Vibiemme Double Boiler OPV and steam boiler pressure

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YasBean
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Joined: 16 years ago

#1: Post by YasBean »

I just received my new Vibiemme Domobar Super Double Boiler Vibe last week, and am in the process of dialing everything in. One thing I noticed which was very different from everything I have ever read was that the OPV was set to 11.4 max (with blind filter). After reading 1st-line's documentation, I went in and adjusted the OPV to read 9.8, which means it is brewing at approx. 9. I also noticed that although the labeling inside the machine states the maximum boiler pressure to be 1.2, my steam boiler came set at 1.5. I wrote to 1st In Coffee, and asked whether the steam boiler should be adjusted down, and why the OPV was also set so high. Had my machine slipped through the QA inspection? 1st In Coffee forwarded my inquiry to Italy, and VBM responded with: "11-12 bar is the standard in Europe. A coarser coffee grind will allow lower brew pressures. The OPV only is to adjust maximum pressures." If I try a coarser grind on my Baratza Vario, the time runs only about 10s, and 1st-line's manual states that if the brew pressure is too high, it is most likely the fault of the OPV. So, should I reset the OPV to 11-12 and just admit incompetence, or should I keep it at my adjust 9.8 bar indicated?
Oh, and as for the steam boiler, they said only that I should keep practicing to make better microfoam. As they did not respond to my question about the high pressure, I guess 1.5 bar is not a safety hazard, and the steam is not too hot, as I had suspected.

Beezer
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#2: Post by Beezer »

I keep my OPV set to give a brew pressure of about 9 bar, and I think most of the other people here do the same. This allows for a reasonable extraction time (assuming your grind, distribution, dose and tamp are correct of course), and it seems to take some of the harsh edge off the shot flavors. If you're going to use a higher pressure, then you need to grind finer to compensate. Coarser grind will just let the shot run even faster.

As for the steam pressure, I haven't used that machine but I believe most prosumer DB machines allow you to set the steam boiler pressure fairly high to allow faster steaming. Since the steam boiler isn't directly affecting the brew temperatures, you can set it higher than you would on an HX machine. For example, I think the GS3 often comes from the factory with the steam boiler set at 1.8 bar, so it doesn't seem unreasonable to have your machine's steam boiler set to 1.5 bar.
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cafeIKE
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#3: Post by cafeIKE »

I've been running my DD steam @1.5bar for 1.5 years and it's yet to blow.
IIRC, the steam safety is 2.2 or 2.5bar.

About 9.8 bar on a blind basket will give you about 8.3 bar on the puck with Scace ~70ml/30s flow ±0.3ish bar.
My DD reads 9.9bar on a blind basket for ~8.3bar on the puck.
No complaints from anyone

Adjust the grinder so you get ~60ml in 30s, then adjust the grinder and temperature for taste.

For great foam, purge the boiler a couple of times. Stretch by sticking the tip all the way down, open the valve then lower the jug until it starts ' frying bacon ' Stretch to 80°F for latte or 90°F for capps. Raise the jug so the the top of the milk is just below the wand junction and keep it there until the milk is 140°F. IMO, better mixing occurs when the tip holes are aligned with the centerline of the jug.

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YasBean (original poster)
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#4: Post by YasBean (original poster) »

Thanks for your suggestions, and great diagram! I will keep things as they are set now, then, and rely on the OPV then level things out on the occasions where the puck is too dense (changing coffees frequently means I am never perfectly dialed in). Perhaps the Italians like 11-12 bar because they use darker roasts. As for steaming, I am sure it will take more time. This is the first time I have had real steam power and I have a small pitcher (8oz), so the milk heats VERY fast. Before the blink of an eye, the pitcher is too hot to touch, and I've scalded the milk. I will keep the steam power lower, perhaps.

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cafeIKE
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#5: Post by cafeIKE »

The Vibiemme DD steams at a 'leisurely' pace compared to the Domobar Super HX, itself not as fast as some.

A thermometer ensures the milk is never scalded. Practice with the steam wand full open 'til mastered. You'll have a shorter learning curve.

The easiest way to master steaming is buy a gallon of the milk you use and practise for a couple of hours. Trying different tip depth and positions in short succession is more instructive than steaming the same quantity of milk over a month.

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YasBean (original poster)
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#6: Post by YasBean (original poster) »

I would think the HX would not be as fast, as the pressure is set lower (0.9-1.2).
I could not bring myself to steam that much milk. I would be far too strung out after that many cappuccinos. :wink: Instead, I used the "drop of detergent in water" method, which also allowed me to see the dynamics of this tip. I actually managed to pour a heart on the cup this morning.

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cafeIKE
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#7: Post by cafeIKE »

The HX has about double the water volume, so produces more steam.

After I added the PID to the HX, I cranked the pStat to about 1.5bar, thinking the steam performance would be awesome. It was, but not overly friendly for small milk volumes. It now coasts around 1.15bar, a compromise between too fast for a small amount and too slow for a large.

When climbing the curve, the gallon of milk goes down the sink.
Someday, I'm gonna have to try the dish soap.