@XS750AU - if the water goes into the group is 100c+ but the group itself is cold it's very much possible that you'd be lucky enough for the water (that goes through the puck) to be cooled enough to hit the right temperature (e.g. ~93c). I think this is the design concept behind these machines, that the water in the boiler is too hot and relies on the group being cold. However, if the group is also very hot, my expectation would be that the espresso would be both brewed too hot and would feel too hot when you try to drink it. Is that not what your experiment shows?

After closer inspection of the pressure gauge I noticed that I previously misread its values. The default pressure (within the green zone) is actually about 1.1 bar or slightly more. The increased pressure setting I tried for better steaming was about 1.4 bar. I updated my posts in this thread accordingly.

Here's an update with my latest measurements:



Note that final numbers in the last row (97c, 1.2 bar) stayed the same between 70 minutes (not listed in the table) and 120 minutes. In other words, it takes the grouphead of the heat-break-free MCaL more than 1 hour to stabilize in its default out-of-the-box setup. Of course the machine is not designed to be used at that point, but when the group is colder. Users are expected to somehow pull the shot at exactly the right moment when it's just cold enough, but not too cold.

FWIW:
My brass sleeve Marcfi with two separately switched elements provides better control than my pstat LaPavoni Pro, even with a heat break. The Marcfi overheats after a couple of shots, but its behavior in pulling espresso and steaming is highly predictable and controllable. The best solution I have found for the Pavoni is a pstat setting of 0.7 and a custom steam tip with a 1.5-2.0 mm single aperture. The low volume, high pressure steam is perfect for steaming small quantities of milk.

It is important to distinguish two issues: predictability of temperature and stability over time. The Marcfi is more predictable, but the Pavoni at 0.7 is more stable within a certain range. I rarely use home machines to pull several shots in a row, so being able to get one on the money matters more to me than several that are sort of ok.

It takes a lot of mass and a certain amount of engineering to get adequate group temperature stability based on using the group as a radiator. However, dipper commercial lever groups mastered that problem more than 60 years ago.

Jim

boren wrote:Of course the machine is not designed to be used at that point, but when the group is colder. Users are expected to somehow pull the shot at exactly the right moment when it's just cold enough, but not too cold.

As you've implied, that's a self-created problem with an easy solution, which you've also applied, a group temperature strip. Good technique can bring the consistency of using a machine outside its design goals.

@Jim: I used to set my 2002 La Pavoni at 0.8 bar and use a heat break. At that setting it cruised below brew temperature and I used half pumps to pull the shot when I reached the target temperature on my group thermometer. A 2nd gen La Pavoni ("pre-millennium" without the brass sleeve), it's more challenging and I would toggle power on and off to keep it at 0.7 bar for successive shots. My brass sleeve Europiccolas are a completely different design that not only has a more massive group, they sink heat by constantly venting steam. Does the dual switch Marcfi vent steam also?

drgary wrote:As you've implied, that's a self-created problem with an easy solution, which you've also applied, a group temperature strip. Good technique can bring the consistency of using a machine outside its design goals.

I think the problem was actually created by Elektra engineers

I'm using a smart power outlet that turns on both machines (MCaL and Alexia EVO) before I wake up, and I usually leave them on for a few hours. I work mostly from home and I like being able to pull a shot at will, without having to deal with any special timing requirements, let alone wet towels or other hacks. I usually have 2 single cups during that period of the day, sometimes 3. My usage pattern doesn't work very well with the default MCaL configuration and until I reduced its pressure I basically used it for steaming during the early hours and only used it occasionally for making espresso in the afternoon or evening (which is a lot less often than I wanted).

Yes, and these were to be turned on when you get up. When you're ready to go to the kitchen, it's ready to pull a shot. It's a home lever and documented my methods and measurements in my review. I've tuned two of these to work to my satisfaction. I've tuned a 2002 La Pavoni and a 1987 Olympia Express Cremina to work the same way. When I'm done typing this I'll pull a delicious shot on my Cremina that has been on for over 5 hours. Any of those machines steam well for me. Let's agree to disagree.

as someone using a la pav pro pre mill for 20 years i can say i have zero issues with this. of course i only make 2 or 3 cups at a time.

Some more data:



The heat break reduces idle temperature from from 95c to 85c, but it takes the machine 45 minutes to get there. I haven't tested how long it would take with flushes of hot water to accelerate the process, but judging from the test without the heat break, it should reduce it to about half an hour.

I think there are two other factors that make the concept of group head as cooler unpredictable:
- The amount of time the hot water are exposed to the colder group varies depending on the time it takes to complete the shot. A 25 second shot would give the group less opportunity to cool the water than a 45 seconds one.
- If you need to adjust the grind and pull another shot, the group is already hotter. Getting a fine tuned shot is a bit like hitting a moving target.

It's like hitting a moving target if you are not measuring group temperature. If you're measuring that you can lock in a portafilter that you've rinsed in tap water. Also heat flushes work very fast. I use them to quickly get my Cremina up to temp for my wife's morning capp.

As you can see, with the heat break installed, group temperature changes greatly between minute 13 and minute 45 (from 60c to 85c), all with the same boiler pressure of ~1.1 bar. How do you get consistent and predictable espresso during that period? I don't personally think it's possible. Maybe you can get espresso that would be acceptable for some, but I'm not looking for acceptable. I'm looking for excellent.

BTW, people complain that thermostats and pressurestats are not accurate enough, and these only vary boiler temperature by a few degrees from the target. This is enough of an issue for people to want a PID. Temperature control matters, and a range of 25c in group temperature, in a machine that's "designed" to use the group as some heat sink, is simply unacceptable. At least now that I measured it, I know I have to switch it to a lower pressure to get consistent and predictable results.