I've been playing with boiler pressure and group-head temps on my ECM Technika Profi IV for a little while now, having bought the Coffee Sensor Pro, which is pretty much the same as "Eric's Thermometer".
On the pressure, I dropped mine to peak at 1.1-bar, but found it degraded steam for milk, so bumped it up to max at about 1.25 - 1.3.
Despite reading thousands of words on the topic, I am still confused as to what the group head reading is telling me. If you read Eric's instructions, on a flush-n-go machine like mine, he says the temperature will read a couple of degrees lower than the temp of the water presented to the puck. In my mind, that means if it settles down at 94C, the water hitting the puck will be 96C.
However, I've read other comments from people who insist the temps register two degrees higher than the water hitting the puck... and ones using a different machine who say the two converge after 15-seconds, so if it reads 94C 15 seconds in, that is the temp of the water hitting the puck.
In partial answer to
1)
If the flush max and shot max are around the same (or within 1 deg C) then the flush appears to make little difference. why would you bother ?
I suppose i would've expected the flush part to run 100+ and the the subsequent shot to run cooler.
2)
How important is the Shot max/min vs the average temp over the extraction? Does a high temp for the first few seconds matter if the temperature drops off for the rest of the shot.
1. The thing to remember is that when sitting idle, the thermometer is measuring the group head temp, but after water has been flowing for a few seconds, it is measuring water temp.
The flush and pulling the shot use different water volumes and so the temp change is very different... therefore will produce very different curves. A 30-second flush will drop temps significantly, whereas a 30-second shot will not. Without the flush, the water temps would stay much higher in pulling the shot, because back pressure restricts water flow. The flush has also drawn cooler water into the HX. The 4+Kgs of brass in the group head also flattens things out.
2. This is where there is debate as outlined above. The water initially hitting the puck will be instantly cooled, because the puck will be at a much lower temp. After 15 seconds my temp stabilises and it makes sense to me that the puck has come up to temp and the group head has stabilised the water temp.... hence I suspect the temp of the water hitting the puck has converged with the group head measurement.
Now who has both a Scace and a Coffee Sensor Pro to give me data?
