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Possible pressurestat problem or adjustment needed for Isomac Millenium?
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fox2000
Senior Member
fox2000
Joined: 18 May 2012
Posts: 46
Location: WA
Expertise: I love coffee

Espresso: Isomac Millenium I
Grinder: Mazzer S.J. Auto & MDX
Posted Sun Jun 24, 2012, 1:51am
Subject: Possible pressurestat problem or adjustment needed for Isomac Millenium?
 

I am still getting to know my machine I bought used a few months back it is an Isomac Millenium I,  I have noticed lately the resting temp after full heat up seems high and my flushes seem longer. I apologize if this has been covered in the past I have been researching all day and haven't found the answer yet. I have only recently been paying closer attention to temps and the boiler pressure gauge so it is possible this has been ongoing since I bought the machine and I am just now noticing (smart I know). After full heat up my group thermometer usually reads 217 f prior to any flushing. When I start flushing it can jump up to 220 f then starts dropping typically I get right around 8-10oz of water to get the group temp to 198-200 f. It quickly jumps back up to 210-212 in 1-2 min. So typically after grinding I have to run another shorter cooling flush bringing the temp to 200 producing about 4oz. The temp will usually stay close to 200 during the shot but does fluctuate sometimes dropping to 198 or climbing to 208 within the 25-30 sec. I am not sure if this much temperature variance is normal? From what I have read so far with HX machines the temp can vary a lot but after getting it in the right ballpark it should stay stable? Maybe I am missing something but it seems like I should be able to pull a 30 sec shot at 200-204. I watched the pressure gauge today while resting and fully heated and it went from just under 1.1 to just over 1.4 as the red brew light and green steam light alternated. Is this a normal range of boiler pressure? I have read about different setting ranging from 1.1 to 1.5 and from what I have read I would think 1.2 would be a good setting for me. However I am unsure of how to figure out what my current setting is. I am concerned its set to high causing my temps to be to high? Or possibly that there may be something wrong with the pressurestat causing the wide swing in bars, if I am even having a wide swing? Any help would be greatly appreciated I am not even sure if there is a problem or adjustment needed.
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NobbyR
Senior Member
NobbyR
Joined: 10 Jul 2011
Posts: 2,021
Location: Germany
Expertise: I love coffee

Espresso: Poccino Opus One, Ariete
Grinder: Eureka Mignon Istantaneo
Vac Pot: N/A
Drip: Melitta Linea Unica de Luxe
Roaster: N/A
Posted Sun Jun 24, 2012, 2:36am
Subject: Re: Possible pressurestat problem or adjustment needed for Isomac Millenium?
 

My Poccino Opus One is identical in construction to your Isomac.

The E61 brew group of your Millenium is heated by way of convection using the thermo syphon that's connected to the HX line.

The cooling flush is supposed to bring down the temperature inside the HX line which tends to overheat when the machine is left idling, because the the boiler is on steaming temperature. The usual cooling flush will not effect brew group temperature that much, after all it's a solid piece of metal we're talking about. However, the drop of hot water temperature will be much grater during the cooling flush than during brewing, because the flow rate is much higher, so that the HX line is not that effective while flushing. The HX line has been designed to deliver water with a relatively consistant (and correct) temperature over the brewing process.

Still, different types of coffee might require different brewing temperatures.

You can influence brewing temperature indirectly by chaning boiler pressure, which usually has a factory setting between 1.2 and 1.4 bar. At 1.4 bar boiler temperature will be at approximately 261 F. Lowering or raising boiler pressure by 0.1 bar will lower or raise temperature by about 2 F respectively.

I recommend to read this resource article on How I Stopped Worrying and Learned to Love HXs on Home-Barista.com for further information on the subject.

From what you described I'd say your machine behaves perfectly normal.

 
***
"This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee, when he was urged to ban the beverage)
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fox2000
Senior Member
fox2000
Joined: 18 May 2012
Posts: 46
Location: WA
Expertise: I love coffee

Espresso: Isomac Millenium I
Grinder: Mazzer S.J. Auto & MDX
Posted Wed Jun 27, 2012, 6:58pm
Subject: Re: Possible pressurestat problem or adjustment needed for Isomac Millenium?
 

Hi Norbert

Thank you for your reply!

I have been waiting to post back to see if it was a technique issue or possibly a coffee issue giving me problems. Its funny I had read that article back when I first got my Millenium and after fixing my initial electrical issue it has been working great. I was also getting fairly good shots in the beginning but had some channeling. Then I had to dial in my MDX (used), I ended up researching techniques and adopted a couple. Later I figured out the burrs were shot so I replaced those which again led me to dialing it in, throughout this process I have gotten good shots that were pretty tasty but have had a lot of issues with consistency and channeling. All the while I have been trying new coffees buying 2lbs of any given blend at a time. I could keep going on my trials and errors but through all of this I have realized a few things, that switching coffees every week with new equipment is a bad idea. That my equipment is working great but the Zoka Paladino I had bought is difficult for me to work with, and even though I liked it while at Zoka apparently it is not my favorite blend. That I was focusing to much on technique and had way to many tricks to make my distribution perfect which ultimately made me think there much be something wrong with my machine because I had fixed everything else. Once I got back to basics after reading an article on HB dosing high, leveling NSEW and tamping 40lbs, low and behold I have good shots again. I also ran out of Zoka and bought some Vivace this week and the improvement is amazing I am finally pulling good to great shots consistently. All noob mistakes and come to find out pretty common ones but I wanted to thank you for the response, it was a reality check I needed to pull it all together.
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