Best flush routine for Bezzera Strega? - Page 4

Need help with equipment usage or want to share your latest discovery?
subq
Posts: 302
Joined: 12 years ago

#31: Post by subq »

Personally, I'm interested in live "monitoring" mods. For me, I just like seeing actual pressures and temps as they are taking place.
LMWDP #357

User avatar
JohnB.
Supporter ♡
Posts: 6579
Joined: 16 years ago

#32: Post by JohnB. »

Basing anything on the OP's graphs seems foolish considering his P'stat info. My Strega is working just find & I'm just going to continue enjoying the shots. I like having the choice of flushing for cooler temps or not flushing or shortening the flush for hotter temps.
LMWDP 267

User avatar
mtn hack
Posts: 39
Joined: 12 years ago

#33: Post by mtn hack »

John, we have only 2 sets of graphs to base anything on, and I am only going to try the no-flush routine because it seems to me, the technology Bezzera has employed would lend to the most stable starting brew temperature with a no-flush routine. Now I am not saying that based on certain roasts, the pre-shot flush would not only be welcomed, but even necessary.


Even Jim's profiling shows the temperature variability within flushes of the same length, not to mention between say 1 and 3 seconds. I am merely searching for a way to minimize variables so that I can get the most consistent results. For all I know, my settings will have the no-flush shot running way too hot and this will be a moot point.
LMWDP #364

subq
Posts: 302
Joined: 12 years ago

#34: Post by subq »

...and if we had a way to see what the temp and pressures were, we wouldn't have to guess about anything...

...I guess it is the network engineer inside me always wanting to see what every variable is doing realtime ;)
LMWDP #357

User avatar
erics
Supporter ★
Posts: 6302
Joined: 19 years ago

#35: Post by erics »

. . . no one has mentioned anything regarding the cartridge heating elements' thermal responsiveness.
Where do I send the bill? :)





Point 1 is a work in progress but it definitely is greatly attenuated and certainly lower in value.

edit - Point 1 values added on 02/07
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

sekihk (original poster)
Posts: 92
Joined: 13 years ago

#36: Post by sekihk (original poster) »

allon wrote:You forgot to take gauge pressure vs. absolute pressure into account.
0.8 bar gauge pressure is 1.8 bar absolute pressure; the water is 242°F
1.3 bar gauge pressure is 2.3 bar absolute pressure; the water is 258°F
Still a spread of 16 degrees fahrenheit.
Hi all, it's my bad here. After all of your comments on the spread, I checked again with the readings from the gauge.
If I let temperature decline naturally, the gauge reading would drop till "about" 1 (it never touched the markings of 1) and the boiler would start. The gauge reading would then touch 1.2 and the boiler would stop.

When I formerly said it's 0.8 and 1.3, it was from my impression that when I manually release the steam to drop the pressure inside the boiler to kick in the boiler, the gauge reading would drop to around 0.8 before I could hear the boiler's sound started vigorously. The gauge reading would then overshoot to about 1.3.

Regarding my second chart, the readings were from various different flushes combination in series so that they all showed in the same chart. That chart is NOT to tell anyone in particular what brew temperature you would get after a particular flushing pattern. It's to illustrate just what kind of inconsistent fluctuation in the peak brew temperature that you may get if you pre-flush with the Strega. To the contrary, you would get pretty stable peak brew temperature (95'C) if you DON'T flush.

My conclusion is that if we PID the thermo control at the brew head, we should be able to control the peak brew temperature with the non-flushing practice. If we intend to change the "declining brew profile", we may also increase the pressure stat setting at the HX for a flatter brew temperature profile (or even upward profile if HX temperature is higher than the brew head temperature.

To persuade someone to use/try Strega is not the intention of my posts. I'm already a Strega user myself and I'm not a sales rep so I don't really care who are going to use the Strega. It's also not my intention to persuade others whether to flush or not because how other users use their machines is never my concern. I'm just trying to state my observations. So, I am not going to waste time to further elaborate my charts or the methodology of tests that I had done.

Anyway, thank you for all of your inputs in the matter. :D

@eric, can you please quote me the price in PM about the thermocouple (k-type) that would fit the brew head? I'm also considering to PID the boiler to test my assumption on the capability to manipulate the brew temperature profiling (upward/downward) but I am not sure if I can fit a thermocouple to the boiler without drilling a hole there. Your advice on this matter is highly appreciated. Thank you.

User avatar
another_jim
Team HB
Posts: 13871
Joined: 19 years ago

#37: Post by another_jim »

The second shot effect and flushing

Eric's work needs to be appreciated when talking about flushing routines. There are cycling components in most espresso machines, as well as random bits and pieces heating up or cooling down. All this activity usually means that the second and subsequent shots from idle taste better than the first. Flushing routines are, in essence, meant to get the machine into its multiple-shots-in-a-row groove.

On the Strega, the group head heaters cycle at a 3 to 3.5 minute rate when idling. When making a shot, the hot water will go through the neck and probably shut the heaters down, since the neck will get heated above 205F. On the first flush or shot, you will be heating the group up. On subsequent shots done asap, in a two minute cycle, my guess is the heaters will stay off, or only run for short periods. But if you do shots at a slower rate, the heaters will kick in unpredictably, the HX temperatures will also be somewhat varied, and you'll get inconsistent brew temperatures.

How important is this? I've used the machine in party mode, making several shots in a row for the people in attendance. The shots slightly improved with time, like on almost all espresso machines. I'm not sure if this is a question of temperature stability or of all the cool and hot spots settling down and evening out. In any case, the effect isn't nearly as extreme as it was on my old Isomac Tea, and about on par with the Elektra Semi.

Perhaps it's time stop flushing and to create a restrictor basket instead (blind filter with needle valve?) that does 75 mL in 30 seconds. Use it to pull a blank shot while grinding and prepping the puck for the actual shot, and benefit from the second shot effect without nearly the hassle.

I'm not really tempted to create one for the Strega, but for folks who value consistency more than me, it may be a simpler way to go than doing complicted flush routines.
Jim Schulman

subq
Posts: 302
Joined: 12 years ago

#38: Post by subq »

another_jim wrote:Eric's work needs to be appreciated when talking about flushing routines.
...
Perhaps it's time stop flushing and to create a restrictor basket instead (blind filter with needle valve?) that does 75 mL in 30 seconds. Use it to pull a blank shot while grinding and prepping the puck for the actual shot, and benefit from the second shot effect without nearly the hassle.

I'm not really tempted to create one for the Strega, but for folks who value consistency more than me, it may be a simpler way to go than doing complicted flush routines.
I appreciate it even apart from that, it is excellent info to know.

Very cool idea, I'm with you though, I am using the Strega for what it is...even though I really want to see what all the variables are just because I like that sort of thing, I am fine with what is being produced.
LMWDP #357

User avatar
JohnB.
Supporter ♡
Posts: 6579
Joined: 16 years ago

#39: Post by JohnB. »

another_jim wrote:Perhaps it's time stop flushing and to create a restrictor basket instead (blind filter with needle valve?) that does 75 mL in 30 seconds. Use it to pull a blank shot while grinding and prepping the puck for the actual shot, and benefit from the second shot effect without nearly the hassle.
Just build a p/f pressure gauge rig with a needle valve drain, check/set your OPV & then use the rig to prep your shot.
LMWDP 267

User avatar
mtn hack
Posts: 39
Joined: 12 years ago

#40: Post by mtn hack »

another_jim wrote:The second shot effect and flushing

Eric's work needs to be appreciated when talking about flushing routines. [snip]

On the Strega, the group head heaters cycle at a 3 to 3.5 minute rate when idling. When making a shot, the hot water will go through the neck and probably shut the heaters down, since the neck will get heated above 205F. On the first flush or shot, you will be heating the group up. On subsequent shots done asap, in a two minute cycle, my guess is the heaters will stay off, or only run for short periods. But if you do shots at a slower rate, the heaters will kick in unpredictably, the HX temperatures will also be somewhat varied, and you'll get inconsistent brew temperatures.
I agree, Eric's data is very appreciated. I was surprised to see the wide span in both temperature and time in the group heaters. However, it is definitely an argument against the no-flush shot, as I was operating under the hypothesis that it was much tighter. Even if your HX temperature was absolutely flat shot to shot, depending on where in the group heating cycle you pulled, you could be warming the group from the 188F range, or cooling (or worse maintaining) a 205F(+) range. Although the 10 or so no-flush shots I pulled since last posting came out decently, there were noticeable variances within the groups. I had only one that seemed hot and over extracted, but maybe I just got lucky hitting median temperatures.

Maybe the consistency resolution is to always do a cappa shot for the wife, and then pull my shot. I guess she had better start drinking a lot more coffee. :twisted:
LMWDP #364