Bezzera Strega, how to cool it

#1: Post by **bostonbuzz** » May 2nd, 2015, 12:04 am

My strega is too hot. I pulled a shot before it was warmed up and it was much improved. What route should I take?

- lower boiler pressure pstat

- pid grouphead, the boiler, or both

This is a bit of an academic affair at the moment since I'm away for a few weeks and can't do anything immediately, even tell you what the pressure is.

I learned with my cremina that grouphead temperature is vastly more important than boiler temp for actual shot temp in levers, but I wouldn't mind some more uniformity in the temp department.

#2: Post by **Bob_McBob** » May 2nd, 2015, 12:09 am

What is your flushing routine and pstat setting?

#3: Post by **DanoM** » May 5th, 2015, 12:10 pm

I played around with boiler pressure and that didn't seem to make much difference in the shots. Flush also doesn't seem to make much difference unless I run water until it's cooler - a long flush on a heavy group.

My guess is you are looking at replacing the group thermosensor with a PID control of some type, and I think it would be a very interesting modification for the Strega. Set the temp for your shot preference, give it 10 minutes to stabilize and then pull the shot, repeat until you have the perfect set point for your beans.

Sounds like a fun thread to follow.

#4: Post by **Bob_McBob** » May 5th, 2015, 1:15 pm

Flushing routine and pstat setting both significantly influence shot temperature with the Strega just like any other HX machine without a very carefully tuned thermosiphon loop. You may not get exactly the same results as me with your own machine but you can see what a difference flushing makes.

Owner experience with Bezzera Strega

May 12th, 2015, 4:23 pm

DanoM wrote:I played around with boiler pressure and that didn't seem to make much difference in the shots. Flush also doesn't seem to make much difference unless I run water until it's cooler - a long flush on a heavy group.
Sounds like a fun thread to follow.

Thanks, I didn't think boiler pressure would make a big difference but I was hopeful. I have the same experience with flushing. It doesn't seem to matter too much, or get the shot to the temp I want. I also get flashbacks to temp surfing machines I used to have.

The temp is consistent enough that I don't have to worry about the grouphead heating elements and boiler temp normally - but just barely, and I would like more consistent temps.

The grouphead is non-adjustable, so yes, I would put in a threaded RTD probe into the existing hole and rewire the old girl (and probably do a number of TomC mods as well). This is a big project since wiring is not my strong suit, and everything looks so neat in there. I once opened her up to check the wiring and it's far more complicated than I had anticipated!

#6: Post by **JohnB.** » May 12th, 2015, 4:38 pm

What shot water temp are you looking for that you can't get with flushing?

#7: Post by **TomC** » May 12th, 2015, 6:44 pm

bostonbuzz wrote:

The grouphead is non-adjustable, so yes, I would put in a threaded RTD probe into the existing hole and rewire the old girl (and probably do a number of TomC mods as well)..

I don't deserve any credit, I was just putting a easy to follow step by step of John Borella's mods and I think he culled them from folks who modded Gaggia pump machines from old CoffeeGeek posts.

#8: Post by **JohnB.** » May 12th, 2015, 9:39 pm

The idea for the dimmer control did come from a Gaggia thread on CG as I mentioned in the Strega Owner's thread. The vac valve drain mod came from my Speedster & the P/I gauge came from my desire for a P/I gauge with thanks to Eric who supplied the nice coupling and adapters.

#9: Post by **erik82** » May 13th, 2015, 2:43 am

For me flushing makes the biggest improvement in shot temperature. I set my Pstat from 1.15 to 1.3. This didn't make a lot of difference but allows me to pull just slightly hotter with light roasted beans. I normally flush the group for 3-4 seconds until the flash boiling stops and that makes the biggest improvement in shot temperature.

The grouphead will be the biggest factor in shot temperature. That temperature of the small amount of water entering the grouphead will make much less difference than the mass of the grouphead. Just make sure that first bit of water isn't too hot to burn the coffee. Putting a PID on the grouphead would be a very nice mod and will make it an even more versatile machine.

May 13th, 2015, 7:22 pm

JohnB. wrote:What shot water temp are you looking for that you can't get with flushing?

I can't really say. Just that I want a cooler one. As I said, with the machine just up to pressure I pull a more interesting/layered shot, and with the machine up to temp it tastes too hot simply. Flushing doesn't seem to do enough to cool the shot and I don't care for flushing and counting, etc.
I realize basically everyone is happy with their machine and not flushing or flushing it, but I'm interested in cooling it.
Just to add, I am extremely happy with the machine and the quality of the components.

I did once measure the temp profile of a shot with a bare thermocouple on top of a bed of coffee. It only peaked at 200f, not that that helps the discussion since it seems rather low for me to be complaining about the heat.