milnerb1 Senior Member Joined: 25 Sep 2002 Posts: 392 Location: Gig Harbor, WA Expertise: I love coffee
Espresso: Vivaldi II, Isomac Tea,... Grinder: Mazzer Mini, Solis Mulino Roaster: Behmor 1600, BBQ drum,...
Posted Sun Oct 27, 2002, 11:19pm Subject: Controlling Temperature Stability in Brewing - Semicommercial Machines
I've been reading a lot about the importance of temperature stability throughout the brewing cycle...and am thinking about getting a nicer thermometer...(by the way...thanks to Jim Shulman for the recent links for inexpensive ones).
However, it would seem that fine tuning the initial brew temperature in a machine is much less important than keeping the temperature stable throught the entire brewing cycle. For example, if I tune-in the brew temperature at the start of a pull to 203 degrees, but it decreases by 5 or 6 degrees by the end of the pull, then I'm not going to be pulling an optimal shot. Furthermore, the thermometer didn't really do me much good other than tell me that there's a problem with my machine!
My thought, therefore, would be to install a thermometer where the HE line goes into the grouphead and use it to control a variable swith that would keep the boiler element on at a level that would best control the brew temp.
A few questions that I have:
- Is this what people mean by PIDing a machine?
- Isn't this what D. Schomer has done with his professional LM machines?
- Would it be worth considering, advisable, or even possible to do this to a semi-commercial machine (I have a TEA but I assume it would be the same procedure to do it to any of the high-end E61 machines and even the Livia or other HE machines)
- Do you see any value in doing this with the TEA, i.e. does the temperature swing by more than an optimal range in the TEA?
- Has anybody done this, and what results have been achieved?
- What is the approximate cost of this?
I'm very interested in peoples' advice on this, as I want to be able to consistently produce the best espresso possible.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Mon Oct 28, 2002, 2:47am Subject: Re: Controlling Temperature Stability in Brewing - Semicommercial Machines
Alas, it's very hard to do. If you get a 2500 watt instant hot type unit, you can heat the water on the fly, but the coils don't cool fast enough to lower temperature when it gets too hot. I got curious if a tempering valve mixing hot and cold water would work; it would, but requires chem lab grade valves and controls at several thousand a pop.
The trick with HX espresso machines is to have a big pf and group at the right temperature, and get the water "roughly right" out of the heat exchanger. The mass of the group damps down and stabilizes the HX errors.
In the Tea, the temperature only declines at unimpeded flow, at espresso making flows, the heat exchanger holds the water in a 5F - 7F range. The head cuts that error rate down to about 3F. I posted some data in an alt.coffee thread here. I can add that I now can control the brew temperature within a 2C range, rather than a 5C one I spoke about in the post, but I think that's about the limit.
Adding a PID lets you choose the temperature more effectively, and would cut down the swings from about 3F to 2F in the final product.
Systematically declining temperature during the shot (rather than temperature variance) is something that only affects single boiler machines, since cold water is flowing into a small boiler as hot water leaves. On machines with .75 liter boilers like the Isomac Zaphiro or Venus, ECM Boticelli, or Brasilia Club, the drop is probably negligable. On .3 liter machines like the Silvia or Solis, it's about 3F - 5F, which is close to the variance of HX machines. Smaller boiler machines have poorer performance.
milnerb1 Senior Member Joined: 25 Sep 2002 Posts: 392 Location: Gig Harbor, WA Expertise: I love coffee
Espresso: Vivaldi II, Isomac Tea,... Grinder: Mazzer Mini, Solis Mulino Roaster: Behmor 1600, BBQ drum,...
Posted Mon Oct 28, 2002, 9:32am Subject: Re: Controlling Temperature Stability in Brewing - Semicommercial Machines
Wow Jim. You really know how to pull it all together. Based on your advice, I will try a few things that will help ensure better temp stability in my machine:
- Make sure the boiler is cycling between 1.075 and 1.175 bars.
- Run the machine a little longer before pulling my shots. I've been giving it 5-10 seconds where the sputtering starts to calm down a little, but have been stopping before it turns into a smooth stream. I was fearing that a smooth stream meant the group was too cold.
- Adjust my routine to extend my brewing time a little bit. With my current grind/tamp, I've been ending up with 2 oz of espresso/crema in about 20 seconds. It sounds like I need to get that kind of volume at about 28-30 seconds instead.
Thanks again for all of your incredibly helpful posts.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Mon Oct 28, 2002, 3:21pm Subject: Re: Controlling Temperature Stability in Brewing - Semicommercial Machines
milnerb1 Said:
- Make sure the boiler is cycling between 1.075 and 1.175 bars.
- Run the machine a little longer before pulling my shots. I've been giving it 5-10 seconds where the sputtering starts to calm down a little, but have been stopping before it turns into a smooth stream. I was fearing that a smooth stream meant the group was too cold.
You don't need to set the pressure stat to this level for temperature stability. Doing the water run at any pressure level will get the group to the right temperature.
I've learnt a little since that alt.coffee post, and here's my latest tricks for "working" the Tea. This probably also holds good for the Millenium, Euro, and newer ECM models.
You can control the machine to stay in a high, medium, or low brewing range. The high range is suitable for lighter, dry bean roasts, similar to Illy, since it doesn't amplify the sour notes one gets at that roast level. The low range is suitable for darker roasts like Peets, where the beans are dark chocolate colored and oily, since it doesn't amplify the bitter notes one can get at that roast level. A medium brew range is the compromise for intermediate, slightly shiny, milk chocolate colored beans, which most roasters call "Full City" or "medium dark."
For the high range, set the stat at around 1.3 bar and run the water prior to the first shot just until it stops hissing (about 5 ounces). Chris quite rightly, for himself, sets his machines up in this way, since he uses Illy coffee.
For the medium range, set the stat at around 1.1 bar and run water 5 seconds longer than the hissing (about 6 1/2 ounces). This is what I do.
For the low range, set the stat at around .9 bar, and run water about 10 seconds longer than the hissing (about 8 ounces). This would be right for a Peet's level or Neapolitan style roast.
Since the first shot's temperature is determined more by the water run than the pressure stat, you can experiment to see which range works best for your beans before going into the machine and making the adjustment.
milnerb1 Senior Member Joined: 25 Sep 2002 Posts: 392 Location: Gig Harbor, WA Expertise: I love coffee
Espresso: Vivaldi II, Isomac Tea,... Grinder: Mazzer Mini, Solis Mulino Roaster: Behmor 1600, BBQ drum,...
Posted Mon Oct 28, 2002, 3:39pm Subject: Re: Controlling Temperature Stability in Brewing - Semicommercial Machines
This is more great information for me to try. Thanks again Jim.
On a related note, I've noticed that my pressure guage changes somewhat depending on how long the machine has been sitting idle, and whether the boiler has kicked on.
Therefore, I want to make sure that I'm reading the pressure properly to get an accurate and consistent reading of what's really happening in the boiler. Here's what I mean:
If my machine been sitting idle for a while (and the boiler light is not on), it seems to sit around .9 bar. However, when I bleed a little steam to get the boiler to turn on, the pressure gradually rises to about 1.175 bars (over about 10-15 seconds), at which time the boiler light goes out, and the guage gradually goes down to about 1.025 bars, and seems to rest there for a while.
In an earlier converstation with Chris, I vaguely recollect him telling me to measure the boiler pressure at the 'highest point' that it reads after the boiler kicks in. Does this make sense?
If so, than in the above example, my boiler pressure would be 1.175 bar, and I would always use this method to measure what my boiler pressure is at any given time.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Mon Oct 28, 2002, 5:15pm Subject: Re: Controlling Temperature Stability in Brewing - Semicommercial Machines
milnerb1 Said:
This is more great information for me to try. Thanks again Jim.
On a related note, I've noticed that my pressure guage changes somewhat depending on how long the machine has been sitting idle, and whether the boiler has kicked on.
Therefore, I want to make sure that I'm reading the pressure properly to get an accurate and consistent reading of what's really happening in the boiler. Here's what I mean:
If my machine been sitting idle for a while (and the boiler light is not on), it seems to sit around .9 bar. However, when I bleed a little steam to get the boiler to turn on, the pressure gradually rises to about 1.175 bars (over about 10-15 seconds), at which time the boiler light goes out, and the guage gradually goes down to about 1.025 bars, and seems to rest there for a while.
In an earlier converstation with Chris, I vaguely recollect him telling me to measure the boiler pressure at the 'highest point' that it reads after the boiler kicks in. Does this make sense?
If so, than in the above example, my boiler pressure would be 1.175 bar, and I would always use this method to measure what my boiler pressure is at any given time.
If the pressure you're going for is anywhere in the operating range of the pressure stat (turn on to turn off point), you're good to go.
You're shooting for a 3F brewing range, and the error that this slight uncertainty in the setting represents is worth about 1F, so it's not too critical. In any case, it's not easy to adjust the pressure any finer than that; since there's a bit of shifting of the on and off points over the course of the day (don't know why).
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