jasonmolinari wrote:Given that the water dance is necessary because water in the HX tubing is sitting at above boiling point, since the boiler is under pressure, could one replace, or augment the pressurestat with a PID, which takes readings from the boiler water (just like Ken's), but instead of setting the PID to 240 or whatever, you would set it to espresso brew temp. The water now idle in the HX would equilibrate with this boiler water (which is accurate, and repeatable given enough stabilization time between boiler water and HX water, which i think should be less than 4-6 minutes), and would be at espresso brew temp. At least for the 1st 4-6 ounces (or however much is in the HX tubing inside the boiler). This is more than enough for a shot. No dance necessary.
Have you read MOSFET's Six Million Dollar Expobar
? He "de-HXed" it by adding a PID and insulated preheat coils.
jesawdy wrote:If it was a simple 1/4" diameter copper coil in a heat exchanger shell, I might agree with you that cold water is just pushing hot water out, but it is a goofy looking test tube shaped reservoir that "dips" into the boiler water.
You're thinking about the Cimbali Junior's HX. The Tea's HX is a straight horizontal copper tube (it's pictured in JimP's article Single Boiler vs. Heat Exchanger?
Back to the original question, I'm interested in hearing if others can reproduce Ken's results on a prosumer E61. When it comes to thermal memory, the Cimbali Junior is an elephant, which plays well to the PID'd steam boiler strategy. I'm not sure the smaller HXs (110ml) of a prosumer E61 and lesser thermal mass will benefit as much. From the machines I've seen, the other extreme of the "thermal memory" range is the Gaggia Achille. My gut feeling is that HX machines whose thermal memory are at the extremes will benefit most from precise control...
Another approach I've been mulling over is to automate the cooling flush. That is, combining an E61 thermocouple adapter
, an inexpensive PID, and a SSR controlling the pump. Non-lever type E61s would be good candidates for this modification (e.g., Valentina and the Expobar Pulser).