Question about the E61 lever position

[cannonfodder]

After looking at the wonderful schematics that Lino did, I had an epiphany. Based on what I see I think I have been going about my brewing process incorrectly so I am looking for a bit of advice.

When my machine is not in use I leave the lever in the mid position. Should I normally keep it in the down position when heating and not in use?

Second, after a cooling flush just before a brew, I have been putting the lever in the down position. That empties the chamber around the cam as well as the brew path. It looks like I should not be doing that. Once that chamber is empty it is obviously full of air. Once I lock in my PF and start the brew cycle, water floods into the cam section then out the brew path. The air in there must be evacuated as the water enters. The only place for it to go is out the brew path and through the puck. Could the pressurized air disrupt the puck and lead to channeling? Does this also affect the pre-infusion process?

[HB]

In a related thread Jimmy asked "Lever up or down, that is the question", to which I replied:

Lever down.

In the patent diagram, the lever is in the downward position (see cam 6). At the midway position, sealing device 5 is (just barely) open. If left in that position, the thermosyphon circuit is open and the heat exchanger will eventually boil dry.

Is empty chamber a bad thing? Michael Teahan (Espresso Resources) suggested the empty chamber absorbs the initially over-temperature water and reduces the chance of a burnt shot. That's not mentioned in the patent description, but seems logical. As for channeling, I would argue flaws in DDT (dose, distribution, tamp) would far outweigh the influence of a transient "E61 burp".

(It's good to have something to blame though and this is the most original excuse I've heard in awhile... "It would have been a godshot if it weren't for the darn E61 burp!" ).

[papalatte]

I'm wondering how this plays out with the Brewtus..........?

Skip

[Abe Carmeli]

Skip,

It applies to the Brewtus as well as it uses both the thermosyphon and a H/X. The H/X is used differently though, than in a single boiler H/X machine, but that is not a relevant difference to the question at hand. In other words - Keep it down man .

[papalatte]

Thanks Abe, I'm down with that
Skip

[cannonfodder]

I have been leaving the lever down for the past couple of days. Prior, my first cooling shot would be nothing but steam for the first five seconds, now I get some steam, but not nearly as much. My group head temp is also different according to my Allen screw thermometer. With the lever in the mid position it always gave me something like 225f, with the lever down it stays in the 210 range (after an hour warm-up). The first cooling flush still shoots the temp up, but before it started high. Any chance of damaging the HX if you boil it dry? Could you get a form of thermal shock when the water from the tank hits the HX. I have never heard of anything before.

I have not had a problem with channeling , it was just an observation. If you had a flaw in your DDT then the 'burp' may dislodge the puck and cause channeling, it was just a thought.

[HB]

Any chance of damaging the HX if you boil it dry?

The HX is nothing more than a copper tube, so there's no risk of damaging it per se. What's a little extra influx of steam, interruption of the thermosyphon loop, and accelerated scale buildup in the grand scheme of things? Hmm-m, that sounds more ominous than I intended...

[cannonfodder]

I did not know if the thermal stress would weaken or crack the copper HX after years of flash cooling. It would think that boiling the HX dry would accelerate the scaling process.