Temperature and Pressure

The reason that the temperature and pressure are being discussed together is because La Pavoni are single boiler machines.   The boiler pressure is solely a function of the temperature of the water in the closed system.  When you take a pressure reading as described below, remember this is the pressure generated by the boiler that we’re talking about and not the pressure at the group head.  The final pressure at the group head is much greater due to the pressure exerted by the piston when you push down on the lever.

My machine came with the brew temperature set improperly so I HAD to mess with the device.  It was such that the water wouldn’t go above lukewarm.  That being said, there is likely probably nothing wrong with your temperature setting so if at all possible, don’t mess with thermostat.  There is a definite risk of burning yourself badly or even electrocuting yourself so be advised that I’m not advocating that you play with the internal electrical components.  If the temperature is set properly, the pressure gauge of the La Pavoni Profession should peak out between .7 to .8 bar.  Let the machine heat up, let some steam out of the steaming wand for 5-10 seconds, wait for the pressure to build up again, and then take a reading. 

Although suggestions for the standard temperature varies from 89 to 95C (192 to 203C), mine is set to 91C or 195F as per Dr. Illy, with the boiler 3/4 full. 

Remember, I’m not suggesting that you alter the factory settings.  This is just an account of what I had to do… 

In the base of my La Pavoni Professional, there is an adjustable pressure limiter (which I initially thought was a thermostat).  The partial  pressure of water vapour in the boiler chamber increases proportionally to the increase in temperature of the water.  We use this simple fact to cut off the heating element when the set temperature/pressure is reached.  First I filled the boiler until it was 3/4 full with water.  To get to the innards, I removed the screw underneath the plastic catch tray that holds on the bottom cover.  Inside, I found a brass screw on the right-hand side of the machine which is held in place with a small setscrew.  I loosened the setscrew and turned the adjusting screw a little at a time while checking where the heating elements cuts off.  This can be accomplished by listening to the sound of the water being heated and noting where it cuts out.  Turning it left lowered the cut off point, and turning it right raised it.  I believe that the configuration is different in newer machines (see Michael Stevens’ comments in the Comments/Discussion section).

There is also an issue of temperature instability.  This is my guess as to what happens.  The pressure switch is slow to react.  When the water in the boiler is used up (by pulling several shots in the same session), there is less capacity to hold the constant amount of heat generated by the heating elements.  As a result, the temperature swings are greater with less water than when the boiler is almost full.  You may end up with water that is too hot for the coffee.  I always fill my La Pavoni to about 3/4 full and only pull one or two shots at a time so this isn’t a big deal with me.  However, I thought you should know…

 

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{ 9 comments… read them below or add one }

Jorge Accame November 20, 2010 at 18:12

Hi

I have recently inherited a LA PAVONI model EUROPICCOLA from my aunt and would like to use it but 1) it has no manual and 2)it has no gauge like the one in the photo in this web page. I lve in Lima Peru where we have excellent coffee and I am an addict of good coffee, speciall expresso so I would like to know if you have a manual for this model of La Pavoni or if the one you have applies to mine.

Thank You

Jorge

Daniel May 2, 2011 at 10:19
HP Bohn June 28, 2011 at 10:17

Hi Daniel,
thanks for a very useful guide on the quirky La Pavoni. I have found it very helpful. But I think you’ve gotten the bit about pressure and temperature wrong. The pressure sensor at the La Pavoni shuts off the power when the pressure has reached 1 bar, correct. But what this really means is one bar above the ambient atmospheric pressure. So if you use the La Pavoni at sea level the pressure inside the boiler is actually 2 bar when it cuts the power. At this pressure, water boils at approximately 120 degrees Centigrade. I.e. the temperature of the boiler, the steam and water in it is MUCH warmer than the ideal temperature range suggested by Dr Illy. Herein lies the key to the third important bit with the La Pavoni (in addition to TAMP and GRIND) as you correctly point out. That is TEMPERATURE at the group head. And I believe this is the variable that is most difficult to manage. The head is warmed by a combination of heat conducted through the metal from the boiler (as you wait for the thing to heat up) and by the water and steam that passes through it when pulling the shot. If you wait too long to pull the shot, the group head will have reached too high a temperature (close to 120 degrees) to be able to cool down (sic) the water to the correct 95 degrees or so for a good result. But if you pull your shot too early, the group head is only luke warm and the the resulting brew will take place at too low temperature. As the group head warms up, subsequent shots will be at a higher temperature than the previous one, so that is also something to making the La Pavoni so quirky.

And by the way – the myth about ‘false pressure’ some Pavoni users write about is also wrong. There is simply no such thing as false pressure.

Happy brewing,
HP

kinross December 31, 2011 at 08:43

I am not sure how the Pavoni is constructed and what kind of venting it might have, but the internal pressure of the tank is going to depend on the mix of the air originally in the tank when filled and the added pressure from the water vapor. I assume the gauge or pressure sensor is reading a differential pressure, that is, the pressure above atmospheric. Assuming the gauge is initially at zero, the gauge pressure would be showing the pressure from the water vapor as well as some (small) pressure increase from the change of the temperature of the air in the tank. This gauge pressure is also the pressure seen by the sensor, ignoring any hydrostatic head from the water itself. I think the gauge pressure would be much less than 2 bar and the temperature much closer to what the gauge pressure would imply.

Jack Dunstan May 13, 2012 at 01:06

Worked for me, Thanks!

Steve August 29, 2014 at 12:02

My new La Pavoni profestional stat is set at max but doesnt go above 0.6 bar and drops to 0.5 when frothing. Does the machine need a new stat as it doesnt froth as well as my old machine of the same type

suzzan December 8, 2015 at 18:33

I just received a La Pavoni Europiccola from a friend made in copper and brass. I assume its an older model as the two buttons are on the side are white and red. No green button as I have seemed to find in most articles. I turned it on and there is water coming out of everywhere! I have no idea what to do and if I going to blow it up or if something just needs to be fixed. I called the number on the bottom of the machine and they said I need to send an email. However there is no way to send an email. If you can offer any help it would be so much appreciated. I may be waiting sometime before I get my morning coffee! I do have pictures but I don’t see a way to attach them here. HELP!

Steve Kelen March 29, 2016 at 12:32

Love your site. Not sure I want to get so bound up with perfecting my coffee – there are dozens of Italian coffee bars within three blocks of my house.

However, I wanted to report a minor error on your Temperature and Pressure page – in the third paragraph that begins “Although suggestions for standard temperature . . .” you have an error in converting Celsius to Fahrenheit. The range stated in parentheses should read “192 to 203F” not “192 to 203C”

Jacob Alstom September 17, 2018 at 17:18

Here’s my method on pulling back to back shots on the La Pavoni.

http://homebrewings.com/how-to-pull-back-to-back-shots-on-the-la-pavonoi-europiccola

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