Finding temperature offset from boiler to grouphead - Page 2

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#11: Post by vrosalescfd »

Good afternoon

I have a gaggia classic pro recently acquired. I read a lot to try to understand the temperature process. Then from some youtube video I saw someone with a cheap thermometrer installed in the gaggia. It was nice to have an option before spending money in a PID.

Then I bought a cheap thermometer and measured the temperature at the boiler wall and at the grouphead. I made some test to identify the temperature range for my shots. I'm happy for now with the results.

Here the graph temperature obtained with the thermometer

You can see in the graph the time cycle in min:sec in the horizontal axe, the temperature in celsius degrees in the vertical axe. The blue line represents the temperature variation at the wall of the boiler (inside the machine) once the machine is stable. The orange line represent the temperature variation on the wall of the grouphead. And the grey line represents the temperature variation at the wall of the bopiler when I made a espresso shot.

As you can see the temperature at the boiler is much greater than on the grouphead. This is because there is a flux of themperature from the wall of the boiler that cross the water inside and finally reach the gouphead. There is a lag of the wave of heat form the boiler to the grouphead. At the grouphead the temperature is much more stable (92 to 96°C) than at the boiler (96 to 108°C). But I have notice that there is steam inside and that is because the temperature at the boiler reach 107°C.

Then I want to get my shot at a 94°C at the grouphead; this is around 100°C at the boiler. I'm monitoring the temperature at the boiler because at the grouphead is unconfortable. So using my cheap thermometer I can roughly surf the temperature wave downhill at 100°C to make the shot. I always run some water to free the steam before the shot.

Here the thermometer I got from Amazon:ómetro- ... 08ZCBQN72/

Hope this can help to get better shots



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#12: Post by Kaffeind »

Brilliant! I want to try this on my Classic Pro (I'm sure others would as well). Where did you attach the probe to the boiler?
Does the probe wire pass through the vent in the back of the machine?


#13: Post by boshk »

I made my own cheap thermometer, nowhere near as good as a Scace but it gave me an idea of my brew temp.

Welcome to check it out, just fast forward to half way in the video....

It says E1 Prima but it will work for any machine with a portafilter of any size.

The only consideration is that my method doesnt really pressurise the portafilter AND the flow rate is excessive since there is NO puck to provide resistance, so the reading will only be accurate for the first few seconds or at least to the amount of water that WOULD have been used on say a double shot.


#14: Post by vrosalescfd »


In my case I attached the probe between one of the screw heads and the boiler wall show in the image.

The original image is here: ... cheap_dyi/

I found the bottom screws more confortable to place the long metal probe. Be sure to make good contact of the tip of the probe with the metal of the boiler.