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What could cause major group temp fluctuations?
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 658
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Wed Mar 6, 2013, 7:32pm
Subject: What could cause major group temp fluctuations?
 

Yet another stupid question, but this is the third time since I started leaving the PF in the group a few days ago that I've gone to my Oscar to pull a shot after being on and idle for a while and the group is cool enough to hold my finger on. Normally it's scalding hot. A cooling flush wasn't even necessary and the ramp from pump start to first pour was probably about 30-40%. The shot was okay, but any idea what gives?
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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 Wed Mar 6, 2013, 7:51pm
Subject: Re: What could cause major group temp fluctuations?
 

My immediate guess is that it's unrelated. It isn't the PF in the group, you're just experiencing a false pressure in the boiler occuring in initial warm-up stopping the machine from actually warming up.  
From your post, it seems to me that this is NOT initial warm-up, but actually after the machine has idled after a complete warm-up which could be the pressostat...  But doesn't the Oscar use a nice sirai p-stat?  Anyhow, My guess is that it is unrelated to your PF.  
What gets it back to working normally?  Opening the steam-valve? Giving it a thump?
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 658
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Wed Mar 6, 2013, 8:06pm
Subject: Re: What could cause major group temp fluctuations?
 

I think just normal use eventually gets it back to baseline. I was thinking Pstat too, since I have a vacuum breaker that has worked perfectly since it was installed (thanks, Plindy!) and it rules out false pressure. I can only assume it's just the pstat having a senior moment? I do have a Sirai pstat, but the machine is almost nine years old at this point, so who knows how reliable that thing is. :/ Any other thoughts?
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CoffeeRon
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Joined: 26 Apr 2009
Posts: 753
Location: Eatonville, Wa
Expertise: I love coffee

Espresso: Wega Lyra, Europiccola(still...
Grinder: Macap M7D, Pharos, Vario W,...
Vac Pot: Sunbeam CoffeeMaster
Drip: Melita BCM-4
Roaster: FR SR500,B-1600, SC/TO
Posted Wed Mar 6, 2013, 10:28pm
Subject: Re: What could cause major group temp fluctuations?
 

I bought my machine used with a Sirai Pstat installed by the previous owner. When I got it I noticed the contacts were pretty burned up- easy to see with the black cover popped off. As it had two sets of contacts I switched the wires over to the new set, if it had not I would have cleaned them up with some fine sandpaper or emery cloth. Just thinking this may be something for you to look at.
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 658
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Wed Mar 6, 2013, 11:19pm
Subject: Re: What could cause major group temp fluctuations?
 

I've never opened my Pstat before. I'm thinking that if it isn't back up to temp by the time of my nightly latte, I should give the adjustment screw a little tweak just to see if the thing is stuck. It's still turning the heating element on every so often and steam pressure seems normal (I don't have a gauge yet).

EDIT: So I turned the Pstat up one half turn, just to get it moving (assuming it was the pstat) and about half an hour ago I went to make my last breve of the day (I keep a late schedule). The group was still pitifully cool and not the searing heat that it usually is that would burn my finger and make the PF nice and toasty. The basket was downright cold. I went through my normal routine and steamed my half and half as usual, but before I did I noticed there seemed to be a lot of water in the steamline when I bled it of condensation. After steaming my half and half, and doing one last blast to get the milk out, I heard the boiler fill kick in and last much longer than the usual top-off. This one was closer to 5-10 seconds. After that, WHAM, the group heated up rapidly to full temperature and stayed there. Now that I think about this, this happened before, and definitely before Plindy's mod. Now I KNOW my probe is very clean (you can see me scrubbing it in the video) and I haven't had this issue up until the last few days. I wonder what's going on.
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plindy
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plindy
Joined: 27 Nov 2002
Posts: 75
Location: Seattle
Expertise: Just starting

Espresso: NS Oscar
Grinder: SJ Pharos Lido HG-One
Posted Thu Mar 7, 2013, 2:35am
Subject: Re: What could cause major group temp fluctuations?
 

If the PF is loosely placed in the group it is not coupled with the rest of the thermal mass, and stay's cool. Not too loose not too tight, yet another espresso balance.

If you want to change to different contacts on the Pstat, be aware that if the wire ends are ring type and you have to remove the screw to move the wires, there could be a small brass contact  plate under the ring and with the screw removed it will fall out, inconveniently.....

been really busy at the kite factory, only 150 b box's  left to build to retrofit all the birds in the wild......
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 658
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Thu Mar 7, 2013, 2:58am
Subject: Re: What could cause major group temp fluctuations?
 

Wow, thanks for the head's up, Pete. We should all write a REAL Oscar owner's manual with all the weird little things we've picked up :)

In my case, the entire group was warm, but not hot, not just the PF. I think the issue wasn't with the Pstat, but rather with the water being low for some odd reason. I still had normal-looking pressure from the steam wand, but excess water in the bleed before foaming the milk. After steaming, the autofill kicked in much longer than usual and suddenly the group was hot again. I didn't want to crank the Pstat up too high, since your gauge said I was right around 1.25bar, which seemed to be within the sweet spot.

I've been super busy with my last quarter at the U. Those kids been keeping your hands full at the plant still :)?
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plindy
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plindy
Joined: 27 Nov 2002
Posts: 75
Location: Seattle
Expertise: Just starting

Espresso: NS Oscar
Grinder: SJ Pharos Lido HG-One
Posted Fri Mar 8, 2013, 1:47am
Subject: Re: What could cause major group temp fluctuations?
 

might explain condition with no PF, and with
Espresso! My Espresso!
Understanding and Preventing Thermosyphon Stall
excellent real world  espresso resource

Today we were ahead of the machine shop...
The weekend, not so much...
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Markarian
Senior Member
Markarian
Joined: 27 Jun 2012
Posts: 658
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Fri Mar 8, 2013, 2:38am
Subject: Re: What could cause major group temp fluctuations?
 

Pete! You're a lifesaver once again. This is exactly what's going on and now the system is back to normal, though running a tad hot, likely due to my pstat ajustment. I'm glad it's not something serious. I'm totally bookmarking that page now. I've been doing short flushes because Helen kept insisting that we only needed to flush like two ounces since you put the gicleurs in. But I noticed my shots were more even when the group was slightly cooler, so maybe I still need a more thourough flush. What do you think? Cheers!

PS - Heard about the batteries on the news. Keeping my fingers crossed.
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Coffeenoobie
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Coffeenoobie
Joined: 11 Dec 2011
Posts: 3,036
Location: PNW
Expertise: I like coffee

Espresso: N S Oscar
Grinder: K30 & Vario W
Posted Fri Mar 8, 2013, 8:51am
Subject: Re: What could cause major group temp fluctuations?
 

My machine clearly needs shorter flushes.  But your water dance should be your guide.  I had to tighten some nuts last week I could hear but not see a leak because it was only under pressure and when hot the water evaporated. You might need to check the tightness of all the nuts.

 
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