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Bezzera pump set to 11.5 bar !!!
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Discussions > Espresso > Machines > Bezzera pump set...  
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RajMeister
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RajMeister
Joined: 25 Mar 2007
Posts: 69
Location: MI
Expertise: I live coffee

Espresso: Bezzera BZ02, Nespresso...
Grinder: Macap MXT
Posted Sun Jun 17, 2007, 10:12pm
Subject: Bezzera pump set to 11.5 bar !!!
 

Last night, I wanted  to measure pump pressure with my new portafilter gauge. First, the pf was leaking all over the place when engaged. Taping with Teflon didn't solve the problem because Bezzera PFs have two holes on the rim. So, filling the holes and re-taping the basket (top and bottom) and the pf did the trick.

Anyhow, I was shocked by the reading.. Pump pressure was set to 11.5 BAR!!! I think this explains why i was having slight problems with extraction (with naked pf)
I don't know why Bezzera's factory would have their pressure set that high.

Finally, I popped up the left panel and tried HARDLY to un-tighten the nut on the OPV. THANK GOD i didn't break it up cuz it was so tight. I found that it was sealed with some green material (looks like limestone). After trial and error, I managed to turn it few turns counterclockwise and set the pressure to 9.5 BAR.

I have one advice for Bezzera owners BE CAREFUL when altering pressure as the OPV is so fragile and can break when using the wrong tools.

My question is, Is my new pressure acceptable (9.5)?
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Beezer
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Beezer
Joined: 17 Oct 2006
Posts: 456
Location: Fresno, CA
Expertise: I love coffee

Espresso: Quickmill Anita
Grinder: La Cimbali Max Hybrid
Posted Mon Jun 18, 2007, 1:28pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

Very interesting.  Thanks for posting this information.  It makes me wonder how many other Bezerra owners are having trouble with channeling and other problems because their OPV is set too high.  Since the machine doesn't have a gauge to measure brew pressure, you can't check without a portafilter gauge.  I guess having a brew pressure gauge really is a good idea.

As far as your setting goes, I believe 9.5 bar is fine.  I have my Anita set at about 9 bar (it came from the factory set to 10) and it works great.  But 9.5 is probably just fine too.  If you continue to have problems with channeling, you might set it lower.  I think some people go as low as 8 bar, though that seems awfully low to me.
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TroyR
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TroyR
Joined: 14 Apr 2004
Posts: 429
Location: St. Albert, Alberta
Expertise: I love coffee

Espresso: bezzera BZ02s
Grinder: mazzer rio normale, solis...
Vac Pot: bodum santos
Drip: french press
Roaster: i-roast 2
Posted Mon Jun 18, 2007, 8:21pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

I just checked my BZ02 tonight... stock pressure relief @ 13 bar.

The thing is though, during a real espresso pull don't we effectively have two pressure setting devices?  One being the OPV, the second being the puck in the basket.

Tell me what you think of this:  During the shot, a properly prepared puck may present the system with 8 or 9 bar worth of resistance.  The result being a tasty 2 ounces of coffee in the prescribed amount of time.  If this is the case our OPV does not even come into play and stays closed.
If the puck is not prepared properly and chokes the machine, the OPV will open to allow flow and prevent damage to the pump.
If this is the case, it makes sense to have the OPV set to open between the pressure of a good shot and the maximum pump pressure.

It's a theory anyway.  Thoughts?  Am I missing something obvious?

Troy
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RajMeister
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RajMeister
Joined: 25 Mar 2007
Posts: 69
Location: MI
Expertise: I live coffee

Espresso: Bezzera BZ02, Nespresso...
Grinder: Macap MXT
Posted Mon Jun 18, 2007, 11:34pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

TroyR you are reading my mind!!

I had the same thoughts last night. I don't know the answer though. Let's assume the following scenarios:

Scenario 1:
1- The machine was set to 9.0 Bar.
2- PF was prepared with perfectly tamped coffee
3- Shot was pulled and taste was perfect (25 sec. & no channeling)


Now, scenario 2:
1- The machine was set to 11.5 Bar.
2- PF was prepared same way and same grinding level as in Scenario 1.
3- Shot was pulled

Shouldn't the taste be the same since the OPV will not kick-in until resistance is higher than 11.5?? and resistance here is the same right?

We need an expert's opinion!
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nobbi4711
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nobbi4711
Joined: 20 Apr 2005
Posts: 338
Location: Germany
Expertise: Professional

Espresso: Dallacorte Mini EX4
Grinder: Casadio Instantaneous
Vac Pot: none
Drip: French Press
Roaster: Mini-500/800N drum roaster;...
Posted Tue Jun 19, 2007, 1:32am
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

Here's the expert's opinion:

With the OPV adjusted to 11,5 you won't get the same shot as the pump releases more pressure onto the puck. You will have more coffee in the same time and will have to grind finer. That's it.

Don't forget that you have about 0,5bar less pressure on the puck then measering with a blind filter or pf gauge. So if you adjust 9,0  you will receive a coffee brewing pressure of about 8,5.

Greetings \\//

Marcus
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RajMeister
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RajMeister
Joined: 25 Mar 2007
Posts: 69
Location: MI
Expertise: I live coffee

Espresso: Bezzera BZ02, Nespresso...
Grinder: Macap MXT
Posted Tue Jun 19, 2007, 4:13am
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

I see.. so i'm surfing around the 9 Bar line if my pf gauge reads 9.5.
Cool! as long as i'm happy with the shot performance.
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Thijs
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Joined: 15 Apr 2006
Posts: 16
Location: Amsterdam
Expertise: I love coffee

Espresso: La Pavoni Professional
Grinder: Rancilio Rocky
Roaster: Popcorn popper
Posted Tue Jun 19, 2007, 6:52am
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

Interesting topic!!
I own an old Bezzera Minibar and need to grine pretty fine to get a normal shot out of the machine, so the problem here could lie within the setting of the OPV valve. I'll check the pressure, but can somebody varify that the red circle I drew is the opv valve?
Thanks.

Thijs: IMG_3501opv.JPG
(Click for larger image)
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TroyR
Senior Member
TroyR
Joined: 14 Apr 2004
Posts: 429
Location: St. Albert, Alberta
Expertise: I love coffee

Espresso: bezzera BZ02s
Grinder: mazzer rio normale, solis...
Vac Pot: bodum santos
Drip: french press
Roaster: i-roast 2
Posted Tue Jun 19, 2007, 1:38pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

Thijs Said:

Interesting topic!!
I own an old Bezzera Minibar and need to grine pretty fine to get a normal shot out of the machine, so the problem here could lie within the setting of the OPV valve. I'll check the pressure, but can somebody varify that the red circle I drew is the opv valve?
Thanks.

Posted June 19, 2007 link

Does the tube coming out of the top of it go back to the water reservoir?
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TroyR
Senior Member
TroyR
Joined: 14 Apr 2004
Posts: 429
Location: St. Albert, Alberta
Expertise: I love coffee

Espresso: bezzera BZ02s
Grinder: mazzer rio normale, solis...
Vac Pot: bodum santos
Drip: french press
Roaster: i-roast 2
Posted Tue Jun 19, 2007, 4:15pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

RajMeister Said:

TroyR you are reading my mind!!

I had the same thoughts last night. I don't know the answer though. Let's assume the following scenarios:

Scenario 1:
1- The machine was set to 9.0 Bar.
2- PF was prepared with perfectly tamped coffee
3- Shot was pulled and taste was perfect (25 sec. & no channeling)


Now, scenario 2:
1- The machine was set to 11.5 Bar.
2- PF was prepared same way and same grinding level as in Scenario 1.
3- Shot was pulled

Shouldn't the taste be the same since the OPV will not kick-in until resistance is higher than 11.5?? and resistance here is the same right?

We need an expert's opinion!

Posted June 18, 2007 link


Yes!

I think what we need is someone with a brew pressure gauge willing to adjust the OPV up to see if the brew pressure changes while grinding and prepping the shot the same.

Oh, the scenarios.
#3 - grind coarser
    - pour is fast
    - pressure at the puck is lower than 9 bar

#4 - grind finer
    - pour is slower
    - pressure at the puck is higher than 9 bar if permitted by the OPV setting
    - you're drinking a ristretto

I wonder if anything can be gleaned from watching flow through the OPV vent line during a shot?


Edited to remove the grammar of a five year old and to prevent embarrassment.
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Thijs
Senior Member


Joined: 15 Apr 2006
Posts: 16
Location: Amsterdam
Expertise: I love coffee

Espresso: La Pavoni Professional
Grinder: Rancilio Rocky
Roaster: Popcorn popper
Posted Tue Jun 19, 2007, 4:56pm
Subject: Re: Bezzera pump set to 11.5 bar !!!
 

Thanks for the reply and, yes it does!
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