Can a short post-shot flush cause thermosyphon stall on non-HX E61 espresso machines?

#1: Post by **boren** » December 7th, 2021, 5:47 pm

And if so, what would be a "safe" minimal time for the flush?

Thanks!

#2: Post by **Giampiero** » December 7th, 2021, 8:23 pm

I don't see any logical reason why a flush should cause thermosyphon stall, if everything is in good shape.
Flush time depend by the thermosyphon design, if the machine has or not restrictor, how is the temperature controlled ( PID or P-stat) etc etc, so the best way to realize the proper flush time is probably to install a group head thermometer.

December 8th, 2021, 3:59 am

I'm not sure about the reason, some suggest it is related to trapping air. It was mentioned many times that a short flush could cause thermosyphon stall. Some examples: 1, 2, 3, 4, 5 (see last sentence).

I have a grouphead thermometer, but why would it help in deciding the length of a "cleaning" flush *after* the shot? I think it's mostly useful for deciding the length of a flush *before* pulling the shot (if at all needed in a non-HX machine).

#4: Post by **Giampiero** » December 8th, 2021, 6:06 am

I don't understand one thing, do you got thermosyphon stall once you "post flush" ?
Yes sorry, my answer about the flush length, was obviously related to a "pre flush" , i frankly never noticed a thermosyphon stall after a cleaning flush, and IMHO i doubt any could happen if "all is in good shape"...unless there is some "weird" thermosyphon design.
Maybe a leaking OPV or a leaking group head infusion valve or solenoid valve can create a thermosyphon stall...but we speak about a defective machine not anymore a "all in good shape".

#5: Post by **Ypuh** » December 8th, 2021, 7:43 am

My machine often has a TS stall when booting up. It usually warms up to about 85-88 degrees, where I would expect 90-93 degrees. After letting some water through by opening the valves, just before pump activation, it works fine the rest of the day.

Somewhat annoying, but doesn't affect the rest of the day. I have no idea how to resolve this and the shop I brought my machine for maintenance even less.

#6: Post by **cafeIKE** » December 8th, 2021, 10:32 am

A stall is unlikely on a non-HX. A stall on an HX requires the perfect storm of variables: inlet water temp, boiler temp, flush volume and HX / TS / group geometry.

Ypuh wrote:My machine often has a TS stall when booting up. It usually warms up to about 85-88 degrees, where I would expect 90-93 degrees.

That seems normal. The group idles a few degrees below brew temp in a PID controlled e61 machine.