Promoting coffee discussion.
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coffee-forum.com Promoting coffee discussion. |
> > Just wondering what bar we are talking about when we're mentioning the > pressure available in an espresson machine. > > I hear 9 bars ideal het the pressure guage in my Wega mininova only > goes up to maybe 3 and I had major problems when I was drawing at 2.5 > AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! > > So what bars ARE we talking aobut here? > > Walt Depending on the design of the machine, there are indeed two different pressure measurements. In a single boiler machine the boiler is maintained at a pressure suitable for steam production. This varies from .9 - 1.4 bar, with my ideal being 1.1-1.2 bar. For espresso extraction you need much higher pressure - 8-9 bars, and this is achieved by either the use of a pump, or in older machine the use of a compressed spring lever. Home lever machine like the Pavoni don't have a spring, instead relying on the operator pulling the lever to generate the 9 bar. In practice, most domestic single boiler machines have a switch and two thermostats to enable holding the boiler at two pressures. This is because higher pressure is needed for steaming, but this pressure would result in water that is far too hot for espresso extraction A switch usually allows the heater to be kept on for longer to increase the boiler pressure (but still only in the range above). After steaming, water needs to be bled to allow the temperature to drop for espresso extraction, the 9 bar pressure required here is created by the pump. -- Regards, Danny http://www.gaggia-espresso.com (a purely hobby site) http://www.dannyscoffee.com (UK advert for my mobile espresso service) swap Z for above characters in email address to reply |
> > > Depending on the design of the machine, there are indeed two different > pressure measurements. In a single boiler machine the boiler is > maintained at a pressure suitable for steam production. This varies > from .9 - 1.4 bar, with my ideal being 1.1-1.2 bar. For espresso > extraction you need much higher pressure - 8-9 bars, and this is > achieved by either the use of a pump, or in older machine the use of a > compressed spring lever. Home lever machine like the Pavoni don't have > a spring, instead relying on the operator pulling the lever to generate > the 9 bar. the guys down at my coffee-shop always bitch about their machines able to generate about 16 bar to extract espresso, and i bitch back about me being a strong guy and working my pavoni lever to put even more pressure on it :-) what do you think, how much pressure can you possibly squeeze out of a pavoni europiccola? tnx, chris |
about 16 bar is clueless. Commerical rotary pump espresso machines are built with with a pressure relief bypass so that pumping volume in excess of that needed to generate the optimum 9 bar is recycled to the input side of the pump. Only by defeating or tampering with that mechanism will a commercial machine generate 16 bar. Unfortunately, some home espresso machine manufacturers make the same idiotic claim - inexpensive vibe pumps are built without pressure relief and do go up to 16 bar in some cases but this is not a good thing. Repeat - more is not always better. By pressing hard enough on the lever you could generate MORE than 16 bar with your Pavoni. A lot more in fact if the coffee is ground too finely. The lever gives you a big mechanical advantage so that 20 or 30 kg of force at the your end of the lever gives you many times that much at the piston end (in exchange, many cm of travel at your end is only a couple of cm of travel at the piston end). This translates to several hundred kg of force on the piston, spread out over only a few sq. cm of piston area. If I had the exact area of the Pavoni piston and knew the leverage ratio it would be easy to calculate the weight needed on the piston to generate 16 bar, but trust me that it is well within ordinary human capabilities and that you probably have exceeded that much if you ever freeze or come close to freezing the lever. The problem with europiccolas is not the pressure they can generate (though generating even and correct pressure by hand throughout the pull requires a trained touch). It is rather the small size of the coffee basket compared to a commercial basket and also a problem with overheating, especially if you are making multiple shots. "Christoph Bueeler" <cb@sub-culture.ch > wrote in message news:3f5224f3$0$10776$afc38c87@news.easynet.ch... > the guys down at my coffee-shop always bitch about their machines able > to generate about 16 bar to extract espresso, and i bitch back about me > being a strong guy and working my pavoni lever to put even more pressure > on it :-) what do you think, how much pressure can you possibly squeeze > out of a pavoni europiccola? > > tnx, chris > |
level. 1 bar is the pressure your body is being subjected to. Multiply 9 bar by 14.7 psi and you get an equivalent extraction pressure of 132 psi. "Walter H. Lewis III" <walt_l@hotmail.com > wrote in message news:6qf3lv0b8noj2tne47bmt8dg9ri1hsemlq@4ax.com... > Just wondering what bar we are talking about when we're mentioning the > pressure available in an espresson machine. > > I hear 9 bars ideal het the pressure guage in my Wega mininova only > goes up to maybe 3 and I had major problems when I was drawing at 2.5 > AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! > > So what bars ARE we talking aobut here? > > Walt |
Honestly not being pissy, but it is 14.5 psi/bar. Tom "Dan Bollinger" <danbollinger@insightbb.remove.com > wrote in message news:7Um4b.238587$Oz4.64260@rwcrnsc54... > Bar is short for Barometric Pressure, usually taken to be 14.7 psi at sea > level. 1 bar is the pressure your body is being subjected to. Multiply 9 bar > by 14.7 psi and you get an equivalent extraction pressure of 132 psi. > > > "Walter H. Lewis III" <walt_l@hotmail.com> wrote in message > news:6qf3lv0b8noj2tne47bmt8dg9ri1hsemlq@4ax.com... > > Just wondering what bar we are talking about when we're mentioning the > > pressure available in an espresson machine. > > > > I hear 9 bars ideal het the pressure guage in my Wega mininova only > > goes up to maybe 3 and I had major problems when I was drawing at 2.5 > > AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! > > > > So what bars ARE we talking aobut here? > > > > Walt > > |
Thanks, Dan > > Honestly not being pissy, but it is 14.5 psi/bar. > > Tom > "Dan Bollinger" <danbollinger@insightbb.remove.com> wrote in message > news:7Um4b.238587$Oz4.64260@rwcrnsc54... > > Bar is short for Barometric Pressure, usually taken to be 14.7 psi > at sea > > level. 1 bar is the pressure your body is being subjected to. > Multiply 9 bar > > by 14.7 psi and you get an equivalent extraction pressure of 132 > psi. > > > > > > "Walter H. Lewis III" <walt_l@hotmail.com> wrote in message > > news:6qf3lv0b8noj2tne47bmt8dg9ri1hsemlq@4ax.com... > > > Just wondering what bar we are talking about when we're mentioning > the > > > pressure available in an espresson machine. > > > > > > I hear 9 bars ideal het the pressure guage in my Wega mininova > only > > > goes up to maybe 3 and I had major problems when I was drawing at > 2.5 > > > AND the "green/ideal" range on the guage is in the .9-1.5 bar > range!! > > > > > > So what bars ARE we talking aobut here? > > > > > > Walt > > > > > > |
walt_l@hotmail.com says... > Just wondering what bar we are talking about when we're mentioning the > pressure available in an espresson machine. > > I hear 9 bars ideal het the pressure guage in my Wega mininova only > goes up to maybe 3 and I had major problems when I was drawing at 2.5 > AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! > > So what bars ARE we talking aobut here? > > Walt > By and large there are two common sorts of espresso machines on the market: single boiler machines like the Silvia and heat exchanger machines like your Wega and the vast majority of commercial machines in the world. The boiler in a single boiler machine does double duty, holding hot water under the approx 9 bars of pressure produced by the pump on its way to the group and your cup. It also heats water to steam and is under much less pressure during that operation as the pump isn't running. Your Wega is a heat exchanger machine meaning that one large boiler contains a smaller tube through which water runs on its way to the group when a shot is pulled. The large boiler doesn't have to survive the whole 9 bar needed for an espresso shot. Instead this large boiler is partially filled with water which is heated to produce steam. The pressure on your gauge shows the pressure inside the steam boiler. A common setting is from 1 to 1.3 bar. In this sealed vessel pressure is related to temperature with higher pressures indicative of higher temperatures (and more steam pressure, too). Meanwhile inside the steam boiler is the heat exchanger tube. It is immersed in all of this super hot water and so as cool water comes in one end by the time it passes through the tube it is heated to the 195f to 205f needed for an espresso shot. The water circuit from pump through the heat exchanger to the brew head is capable of holding the 9 bars or so of pressure needed for the production of espresso, but the circuit for steam (which includes the pump not to produce pressure but only to move water into the boiler when it runs low) is rated for much less pressure. So practically speaking, your steam boiler will run at around 1 to 1.5 bar and your hot brew water system will run at about an average of 9 bar for espresso production. Low pressure for steam, high pressure for hot brew water. Hope this helps! Ted -- Please take the '.doggie.' out of the email addie and make it swim laps in the basement before emailing me. |
Further to the same, the gauge on Walt's machine is reading steam boiler pressure only, so that the 2.5 reading was in fact much too high. . Some machines have dual gauges that show both steam and pump pressure, but when there is only one pointer it usually indicates steam pressure only. Pump pressure gauges on vibe pump machines without adjustable relief are fairly useless as there is not much you can do with the information, so manufacturers often omit them to save cost. So a bar is a bar, but there are 2 kinds of pressure in an espresso machine. "Simpson" <tnjsimpson1@com.doggie.cast.net > wrote in message news:MPG.19bbcb9ce252121a9899b1@news.va.comcast.giganews.com... > In article <6qf3lv0b8noj2tne47bmt8dg9ri1hsemlq@4ax.com>, > walt_l@hotmail.com says... > > Just wondering what bar we are talking about when we're mentioning the > > pressure available in an espresson machine. > > > > I hear 9 bars ideal het the pressure guage in my Wega mininova only > > goes up to maybe 3 and I had major problems when I was drawing at 2.5 > > AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! > > > > So what bars ARE we talking aobut here? > > > > Walt > > > > By and large there are two common sorts of espresso machines on the > market: single boiler machines like the Silvia and heat exchanger > machines like your Wega and the vast majority of commercial machines > in the world. > > The boiler in a single boiler machine does double duty, holding hot > water under the approx 9 bars of pressure produced by the pump on its > way to the group and your cup. It also heats water to steam and is > under much less pressure during that operation as the pump isn't > running. > > Your Wega is a heat exchanger machine meaning that one large boiler > contains a smaller tube through which water runs on its way to the > group when a shot is pulled. The large boiler doesn't have to survive > the whole 9 bar needed for an espresso shot. Instead this large > boiler is partially filled with water which is heated to produce > steam. The pressure on your gauge shows the pressure inside the steam > boiler. A common setting is from 1 to 1.3 bar. In this sealed vessel > pressure is related to temperature with higher pressures indicative > of higher temperatures (and more steam pressure, too). > > Meanwhile inside the steam boiler is the heat exchanger tube. It is > immersed in all of this super hot water and so as cool water comes in > one end by the time it passes through the tube it is heated to the > 195f to 205f needed for an espresso shot. The water circuit from pump > through the heat exchanger to the brew head is capable of holding the > 9 bars or so of pressure needed for the production of espresso, but > the circuit for steam (which includes the pump not to produce > pressure but only to move water into the boiler when it runs low) is > rated for much less pressure. > > So practically speaking, your steam boiler will run at around 1 to > 1.5 bar and your hot brew water system will run at about an average > of 9 bar for espresso production. Low pressure for steam, high > pressure for hot brew water. > > Hope this helps! > > Ted > -- > > Please take the '.doggie.' out of the email addie and make it swim > laps in the basement before emailing me. |
to mind. As I said when I recieved this unit -- used -- the pressure guage was broken and once I got it replaced I found the machine had been running at 2.5 bars!! From the beginning I was not getting a puck from my protafilter. The grounds would shatter and disintegrate when knocked. After lowering the pressurestat to the "green zone" I am now getting a nice dry consistent puck. Mostly a matter of curiosity and personal education, the shots are wonderful. Thanks again, Walt On Sun, 31 Aug 2003 10:09:19 -0400, Simpson <tnjsimpson1@com.doggie.cast.net > wrote: >In article <6qf3lv0b8noj2tne47bmt8dg9ri1hsemlq@4ax.com>, >walt_l@hotmail.com says... >> Just wondering what bar we are talking about when we're mentioning the >> pressure available in an espresson machine. >> >> I hear 9 bars ideal het the pressure guage in my Wega mininova only >> goes up to maybe 3 and I had major problems when I was drawing at 2.5 >> AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! >> >> So what bars ARE we talking aobut here? >> >> Walt >> > >By and large there are two common sorts of espresso machines on the >market: single boiler machines like the Silvia and heat exchanger >machines like your Wega and the vast majority of commercial machines >in the world. > >The boiler in a single boiler machine does double duty, holding hot >water under the approx 9 bars of pressure produced by the pump on its >way to the group and your cup. It also heats water to steam and is >under much less pressure during that operation as the pump isn't >running. > >Your Wega is a heat exchanger machine meaning that one large boiler >contains a smaller tube through which water runs on its way to the >group when a shot is pulled. The large boiler doesn't have to survive >the whole 9 bar needed for an espresso shot. Instead this large >boiler is partially filled with water which is heated to produce >steam. The pressure on your gauge shows the pressure inside the steam >boiler. A common setting is from 1 to 1.3 bar. In this sealed vessel >pressure is related to temperature with higher pressures indicative >of higher temperatures (and more steam pressure, too). > >Meanwhile inside the steam boiler is the heat exchanger tube. It is >immersed in all of this super hot water and so as cool water comes in >one end by the time it passes through the tube it is heated to the >195f to 205f needed for an espresso shot. The water circuit from pump >through the heat exchanger to the brew head is capable of holding the >9 bars or so of pressure needed for the production of espresso, but >the circuit for steam (which includes the pump not to produce >pressure but only to move water into the boiler when it runs low) is >rated for much less pressure. > >So practically speaking, your steam boiler will run at around 1 to >1.5 bar and your hot brew water system will run at about an average >of 9 bar for espresso production. Low pressure for steam, high >pressure for hot brew water. > >Hope this helps! > >Ted |
<walt_l@hotmail.com > wrote: >I hear 9 bars ideal het the pressure guage in my Wega mininova only >goes up to maybe 3 and I had major problems when I was drawing at 2.5 >AND the "green/ideal" range on the guage is in the .9-1.5 bar range!! The pressure guage in your Wega shows boiler pressure, not brewing pressure. The boiler pressure determines the temperature of the water to your espresso, not it's pressure (confusing isn't it?). The pressure reading tranlates to the temperature of the water in the boiler (120C at 1 bar). This water heats the water going through the heat exchanger on its way to your espresso; most manufacturers seem to shoot for 90C heat exchanger water at 1 bar boiler pressure, but YMMV. There's no guage on the miniWega for pump pressure; however, you can be quite confident, if everything is in working order, that it's around 9 to 10 bar for a regular speed extraction, since the machine has a pressure limiter set to that level. -- Jim (jim_schulman@ameritech.net) |