La Pavoni without pressurestat

A haven dedicated to manual espresso machine aficionados.
flamenkito
Posts: 12
Joined: 12 years ago

#1: Post by flamenkito »

Need advice on how to safely pull a shot using a La Pavoni 16 "Ambassador" from the 1980's. I bought it off eBay, refurbished it, and have been using it for a couple year without any problems. The only way I can tell when it's ready is if the release valve starts steaming. At that point, I switch it to low, pull my shot, then switch it to high, and steam my milk.

Is that safe? What happens if the release valve breaks and doesn't release the steam? Will it explode?

User avatar
crazy4espresso
Posts: 677
Joined: 14 years ago

#2: Post by crazy4espresso »

Hi,
There is virtually no way of the safety valve seizing and preventing steam escaping, as it's just a spring with a ball on the end of it. If you're concerned, you can inspect it periodically and ensure it's kept clean and free of scale. It's more likely it will open sooner than preferred, as the spring wears out over time.
"I would rather suffer with coffee than be senseless." — Napoleon Bonaparte
LMWDP #427

forbeskm
Posts: 1021
Joined: 11 years ago

#3: Post by forbeskm replying to crazy4espresso »

X2 on that, in fact that is one reason I love the old two switch pavoni's. I miss the noise with my Cremina.

You can change the valve to a Teflon ball and spring from Stefano's , but that really it. There are two, make sure not to get the one for the pressure stat machine. Never had an issue, sometimes I have had to tap the relief valve to make it stop as the ball did not make a good seal.

jonr
Posts: 610
Joined: 11 years ago

#4: Post by jonr »

I use an IR temp gun to monitor the group temperature and then pull the shot when it's correct. But this is a taste, not safety issue. And the valve does release steam.

realdoctor
Posts: 192
Joined: 16 years ago

#5: Post by realdoctor »

The system used in all boiler safety valves is not really much different - spring and something to block the flow of steam. The old wobbler weights used on pre-pstat commercial machines used gravity instead of a spring but the pressure control principle was the same. Many of those machines had no additional safety device. Pressure cookers work the same way too. This is one of the most tried and true technologies around. When the spring fails, the valve just lets more steam out.

I second the opinion on the old two switch machines. I really like them better than the pstat machines.

Jim

petr0x
Posts: 81
Joined: 9 years ago

#6: Post by petr0x »

Hi,
can anyone help me recognize year of this La Pavoni europiccola?
It is switch version - without pressurestat, 200 and 800W, 49mm basket. Metal base where logo is located is flat (not embedded).
Thanks.
And if someone is interested, I can also post picture of DIY tamper, made of stainless steel and walnut wood.

forbeskm
Posts: 1021
Joined: 11 years ago

#7: Post by forbeskm »


User avatar
rpavlis
Posts: 1799
Joined: 12 years ago

#8: Post by rpavlis »

It is sometimes difficult to date La Pavonis because they often were produced with components made at different times, they seem to store components and then assemble machines from the stock. This one has a brass and plastic boiler cap which puts it in the early 1980s. The base is not real early.

Anyway, I just used my 1978 two switch La Pavoni. It still has a lipless boiler and screw on heating element. It can do just as well as later models, often better. I had problems with the original steel ball in the pressure relief. I replaced it with the plastic mushroom described earlier in this thread. I also put a flow restricting device on the end of the dip tube because early second generation la Pavonis have two holes for water to enter the cylinder, and this results in too fast a fill, I think. The flow restriction needs to be have a diameter of about 1.9mm to 2.0mm.

Here is my two switch procedure:

1. Be sure the thing is filled with water and both switches are turned on. Connect to the power. After about six minutes it will begin to hiss. At this point put a container like a ramiken under the group and slowly raise the handle, letting the steam continue to rush out the pressure relief valve. When you get the handle near full up position, very quickly raise it up and bring it down so just a bit of water escapes. Lower the handle to about mid range and move it up and down to near the point where water would be released. This bleeds the group of air. This must be done to be consistent. Now lower the handle all the way and turn off the 800 watt element, leaving just the 200watt one. It will soon stop the loud hiss and just barely release steam. If you should put a pressure gauge on the machine you will find that the pressure is very constant whether one or both switches are on. It will take a VERY long time to get heated up with just the 200 watt element! When ready the pressure should be about 0.7 or so bar.

2. Wait a bit after turning off the 800 watt element. If you do not raise the handle to near release of water before tightening down the portafilter, you will get a spongy pull if you fail to wait long enough. I always believe in "late lock down". In my experience the bottom part of the portafilter needs to be around 90 degrees for the best final results. The first espresso that emerges should be about 50-60 degrees, and toward the end of the pull it should be around 93 degrees. If it get much higher than that it will begin to be bitter. If you get near 100 degrees the espresso will be boiling as it emerges, and the espresso will be, in general, fairly awful.

3. It is best to pull the lever down until perhaps 2 or 3 mL of espresso has emerged, then raise it all the way before making the pull. This will reduce channeling. With experience you will find from the amount of force required to make the pull whether or not the beans were properly ground. You should not require gorilla pulls! Nor should espresso emerge without force on the handle.

petr0x
Posts: 81
Joined: 9 years ago

#9: Post by petr0x »

Thank you both. I am surprised I bought so old machine, which is not bad at all, but it is in so great condition I cannot beliveve it is old almost as I am :-).

rpavlis: I read your procedure for making espresso and I will have to read it more times probably :-). I am still learning, but mostly I get decent shot of espresso, I think. Sometimes it feels spongy, but I will figure out the technique.
At the beggining the lever was very spongy, which was probably due to resudues in the piston. I cleaned it and polished and works much better.

My procedure is: get in water, close everything, turn on full power, wait until it starts to hiss then swich to LOW. At this moment I want to heat the grouphead with portafilter in and the cup so I run about 50 ml of water through. Lever goes down. Then I prepare the milk, switch to FULL and do the steaming. Then to LOW power again. Milk is prepared, cup heated... I grind the coffee, put portafilter, clean the cup and raise the lever. Then I wait until few drops emerge (10 seconds) and start lowering until it is completely down. I leave the portafilter in until I do next coffee or when I turn it off, because some pressure can remain in the grouphead. I remove the portafilter slowly, because sometimes a little bit of pressure is released.

That is my routine. I did not fully understood why to insert portafilter with lever near the top?

I also noticed after about 7 espressos the thermal protection started to switch off the machine, even on low power and with some water. I usually do not make so many cups, but now I know I should not keep the machine on for long time.

User avatar
rpavlis
Posts: 1799
Joined: 12 years ago

#10: Post by rpavlis »

The advantage of attaching the portafilter with the handle near the top is that air is not pulled through the coffee, which tends to crack the puck and make a bad extraction. Also if you briefly raise the handle just before putting the portafilter in place you will fill the space beneath the piston with mostly water vapour, so you will have less a tendency to get a spongy pull.

Be careful not to let the level of water go all the way down, you should stop pulling shots when it gets perhaps a centimetre or so above the bottom of the sight glass. If you get it too low you can destroy the heating element. Do not leave these machines connected to power when you are not actively making espresso. It only takes about six minutes for them to be reach operating temperature. When they are on for longer they also tend to become to hot, and that results in eluting very bitter compounds.

Post Reply