ambiguous "boiler pressure gauge".
Dan Kehn

boren (original poster)

#9: Post by boren (original poster) »

Good point. I was referring to my Quick Mill's brew pressure gauge, which goes all the way to 9+ bar when I backflush the machine. Will it just be oblivious to the flow control system being using? If I block all flow with that system, will it not mimic backflushing?

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HB
Admin

#10: Post by HB »

The current brew pressure gauge tee is installed upstream to the gicleur in the E61. This diagram from Internals of an E61 Brew Head [video] may help explain:

Image

The gicleur is the tiny yellow jet (orifice) at the top of the mushroom. The onboard brew pressure gauge will be close to the actual brew chamber pressure, but not the same. The onboard gauge will read higher; how much higher depends on how much restriction the gicleur offers. To better understand the mechanics involved, watch the video in Internals of an E61 Brew Head.
Dan Kehn