Adjusting Rocket Appartamento Brew Pressure

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#1: Post by achosid »

After watching the recent James Hoffman video, as an owner of a Rocket Appartamento I wondered whether my machine is brewing at too high of a pressure. I'm going to measure brew pressure, but in the interim: has anyone adjusted the OPV on an Appartamento to lower the brew pressure? If so, how is it done on this machine?


#2: Post by Bluenoser »

Google search will bring up a few videos on adjusting its brew pressure.. If you borrow a SCACE2 you can verify its absolute value.. I've lowered the brew pressure twice on my Pro500 HX. I don't have a SCACE2 to see its actual value.. on my machine I am assuming pressure at PF is 1bar lower than the gauge reading.

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#3: Post by JRising »

What makes you wonder if your machine is brewing at too high a pressure? Is there too little flow? Is the pump stalling?

You can adjust it by adjusting the expansion valve. The expansion valve is the somewhat cylindrical brass valve on the floor of the machine in the center. I wouldn't if you don't have a gauge or a reason to. If it seems to be working, it's probably working. If your pump doesn't stall when backflushing, it's probably working.

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#4: Post by Jeff »

JH mentions that most machines in the 1500£ range come set at too high of a brew pressure for better taste. My own experience with E61 machines concurs that the typical 9-11 bar on the gauge (post OPV) is not optimal for my tastes either.

achosid (original poster)

#5: Post by achosid (original poster) »

Are there any easy sources to borrow a scace?


#6: Post by randytsuch »

If you have a portafilter with a threaded exit, its fairly simple to make something ... gauge.html

Cost maybe $50 by the time you buy the gauge and the adapters/valve/fittings.

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#7: Post by Jeff »

Cheapie gauges are probably "good enough". I would be surprised if the gauges in the machines were much more accurate than 5% FS. Repeatable is what I value. If I set it to "8" and it tastes good, then try "7.5" and it is not as good, I want to be able to get back to "8", whether that is 8.0 bar, or something else in the 7-9 bar range.

There are some static-pressure kits on the market at around the US$25 price, such as the Joe Frex (seemingly sold out right now). I chose to purchase parts through McMaster for something similar to Randy's rig, as I wanted to be able to measure pressure with varying flow. I ended up choosing 4053K18 160 PSI as a reasonable compromise for me between accuracy (1% at mid scale) and price ($33). It is probably overkill unless you're trying to calibrate a DE1 or similar.

achosid (original poster)

#8: Post by achosid (original poster) »

It's all coming back to me: I built a cheap pressure tester for my Gaggia Classic OPV many moons ago. Here's hoping the parts are still in my work bench.

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#9: Post by jmarcus »

how accurate is using a gauge on the E61 group head? Can i just something like this?

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#10: Post by Jeff »

At that price, I'd put in an EricS group-head thermometer for not much more and get better control of your temperature in every shot.

Absolute accuracy isn't important to me for a conventional machine. Being able to try roughly 1/2 bar less or more from wherever you are, taste many shots, then continue exploring or go back, for me, is the goal.

(There is at least one machine that benefits from absolute calibration, the DE1. I can't see significant benefits on an E61 as there are no pressure-based calculations occurring.)