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The boiler was actually a lot more of a pain to clean than I had hoped. Initially when I pulled it apart, the scale seemed to wipe away. After several months without touching it, it no longer wiped away!!! I think that probably the test heatup may have cracked the scale apart a little, making it temporarily removeable. Anyway, i got there, and after inspection with a small mirror and light there is not a speck left in the boiler or HX. It all came off using citric acid, and I encouraged the last bits along with a toothbrush. It was a bit tricky with a small access hole trying to inspect/clean around the hx joins where the last remains of scale seemed to sit. The hx didnt actually have scale inside, oonly outside.
Im starting to really want a coffee from this machine!
I have been trying to understand teh pre-infusion on my machine a bit more. I have included a pic of the group with illistration of important bits.
Here is wht I think: but I could be wrong!
The water flows from the HX into a gicleur. From here it goes one way to the OPV, and the other to the 3 way valve. reentering from the 3 way, it enters the pre-infusion chamber at quite a low point in the chamber. It also exits the pre-infusion chamber at quite a low point.
As the water gradually enters via the gicleur, the pre-infusion chamber will form an air pocket. I estimate around a 10 cm3 air pocket. Once the air pocket is formed, the water has to go out the puck, or compress the air pocket. As the puck will not let much through til higher pressures, the air pocket will gredually compress (the ramp) based on the water flow (size of the gicleur). I gather the pressure rise will result in the air pocket being compressed to about 1 cm3 at 130psi. How long this process takes, I will have to see when I have it back together.
Pretty cool I think! Unless of course I have completely misunderstood what it does!!
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