I have what some might consider a very obvious or stupid question. I just purchased a GS3 AV model which arrived Friday evening. From what I understood it is possible to preinfuse without the need to hook up to your homes internal water supply. Instead, the pump would provide a type of "sudo-preinfusion" by taking water from the internal espresso machine's reservoir and delivering it at about 3 bar.

Try as I might I can not get my GS3 to preinfuse in this manner. When I program it to preinfuse I hear the pump running but no water exits the group until the programmed preinfusion stops then the brewing cycle begins. Maybe I'm programming incorrectly but I double checked the instructions.

Is there something I'm not dong correctly? Or, was I mistaken in thinking I could preinfuse on this model. According to the computer I'm running version 1.15.

Any suggestions would be appreciated.

It's supposed to work with the reservoir.

Check out Explanation of La Marzocco GS3 Preinfusion Options if you haven't already.

Also, be sure you follow the exact steps in the programming manual. If you're not doing it already, remove the PF and watch the cycle without it to make sure that there's really no water coming out of the group.

If none of that helps, please post the exact steps you are taking to program the pre-infusion and to verify that it's not happening as expected.

Thanks for getting back to me.

Yes I ran the tests with and without the PF in place.

I will write back as soon as she is up to temp and describe the whole procedure I am using. PLEASE STAND BY.

For the sake of clarity let's label the buttons 1-6 moving from right to left on the panel.

1. Hold down button 2 while pushing button 3 which enters you into the preinfusion setup screen PREBREWING ENABELED
2. Press button 2 again and the words PREBREW ON ESPRESSO 5sec ... this tells me that I have set button 2 to preinfusion for 5 seconds which is what I want.
3. Press button 2 again and screen reads 2 ESPRESSO ON 5sec ... I assume I have just programmed button 3 or the double shot button.
4. Press button 2 again screen reads COFFEE ON 5sec... now I assume I have programmed the single shot button 4
5. Push 2 again screen reads 2 COFFEE ON 5sec.... Now I assume I have programmed button 5 or the 2 ½ shot button
6. Push 2 once more and I go into the PREBREW OFF SCREEN which I assume tells the machine to rest fro 5sec before beginning the brewing process. I program buttons

I assume, probably incorrectly that I have now set all my different coffee buttons 2-6 the to preinfuse for 5 seconds - stop preinfusion for 5 seconds before the pump should begin the brewing process. This does not happen. Instead the pump just turn on full right for the moment I push any of the buttons.

I'm sure it's something I'm not doing right. Even reading this doesn't really make a lot of sense to me. Can you set me straight PLEASE?

Thanks,

Rob

Rob,

As soon as you press one of the brew buttons, the pump will turn on. The preinfusion is controlled by the solenoid valve. It will shut off the flow for the programmed time and then open again. The pump runs during the whole process. As stated above, test without the portafilter in place to see the water flow.

It appears to me that you have the buttons mixed up and you're not programming the button(s) you think you're programming. Numbering the buttons for our discussion doesn't help because the manual doesn't use numbers to refer to the buttons. Also, most Western cultures count from left to right, not right to left. Counting the other way just confuses things.

Let's use the button identification scheme that the manual uses:

- The first button on the left has one cup filled halfway. This is the "Espresso" button.
- The second button from the left has two half-filled cups. This is the "2 Espressos" button.
- The third button from the left has one cup fully filled cup. This is the "Coffee" button.
- The fourth button from the left has two fully filled cups. This is the "2 Coffees" button.

These first four buttons (from the left!) are the only buttons that can be programmed for pre-infusion. The names are important because they appear in the menu screens so you'll know which button you're programming.

- The fifth button from the left is the Function button, and also serves as the continuous brew button (max 50 seconds.)

- The sixth button from the left is the tea water button.

Now, when you enter the pre-infusion parameters screen (the one after PREINFUSION ENABLED), it's showing you the On time for the Espresso button, which is the first button on the left (single cup, half full). The next screen sets the On time for the 2 Espressos button, the screen after that sets the On time for the Coffee button and the screen after that sets the On time for the 2 Coffees button. In other words, you set the On times for all four buttons first. Then the next screen is the Off time for the Espresso button (first on the left), and so on. You are now setting the Off times for all four buttons. Clear?

One other thing you should know: pre-infusion only works in conjunction with volumetric dosing. So you must program a button with the total dosing time in order to use it with pre-infusion. You do this by holding down the function button and pressing the desired button (one of the first four buttons: Espresso, 2 Espresso, Coffee, or 2 Coffees.) Let the water flow for the total shot time you desire, then hit the desired button again to stop the flow. The button is now programmed to dose water for the time you let it run. Hit the button by itself to verify that the water runs for the desired time. To eliminate confusion, Pre-infusion should be disabled when you test the button. You can do that from the menu or with the Pre-Brew Quick Key sequence: Hold down the Function key and hit the 2 Coffee button (fourth from the left.) This toggles Pre-Infusion on and off.

It's possible that the key or keys you tested earlier were not programmed yet, or the shot time was very short. It's easy to accidentally program those keys so that no water comes out (i.e., ultra-short on time.)

BTW, the tea water key can also be programmed for volumetric dosing.

Hope this helps.

Thank you that was very very helpful to me. I have programmed the buttons as you described.

However, when I go to preinfuse the pump still holds steady at 9.5 bars throughout the preinfusion. The pump also runs continually. The preinfusion time and dwell time are running correctly in regards to what I programmed but the pump continually runs. When the machine preinfuses shouldn't I just see a trickle of water from the group and see the pressure drop to around 3 bars? I don't, it stays steady at 9.5. The only time in drops is when the preinfusion has completed and it goes into the 3 second dwell time I have programmed.

Here is a video that demonstrates the sounds of preinfusion on a GS3 AV.
You can clearly hear the pump being activated during preinfusion. But then once preinfusion has finished I can hear a discernable click of the solenoid opening up to begin the full brewing process. From this video I assume that on the AV model the pump runs during preinfusion stage but at a reduced capacity. The pump runs on my unit as well during preinfusion but at full force. I also don't get a clicking sound of the solenoid opening up to begin the brew process because I suspect it's already opened fully. This coupled with the fact that the brew pressure throughout the whole process stays steady at 9.5 bars tells me that I have not preinfused.

Does that make sense?

It's working correctly. The pump stays on during the entire pre-infusion sequence. Go back to the thread I cited earlier and read what BillC posted (in case you don't know, Bill designed the GS/3). Here's the key quote:

BillC wrote:The "electronic" pre-infusion on the GS3 operates like this. Press the button and the 3 way valve opens and the pump turns on for T(on) seconds. Then the 3 way valve closes but the pump stays on for T(off) seconds. Then the pump turns back on for the remainder of the shot.
Since the valve closes during pre-infusion the pressure is "0" in the portafilter. This is because the 3 way valve has opened to the exhaust side releasing all of the pressure in the portafilter.

You may be confused about this because Bill typoed in the fourth sentence. I believe he meant to say, "Then the 3-way valve opens for the remainder of the shot."

First thing to realize is that when water is flowing into the portafilter during the first phase of pre-infusion, the pressure is zero until the basket is completely full. However, since the pump is set to 9 BAR, the flow rate is the same as it would be with pre-infusion disabled. But this isn't a big deal because the gicleur in the group head slows the flow rate so that it's very gentle.

During the second phase of pre-infusion, the 3-way is closed. Even though the motor continues to run, it has no effect on the puck because the input valve is closed. BillC says that the exhaust side of the 3-way is open during this time, so the pressure at the puck is essentially zero.

You can't go by the reading at the brew boiler pressure gauge. That only tells you the pressure at the brew boiler, not at the group head. Even though the pump is running and is maintaining 9 BAR at the brew boiler, the pressure is zero inside the group head because the 3-way input is closed and the exhaust is open.

This suggests that you want to set your pre-infusion On time so that the water just covers the puck and does not completely fill the basket (i.e., before pressure begins to build up.) You can get a good sense of how long this takes by pulling a shot with pre-infusion turned off. Watch the brew boiler gauge and count the number of seconds between turning on the pump and the gauge rising above the nominal 9 BAR pressure setting (on my machine it usually rises to 10-10.5 BAR.) Set the pre-infusion On time a little lower.

Note: Earlier I said you have to use pre-infusion in conjunction with volumetric dosing. That's true, but volumetric dosing is a poor way to time a shot. I would program the button for the max time (50 seconds) then turn it off when the shot reaches the proper level of extraction (i.e., blonding point at the target beverage weight.)

FWIW, after a lot of experimentation with the GS/3's programmed pre-infusion, I stopped using it. There was no real taste benefit. The 0.6mm gicleur in the group head ensures that water fills the basket gently. I believe pre-infusion will only help in cases where distribution is poor or an inferior grinder has been used.

WOW thank you for explaining all that. This information is not available in the manual so how is one to understand how it works?


TWO THINGS THAT ARE STILL TROUBLING ME:
1. When I run the GS3 using preinfusion without the PF I do not see any difference in the water flow rate at all accept when preinfusion ends and dwell time begins. You stated that the "gicleur in the group head slows the flow rate so that it's very gentle." I dont visually see this.

Is this normal? Shouldn't I see a slow trickle?


In your quote it states that:"Since the valve closes during pre-infusion the pressure is "0" in the portafilter. This is because the 3 way valve has opened to the exhaust side releasing all of the pressure in the portafilter."

2. If that were the case wouldn't you see the water being discharged from via the small round screen just above the drip tray?

I'm sorry if I seem difficult. I just want to be sure that my GS3 is doing what it's suppose to do.

One final small question.

In terms of adjusting the expansion valve: In the manual they tell you to turn the valve clockwise to increase brew boiler pressure and turn in counter-clockwise to decrease pressure. I tried this but my expansion valve works in the exact opposite. To increase I turn counter-clockwise and decrease clockwise. Is your GS3 the same?

Very interesting Thread, since I have the paddle version some of this still applies.

#2. I think you would see water in the drip tray unless it bleeds that pressure back into the boiler some way.

"Small final question". If you are looking from the top down then counter-clockwise is tightening the valve and raising the pressure. Looking at the valve from the bottom works in reverse, counter-clockwise decreases pressure. The manual is dodgy at best.

Did you know that the numbers you see depicted in the funky photos/cartoons of the PID are the actual numbers they want you to use? It does not say that in the Manual but LM-USA told me that in person when I was having my machine looked at by them.


Cheers!

Stephen