NobbyR Senior Member Joined: 10 Jul 2011 Posts: 1,604 Location: Germany Expertise: I love coffee
Espresso: Poccino Opus One, Ariete Grinder: Eureka Mignon Istantaneo,... Vac Pot: N/A Drip: Melitta Linea Unica de Luxe Roaster: N/A
Posted Mon Oct 29, 2012, 1:25am Subject: Pump pressure for domestic espresso machines
There's an ongoing debate about the optimal pump or brewing pressure for your machine. Manufacturers especially of superautomatics often advertise theoretical maximum pump pressure as a quality trait and seem to outgun themselves, e.g. the DeLonghi Lattissima Premium EN720 offers 19 bar for brewing Nespresso.
We all know that espresso should be extracted at around 9 bar. However, the safety valve on domestic espresso machines with a vibration pump is usually set at 10 or even 11 bar which seems to be a cause of concern for some CoffeeGeeks, and some people even advise to change that setting to lower levels. I just stumbled upon this video, in which Luca Bezzara, head of production at the Bezzera manufactory in Rosate, discusses the question of "9 bar or 11 bar - What is the right pump pressure for the espresso machine?". He claims that brewing pressure does not equal maximum brewing pressure and that there's a difference between consumer/prosumer and commercial machines.
What are your thoughts on this matter? Is there a need to change factory settings?
PS: Don't be scared off by the German introduction which is translated later on. Most of the video is in English.
*** "This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee)
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,642 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Mon Oct 29, 2012, 6:17am Subject: Re: Pump pressure for domestic espresso machines
I am going to make the best machine ever made, I am going to use the pump from a commercial pressure washer, I guess I will have around 1500 pounds of pressure (limited by my random desired pressure, the pump will go more), if more pressure is better, my machine will be the best! ;P
OK a little more serious, they are really two different things, a rotary pump has a lot more power behind it to be consistent with pressure and a vibe pump (like your video points out) is a toy in comparison so to make up for the lack of power, it is set higher so as to be a little more consistent in pressure at the puck.
They reference Illy as saying that the pressure should be 9 bar OR MORE, (I never read Illys book so I can not make a comment on this point) I do know my machine is a little higher at 10.5 bar and I have a rotary pump, this is when plumbed in, on the internal tank, it reads about 9 bar give or take a little.
I just alter my grind a little and all is well YMMV!
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Posted Mon Oct 29, 2012, 4:04pm Subject: Re: Pump pressure for domestic espresso machines
A rotary pump is capable of much higher volume pumping at higher pressure. The pressure regulator is built into the pump to re-circulate the excess volume. So much extra that flow restriction is usually required in the brew water path. For a single group machine a vibe pump is more than capable of delivering the required pressure and flow rates. The lower volume issue actually works to an advantage in providing a gentle ramp to the full brew pressure (...without the flow restriction). As for what pressure is best to brew espresso, I think it is best to adjust and taste. For my taste, I keep my (vibe pump) brew pressure at 8.5-9 bar. Higher pressures tend towards more intense and/or harsher flavors, much lower pressures tend more towards a cafe crema.
NobbyR Senior Member Joined: 10 Jul 2011 Posts: 1,604 Location: Germany Expertise: I love coffee
Espresso: Poccino Opus One, Ariete Grinder: Eureka Mignon Istantaneo,... Vac Pot: N/A Drip: Melitta Linea Unica de Luxe Roaster: N/A
Posted Mon Oct 29, 2012, 11:45pm Subject: Re: Pump pressure for domestic espresso machines
Frost Said:
... As for what pressure is best to brew espresso, I think it is best to adjust and taste. For my taste, I keep my (vibe pump) brew pressure at 8.5-9 bar. Higher pressures tend towards more intense and/or harsher flavors, much lower pressures tend more towards a cafe crema.
Over a period of months I have run brew pressures from 7 to 11 bar. (this was a few years ago) Generally leaving the selected pressure for a period of days or weeks to get a good idea of the effects. The range of 8-10 bar was most workable. I tend to prefer coffees and roasts on the lighter and lively side, so settled on the lower pressure brew for my taste.
Posted Tue Oct 30, 2012, 8:44am Subject: Re: Pump pressure for domestic espresso machines
As stated above, I've been running at 8.5-9 bar for the last couple years. (this will depend on flow rate with an OPV for regulation) It only takes a few minutes to adjust, but I have not been compelled to adjust for different coffees.
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