Greetings,

I have a Europiccola with a pressure gauge mounted above the sight tube. Now that I can pull a pretty decent shot with it, I thought I'd try to fine-tune it for that elusive ultimate shot. The boiler pressure (and thus the water temperature) is easily adjusted via a set screw, once the base plate is removed. Out of the box, my machine had a "green-light-off" pressure range of about 0.7-0.8 bar. I'm assuming this was set at the factory, which is more or less at sea level. From the pressure/temperature discussions and links in this forum, I've learned that this equates to roughly 240-243 F. Of course, this temperature drops significantly as it makes its way to the piston and on to the coffee.

So, my question is this: Has anyone fiddled with the pressure setting to compensate for your local elevation (or brew temperature)? So far, when I travel with my machine (as any faithful addict would do), I've been compensating for the noticeable differences in taste and character associated with pulling a shot in the lowlands versus pulling one in, say, Santa Fe by adjusting the grind (Pharos) or extraction time. Before I go all anal crazy with the P-stat settings, I thought I'd check to see if anyone has already gone down that road.

Cheers,
Mel

From what I have read the elevation doesn't matter as its a sealed pressure vessel so elevation doesn't apply, a bar is a bar. I just use a temp strip and at elevation when I am flushing the group be a bit more careful as it flash boils that much faster.

I think that only holds true in a complete vacuum. An externally-mounted pressure gauge displays a value called "gauge pressure" and that reading is affected by ambient pressure. So, a boiler at sea level with a gauge reading of 0.7 bar equates to a water/steam temperature of about 240 F. The same system at 7,000 ft elevation, again showing a system pressure of 0.7 bar, equates to a steam/water temperature of about 232 F. At least that's the way I understand it from the science nerds on the Home Barista channel!

Yes, both the gauge and the pressurestat operate on the difference between the inside of the boiler and the atmospheric on the outside. Exactly as bosango said. EricS has shared a nice graph showing the relationship between temp, gauge pressure and altitude: /downloads/ ... essure.jpg

Lots of discussion on this site can be found by searching with the 'altitude' search term, with one related to Pavoni levers here: Levers at higher altitudes

Some folks do tune their pStats differently when moving to a higher altitude, but I think that most folks who travel to high altitude with a Pavoni simply adjust their technique so that the lower boiler temp is compensated for by pulling with a slightly hotter group head.

I forgot about that picture, I don't change mine, I am at 5700 feet and I go up to 10,000. I just watch my temp strip, no gauge needed.

(Before I get into this any further, let me just say that this really is sort of a fun hobbyist discussion for me. I'm a firm believer that if you like the way it tastes, then that's what's best for you. For instance, my shots have little crema, regardless of bean age, variety, etc., but I love the way they taste.)

forbeskm - I guess I'll have to read up on using the temp strips. How do you control the head temp when the water coming out of the boiler is at different temps depending on elevation?

homeburrero - Thanks for the "levers at altitude" link! I somehow missed that entire discussion. At least in theory, it seems like adjusting the P-stat depending on elevation might be the best way to control the temp of the water hitting the coffee. In practice, that might be a different story, unless you were planning on staying a while.

I use a gen 1 so temp stability is not much of an issue. I generally ignore the elevation and just go about my routine. If the group gets to hot I will cool it down with a cold dish cloth.

I turn it on, heat it up, take a shot out to warm my group, then pull my shot. But this is not a Millenium, no pressure stat and a brass sleve. I get lots of crema but that I find is a combo of tamp, grind and bean. I had someone over who used the same grinder, same bean and had zip for crema on my Cremina, I pulled the next one, lots of Crema. Tamp was the culprit that time. Some reason my Luna Roasters Espresso Ottimo makes lots of crema, more than other beans I have tried. Then again Crema is usually bitter .

I

Changing the boiler temp and then adjusting the amount of group warm-up to compensate should effect the temperature profile (ie, how temp varies during the shot). A side effect will be the steaming performance.