Rocket Espresso: Wrong brew pressure from factory?

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HedonisticBeans

#1: Post by HedonisticBeans »

I consistently see people say "the Appartamento group head brew pressure is wrong".
It should be 9-11 and not 14 as it comes from the factory.

How can that be?
Rocket is an espresso-machine company.
I would imagine they know what pressure their machines should run on.

Before someone asks me how my coffee tastes - thats not the point.

Firstly, I don't know what pressure my machine is set to.

But if somehow Rocket is wrong, then dialing mine down may yield better results.

So, is Rocket sending out uncalibrated machines?

Seems farfetched.

Willing to stand corrected - hence this thread.

Thank you.

JRising

#2: Post by JRising »

I'll jump in with "I believe 14-Static is rather high". 10.5 Bar static should be plenty to find a good flow-rate:pressure drop ratio in the brew chamber. 14 Bar is perhaps even a little stressful on the pump and likely to contribute to the pile of Ulkas that die between 7 and 9 years of age, if people are stalling them all the time. The people who buy Appartamentos often don't know much about espresso machines (I'm not saying "YOU", I'm saying "People") and perhaps it's easier from Rocket's support-desk point of view to have the machine capable of pushing out something when the user has ground a little too finely, than to have to put up with another customer saying their machine doesn't work because no water flows through the brewhead when they choke the poor thing with something the local grocery store calls "Preground espresso".

This, of course, leads to "Can you improve your extraction by adjusting your machine and using it really well once you are familiar with it?"

Yes. of course you can.

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HB
Admin

#3: Post by HB »

According to WholeLatteLove, the Rocket Appartmento has a vibratory pump. I don't know which specific model, but for the common Ulka E5 at espresso flow rates, there's no need adjust it. From another thread asking essentially the same question:
HB wrote:Check out this diagram from Espresso brew pressure - conflicting answers:



For vibratory pumps, actual brew pressure is inversely proportional to flow rate. The higher numbers you hear quoted for vibratory pumps refers to their maximum pressure at zero flow. At double espresso flow rates, most are around 9 to 10 bar. The OPV adjustments you read about only apply to ristretto flow rates. If you want to experiment with low brew pressure, say 7 bar, then an OPV is a must-have. But if it's in the typical 9-10 bar range for double espressos, the OPV does nothing.
If a Rocket Appartmento owner can post a photo of the pump's label, we can confirm/refute the above. Assuming it holds true, you can adjust the over-pressure valve (OPV) to reduce the maximum pressure to 9 bar, but it will only affect pours at ristretto flow rates, not double espressos.
Dan Kehn

HedonisticBeans (original poster)

#4: Post by HedonisticBeans (original poster) »

JRising wrote:I'll jump in with "I believe 14-Static is rather high". Perhaps even a little stressful on the pump and likely to contribute to the pile of Ulkas that die between 7 and 9 years of age. The people who buy Appartamentos often don't know much about espresso machines (I'm not saying "YOU", I'm saying "People") and perhaps it's easier from Rocket's support-desk point of view to have the machine capable of pushing out something when the user has ground a little too finely, than to have to put up with another customer saying their machine doesn't work because no water flows through the brewhead when they choke the poor thing with something the local grocery store calls "Preground espresso".

This, of course, leads to "Can you improve your extraction by adjusting your machine and using it really well once you are familiar with it?"

Yes. of course you can.
I see your point and while I am not trying to be argumentative - it still seems farfetched.
Plausible but farfetched. Someone picking up this machine will have some know-how of grind-size effect on extraction time.

HedonisticBeans (original poster)

#5: Post by HedonisticBeans (original poster) »

HB wrote:If a Rocket Appartmento owner can post a photo of the pump's label, we can confirm/refute the above.
From a quick search on the internet, it appears the Rocket Appartamento uses the Ulka Vibration Pump EX5.

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Jeff
Team HB

#6: Post by Jeff »

Some dealers will pre-check machines before final delivery. This sometimes includes adjustment of the operating parameters such as OPV and PID offset. That they do this suggests to me that it is not uncommon for a "factory-fresh" machine to be a bit "off" in its settings.

My experience with E61-style machines with my coffees, grinder, and tastes suggest that a blind-basket pressure in the 8-9 bar range produced slightly better espresso than at 10 bars. My experience with other machines suggest that exceeding 8 bars in the basket (so perhaps 9 bar blind in a conventional machine) results in muted flavors or even cardboard notes with medium-light or light roasts.

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homeburrero
Team HB

#7: Post by homeburrero »

I'll add that at one time many machines were purposely adjusted to deliver around 12-13 bars max because that was thought to be best for ESE pods. My old vibe pump ECM Giotto was one, and I'm convinced that after I adjusted my OPV down to ~10 bar blind basket max, my ristrettoish shots noticeably improved in taste and in spritz-free flow from the bottomless PF.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

boren

#8: Post by boren »

For whatever reason this is quite common. I've seen machines from VBM and Quick Mill set to about 12 bar from the factory, and it was also a complaint from James Hoffmann about several machines (I don't remember the specifics) in his $1500 espresso machine shootout. Maybe they know something we don't.

Pino

#9: Post by Pino »

Here the response from Luca Bezzera on Espresso TV.

Title: "9 bar or 11 bar - What is the right pump pressure for the espresso machine ??"

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Jeff
Team HB

#10: Post by Jeff »

That was pretty hand-wavy and seemingly unsupportable. At the typical flow rates of espresso extraction, around 1-2 mL/sec, a vibe pump is not near its flow capability at 9 bar. If anything, increasing the OPV to a higher pressure brings you closer to the capacity of the pump and effectively removes the OPV function.

I don't care what 1950s, robusta-rich, blended, dark-roast coffee led Gaggia to determine. Taste in the cup suggests 11 bar is notably suboptimal for today's coffees.

Ref: http://www.ulka-ceme.co.uk/E_Models.html - An E5 pump at the bottom of its spec, at 9 bar, should be capable of roughly 180 cc/min, 250 cc/min mid-range, or 3-4 mL/sec.