SB E61+PID, Episode 1: A rude awakening about temperature stability - Page 2

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boren (original poster)

#11: Post by boren (original poster) »

Bluenoser wrote:After your machine is fully warm.. try a quick 3-second flush and then pull your shot..
If you go over the results I linked in the first post you'll see that in my machine even a 6 second flush is not sufficient to get temperature close enough to the target. In many cases it's still climbing up and is 3 or 4 degrees centigrade from the peak temperature. This is a far cry from brewing at a specific target temperature.
You can experiment with the PID which will make the brew water hotter/cooler, but only after a 15 minute wait. As BaristBoy said, you can experiment and find a taste you like and then duplicate that workflow each time.
What's the point of experimenting with temperature if brewing starts, continues and ends in very different temperatures than the recommended target for coffee beans based on roast level? Take for example the shot at the 88 mark (in the spreadsheet). It started at 87.3c which is too cold even for very dark roasts, then went on to 93.3c which is considered fine for most medium roasts, then climbed to 94.9c which is suited for light roasts. And this is just one of many attempts with wildly different results. Some below, some above these temperatures.
You do want to know when your machine has rebounded. Sometimes after pulling a few shots you'll need to let the water in the Thermosiphon reheat.. Your group thermometer can tell you after a shot when your water has reheated. You don't need a group therm forever.. just to learn how your machine behaves.
Is the Thermosiphon functional in a single-boiler machine like mine or does it need to be HX? If I correctly understand the post above from Jeff, it seems this is mostly relevant to HX machines.

boren (original poster)

#12: Post by boren (original poster) »

HB wrote:There's a few problems with your methodology.
Thanks for the suggestions, but I don't plan to buy additional gear to measure temperature stability. What I can do is brew actual back to back shots (with coffee) using my regular routine, and measure that. How about the following procedure:

1. Let the machine warm up for 1 hour, with the PID set to 95c (as is my default preference).
2. Flush for 6 seconds (this is up from my regular 4 seconds, which seems to be too short)
3. Brew a single shot (11.5 gram, dialed in to produce 23 gram espresso in 30 seconds).
4. Finish by lowering the lever all the way down. Avoid releasing any excess pressure even if the pressure gauge shows abnormal numbers.
5. Wait 1 minute, then brew another shot (repeat 5x times).

Would this be a more realistic and useful test?

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HB
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#13: Post by HB »

What is the goal here? It's not clear to me.

Prosumer espresso machines, including E61s, need more than 60 seconds of recovery time. Most need at least 90 seconds; those with restrictors may need as much as 3 minutes. If your goal is shot-to-shot temperature stability, allow a few minutes between pulls and minimize flushing. That is, once the group is fully warmed up, flushing doesn't help stabilize the brew temperature, it makes it less stable.
Dan Kehn

boren (original poster)

#14: Post by boren (original poster) »

The goal is to identify the cause of my machine inconsistent output. As I mentioned, with the same beans, not all shots are as good. Is it inconsistent by-design, or is it something about my workflow?

As for shot-to-shot timing, I don't mind extending it to 2 min if you think this should ensure consistent results. I suggested 1 min because when I'm hosting I sometimes brew back-to-back-to-back at even shorter cycles. Granted, in most cases people want milk-based drinks, so temperature instability is less noticeable.

To summarize, stick with the proposed test but pull shots 2 minute apart?

Bluenoser
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#15: Post by Bluenoser »

If you insist of looking at numbers and flushing, you'll get nowhere until you use a home-made or professional SCACE.. you are not seeing the effect post-E61.

The group thermometer is only useful when you experiment with a SCACE to see the relationship between it and your brew water and how the E61 influences that difference.

boren (original poster)

#16: Post by boren (original poster) »

@Bluenoser - I know I may be unreasonable here, but I'm not interested in spending hundreds of dollars on a SCACE for this test. The grouphead thermometer and PID readings are the data points that I have, and I'll try to come up with something useful based on them.

Now, if a SCACE could reveal that my machine actually has good temperature stability, despite the grouphead thermometer showing that flush peak temperature ranges from 85 to 97 degrees, then allow me to remain skeptical.

boren (original poster)

#17: Post by boren (original poster) »

HB wrote:Prosumer espresso machines, including E61s, need more than 60 seconds of recovery time. Most need at least 90 seconds;
My machine has a 750ml boiler with a 1400 watt heating element. Would a single 23ml espresso shot really require the machine 90 seconds to recover from? Even if it consumes twice the amount of water, it's still tiny in comparison to the boiler volume.

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HB
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#18: Post by HB »

boren wrote:...I'm not interested in spending hundreds of dollars on a SCACE for this test.
The DIY option I linked earlier would cost < $20 and an hour of your time, if you already own a digital thermometer that accepts a thermocouple. That said, if you're interested in measuring brew temperature, the foam cup technique is more accurate than what you're doing (I used it for years before the Scace thermofilter even existed).
boren wrote:Would a single 23ml espresso shot really require the machine 90 seconds to recover from?
Not to put too fine a point on it, but the beverage weight is a lot less than the brew water weight. It's been my experience that prosumer espresso machines are less temperature stable under load and it doesn't take much load to destabilize them. The behavior you're describing sounds like what happens when the barista flushes too much and doesn't allow enough time to restabilize. For prosumer espresso machines, it's an easy mistake to make.
Dan Kehn

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Jeff
Team HB

#19: Post by Jeff »

Boiler temperature is not brew temperature. It is several degrees hotter in the boiler than brew temperature. The boiler will rebound quickly. The problem with brew temperature is that last shot heated the group from the inside as it pulled heat from the brew water. Next shot and the hotter group will pull less heat from the water so your shot temperature will be a bit hotter. This thread started with noting the that the time for an E61 to stabilize was on the order of 40-60 minutes. That suggests a system with a dominant time constant around 10 minutes.

Many people find the couple-degree repeatability adequate for their coffee.

Those that don't either deal with manual, repeatable monitoring and control (such as flushing), close-coupled ("saturated") groups, or groups with active control.

boren (original poster)

#20: Post by boren (original poster) »

If it's only a couple of degrees I might consider keeping the machine, but if it's closer to the huge fluctuations in my original test then it's time to move on (probably to a Lelit Elizabeth). I'll perform the test I described above, in comment #12, and will decide based on the results.