The mass of brass in my picture is from a 2 group La Cimbali M28, which is a commercial machine designed to continuously pull non-stop shots from both groups. I've not had any hands on experience with the Junior model and so I can not speak to whether the grouphead on it is the same size/mass as the truly massive one on the M28, also the interior channels may be different on the two models. Plus I suspect that the Junior is not designed to pull shots with no rest between them as the M28 is. My M28 is also an older design (20 years old?) so no doubt their design has changed over the years.I have a few questions if you don't mind:
So i see how it works but... Why? The junior has the same group but without all of the passes through the group head (from what i can see in pictures).
what advantage is their in not running the pup directly into the heat exchanger and the out the shower screen?
It works very well.Second how well does what is going on here work? Does it need a cooling flush? what kind of a temperature profile does it produce?
If you're not pulling continuous shots then it needs a cooling shot/shots. The volume, timing, and number of which is dependent on how low it has sat since the last shot.
I've never hooked a Scace device to it so I couldn't say.
If you're talking about the solenoid on the 3-way valve the water going into the heat exchanger never passes through the 3-way valve. If you're talking about the solenoid that allows water from the pump to flow into the heat exchanger it is far enough away from the grouphead not to be affected by its heat. The water between the pump/solenoid and the heat exchanger is heated where it passes through the grouphead via the grouphead's latent heat so it is cooling the grouphead not heating it. No water is left in the heat exchanger as any injected into it is flash heated to steam upon entry.while the machine is idle between shots what happens with the water that is between the solenoid-the heat exchanger- and the pump(or whatever point it stops being able to flow backwards)? Is that section of pipe acting as a kind of boiler where water is heated in the exchanger and gradually heating up that whole section?
Any change to the length of the piping between the pump and the grouphead would have no impact on anything as the water isn't heated until it gets to the grouphead/heat exchanger. Insulating the grouphead and/or any piping passing through it would dramatically change the thermodynamics of the grouphead, to the detriment of the coffee no doubt. The only possible change to look at that I can think of would be the size of the hole in the group jet (Part number 700230 on this page: Group head solenoid operated - Cimbali | Coffee Parts ). Some suppliers offer them with different size holes to change the profile of the shot.what improvements (If any) could be made to the design. For instance would a longer or shorter section of pipe between the pump and the group help to provide a better temperature profile?
Would insulating any of the pipe or the group have a positive effect?
Java "Cimba!" phile