drgary wrote:the OPV may need adjusting, because it hisses loudly and constantly when the low heating element is at temperature.

I don't have any experience at all with La Pavonis, but my MCaL had the line between the boiler and pressurestat fully scaled, which resulted in the pressurestat keeping the contacts for the heating element closed at all times. What it meant... with the element always on, there was a constant loud hissing as the overpressure valve was constantly releasing the excess pressure (to stop the boiler exploding). Without knowing the machine, it would pay to check that this is not the case from what you have described.

Cheers, Chris


...split from Lever Espresso Machine Gallery by moderator...

gyro wrote:I don't have any experience at all with La Pavonis, but my MCaL had the line between the boiler and pressurestat fully scaled, which resulted in the pressurestat keeping the contacts for the heating element closed at all times. What it meant... with the element always on, there was a constant loud hissing as the overpressure valve was constantly releasing the excess pressure (to stop the boiler exploding).

That could be. I'll check and see if the the next brew run hisses less. Just descaled twice and the first run created a bright lime green dribble down the back because of a slightly loose boiler cap.

On my 2nd hand MCaL, the pipe was completely blocked and scale had totally invaded the pressurestat itself, almost no amount of descaling was going to fix it. I replaced the pressurestat and manually cleaned the pipe with brushes, toothpicks etc to scrape it all off. Its a dangerous situation, as if the OPV/safety fails, you are talking a fairly catastrophic explosion. And of course the espresso will be awful as well as the feed water will be too hot and the group will also rapidly overheat, more so than it usually does.

Luckily in this case the OPV is letting off steam, so there's no risk of explosion, but if continuous steam venting isn't normal function, I would love to resolve that issue because this would allow it to be left on without monitoring to prevent it steaming dry.

On today's brew run the OPV was a bit less intense, so descaling may have helped. I descaled again after the morning brew just to make sure and the tank and heating element look spiffy clean at this point. I thought there was some black deposit inside the boiler cap that wasn't dissolving until I felt it and realized it's a rubber lining, a nice quality touch.

Now that we've got this thread split, I'd like to add some anecdotes.

When Doug Garrott restored my Lady Duchessa, he alerted me that I'd had a "near-death experience." He discovered that the OPV was purposely prevented from functioning with a neatly machined metal disk. Why anyone would want to do that, I don't know, but I had tested the machine before sending it to him, and the prior owner had used it on and off for 15 years without any mishap.

TUS172 (Bob C) posted a wonderful thread awhile back on old Pavonis and commented on their hissing OPVs here: La Pavoni Europiccola instructions... for newbies. He wrote:

"These La Pavonis are a well built machine and if properly cared for will last for ever. They are designed to never overheat or build up too much pressure. A fuse wired into the boiler on the older models (later models have them as replaceable or resettable fuses) to prevent overheating and a pressure relief valve for too much pressure solves that problem. The pressure relief valve is what you will hear hissing once the machine gets up to pressure on setting I.
So anyway the pressure relief valve is the part of the unit that has the small tube that is closest to the boiler. It is a small spring with a metal ball at the end that fits into a venturi mounted on the boiler. The spring is set so that it allows pressure in the boiler to be let off once the unit is up to the appropriate temperature. Why am I explaining all of this? What the last owner did to this unit was to put a heavy spring in the pressure relief valve that must have increased the pressure and heat in the boiler until it forced leaks. The only thing I can think of is that they must have thought that these units use the pressure and steam from the boiler to make espresso. So when they heard the unit hissing they thought something needed to be fixed. WRONG!
I can tell you one thing it did... it must have made the worst tasting espresso they ever tasted. By forcing steam through the grouphead to the shower screen it not only overheated the espresso grind in the portafilter; it put undo stress and heat on the grouphead gaskets, boiler gasket, sight glass seals, and to much air from boiling the water continuously burner out the heating element itself. (The older La Pavonis did not have a reset able or replaceable fuse it was inconveniently wired up inside of the heating element body and almost impossible to replace). In other words these people really messed up."

Looking at his write-up, I wonder if a constantly venting OPV is normal function for these machines?

I do not know much about La Pavoni history, and what feature appeared when, but my Europiccola does not have pressure stat and has no pressure or temperature control other then the hissing vent valve.
When I first tried it, I too thought that something was wrong with the pressure stat. My understanding is this is normal and it is the way that I have been using it up to now.
I must admit to not having giving it much time and experimentation but I will eventually get to it.

Very handy web site for Pavoni history (and other info):
http://www.francescoceccarelli.eu/lapav...mi_eng.htm

The Pro always had a pStat and a gauge, but a pStat on Europiccola did not show up til the single element 1990 versions.

drgary wrote:
Looking at his write-up, I wonder if a constantly venting OPV is normal function for these machines?

If your La Pavoni is old enough it doesn't have a pressure stat and the OPV should be constantly venting when the machine is hot, especially on the high setting it can really get whistling.

Thanks, Tera. It seems like a more refined version of the Microcimbali. Both of them have high and low switches, manually operated. Both constantly vent steam to stay at equilibrium. Both can pull really good shots and produce more intense steam when throttled up. And they weren't designed to be left on all day because doing that would run them dry.

Don't forget that you can make it adjustable if you want

La Pavoni Mods - DIY adjustable pressure regulator

Ray