Temperature Offset on the Izzo Alex Duetto
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The offset is a simple way for the machine to display an "estimated" brew temperature at the coffee puck, whilst maintaining a Brew boiler temperature somewhat higher than that. The temperature probe of the Duetto is in the brew boiler and whilst the brew boiler of the Duetto might be at 102C, the water exiting the group may only be at 93C. It's usually much more convenient for the temperature display to show this lower "estimated" temperature and is how all machines of this type seem to work e.g. Brewtus II, La Spaziale Vivaldi, Vibiemme Double Domo PID etc…
It is actually surprising how much the brew water can actually cool down on it's journey to the coffee and of course depending on the temperature this offset will change very slightly (on any machine), so whatever you set is an average within the range.
To get a rough check of your offset and it’s accuracy, with the machine warmed up properly (which is really at least 45 minutes) and at the offset at the factory default of 10 (centigrade), simply set your brew temperature to 96C and run some water through the group (listen and watch the water), you should not see or hear it flashing off to steam. Then raise the brew temp by 1C, wait for the display to stabilise and repeat the above procedure. Keep raising the brew temperature by 1C until you get a definite change in the sound (it should be obvious when flashing off to steam occurs). Of course at this point the group won't have fully adjusted to the new temperature, that takes around 10-20 minutes. BUT, you will know for sure that the water temperature is 100C as it's flashing to steam. Now it is quite likely that the brew boiler is a degree or so hotter than it should be, because as mentioned earlier, the group is still warming up to the new temperatures….but it's faster to do things this way round.
So next you lower the brew temp by 1C and wait 10-15 minutes, then pull some more water from the empty group, if it still flashes off to steam, simply repeat the process waiting 10-15 minutes each time until it doesn't….at that time adjust your offset so that the displayed temperature is 99C and your offset will be pretty much OK
* Switch the machine on and immediately press (and hold) both PID buttons whilst the software revision is showing and release when F03 is shown note: it's best to press and hold the left button and then immediately press and hold the right…this avoids the risk of resetting the PID to factory settings
* Press the left had button 4 more times until F04 appears in the display
* Press the right hand button to raise and then the left hand button to lower the offset.
I have been doing quite a few more tests and the factory default settings are about right at an offset of 10C. A range between 9-10C is likely to be right for most if not all machines. My own machine seems to operate most accurately with an offset of 10C.
Note: you can change to F for a slightly more accurate reading when doing this test.