E61 preinfusion for plumbed and reservoir-only models

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FirstBetta
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#1: Post by FirstBetta »

From this and other forums I understand that plumbed in E61 groups provide "passive" preinfusion during extraction from plumbing line pressure. What happens with a tank model E61, there is no line pressure to push the water? The lever is lifted to the preinfusion position, the pump starts, or does it, water starts to flow into the group including the preinfusion chamber so there is minimal pressure until the chamber fills up then the pressure builds on the puck to max brew pressure. If the pump doesn't start what provides the force to get the water flowing?

Is the effect the equivalent of the line pressure preinfusion?

davebm
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#2: Post by davebm »

I am currently running my Rocket via reservoir for now. It does do preinfusion from the reservoir but its not great. Very little water comes out when you lift the lever half way (more of a dribble - like its depressurizing).

Have a look at the following article to clear things up.

http://coffeetime.wikidot.com/e61-pre-infusion

In short - you need ~2 bar line pressure for preinfusion

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HB
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#3: Post by HB »

FirstBetta wrote:From this and other forums I understand that plumbed in E61 groups provide "passive" preinfusion during extraction from plumbing line pressure.
The E61 does not require line pressure for preinfusion; it uses an expansion chamber for that purpose as explained in Internals of an E61. Last month we discussed the merits of "passive preinfusion" (also known as "prewetting"), which does require line pressure, in Is preinfusion a feature of all E61 groups? There's no clear consensus this "prewetting" capability is by design or oversight.
Dan Kehn

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canuckcoffeeguy
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#4: Post by canuckcoffeeguy »

Here's a video of what E61 passive preinfusion looks. It's my Bezzera Magica HX which has a vibe pump. Not plumbable. I'm not sure if it's beneficial or not.

I used to go halfway at the beginning of my shots. Now I just activate the pump fully from the start. The vibe pump ramps up slower than a rotary anyway, so it may be moot.

Also, some E61 owners, who thought their machines didn't do passive preinfusion, discovered the small activation switch behind the lever wasn't positioned appropriately for halfway activation. That led to mistaken conclusions about the inability of some machines to passively preinfuse. When the reality was the activation switch just needed adjusting.

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boar_d_laze
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#5: Post by boar_d_laze »

Not to be pedantic, but Dan has "passive preinfusion" vs regular preinfusion backwards.

E61 Passive Preinfusion
"Passive preinfusion," occurs when an E61 empties it's preinfusion reservoir when the motor starts. The preinfusion water leaves the preinfusion reservoir and exits the group head and enters the basket as incoming water, when pressure in the group reaches around 1.5bar and opens a series of spring loaded valves. Passive preinfusion pressure is not constant, but ramps up from 1.5bar to 9bar (assuming that's what the machine is set to run at) as the valves fully open.

Preinfusion
When a semiautomatic E61 is opened to the water line without turning on the motor, the water eventually enters the basket at line pressure, and you get line pressure (regular) preinfusion for however long the barista desires.

To be clear, the E61 doesn't have a special channel for preinfusion water. In the case of line pressure preinfusion, it enters the basket at line pressure after the couple of seconds it takes to open the preinfusion valves. That is, line and preinfusion pressure is around 3bar, and the amount of preinfusion water is determined by duration. After a couple of seconds that's a great deal more water than required for mere "prewetting."

Compare this to "passive preinfusion," which -- by definition -- is limited to the amount of water in the reservoir (around 15ml, IIRC), and runs at rapidly increasing pressure.

Active Preinfusion
There are also pump driven preinfusion schemes in electric pump "pressure profiling" machines, and of course with manual levers. Pump driven preinfusion, is "active."

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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HB
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#6: Post by HB »

boar_d_laze wrote:Not to be pedantic, but Dan has "passive preinfusion" vs regular preinfusion backwards.
I've re-read what I wrote and it seems correct to me, but I'm unaware of a widely accepted definition of this term. Searching a bit, I see that prior to this thread, I've used "passive preinfusion" 10 times versus the total of 58 mentions since the site started in 2005. Going forward, I'll make a mental note not to use it again.
Dan Kehn

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boar_d_laze
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#7: Post by boar_d_laze »

Dan,

After you posted, I did a brief search and found "passive preinfusion" ambiguous. Some people include full line pressure preinfusion under the definition, and some people don't.

Whatever its original meaning, common usage renders it meaningless for distinguishing between the two types of E61 preinfusion. If we stop using the term though, what should we call E61 (and La Spaziale) reservoir-fed preinfusion?

Also, after looking at a number of threads here and elsewhere, I was surprised at how poorly the subject of "E61 reservoir fed preinfusion" is understood.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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Randy G.
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#8: Post by Randy G. »

boar_d_laze wrote: E61 Passive Preinfusion
"Passive preinfusion," occurs when an E61 empties it's preinfusion reservoir when the motor starts. The preinfusion water leaves the preinfusion reservoir and exits the group head and enters the basket as incoming water, when pressure in the group reaches around 1.5bar and opens a series of spring loaded valves. Passive preinfusion pressure is not constant, but ramps up from 1.5bar to 9bar (assuming that's what the machine is set to run at) as the valves fully open.
Rich
When brewing ends, the preinfusion chamber is emptied when the lever is moved to the downward position. It empties through the 3-way valve (which I call the exhaust valve). When the lever is moved to either the middle position or to the brewing position the infusion valve is closed and the infusion chamber is empty. In the brewing position that changes as described below:

The chamber below the cam, which we often refer to as a preinfusion chamber, is meant to buffer the first few seconds of brewing so that the coffee is subjected to a lower flow rate and pressure before the "real" extraction pressure is presented to the compacted coffee. This early pressure is regulated by the force of the infusion valve's spring which normally would close the infusion valve when the lever is in the brewing position (up). It works like this:
- The pump is activated and water flows into the area above the coffee and in the void leading to it.
- When the pressure surpasses a point regulated by the force of the infusion spring, which has, up to this point, kept the infusion valve closed, the infusion valve opens and water now also flows into the now-empty infusion chamber as well as the void above the coffee. So the valve is closed until:

(Pressure of water above the closed infusion valve)
is greater than
(The force of the infusion spring which is exerted on the infusion valve)

- When that water pressure exceeds the spring's force, the infusion valve opens and the chamber is filled with water.
- Once the chamber is filled, pressure rapidly builds in the group as water cannot be compressed. The maximum force of the water in the group is now regulated by the amount of restriction that the puck presents to the flow of water.
- The above continues until:

(pressure of water below the infusion valve + the force of the infusion spring)
is greater than
(the pressure of water above the infusion valve)

At that point the the infusion valve closes and the pump's full regulated force (regulated by the pump's setting, the pressure relief valve, and the restriction of the coffee) is sent to the area above the portafilter and coffee.

So physics regulates when the infusion valve is open and when it closes. It HAS to close when the pressure of the water above and below the valve's sealing area is as described above because of the presence of the spring and the force it exerts on the valve.

I presented that to the VBM factory, through a knowledgeable and interested third party, and they had never thought about that, but agreed that this is accurate. it is possible for the valve to, at times, open and close SLIGHTLY during the extraction, but that would mean that pressure below the closed valve is somehow decreasing. That might indicate a leak in the 3-way valve at the bottom of the group.

[note: I was an art major so some of the terms used may not be scientifically accurate]
EspressoMyEspresso.com - 2000-2023 - a good run, its time is done

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Randy G.
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#9: Post by Randy G. »

boar_d_laze wrote:Dan,

After you posted, I did a brief search and found "passive preinfusion" ambiguous. Some people include full line pressure preinfusion under the definition, and some people don't.
I would define it this way:
Reservoir-fed machines feature "passive preinfusion" since it is done by pressure from the boiler only if moving the lever just past the "mid-way" position (pump off, brew valve in group open).

Plumbed machines would have "active preinfusion" as the same action at just past mid-lever position would continually force water through the coffee even if the pump was off.
EspressoMyEspresso.com - 2000-2023 - a good run, its time is done

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boar_d_laze
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#10: Post by boar_d_laze »

Cut To The Chase

Line Pressure
E61 line pressure preinfusion, like any line pressure preinfusion, is an indisputably good thing. It takes some of the onus off of puck preparation and adds some flavor "layering."

Indisputably good compared to no preinfusion at all. But Nuova Simonelli's "SIS" "soft preinfusion" provides greater help with the puck; and more complex pressure schemes as in a "lever" or "pressure profiler" give a great deal more layering.

Reservoir
Depending on whom you speak with, E61 reservoir-fed preinfusion, it's either: (A) Not much as preinfusion goes, but better than no preinfusion at all; or (B) Indistinguishable from no preinfusion.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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