Slayer single group - Temperature accuracy and stability issues - Page 2

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Bob_M (original poster)
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#11: Post by Bob_M (original poster) »

Well we've been getting much needed rain the last few days, so motorcycle stays in garage and time to play around with my new machine. First thing I set out to do was to adjust the offset. It looked like its current value was -5 so I figured i'd move it to -10 for starters...the manual says it's an abstract number so no reason to believe it reads degrees F. Well I went in menu to offset and hit select and moved it to -10. When I then pressed the circle to set it the value changed to a blank...Hmm. Well I checked temp with Scace and no difference. So I moved it to -20...Still no difference. In meantime I got a response to an email I had sent Slayer about a 3+ degree temp discrepancy...The email explained some things:
In the advanced menu there is a page titled "brew temp offset" enter this page. With your Scace installed in your Slayer you can now turn your brew handle all the way to the left. The number on the left of the screen shows the temp of water at the RTD in your Slayer. Your Scace device will be displaying a number also. You can now use the up and down arrows to adjust the temp on your Slayer to match the temp on your Scace. We do this here in Seattle for you, unfortunately our Scace was malfunctioning and had to be rebuilt. We did not realize there was an issue with our device until just recently.
I'm including this email because I'm probably not the only one with this problem...When I opened offset menu and moved paddle to left it seemed to have unlocked my offset adjustor so I could use it. I settled on a value of -20 which oddly reads as 200 when in offset menu in set mode..
Mike & John I checked pressure and got 10 bar with blind PF and a smidgeon under 8 bar with Scace II..My Scace poured out 65 gm of water in 25 sec. Which seems high to me

UFGators
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Joined: 15 years ago

#12: Post by UFGators »

Does scace two operate differently in terms of how the water pours out of the end?

Slayer recommends 60/g per 30 seconds as a starting point. Lighter roasted or intensely blooming coffee is require a flow rate closer to 40 g per 30 seconds and darker less acidic coffees work best at 60 g or greater. And an ad slayer was telling me that they have one of their machines set at 200 g for 30 seconds want to for one of their coffees. I have mine set at 50g 30 seconds. The slower the flowrate more finely the coffee needs to be ground.

Bob_M (original poster)
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#13: Post by Bob_M (original poster) »

UFGators wrote:Does scace two operate differently in terms of how the water pours out of the end?
.
I don't think they would differ but if one were partly clogged with something it would have more resistance to flow and therefore more pressure. And I believe would have a slower flow rate. I have not looked closely at at pressure readings and flow rate through Scace II during prebrew

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erics
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#14: Post by erics »

My Scace poured out 65 gm of water in 25 sec. Which seems high to me
The thermofilter designed by Greg is designed to flow 3 ml/sec at a pressure of 9.0 bar at the grouphead or 75 ml in 25 seconds. This value is contained in section 4.3 here: WBC Procedure for Measurement of Brewing Water Temperature.

If one really wants to get "cat's meow" specific about temperature, you need to calibrate the thermofilter and your meter (as a system) based on your altitude and barometric pressure at the time of calibration. It can get complicated . . . and time consumming :)
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

Bob_M (original poster)
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#15: Post by Bob_M (original poster) »

Hi Eric. Thanks for the information and the link. . I tested the device's temp reading by hooking the installed probe to my Fluke. I then added water from tea dispenser and checked by placing a k probe with the other end hooked to an Amprobe next to the scace probe. Temps agreed to with in a few tenths, F so good enough for now. Maybe later on this week if forecasted rain gets here and I'm confined to indoors, I may run the steam calibration test.

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shadowfax
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#16: Post by shadowfax »

Bob_M wrote:First thing I set out to do was to adjust the offset. It looked like its current value was -5 so I figured i'd move it to -10 for starters...the manual says it's an abstract number so no reason to believe it reads degrees F. Well I went in menu to offset and hit select and moved it to -10. When I then pressed the circle to set it the value changed to a blank...Hmm. Well I checked temp with Scace and no difference. So I moved it to -20...Still no difference.
Mine was set initially to "-5," and I found the same problem you had-shots were peaking about ~3-4F° below set point. I also found that small changes in offset did nothing, and I eventually had to use "-15." I wonder what that means, because it sure as heck doesn't mean -15F°. It also seemed that the temperature displayed on the left didn't actually change in real time as I changed the offset, but I don't know for sure. That was definitely the weirdest and most negative experience I've had with the programming interface so far, but it's working very well now.

The temperature error from the factory also explains a lot. I had mistakenly thought that the Slayer allowed brewing at very hot temperatures (I was up as high as 206°F for one particularly bright coffee when I first got the machine), and I was kind of wondering why-I'm glad I invested in a Scace, and pretty disappointed that Slayer had a miscalibrated Scace device for setting up their machines.
Bob_M wrote:Mike & John I checked pressure and got 10 bar with blind PF and a smidgeon under 8 bar with Scace II..My Scace poured out 65 gm of water in 25 sec. Which seems high to me
I wouldn't set pressure with a blind filter or a Scace device. I would just prep a shot and pull it in pressure adjustment mode. It works perfectly.
erics wrote:The thermofilter designed by Greg is designed to flow 3 ml/sec at a pressure of 9.0 bar at the grouphead or 75 ml in 25 seconds.
I actually just bought a Scace last week, and found that my Scace had what I thought was an insanely high flow rate (~4 mL/sec). In trying to figure out what to do about that, I realized that the WBC spec calls for delivering 75 mL +/- 5% in 25 seconds +/- 5 seconds. I'm astonished by the flexibility there, and it turned out that mine was actually narrowly in spec. However, I contacted Greg and he was more than willing to send me a new end cap with an orifice drilled for a tighter flow rate on the low-flow end of the spec.

Right now, my Scace 2 gives ~80 mL in 20 seconds at 9 bars, and it actually peaked at ~7 bars with the pump set to give me 9 bars at my usual espresso flow rate.
Nicholas Lundgaard

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erics
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#17: Post by erics »

. . . and pretty disappointed that Slayer had a miscalibrated Scace device for setting up their machines.
You are being too kind. Calibrating the thermofilter designed by Greg with a given meter is very easy.

The flowrate is another matter altogether. There has been (behind the scenes) much discussion re this flowrate and individuals more knowledgeable than I came up with this number. It requires a lot of thinking especially when you realize that the thermofilter is applied to various machines and that the original intent of this device was to compare like machines . . . not necessarily machine A to machine B.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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shadowfax
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#18: Post by shadowfax »

erics wrote:You are being too kind. Calibrating the thermofilter designed by Greg with a given meter is very easy.
I agree. It took me 15-20 minutes to set mine, including getting together the steam setup and figuring out how to set the offset on the Amprobe.
erics wrote:The flowrate is another matter altogether. There has been (behind the scenes) much discussion re this flowrate and individuals more knowledgeable than I came up with this number. It requires a lot of thinking especially when you realize that the thermofilter is applied to various machines and that the original intent of this device was to compare like machines . . . not necessarily machine A to machine B.
I understand the general reasoning (60 mL espresso, 15 mL absorbed by the puck) and the general timing. In general I think the number is very, er, "Italian." That doesn't surprise me, and it is what it is. However, I was surprised more by how wide the range is. The allowable variation in flow at "nominal 9 bar" is between 71.25 mL / 30 s (2.4 mL/s) and 78.75 mL / 20 s (3.9 mL/s). That is an incredible allowable variation in flow rate to me, and the high-flow side seems just so fast.
Nicholas Lundgaard

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shadowfax
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#19: Post by shadowfax »

Bob_M wrote:The good news is I sent a .csv to Nichols Lundgaard. And he has volunteered to massage this data into a nice easy to read format. I'll post it as soon as I get it. For me this data indicated that the indicated brew temperature (203 degrees F), is four and more degrees higher than the actual brew temp. I also performed a "Scace test" on my GS/3 and it came out with actual vs indicated within about 1 degree.
This was a well-timed coincidence that Bob sent me his data. Near the end of last month I talked myself into buying a Scace 2, which I just received last week. I'm so glad I did, too-realizing how far off the factory calibration really explained a lot.

I'm hoping to do the actual WBC test on the Slayer over Christmas break. I pored over Bob's data and did my best to line it up, and when I looked at it and sent it to Bob, we both realized that Jim's Duetto Protocol had some problems with it that skewed the results (unnecessarily large flushing, keeping the thermofilter out of the group for too long) to the point of them not being very useful as is. So I think at some point Bob will redo his testing with a fully calibrated setup and a more WBC-esque protocol, with the shorter 2 second pre- and post- flush, as well as keeping the thermofilter in the group during the intervals, other than for simulated prep (15s) and puck knockout (10s). I don't mean to speak for him, but I at least will be obtaining that data for my review.
UFGators wrote:Does scace two operate differently in terms of how the water pours out of the end?

Slayer recommends 60/g per 30 seconds as a starting point. Lighter roasted or intensely blooming coffee is require a flow rate closer to 40 g per 30 seconds and darker less acidic coffees work best at 60 g or greater...
Just to clarify, we are not talking about pre-brew type needle valve setting here. The Scace 2 has a simple brass cap on the end of a sintered bronze/brass filter that protects it from stray coffee particles. The cap has a hole bored through it that is supposed to be the correct diameter to deliver a flow rate within the WBC spec (above) when ~9 bars of water pressure is applied to it. If the hole is the wrong size, then it has to be either bored out more or replaced with a cap that has a smaller hole-there is no "adjusting" it. And since it's a hole drilled through brass, there is inevitable variation in the hole size when it is manufactured. According to Greg, it would be better to use laser-cut ruby, but the extra cost is hard to justify. The setup on the Scace is not meant for dialing anything in, it is simply to benchmark machines with a water flow that approximates the water flow out of an espresso machine when pulling a shot.
Nicholas Lundgaard

waroros
Posts: 67
Joined: 12 years ago

#20: Post by waroros »

Did anyone succeed in finding best PID parameter & temp offset? Please share me a cheat.

I contact Slayer and found that my unit also affected with the temp issue. Will need to wait for a fix. If the issue is only about parameters, and can be fix by fine tuning by user, that would be great.
Let's get it slayed