Hot grouphead La Pavoni Pre-millenium Professional - Page 2

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IamOiman

#11: Post by IamOiman »

Here is a question: does your shot taste bad when you pull it? You mention all of these issues with the temp strip showing 110C, which is frankly HOT for a grouphead. Can you describe what notes you taste, or if it seems bitter/sour or even 'off' from what you expect? Literally the only thing I can think of is your heating element is not 1kW but something else if the temp strip is accurate as I have not seen a Pavoni Professional ready before 10 minutes at the minimum safe water level in the boiler.

Try pulling a shot ignoring the temp strips and see where that takes you.
-Ryan
Using a spice grinder violates the Geneva Convention
LMWDP #612

Essprezu

#12: Post by Essprezu »

jtrops wrote:Something seems off. How does the coffee taste? Is it possible that your strips are reading high, and that you are actually in the right range, or close to it?

I have never used temp strips on my machine, but I have used two different electronic thermometers with thermocouples. The first one would go to around 70c for good shots. The second one is probably the more accurate of the two with readings between 85-87 for a great tasting shot. Both thermocouples attached in the same spot, and the same way to the group bell.

So, without some shot quality assessments the temperature discussion is missing important information.
The temp strips might be reading high, that's why Im going to get a second digital thermometer.

As for the coffeetaste: bitter, I do have to add that the coffeebeans are not fresh. But I'm going to get some fresh beans.

Essprezu

#13: Post by Essprezu »

IamOiman wrote:Here is a question: does your shot taste bad when you pull it?
Yes. Really bitter.
IamOiman wrote:
You mention all of these issues with the temp strip showing 110C, which is frankly HOT for a grouphead. Can you describe what notes you taste, or if it seems bitter/sour or even 'off' from what you expect? Literally the only thing I can think of is your heating element is not 1kW but something else if the temp strip is accurate as I have not seen a Pavoni Professional ready before 10 minutes at the minimum safe water level in the boiler.
That's why I want to buy a second thermometer to rule that possibility out. But if the reading is still around 110 after let's say 8 minutes of heating, then the heating element might be faulty. Would resetting the thermostat help you think?
IamOiman wrote:
Try pulling a shot ignoring the temp strips and see where that takes you.

RobAnybody

#14: Post by RobAnybody »

At 110°C your grouphead should be radiating heat, you should be able to feel it if you have your hand close to the grouphead.
On my LPP I'm still able to touch the grouphead after 6 minutes of heating (in my experience with hot surfaces, this means it is still below 70°C).
I don't think resetting the thermostat will do anything, it's only there in case the pressostat doesn't work or the water gets so low that the element starts overheating.
Since pressure and temperature are nicely related in a closed system, the only way for the grouphead to overheat like that would be if there is a small pressure leak and the heating element is constantly working to keep up the pressure.
Does your pavoni hiss a lot when warming up?
Cheers,
Rob
LMWDP #647

ojt

#15: Post by ojt »

The second generation Pavoni groupheads are like that. Some have learnt how to use them. I would do the water heating mod if I were you. It would make your machine work more like the first and third generations, much more temperature stable.
Osku

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IamOiman

#16: Post by IamOiman »

That is what I find curious about this matter, as my Pavoni is second gen as well and does not experience this very rapid heating cycle. Besides a new power switch the one issue I've had with mine was an old boiler gasket that I replaced last year, pic shown being me testing it right after replacing the gasket.
Image
-Ryan
Using a spice grinder violates the Geneva Convention
LMWDP #612

Essprezu

#17: Post by Essprezu »

RobAnybody wrote:At 110°C your grouphead should be radiating heat, you should be able to feel it if you have your hand close to the grouphead.
On my LPP I'm still able to touch the grouphead after 6 minutes of heating (in my experience with hot surfaces, this means it is still below 70°C).
I don't think resetting the thermostat will do anything, it's only there in case the pressostat doesn't work or the water gets so low that the element starts overheating.
Since pressure and temperature are nicely related in a closed system, the only way for the grouphead to overheat like that would be if there is a small pressure leak and the heating element is constantly working to keep up the pressure.
Does your pavoni hiss a lot when warming up?
Cheers,
Rob
No I don't experience any radiating heat when it's at 110. And the release valve doesn't hiss at all. Except for once when I had the pstat at 1.5, then it started hissing. So there is no pressure leak.

I've also recorded the proces again and scribled down some notes:
Image
Image

RobAnybody

#18: Post by RobAnybody »

Essprezu wrote:No I don't experience any radiating heat when it's at 110.
So have you tried touching it? :wink:
That is what I find curious about this matter, as my Pavoni is second gen as well and does not experience this very rapid heating cycle.
Same here, I have a copper/brass '94.
After releasing cold air when the manometer reaches 0.9 for the first time it takes at about 15 minutes before the grouphead gets to hot to touch. Unless I speed up the process by flushing some air in and out of the area above the piston with the lever.

Have you ever removed the group from the boiler and looked at the back of the neck of the group? I remember it being mentioned that there is a version which has 2 holes connecting the headpace of the boiler with the grouphead [citation needed, I'll look it up]. This would allow for the air to be exchanges way more efficiently thus leading to a faster overheating grouphead.
Cheers,
Rob
LMWDP #647

RobAnybody

#19: Post by RobAnybody »

Found it:
La Pavoni Europiccola CAD Model
homeburrero wrote: Some gen2 groupheads have only one inlet port drilled through, others have two.
Cheers,
Rob
LMWDP #647

Essprezu

#20: Post by Essprezu »

RobAnybody wrote:So have you tried touching it? :wink:
Actually no I haven't. I should try this. What's a good indication of too hot? Screaming at first contact? :lol:
RobAnybody wrote: Same here, I have a copper/brass '94.
After releasing cold air when the manometer reaches 0.9 for the first time it takes at about 15 minutes before the grouphead gets to hot to touch. Unless I speed up the process by flushing some air in and out of the area above the piston with the lever.

Have you ever removed the group from the boiler and looked at the back of the neck of the group? I remember it being mentioned that there is a version which has 2 holes connecting the headpace of the boiler with the grouphead [citation needed, I'll look it up]. This would allow for the air to be exchanges way more efficiently thus leading to a faster overheating grouphead.
Cheers,
Rob
Well I have this Pavoni for over a month perhaps, so I haven't really gotten that intimate with it. I will upload the video on youtube and post the link here. That should give you a better image of what I'm dealing with.