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Pressure Fluctuation During Extraction with Bezzera BZ10
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SThacker
Senior Member
SThacker
Joined: 26 Apr 2014
Posts: 1
Location: Ontario, Canad
Expertise: I love coffee

Espresso: Bezzera BZ10
Grinder: Baratza Vario
Vac Pot: None
Drip: None
Roaster: None
Posted Mon Apr 28, 2014, 7:33am
Subject: Pressure Fluctuation During Extraction with Bezzera BZ10
 

Hi all,

Wondering if anyone could provide some insight on the the pressure fluctuations while I'm pulling a shot on my Bezzera BZ10.  During extraction, the pressure gauge ramps up to approximately 9 bar and holds for just a couple seconds before dropping off to about 6 bar where it then sounds as if the pump is 'revving' between 6 and 9 bar for the duration of the shot.  When I backflush with a blind basket, it holds a constant pressure, but not nearly at the 12 bar mark where it used to, more like 9 to 10 bar.  The taste of my shots is still acceptable [Pilot Roasters Big Bro or Level Ground Tanzania (surprising works very well as espresso or in milk-based drinks.....)], but I have to hold the shot a little longer than I'd prefer.

In reading other forums and comments online, I've read that this could be a pump, OPV, or even an electrical issue.

If anyone has a similar experience and/or a 'fix' for this, I'd welcome the feedback....

Thanks in advance.
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jferreir
Senior Member


Joined: 23 Apr 2014
Posts: 16
Location: Toronto
Expertise: Just starting

Posted Fri May 30, 2014, 9:07am
Subject: Re: Pressure Fluctuation During Extraction with Bezzera BZ10
 

SThacker Said:

Hi all,

Wondering if anyone could provide some insight on the the pressure fluctuations while I'm pulling a shot on my Bezzera BZ10.  During extraction, the pressure gauge ramps up to approximately 9 bar and holds for just a couple seconds before dropping off to about 6 bar where it then sounds as if the pump is 'revving' between 6 and 9 bar for the duration of the shot.  When I backflush with a blind basket, it holds a constant pressure, but not nearly at the 12 bar mark where it used to, more like 9 to 10 bar.  The taste of my shots is still acceptable [Pilot Roasters Big Bro or Level Ground Tanzania (surprising works very well as espresso or in milk-based drinks.....)], but I have to hold the shot a little longer than I'd prefer.

In reading other forums and comments online, I've read that this could be a pump, OPV, or even an electrical issue.

If anyone has a similar experience and/or a 'fix' for this, I'd welcome the feedback....

Thanks in advance.

Posted April 28, 2014 link

Purchased from idrinkcoffee.com in Milton, I take it?

Oddly enough, I also bought the Bezzera BZ10 with the intention of using Pilot's Big Bro blend. Unfortunately, I also experienced the same issue with fluctuating brew pressure. The pressure would initially climb to about 9 bar, and then immediately drop and oscillate between 4-6 bars (sometimes with the pump chugging back and forth). With a blind filter, the pump would take about 30 seconds to reach the factory OPV setting of 11.5/12 bars.

The result was under-extracted/sour coffee. To compensate, I had to extend the extraction time just like you described, but then the coffee was overly bitter. In the end, I returned the unit for servicing and they lowered the OPV to 9 bars and replaced the pump. A week later, the problem resurfaced. I returned the machine for a direct replacement, and to my astonishment, the new machine exhibited the exact same problem. If I remember correctly, the machines were built in Sept and Oct of 2013 respectively. I returned the second machine about a week ago, requesting that a better pump be installed, but they're currently waiting on parts (~2 week ETA).

There was a bit of a language barrier with the technician, but I think he said something about a bad batch of pumps. What I do know is that this fluctuation is not normal, and a few people have reported it. I suggest you call and discuss the issue with the store manager directly, and not to bother with the actual sales reps. I was initially given the runaround with a bunch of bogus excuses:
- Insufficient power
- Incorrect grind/tamp
- Incorrect OPV setting from factory (the technician was wrong -- factory OPV is 11.5/12 and NOT 9)
- Cheaper quality pump now made in China, so higher rate of failure
- Bad batch of pumps

In their defense, they did exchange my machine for a direct replacement, and then agreed to upgrade the pump. That said, I had to drive there on 3 separate occasions, and their customer service left a lot to be desired. If you're persistent, they will try to make things right, so best of luck and let us know how everything goes.
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