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Adding Thermometry to a La Pavoni Europiccola

Postby drgary on Sun Sep 09, 2012 1:25 am

Edit per May, 2013: Do not get the Polder thermometer illustrated here. Three out of four I've tried to disassemble wouldn't come apart. GS

Inspired by AndyPanda's use of thermometry on a Gaggia and a Cremina, I've attached the same thermometer to my pre-Millennium La Pavoni Europiccola. I'm employing the same Polder thermometer he uses that sells for about $10 at Bed, Bath and Beyond and probably other places. This is a food thermometer with the temperature sensor inside a steel sheath. Adapting this to my Europiccola involved removing the sheath, finding a place to mount it, and shielding the thermometer from the heat of the machine. With my first test this evening it works. We used this type of thermometry to carefully monitor the temperature of the group on this machine and compare it to an Olympia Cremina '67 with a similar thermometer attached. Doing this we were able to use identical dose and grind in an Elektra double basket to reliably duplicate shots across machines.

Here are photos of the procedure. First, the thermometer and the rotary tool with a cutting wheel used to cut the plastic around the steel sheath for removal. Be sure to use protective eyewear when using a cutting wheel as these can fragment and fly off. At the top are two high temperature silicone rubber pads I cut to shield the thermometer from the heat of the machine.

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The pads were cut using a leather punch on the gasket material:

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The leather punch was an inexpensive eBay set that came in metric sizes:

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I used Blue Tack to stick the thermometer and the tip of the probe wires to the machine.

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First I rolled and applied a bead of tack to the sightglass bracket:

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Then I applied a silicone pad as a heat insulator:

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Next I applied tack on top. To securely hold the thermometer I added a second set of these:

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I used some more tack to make sure the wire leads are not touching the Pavoni boiler. Here tack is attaching the end of the probe wires to the back of the group:

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Here's how the machine looks with the thermometer installed:

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I will dial in shots using taste as a guide and correlate that with the group temperature readings. These will not be the actual temperature inside the group but should correlate very closely. AndyPanda used partial pumps to heat the group, and I'll follow that procedure. Without thermometry one otherwise monitors temperature with the manometer I installed on top of the sightglass. This is a machine that is manually operated with Low and High switches to get to temperature. It pulls great shots and is a powerful steamer once you learn how to "drive" it.
Gary
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Postby uyeasound on Sun Sep 09, 2012 6:19 am

High temp silicone has worked well for me to glue a thermometer to my group.
And i agree the installation turns a machine which not temperature stable, ito one which is entirely temperature predictable. I often adjust my brew temperature by .1 or .2 to adjust the taste profile.
La pavoni is a wonderful machine.
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Postby mborkow on Sun Sep 09, 2012 9:24 am

Nice work Gary.

> I will dial in shots using taste as a guide and correlate that with the group temperature readings

Looking forward to seeing those findings
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Postby drgary on Sun Sep 09, 2012 9:39 am

uyeasound wrote:High temp silicone has worked well for me to glue a thermometer to my group.


What product do you use or suggest? Is it removable for when you want to service the machine?
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Postby rpavlis on Sun Sep 09, 2012 11:01 am

I think it extremely important to monitor temperature and/or pressure on these machines. I pondered a long time whether to have the monitoring system attached all the time or whether to have a "test setup". I eventually decided on the latter.

I made two brass caps with M32x2 threads. I made a thermometer well on one, and I attached a pressure gauge on the other. I periodically use them to check the condition of the machines.

If I were to do this again I would make a single brass cap with a thermometer well on one side of it and a pressure gauge on the other.
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Postby Chert on Sun Sep 09, 2012 11:07 am

I made two brass caps with M32x2 threads. I made a thermometer well on one, and I attached a pressure gauge on the other. I periodically use them to check the condition of the machines.



This sounds good. Could you post a picture of this setup?

My thermometer is a TC wrap around the group with piece of metallic tape securing the probe to the group.

Gary, my probe is basically at the level where you attached your but more forward on the group. The range of temperatures that pull the most pleasing shots for my taste are 74 - 82 C measured at the location.

EDIT: lately I've moved up to 74 C to 91 C same sensor location.
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Postby rpavlis on Sun Sep 09, 2012 11:31 am

Here is an image that shows both of my special caps:

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I had some problem finding gauges that read standard SI units. I finally found one from China. It was amazingly inexpensive, about $US 12 or so. (Remember 1.0 bar is defined as 0.1 MPa.)

I considered putting an O ring seal on the temperature one instead of the thermometer well to reduce the problem of thermal intertia, but I was concerned that there might be leakage problems.

The two little protrusions on top of the one with the thermometer well are there to remove the cap! Brass is slippery!
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Postby uyeasound on Sun Sep 09, 2012 1:54 pm

Drgary - I just bought some clear high temp silicone from amazon. The brand i got is Granville (instant gasket). As to removal- I don't pull it; I slice it with a razor to remove the temp probe, then shave off the remainder of the silicone slowly. That way you're not forcing the chrome to choose which surface to stick with as you pull.
I love the temp probe.
I chose group placement for the probe as i have a millennium model, and trust the pstat.
I find .2 of a degree can turn a shot from good to great, and since i have a rocky, temp is my way of adjusting taste profiles.
I'm not certain how micro temp adjustment compares to the ability to micro-adjust dose&grind with, say, a mazzer. Anybody try both?
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Postby drgary on Sun Sep 09, 2012 7:50 pm

Adam:

Fortunately I'm working with a Pharos and a Super Jolly, so grind is so consistent I usually adjust dose just a little bit. But this is just the start of such measurement. Thanks for letting me know about the silicone you're using. Once I've worked with the thermometry I may go to silicone to make it more permanent, at least until I need to change out the thermometer.
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Postby drgary on Mon Sep 10, 2012 12:22 pm

mborkow wrote:Nice work Gary.

> I will dial in shots using taste as a guide and correlate that with the group temperature readings

Looking forward to seeing those findings


Since I was already familiar with the machine I tried it out this morning as usual while looking at the temp readings. Temp reading of 182F at the group seemed to hit it just right on the first shot, dosing 16 gm into an Elektra double basket. A scrumptous shot with beautiful, flecked crema. This was a Full City+ roast. Next coffee was a Full City roast. I pulled it with the group tem reading at 184F. That was good too. Just pulled a City roast for a capp, wanting it a little acidic. Pulled it at 184F. Very good. I think I've got it dialed in at the get-go. :D

An accurate temperature reading at the group gives me great confidence with this machine now. It was so easy to do this and so worthwhile! The importance of that reading was apparent when preparing the third shot. I watched the group come up to temp from 143F when I turned on the thermometer and waited until it was up to temp. I'm really glad to be avoiding guesswork. I suppose a temperature strip would help but this thermometry is much more accurate.
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