After a long-long time, finally I have managed to dedicate some time to complete my preheat coils for the Classic boiler.
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I have made a dedicated brass block to piggyback between the OPV (or water inlet on the Pro) and the grouphead, so it only preheats the water getting into the boiler and not the overpressure flow, returning to the water reservoir. I use about 2.6 metres of 8mm OD 1mm wall tubing to avoid flow restrictions even at the corners where it kinks slightly.
The overall mass is just above the weight of the boiler (530g) and overall capacity is 75ml. It makes it suffices even for a double lungo (18g in 54g out +20g water left in the puck).
It keeps the water at around 75°C instead of room temperature in the water reservoir.
The intake beginning at the bottom of the outer layer, water travels to the top, there it reaches the inner layer touching the boiler and proceeds to the bottom where it gets fed in at peak temperature.
It makes a significant impact on temperature stability according to my experiences. I had the temperature drop around 4°C with the PID during a standard double shot (18g in 36g out). Now this is reduced to 1.0°C.
![Image]()
I made a video about it:
Looking forward to hearing your thoughts guys.
I have made a dedicated brass block to piggyback between the OPV (or water inlet on the Pro) and the grouphead, so it only preheats the water getting into the boiler and not the overpressure flow, returning to the water reservoir. I use about 2.6 metres of 8mm OD 1mm wall tubing to avoid flow restrictions even at the corners where it kinks slightly.
The overall mass is just above the weight of the boiler (530g) and overall capacity is 75ml. It makes it suffices even for a double lungo (18g in 54g out +20g water left in the puck).
It keeps the water at around 75°C instead of room temperature in the water reservoir.
The intake beginning at the bottom of the outer layer, water travels to the top, there it reaches the inner layer touching the boiler and proceeds to the bottom where it gets fed in at peak temperature.
It makes a significant impact on temperature stability according to my experiences. I had the temperature drop around 4°C with the PID during a standard double shot (18g in 36g out). Now this is reduced to 1.0°C.
I made a video about it:
Looking forward to hearing your thoughts guys.
