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How to adjust the brew pressure of a Giotto Premium?
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Sat Aug 7, 2004, 8:29pm
Subject: How to adjust the brew pressure of a Giotto Premium?
 

Any Giotto owners adjusted the brew pressure of their machine?  Below is what I believe is the expansion valve, but it doesn't appear to be adjustable.  I am measuring 11 bar with a portafilter pressure gauge.  There's no built-in gauge to measure during the pull itself, but the shots taste slightly overextracted and I would like to reduce the pressure a little to smooth them out.  Am I overlooking something?

-- Dan

HB: giotto_expansion_valve.jpg
(Click for larger image)

 
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Ian
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Ian
Joined: 21 Jan 2003
Posts: 1,466
Location: England

Espresso: Euro2000,Rancilio
Grinder: Mazzer,La Cimbali
Vac Pot: Cona-->CraigA
Drip: Belgique for emergencies
Roaster: Primas with variac
Posted Sun Aug 8, 2004, 1:00am
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

If you take the valve apart there may be a shim (washer) that you can remove to reduce spring pressure - that's a common method of adjustment in hydraulics. Alternatively, you could fit a weaker spring or install an extra washer in the body which would also reduce the spring tension.

Cheers

Ian

 
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Sun Aug 8, 2004, 4:55pm
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

Thanks Ian!  (thinking out loud)... and yet there's something that doesn't sound right.  Howard (easyrotor) reports the Salvatore has no means of adjusting its brew pressure other than changing the grind (link), the Giotto Premium and Livia 90 (link) apparently have limited means.  This wouldn't be too inconvenient if either of these costly machines had brew pressure gauges, which leads me to wonder...  

Is the message from these manufacturers essentially, "ignore the brew pressure -- it doesn't matter if it is 8.0 bar or 11 bar"?


Update: Excerpt from the thread "Brew Pressure and Salvatore" and my reply, copied here to consolidate the discussion...

jim_schulman Said:

The old line Italian firms never worried much about vibe pump pressure on home machines. Presumably they figured that the coffee and grinder being used wouldn't be too good, and if the pour volume/timing was in the ballpark, the pressure would be too. Even the Cimbali Juniors, which did come with adjustable pressure relief, were set to 15 bar from the plant. In bars, the tech would set it down and plumb the drip tray or reroute it back to the tank (for pourovers).

Italian roasters have bulletins that specify the temperature and pressure they want on each commercial machine model for their blends (Jolly's is somewhere on their site, but I can't find it anymore); so they take a lot more pains with the commercial market than they do the home market. But there really is no home espresso geek culture in Italy like in many other places; for instance, we don't have any Italians posting here, and I'm not aware of any Italian language ngs or forums for home espresso (there are some in almost every other language). So I don't believe they are aware of how their small one group machines are being used almost everywhere else in the world.

Posted August 9, 2004 link

That would explain why some Italian machines are not easily regulated.  But Salvatore's machine is made in the USA and they certainly spared little expense choosing components.  So why would they omit an expansion valve?  I can't think of a disadvantage of installing one (well, other than cost and filling the driptray faster for plumbed units).

-- Dan

 
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dspringston
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Joined: 2 Dec 2003
Posts: 47
Location: Fairfax Virginia
Expertise: I live coffee

Espresso: Salvatore
Grinder: Mazzer Mini, Pasquini Moka...
Drip: Old Braun
Roaster: Hottop
Posted Sun Aug 8, 2004, 8:25pm
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

Do large commericial machines actually have a way to adjust the brew pressure or is it strictily up to the operator to get the grind and tamp right?

David
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Mon Aug 9, 2004, 5:17am
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

Yes, commercial machines have a brew pressure adjustment.  They usually have rotary pumps, which have a much greater flow rate than vibratory pumps, so they're capable of running multiple groups.  Most are regulated to between 10 and 8 bar.

-- Dan

PS: Chas Rimpo's S1 website has a good picture of this adjustment, labeled F in Picture 2.

 
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dspringston
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Joined: 2 Dec 2003
Posts: 47
Location: Fairfax Virginia
Expertise: I live coffee

Espresso: Salvatore
Grinder: Mazzer Mini, Pasquini Moka...
Drip: Old Braun
Roaster: Hottop
Posted Mon Aug 9, 2004, 5:56am
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

Dan,
Thanks for being so helpful.

David
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Fri Oct 8, 2004, 5:31pm
Subject: How to adjust the brew pressure of a Giotto Premium
 

FYI for future Giotto owners... I took the top off Giotto's expansion valve and indeed it does adjust (below left).  Stick a small screwdriver blade in one of the slots and push the retention washer counter-clockwise to reduce the brew pressure.  It was originally set to 11 bar and about 3/4 turn reduced it to 9 bar.

(continued)

HB: giotto_expansion_valve_adjust.jpg
(Click for larger image)

 
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HB
Senior Member


Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Fri Oct 8, 2004, 5:38pm
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

While I was there, I added an external brew pressure gauge.  The size of the exit tubing was conveniently 1/4" OD, so I was able to splice in a John Guest push-in tee.  It took longer to get off the covers than add the gauge (six screws for the top, six 7mm bolts for the bottom casing, two 7mm hard-to-reach nuts for the front of the casing).

Updated: See "Help Me Adjust Overpressure Valve on a Giotto Premium" for additional details.

-- Dan

HB: giotto_brew_gauge.jpg
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bigm
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Joined: 17 Jun 2004
Posts: 58
Location: australia
Expertise: I live coffee

Posted Sat Oct 9, 2004, 8:43am
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

good work

how did you know where to put the tee etc.   do you have front photo please....love to see the gauge...is it from ecm                                    

did you have to drill the case ?? how long did it take ??

thanks
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Sat Oct 9, 2004, 11:28am
Subject: Re: How to adjust the brew pressure of a Giotto Premium?
 

M, since this is an evaluation machine, I didn't cut into the casing and used an inexpensive gauge (similar to this one).  The threads "PRESSURE GAUGE on MISS SILVIA?" and "Expobar with Gauge" have hints on installing a built-in gauge, to name just two.  I'm sure the hardest part is driling / cutting the hole; Pepe provides detailed instructions on alt.coffee for doing a very clean job.

-- Dan

 
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