Livia 90 Altitude Adjustments

Q: If I were you, I'd try it out in its new location and see how it works for you. My machine (a Cimbali Jr.) is operating at a hair under 6000 feet. It was recently serviced in a town at about 2500 or 3000 feet, and I haven't done anything to it since the servicing. The service guy brought it back and let it warm up, took the side panel off and showed me how to adjust the pressurestat, but given the readings we were getting (about 1.1 to 1.2 barr) advised leaving well enough alone.

A: Also, I'm not sure how reliable the internal guages are, so you might want to invest in one of those PF with a pressure gauge (or borrow one) before you got too far into this. The gauge you're looking at is boiler pressure. This tells you steam pressure in the boiler, and indirectly, temperature. 1 bar = ~14psi. Guage pressure does indicate the difference between internal and local atmospheric pressure. A gauge reading 1.2 bar at sea level will not be indicating the same absolute pressure as one reading 1.2 bar at 6000 feet. How that all ties into the quality and/or methodology of superb espresso making... I'll leave to someone who knows, or who can at least speculate better than I can. It is a spring, but the reference is not absolute even though the spring value (or the weight of a pressure cooker counterweight) is constant. The pstat has a diaphragm. On one side you have boiler pressure pushing it out. On the other side you have atmospheric pressure PLUS the spring pushing it in the other direction. When go up in altitude, the spring remains the same, but the atmospheric pressure drops, so the absolute pressure (the sum of atmos. plus gauge) drops. The gauge (which also reads relative pressure) would read the same, but the absolute pressure would be lower. The ultimate example would be to put the machine in a vacuum chamber (or in space). There, the only thing pushing from the outside would be the spring, and gauge = absolute, so the machine would show 1 bar gauge at 212 F, instead of 249F as it does at sea level. At 6000 feet, the boiling point of water is about 11 degrees F lower (should be around 201F, not 194F as stated = the formula is 1F fdecrease in BP for each 540ft of altitude - note though that water begins to "simmer" long before it boils), so the gauge should be set about 4 psi (.2 bar) higher than at sea level to achieve the same absolute pressure and temperature. Another problem is that though the boiler is a closed system, if the espresso you brew emerges at higher than the local boiling point it will boil as it emerges, which will at the very least disrupt the even flow from the portafilter. Actually they have been available as galley options for several years on Boeing (and presumably Airbus) aircraft. I know that Saudi have them on their 777 First Class galleys. Airlines specify and purchase their galleys directly from the galley suppliers (Jamco & BEAerospace to name but two) as opposed to having Boeing manufacture them. As to the maker of these machine I do not recall, but I will try find out from some of my contacts if members of alt.coffee are interested.