Can anyone explain preinfusion on the E61?

Need help with equipment usage or want to share your latest discovery?
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bigdog002

#1: Post by bigdog002 » Dec 03, 2007, 1:20 am

I've asked several people about the mid-position of the lever and whether or not to use it before a pull. All have dismissed it as a worthless practice. I would like to hear if anyone manually preinfuses.

When I lift the lever on my Anita to mid-way the pump turns on but it seems a bit less noisy than normal and my pressure gauge displays pressure (seems to be equal to the blind pressure). I do understand about the gauge reading relative to the position of the T. When I lift the lever to the top I can hear the pump growl fully as it starts pumping water for a shot.

-- What exactly is happening when the lever is at mid-point?
I've looked at the diagrams dan provided, but I'd rather have it explained in simple english.

- is there any benefit to holding the lever at mid-point for any length of time? and does this time count against the total shot time?

- the sound of the pump at mid-point scares me for some reason .. makes me fear I am going to burn it out. Is this dangerous?

I've been told the machine designers count on the vibe pumps characteristic (slowly starting flow) as preinfusion .. is this correct?

If all this is covered elsewhere forgive me and direct me to it. I'd really like to understand this 'feature'? of the E-61 that nobody seems to use or discuss.


Chris

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cafeIKE

#2: Post by cafeIKE » Dec 03, 2007, 1:39 am

In the mid position, both the inlet out outlet valves are closed.

If the pump turns on in the mid position, the switch is misadjusted. The pump should start just as the inlet valve opens. If your gauge reads the blind pressure, the pump is pumping against the upper valve and simply cycling water thru the OPV.

The e61 pre-infuses as the valve fills.

User avatar
bigdog002

#3: Post by bigdog002 » Dec 03, 2007, 1:45 am

cafeIKE wrote:In the mid position, both the inlet out outlet valves are closed.

If the pump turns on in the mid position, the switch is misadjusted. The pump should start just as the inlet valve opens. If your gauge reads the blind pressure, the pump is pumping against the upper valve and simply cycling water thru the OPV.

The e61 pre-infuses as the valve fills.
Should I be concerned about the misadjusted switch and can I adjust it myself?

User avatar
Randy G.

#4: Post by Randy G. » Dec 03, 2007, 1:46 am

On the VBM's, the E-61's midpoint lever position opens the HX and water path and allows the pressure of the heated water in the HX to be released into the brewhead and onto the coffee. I believe I have heard that referred to as a passive pre-infusion. I don't use it because the slow ramp up of pressure over the first 8 to 10 seconds that is designed into the group takes care of the preinfusion (IMO). Additionally, if you have flushed the group to bring the temperature down before pulling a shot, there is little if any built up force to deliver any significant amount of water to the coffee... IMO.

From your description, if that happened to my machine, I would assume that the switch that energizes the pump is being closed too early in the lever's arc, but I do not know how the Anita is supposed to operate— just guessing based on how my E-61 operates.
Espresso! My Espresso!
http://www.EspressoMyEspresso.com

User avatar
HB
Admin

#5: Post by HB » Dec 03, 2007, 1:47 am

bigdog002 wrote:If all this is covered elsewhere forgive me and direct me to it. I'd really like to understand this 'feature'? of the E-61 that nobody seems to use or discuss.
Then you should check out the FAQs and Favorites Digest. It even includes obscure topics like Is there a purpose for the E61 middle brew lever position? under the heading E61. If you really want to understand the internals, there's also detailed discussions using Lino's CAD drawings.

Image
bigdog002 wrote:I've been told the machine designers count on the vibe pumps characteristic (slowly starting flow) as preinfusion .. is this correct?
It depends on the group design. For E61s, the expansion chamber does the job. If the designers were concerned about excessively fast pressure ramp up, they'd add a gicleur (a small orifice in the grouphead to slow the onrush of water).
bigdog002 wrote:Should I be concerned about the misadjusted switch and can I adjust it myself?
If you want to play with passive preinfusion using the mid-position, I suppose you could, but I wouldn't bother. Awhile back I toyed with the rotary Vetrano using line pressure to presoak the puck at the lever's mid position and wrote about it in The Secret Life of Ristrettos, but I don't consider my observations in that thread adequately tested to be considered reliable. Since your Anita doesn't have line pressure, that option isn't open to you. The mid position will spittle forth a half ounce or so of water and then stop until the vibe pump engages.
Dan Kehn

User avatar
bigdog002

#6: Post by bigdog002 » Dec 03, 2007, 2:07 am

Thank you all.

I guess I won't worry about it. As long as the pump kicking in 'early' in the lever path won't do any harm. I might give Chris' a call tomorrow and talk to one of the techs about it.

Off I go to read the thread Dan provided.


Chris

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erics

#7: Post by erics » Dec 03, 2007, 8:22 am

When the lever is in the fully down position, there is a clearance between the cam surface and the "button" on the pump switch of ~ 1/16" or 1.5 mm. Engaging the pump when the lever is in the mid-position, as Ian said, most definitely shows that the switch is misadjusted. I suspect that the switch's locknut is a tad loose.

It does no physical harm to the machine but DOES DO harm to a flushing routine because Anita's blind flow passes THROUGH the heat exchanger. See below:

Image

The image of the E-61 group is copyright 2005 by Verna Design, Inc. It is shown in the brew position.
Skål,

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

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bigdog002

#8: Post by bigdog002 » Dec 03, 2007, 8:41 am

erics wrote: It does no physical harm to the machine but DOES DO harm to a flushing routine because Anita's blind flow passes THROUGH the heat exchanger. See below:

I played with the lever more, if I raise it slowly I get a 'click' , no pump, at the very bottom of the mid-position. I assume this is proper operation. If I raise the lever slightly to the top of the mid-position the pump engages. It's not as out of adjustment as I first thought.

I'm confused how it would hurt my backflush. I engage the pump as normal during a backflush ... ?

User avatar
bigdog002

#9: Post by bigdog002 » Dec 03, 2007, 9:42 am

Ok, I've made another discovery ..

When I pull OUT (towards me) on the lever as I lift it does not engage the switch behind the lever (pump) at the mid-point, however at this point it does NOT open the valves as it should. At this point, if I put slight sideways pressure on the lever toward the group head the valves open up and the pressure is released. Neither of these require much force at all, just slight pressure on the lever out and in at the same time.

I talked to a tech at Chris's .. he is sending me a spacer to install and he says it should fix that problem.


Chris

User avatar
erics

#10: Post by erics » Dec 03, 2007, 10:05 am

It is not easy to explain because temperatures can vary quite a bit depending upon how much you flush and whether or not this is the first shot after an hour's warmup or the 2nd shot a minute or so after the first AND whether or not your reservoir is 90% full or 90% empty.

It seems, now, as though your machine's pump switch is properly adjusted after all.

HOWEVER, if this were NOT the case, you would be cooling off the hx and NOT passing any water through the group during this "misadjusted" flush. As you can probably imagine, there are numerous ways in which Anita (and other similar machines) can be operated with the goal being to deliver a consistent water temperature to the espresso grounds regardless of when the shot is produced.

Good explanations are contained here: Managing the Brew Temperature of HX Espresso Machines
Skål,

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