Diagnosing low brew temperature Bezzera Mitica - Page 2

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Ukdazz (original poster)
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#11: Post by Ukdazz (original poster) »

Thanks for all your replies, to confirm machine is new so wouldn't expect scale buildup already and machine warmed up for at least an hr and its first shot.
I'll tighten the grind more and feedback but my feeling is that shouldn't cause such a big drop. Good place to start though to rule that out.

Ukdazz (original poster)
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Joined: 8 years ago

#12: Post by Ukdazz (original poster) »

Bill33525 wrote:If you run the flush cycle past the point of 207 degrees will the temp drop into the 180's?
Seems like your boiler is running out of hot water rather fast. Could it be loaded with scale?
I've done this test today and in 30 secs it was in the 160s, then 30 mins to get back up to temp Is that expected?

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Ukdazz (original poster)
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#13: Post by Ukdazz (original poster) »

Ok I've done a few tests this morning some interesting results.
1st shot after hr warmup, upped dosage to 20g and tightened grind
Flush to 205, 13 secs
Shot dropped to 193 during the shot big improvement
24 sec shot still to fast for my liking
Took 20 mins to recover to 200

2nd shot, 10 Sed flush to 205
Wait 45 secs (as per some of your advice)
Shot at 201 to 196 during the shot of 25 secs (tighter grind again)
Dropping continually for a few more mins to 190 before climbing again
13 mins recovery to 200

From this it seems no2 was steady and tasted ok, tomorrow going to try different beans as not happy with the grind I'm getting or maybe my grinder isn't up to it anymore. Never had a problem before with fast pulls..

I also want to try Rads suggestion to wait 150-180 secs to see what results I get. Any thoughts on how long it should take my machine to recover for next shot?

Thanks for all the good advice so far!! Feel better with these tests gone through a lot of coffee today!

Ukdazz (original poster)
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#14: Post by Ukdazz (original poster) »

radudanutco wrote:why not trying the no-flush-and-go procedure from my previously post:

after an hour of warm-up, make a flush with 3-5 secs added after the stopping of the flash-boil, that is a 13-15 sec flush,
then wait for 150-180 secs (preparing the first shot) and only after, start the first shot!
the right moment for starting the (next) shot is when the group temperature which was descending, becomes steady for, say, 5 secs at least;
the machine is now recovered for the next shot;
if there are succesive shots, the intervals between them would be 90-120 seconds; no cooling flush;
I used to make a very short cleaning flush (1-2 secs) at the end of the shot;
here is the temperature profiles for such an initial flush and the first shot:
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Brilliant ! Just tried this method with flush 13 secs, prep shot and pull 180 secs later. Even tho GH temp read 194 once shot started it was 205 and was steady at 203 during entire shot of 30 secs. Taste very good.

I think I'm getting hung up on GH temperature a bit too much as this proves. I'm keen to try successive shots to see what the recovery is like but so far it looks like my issues are down to a combination of grind and flush process...

and worked like a charm with the shot steady at 203.

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radudanutco
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#15: Post by radudanutco »

yes, it's quite a normal behavior!
mostly it's about recovery time;

there is an idle status (or full recovery status, I would say) and in this situation a flush is necessary to precede the shot, and the brew temperature for the first shot (after the preinfusion bump) depends of the flush itself, better on the temperature of the flush water reached at the end of the flush; providing the shot itself follows after a reasonably long interval of, say 120-180 min;
this would be important for the consistency of the first shot each day, and it is about waiting the inversed thermosyphon (after the flush) to restart and warm up the group a little;

if there are consecutive shots, each successive shot would start after the machine reached a recovered for shot status that is, the HX reached its idle temperature, and the group is recovered to a flat temperature profile, before starting to rise to the full idle status;
in this status, a consistent brew temperature depends on the boiler pstat settings;

it is about the water in the HX reaching always the same temperature (pstat setting dependent) which is then pumped (at the right moment) through the channels into the group, over the shower screen; and the group temperature reached under the heating effect of the thermosyphon, and measured with the Eric's thermometer when the pump is stopped;
if the resulting water temperature profile - measured with that Eric's thermometer, or T/C sensor in my case - is linear during brew, as a resultant between the water and the group heat exchange, it seems that the E61 concept is working fine enough!

perhaps, it is worth mentioning that the recovery procedure above is only one way of reaching rather consistent results; the flush-and-go, or kind of the flush-and-wait, are working too, especially for one shot in full idle status, but in this case the right timing is important, and I was also using the HX output temperature for it;

and these are about temperatures, not the resultant taste in the cup; so, at least the brew rate and the flow rate are to be considered!

I have to mention also that (1) all above are kind of speculations based on my experience, and (2) I have omitted intentionally any quantitative references (i.e. temperature values), as they are dependent on the machine; in this case I would suppose that Mitica would have rather shorter thermal response, as the unrestricted flow (during the flush, and in preinfusion at the beginning of the pump on interval) of the rotary pump is higher then that of the vibe pump;

as I wrote, there are some posts with temperature values and procedures for Magica;
and this are the shot profiles in a session, to note the different temperatures of the grouphead metal and the water flowing in, measured in that "Eric's point":

h3yn0w
Posts: 476
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#16: Post by h3yn0w »

Ukdazz wrote:Brilliant ! Just tried this method with flush 13 secs, prep shot and pull 180 secs later. Even tho GH temp read 194 once shot started it was 205 and was steady at 203 during entire shot of 30 secs. Taste very good.

I think I'm getting hung up on GH temperature a bit too much as this proves. I'm keen to try successive shots to see what the recovery is like but so far it looks like my issues are down to a combination of grind and flush process...

and worked like a charm with the shot steady at 203.
Glad you got it sorted. And I would say yes you are getting too hung up on GH temp, and probably temp in general. Temp is the last variable to worry about IMO. Brew ratio and grind are many times more critical.

I feel like these GH thermometers can be fabulous tools but also very dangerous tools. There was a similar thread recently where someone purchased a new machine, had shots running way, way too fast and was completely focused and consumed on what the thermometer was saying and his flush routine. When he should have been focused on his grind. I believe he ended up spending hundreds more on a new machine when the machine was not the problem.

Now that you have your grind dialled into a 30 second shot, There are likely multiple easy flush routines that will work well for you, including a quick flush and go.

DeGaulle
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#17: Post by DeGaulle »

Dose and grind at one end and brew temp at the other are also interrelated; if the brew temp is (too) low, the shot will run faster as well, so you would have to tighten your grind to extend the shot time to 30 seconds. That said, on my "dragon" HX machine I try not to obsess too much over brew temp either and focus on dose and grind setting. However it is an eye-opener to learn how a "mixer" type of HX machine with a tuned TS loop may behave, in that when we are tallking about "flush and wait", the wait could be as long as 2-3 minutes rather than 30 seconds to nail the brew temp consistently. Great input from Radu, a very informative read indeed.
Bert

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canuckcoffeeguy
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#18: Post by canuckcoffeeguy »

Ukdazz, glad you're on the right track. Enjoy the ride!

Ukdazz (original poster)
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#19: Post by Ukdazz (original poster) »

Thanks again everyone for your great advice! I'm experiementing with flush routines now to see what's the most effective and repeatable...cheers

Ukdazz (original poster)
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#20: Post by Ukdazz (original poster) »

[quote="radudanutco"]yes, it's quite a normal behavior!
mostly it's about recovery time;

excellent analysis! I've read this post before some really good points and now really starts to make sense as I understand more...

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