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Unable to get consistent temps with new Rocket Giotto Evo II
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Discussions > Espresso > Machines > Unable to get...  
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Inflictionmitch
Senior Member


Joined: 30 Oct 2011
Posts: 27
Location: Montreal
Expertise: I love coffee

Espresso: La Pavoni Pisa
Posted Sun Nov 3, 2013, 2:46pm
Subject: Unable to get consistent temps with new Rocket Giotto Evo II
 

Hi everyone,

I've had a Rocket Giotto EII for several days now, and I'm finding it extremely difficult to get consistent temperatures from one pull to the next, often getting lukewarm espresso even after the machine has been on for hours. I've tried not performing cooling flushes and even that doesn't make a difference. Sometimes a shot will be pleasingly hot, other times it will be warmish at best. I've pulled when the gauge reads 1 bar, I've pulled a few seconds after it reaches 1 bar, I've pulled while it's dropping, while recovering, nothing seems to make any repeatable difference. Is there something I'm doing wrong? This is my first HX machine.
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boar_d_laze
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Joined: 21 Nov 2006
Posts: 1,218
Location: Monrovia, CA
Expertise: I live coffee

Espresso: La Cimbali M21 DT/1 Junior...
Grinder: Ceado E92; "Bunnzilla"
Vac Pot: Royal Coffee Maker
Drip: Chemex + Kone; Espro Press
Roaster: USRC Sample Roaster
Posted Sun Nov 3, 2013, 7:08pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

At first blush it seems like either your p-stat is set too low or your breaker is sticking.  However there's a considerable check list to work through before reaching any conclusions.

Most HX boiler pressures should be in the neighborhood of 1.1 to 1.2 bar.  I'm concerned that you're only seeing 1 bar.  But I'd like to go into it a little more thoroughly:
  • What does your boiler gauge read after the machine has warmed up?
  • What does it read after you've temped for the first shot?
  • What does it read thirty seconds after pulling the first shot?
  • Ten minutes later?

Also:
  • What kind of steam performance are you getting before the first shot?
  • What about immediately after pulling the shot?
  • Ten minutes after pulling the shot?

BDL
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,734
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
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Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Sun Nov 3, 2013, 8:08pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

A lot of us run even hotter, 1.2 to 1.5 is normal 1.0 is too low. :-)

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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SStones
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SStones
Joined: 24 Nov 2012
Posts: 477
Location: Canada
Expertise: Professional

Espresso: Giga 5, ECM Giotto, Rocket...
Grinder: Anfim Milano-Best
Vac Pot: No  :(
Drip: Some $30 thing from Walmart
Roaster: I buy pre-roasted.
Posted Sun Nov 3, 2013, 8:15pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

Luke warm should be nearly impossible, after the machine has been warmed up for hours.  If you're not being facetious, then there is something seriously wrong with your flow through the upper end of the heat-exchanger. You're brewing with almost all cold water, dumping back through the bottom of the heat-exchanger inlet.

After letting it heat normally to stability, does your cooling flush with no back-pressure steam nicely?
Is the group head already getting hot enough to burn your hand within minutes of the boiler pressure reaching 1 bar, the first time it warms up?

is your steam decently powerful?
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dsblv
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Joined: 2 Dec 2006
Posts: 191
Location: Bellevue, WA
Expertise: I like coffee

Espresso: Rocket Giotto Evoluzione
Grinder: MACAP MC4
Posted Sun Nov 3, 2013, 10:45pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

Your machine is probably working just fine.  A average boiler temperature of 1 bar is normal for a Rocket.  They do this to balance temperature of the group head with shot recovery time. I ran my Evo at 1 bar for a year with very good results. I eventually increased the boiler temp to an average of 1.1 bar to get a little hotter brew temp and faster recovery time.

You said you waited to pull shots when the boiler gauge hit 1 bar. The Evo is a heat exchanger machine.  The boiler gauge is an indication of steam pressure. It is not a direct indication of brew temperature.

Brew temp is determined by the temp of the group head and water in the thermosyphon loop.  The brew water is heated as it passes through the boiler and the group head.

To ensure the brew water is at proper temperature, leave your machine on for at least 45 minutes. You'll need to do a short cooling flush, then you can pull your shot.

You also need to allow adequate recovery time before pulling another shot. It takes time to heat the water that was added to the thermosyphon loop when you pulled your last shot.
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uscfroadie
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uscfroadie
Joined: 2 Aug 2008
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Location: San Antonio
Expertise: I live coffee

Espresso: GS/3 Strada MP, BDB; owned...
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Roaster: owned Behmor
Posted Mon Nov 4, 2013, 5:49am
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

Post a video on YouTube so we can see what you are seeing/doing.  Make sure the machine has been on for at least 30 minutes before doing so to stabilize the grouphead; 45 minutes is even better.  Your 1.0 bar is normal for a Rocket (.9 - 1.1 cycling pressure).  As already mentioned, you should have to do a cooling flush to get your grouphead DOWN to the correct temp.

Are you by chance leaving the portafilter out of the grouphead or pulling into a cup that has not been warmed up?  Both of these will suck heat out of your espresso.
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Inflictionmitch
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Joined: 30 Oct 2011
Posts: 27
Location: Montreal
Expertise: I love coffee

Espresso: La Pavoni Pisa
Posted Tue Nov 5, 2013, 12:08am
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

I've gotten to the bottom of it (I think)!

Seems the issue I was having was due to the grind I was using, which was very, very fine. The moment I dialled it back just a bit, the flow became slightly faster (though still thin and slow, making for a nice pour within the 30-35 second range), the temps become consistent and hot. Shots have been beautiful and it's been repeatable and consistent all day / evening!

@Uscfroadie: I've been keeping the portafilter out of the group head until just before I'm ready to pull a shot. The Rocket manual included with the Giotto states that the portafilter should not be in place when the machine is not in use. The very second I read your post, I had a "d-oh!" moment of realization as certainly, letting the portafilter be at a cool room temp while the rest of the machine is nicely warmed up completely negates all efforts to let the Giotto warm up to even temps. Is it safe to leave the portafilter in the group head full-time?

As for warm-up time, I've been starting the machine up when I wake up and turning it off in the late evening. When I was having the odd shot with lukewarm temps (with the fine, fine grind), it was often after the machine had been on for hours. But again, now that I've dialled back the grind setting a touch, it seems to have made all the difference in both heat and consistency. Could using too fine a grind make that big a difference? I suppose if the portafilter is cool / room temperature and the water stays longer than it should in the coffee grounds during a slow extraction, it would have more time to cool in that space.

@Dsblv: This is a very good point. In that case, what should I be looking at to determine recovery time between shots?
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uscfroadie
Senior Member
uscfroadie
Joined: 2 Aug 2008
Posts: 398
Location: San Antonio
Expertise: I live coffee

Espresso: GS/3 Strada MP, BDB; owned...
Grinder: Forte, Zass and PeDe hand...
Vac Pot: Nope
Drip: Nope
Roaster: owned Behmor
Posted Tue Nov 5, 2013, 5:33am
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

Leave the portafilter loosely in the grouphead all the time.  No wear on the portafilter gasket, yet keeps it properly warmed up for your shots.  Just dump the puck after shots, clean the portafilter basket, and re-insert loosely into the grouphead to maintain its warmth.

I see one of these in your future.  And this will help you understand how to use it.
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Inflictionmitch
Senior Member


Joined: 30 Oct 2011
Posts: 27
Location: Montreal
Expertise: I love coffee

Espresso: La Pavoni Pisa
Posted Tue Nov 5, 2013, 1:30pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

I'm happy to report what I suppose should have been the obvious, leaving the portafilter in has resulted in a difference that is truly night and day. Thanks a bunch for your help!

I've thought about Chris E-61 thermometer mod, but to be honest, I'd hate to corrupt the Giotto's looks with that thing. :) I may ultimately end up buying it for temporary use, to help me get a better sense of temps and cooling flush timing, like Rocket training wheels.
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dsblv
Senior Member


Joined: 2 Dec 2006
Posts: 191
Location: Bellevue, WA
Expertise: I like coffee

Espresso: Rocket Giotto Evoluzione
Grinder: MACAP MC4
Posted Tue Nov 5, 2013, 8:32pm
Subject: Re: Unable to get consistent temps with new Rocket Giotto Evo II
 

The group thermometer is well worth installing.  It takes the guess work out of pulling consistent shots.
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