No pre-infusion on Vibiemme Domobar Super with rotary pump

by **jdrock** on Thu Mar 03, 2011 5:29 am

Just got my Vibiemme Domobar Super with rotary pump and plumbed-in water line.
Everytime when I start the brew, the pressure always ramp up immediately to 9 bar and pause for 1 second following with a "hsss" sound then stable at 9.5 bar.
By watching the Vibiemme Junior, I can see the pressure slowly climbed to 4bar with a long pause for 4 seconds then only shot up to 9.5 bar quickly.
I believe this is the function of pre-infusion on the E-61. To wet the puck at the low pressure following with the full pressure brew.
But why is it not happening on my rotary version? Is that the rotary pump has no pre-infusion? Or I didn't notice?
Here is my setup, instead of directly connect the machine to the direct line water, I use an external 5 gallon water tank. Then I have an external water pump connect to the tank and supply the water to the machine constantly, this is to ensure the rotary pump does not suck the water directly from the tank. I have read from the forum that we should not let the rotary pump sucks the water from the external reservoir.
So I am not sure if it is to do with the external water pump or my setup is wrong.

by HB on Thu Mar 03, 2011 7:56 am

jdrock wrote:But why is it not happening on my rotary version? Is that the rotary pump has no pre-infusion? Or I didn't notice?

Because of where the tee is located, the gauge measures the pressure at the pump exit, not the pressure in the brew chamber itself. If you measured using a thermofilter (Scace device), you would see the slowly rising pressure profile that the E61 is known for, albeit slightly different for rotary pumps. This chart from Pressure profiles, preinfusion and the forgiveness factor show this distinction:

Two E61 espresso machines, two different types of pumps

Bottom line: Rotary pumps pressurize almost instantly; vibratory pumps require several seconds to fully pressurize. As you can see above, this difference does impact the brew pressure profile for an E61, but I haven't noticed an appreciable difference to the cup (e.g., comparing Quickmill Anita and Vetrano).

PS: Click here to follow responses to Jack's cross-post of the same question on CoffeeGeek.

by **jdrock** on Fri Mar 04, 2011 12:37 am

Alrite, now it solved the myst.
Thanks.

http://users.rcn.com/erics/ · by **erics** on Fri Mar 04, 2011 1:16 am

. . . or my setup is wrong.

Its not that your setup is "wrong", but it could be vastly improved by adding an accumulator tank (say, two gallon size) between your bottle's pump and the Vibiemme. Do a search here on HB for "accumulator".

Is your Vibiemme Super a push button model (i.e. automatic) or a lever like the junior?

by **jdrock** on Sun Mar 06, 2011 11:03 am

My Domobar is the manual level type just like the Junior.

by **godshot** on Sun Mar 06, 2011 2:57 pm

I have the same machine as jdrock, although mine is plumbed in to my water supply, pressure-regulated to 30 psi. I'm not using an external water tank and pump like jdrock.

But I also wonder about pre-infusion. It seems that pressure builds continuously as soon as the water starts flowing into the group head. What I understand from Dan Kehn's comments above is that a plumbed-in rotary Domobar Super doesn't have pre-infusion. Is that true?

by **Randy G.** on Sun Mar 06, 2011 3:35 pm

I do not have my hands on a rotary at this time (soon, I think), but the passive pre-infusion of the vibratory VBMs sounds like a function of a combination of the placement of the feed line to the pressure gauge and the faster delivery of water in regards to volume and pressure of the rotary pump. From what Eric and Dan said, if you were to place a pressure gauge on the group (when his excellent thermometer adapter is inserted) you would see a different result than what is shown on the panel mounted gauge.

In other words, just because the gauge does not show a preinfusion, that does not mean it is not taking place.

HEY MA! Lookee here! I am getting me an edjumakation! :wink:

by **peter12345** on Sun Oct 23, 2011 9:34 pm

I have a plumbed in domobar with a rotary pump, so i can't speak for ones that have a reservoir. If you want to have a controlled pre-infusion all you have to do is adjust the switch behind the lever. If you adjust the pump switch so the lever engages the switch later in the lift the initial flow will be from your home water pressure, around 4 bar.

To do this remove the back panel.
Then remove the nut on the switch behind the lever.
Pull the switch out and adjust the back nut to the proper position.
You can test your position by holding the switch in from the back and lifting the lever. If you get water flow before the lever hits the switch you can it should be good for pre-infustion.

When you are done with pre-infusion just lift it all the way and it will engage the pump. It may take a little bit of toying with the switch location, but it is pretty easy to access and adjust. It is a good idea to unplug the machine before messing with the switch so you don't shock yourself. I hope this helps, let me know if you get it working.

Here is a picture of the switch:
http://www.google.com/imgres?q=domobar+...eBQ&zoom=1

Peter

by **Randy G.** on Sun Oct 23, 2011 10:44 pm

Now that I have finished the manual for the DD and have done quite a bit of personal research into these machines (besides learning from my own DD), I can relate how it works in more detail:

When you lift the lever to the "middle" position, which is just to the point that you feel resistance, all three valves in the group are closed (brew valve on top, and below the group, the infusion valve and the exhaust valve). Lifting it just a little more opens the brew valve but does not turn the pump on. If you have a plumbed machine, the line pressure goes past the rotary pump, into the brew boiler displacing hot water, and water flows into the group wetting the coffee at line pressure. This is the preinfusion of which most speak. You can hold this position as long as you like. I have found that preinfusing until the first drop of espresso falls into the cup, or when the first droplets form on the bottom of the basket (using a bottomless portafilter). About ten seconds with a standard portafilter should work.

With reservoir fed machines (or those drawing from an external water tank which does not supply pressurized water to the machine) that isn't going to happen. here is no line pressure to force the water into the machine in the manner described above. A few drops of water might hit the coffee from the convection of the hot water in the boiler, or just expansion of the water that is under pressure in there, but that is all. In this case, the infusion valve in the group will supply a buffer, keeping the pressure in the group at about 1.5BAR for the first few seconds until the infusion chamber fills with water. This helps protect the coffee from the fast delivery of water from the rotary pump.

Download the new owner's manual from Stefano's site :
http://espressocare.com/PDF-Files/DDManual_DRAFTvD8.pdf
How virtually all manual E-61 groups work (and it still applies to other E-61 groups as well as those not made by Vibiemme) is explained in detail. It is still marked as a Draft version as it awaits Jim's approval.


Contact Us	Legal disclaimer and copyright: This content and all its parts are copyrighted, all rights reserved. Content including all text and images in part or in whole may not be reproduced in any electronic or printed medium without prior permission. Home-Barista, Home-Barista.com and related logos are trademarks of Home-Barista.com, LLC. Other trademarks are the property of their respective owners. By accessing this site, you agree to the terms of service. Overall speed: , current page: s, avg: s, max: s