Adding Thermometry to a La Pavoni Europiccola - Page 2

#11: Post by **mathof** » September 11th, 2012, 1:29 am

Do you know what the pressure reading of the water was? I find that pulling when the pressure is around 0.7 bar through a group head that is around 80C (176F) is my sweet spot for the Londinium roasted beans that I use.

September 11th, 2012, 1:37 am

Matt:

Pressure was at about 1 bar. But I was more carefully monitoring temperature. I'll try some more shots soon to answer your good question. This was the day after hosting an H-B party so I was a bit bleary.

September 11th, 2012, 10:38 am

It turns out I wrote about that detail yesterday and then quickly wrote the update on this thread. Here is the core of the other post with more detail:

drgary wrote:It took 6 minutes to heat from cold. Pressure passed 1 bar and I toggled off power. Using a Super Jolly grinder dialed into the machine I dosed 16 gm into an Elektra double basket in the bottomless portfafilter .... My group temperature reading started at about 173F and came up to 182F after I raised the lever. I'm just learning to use the group thermometer and thought this would be about right. Pulled a perfect shot with tiger flecks. Yum. 20 minutes later I started the machine again from 0 pressure. It took 1 1/2 minutes to heat while I was dosing the basket with a different coffee. It was a lighter roast so I let the group temp reading go to 184. Delicious shot.

What's working here? I'm using a gram scale. Dose and grind are dialed into the machine on a consistent grinder. I'm not guessing about group or boiler temperature. Perhaps one of these days I'll drill out a double basket, put a thermocouple up there and determine the difference between temperature in the coffee cake and at the lower back of the group. But does that really matter if I want to pull consistent shots on a Pavoni? No.

#14: Post by **uyeasound** » September 17th, 2012, 5:57 am

I'm beginning to have problems surfing to the correct temperature. It could be the thermistor isn't taking sufficiently frequent readings because it's had its day, or the battery is running out, but i find it regularly shows 0.1degrees above my target, then a moment later, it's dropped to 0.3 below, and i have to do a half pump to shoot the temp upwards. Irritating. I've order a thermometer with a faster sample rate. I hope this will help.

Out of interest, at what temp do folks find their machine settles, with respect to their target? Obviously the exact value will depend upon probe placement, but relative to brew temp it should be meaningful. I have no pressure gauge, but my machine rests 4 or 5degrees below my brew temp (that's 89 C compared to my brew temp of 93.6 C, for the beans i'm using this week).

http://users.rcn.com/erics/ · #15: Post by **erics** » September 17th, 2012, 7:42 am

As an FYI, the Taylor 9844 digital thermometer disassembles in about 5 seconds, high temp velcro is available as a 3M product, and a 1/4" square piece of the relatively expensive aluminized duct tape will securely hold the thermistor bead in place. A disadvantage is the size of the thermometer but . . .

The thermistor wiring can be enclosed in heatshrink tubing and the thermometer calibrated in a "bucket" of steam. I thought that some(?) of the La Pavoni Euro machines had a pstat and, if so, grouphead temperatures will naturally vary.

September 17th, 2012, 10:32 am

uyeasound wrote:I'm beginning to have problems surfing to the correct temperature. It could be the thermistor isn't taking sufficiently frequent readings because it's had its day, or the battery is running out, but i find it regularly shows 0.1degrees above my target, then a moment later, it's dropped to 0.3 below, and i have to do a half pump to shoot the temp upwards. Irritating. I've order a thermometer with a faster sample rate. I hope this will help.

I don't think anyone needs that degree of precision. If I'm at the degree I want, not the fraction, that seems enough for the coffee to consistently taste good. Can you taste the difference with 0.3 degree variation? Jim Schulman wrote somewhere that he doesn't find brew temperature to be the most critical measurement. YMMV.

erics wrote:I thought that some(?) of the La Pavoni Euro machines had a pstat and, if so, grouphead temperatures will naturally vary.

Yes. Some have the PSTAT and some don't. The machine in my original post here has no PSTAT. My Millennium machine does. I'm not sure Eric if I understand your point though about groupheads naturally varying related to PSTAT. Are you talking about temperature stability? I'm trying to help folks find the right temperature for a pull and different types of Pavonis vary for stability.

http://users.rcn.com/erics/ · #17: Post by **erics** » September 17th, 2012, 10:40 am

The boiler temperature will vary with boiler pressure and the grouphead temperature will also cycle albeit attenuated some.

September 17th, 2012, 11:20 am

Yes i definitely find that even a temp variation of only 0.2 c of the group, at the moment i lift the lever fully, will change the shot. In fact the first drop tells the story i find. If i got the temp bang on, the first drop comes out thick and heavy like tiger-eye paint, but if i'm high or low, it comes out thin like coffee water.
What i meant by sample rate was only really that it should react each second, instead of ever four seconds or so (which i think mine does).

September 17th, 2012, 11:37 am

uyeasound wrote:Yes i definitely find that even a temp variation of only 0.2 c of the group, at the moment i lift the lever fully, will change the shot. In fact the first drop tells the story i find. If i got the temp bang on, the first drop comes out thick and heavy like tiger-eye paint, but if i'm high or low, it comes out thin like coffee water.

Adam:

That doesn't sound like a temperature issue -- more like another variation in technique that you may be correlating to temperature.

Another machine on my counter is this Isomac Amica. Its PID can be adjusted to one degree F. It has the e61 group with 8 lbs. of brass for temperature stability. If I change the temp by one degree and let it stabilize there, the flow characteristics don't change at all. BTW the temperature reading you see from the boiler is higher than inside the group.

September 17th, 2012, 11:46 am

I'm not sure. Temperature correlates perfectly with what i taste in the cup, but what you suggest is interesting. I wonder what the variant could be. Ideas? Perhaps the new temp probe may show me that something else is at play...