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3 minutes ago, TomR said:

Thats that clears up my understanding considerably 

 

alex Leva has a low and a high level probe- presumably the refill duration is not timed, but switched off when the high level probe is covered / i guess refill time very dependent on water line pressure so a single probe timed refill would not work

If it has two probes, then you are correct. As you say, they may well have done that due to the very large variations in water line pressure and the fact that people don't use pressure regulators, when really they should.

The same principle of needing a certain overfill still applies, of course. I personally would set an overfill of 100ml on a home machine....so you will have to calculate, for the boiler size and orientation the distance required between the probes. Definitely don't go too low with the water level and risk exposing the heating element. I would recommend not changing the minimum level set by Izzo.

I don’t like – Sticks and Stones, beans that are sour, green…or rancid (horrible). Quakers hide until you roast them, then they scream out at you in the cooling tray, pick em out and flick them in the bin.. Lifes too short for bad coffee!

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Yeah, that's the single probe situation you described. We have the boiler max probe handling the hysteresis. Around 700 mL between high and low.

So the video shows my confusion as to the algorithm, but maybe it's just a combination of poorly positioned probe and pure science. The machine brand new received days before.

Summarising:

0:03 First cup flow rate a healthy 35 mL/s.
0:20 2nd cup, 21 mL/s - still fine.
0:45 Next half cup - 11 mL/s - getting painful waiting   
1:07 Next half cup - 7 mL/s - more painful.
1:20-2:58 Waited 1m37s - no refill.
2:58-3:04 Another 20 mL of splutter at 3 mL/s.  
3:04-5:00 Waited 1m56s  - no refill.
5:00-5:12 Another 30 mL of splutter at 2.5 mL/s
5:12:5:45 33 seconds passed.
5:45 Refill.
 

Moving the boiler min probe up has made things definitely better - more frequent refills but temp will drop to 117°C instead of 112°C after refilling, recovering far quicker.

So my intrigue was about the boiler refill eventually kicking in well after the last water extraction (here 33 seconds).

I'm thinking it's feasible that as hot water was removed, pressure would drop, steam would cool and go back into liquid raising the level. Then while waiting, heater back on increasing temp and pressure taking more water into steam and dropping the water level. But not my field.

Edited by shimon
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On 15/06/2021 at 23:31, TomR said:

How are your early shots?

I have had a few beauties now - probably experimenting too much that they've gone off again. Either that or my standards are getting higher. Actually come to think of it, I have moved to a new bean since. Not at the level to know how to handle different beans.

The flow's remarkably consistent - it's nearly like a Breville/Saeco pressurised basket or something. I guess that's the depth of the 55mm and the coarser grind. And when it's slightly off, the ability to assist or retard the lever to correct is priceless. I feel I'm in a better position now to learn about tweaking for different beans.

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