D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Wed Mar 28, 2012, 9:16am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
I was hoping that the digital thermometer would work, but suspected not. I do not yet have the thermocouples or instrument to read, though a PID can do that part. I was hoping for a simple way to do this that anyone could do without a lot of euipment that nay not be otherwise used. I thermocouple or thermometer in the cup wuld be the best dial in for settng temperature. It seems like a thermocuple wire would break fairly quickly when folded over the lip. The alternative seems to be to try to make a PF or basket with a hole and then seal in a thermocouple, also not inexpensive. The thermometer is a great bang for the buck tool, just looking for more.
D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Fri Mar 30, 2012, 2:26pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
I guess I am talking, replying, to myself, not sure what that says about interest in the topic.
If I summarize the prior thread correctly, then the brew temperature was not controlled in a range that was felt useful the participants. Some interesting preheat, including adding a boiler as preheat.
I believe that AndyPanda’s method largely accomplishes what they were trying to do. There is less temperature drop within a shot and corresponding quicker recovery. I have not yet proven that a PID device using the alarm function can duplicate, though recovery using thermometer in a cup is good, and suggests a similar result. Math seems to show and Andy demonstrated that the Gaggia is capable of putting enough heat into the system to overcome incoming cool water and ambient losses. Having a sensor at the brew stat is a little unnerving, as the temperature swings are fairly large. Even though the initial “on” time is about only 4-5 seconds, the stat sensor will see over 240f before starting back down. The impression is destabilization, but the brew stat location is not a great reflection of the water temperature. I got a similar rise when flicking on the steam switch for a preheat, the manual method. I used the manual method to try to find out how much temperature rise to try to get, and then set the alarm temps according. The manual method uses preheat, and the alarm function starts with the brew switch, though can start ahead with the steam switch, and then to automatic with the brew switch. In practice, just using the brew switch seems to be fine. You need to run the “on cycle” enough of the brew time to put the heat calories in, and evenly enough in time to avoid steam. The “on cycle” time is determined indirectly by the set alarm temperatures. I find that at the end of the brew, there is residual heat in the wall, over set temperature, and the temperature then returns to the set brew temperature by decline. The water temperature within the tank is probably slightly cooler and slowly absorbing the remaining tank wall heat.
It would be interesting to see what others experience with either method.
D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Wed Apr 4, 2012, 4:30pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Found a couple low budget toys to help with dialing in temperatures, but I have not gotten to use them yet. If you are reading this, then you might also like them.
Digital multimeter with k thermocouple. A cheap unit, but probably adequate for home use. I do not like having to calculate from C to F or to set voltage ranges, but I have better DMM. I needed or wanted the temperature ability. Not bad with a 20% coupon, about $15.
D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Fri Apr 6, 2012, 10:00am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
I got a chance to play with the DMM and K thermocouple. Nothing new to report, but I confirmed that warm up is about 20 minutes, or more. The PID reads from a sensor at the brew t-stat location. The PID showed a stable temperature in about 5 - 6 minutes. Turns out that all it means is that the PID can blip power and hold the brew pot temperature stable, or stable at the b-stat location. The k thermocouple was placed sitting on the PF ear with it locked in place. That took 20 minutes to reach a constant temperature. Even if the water comes up to a stable temperature sooner than the 20 minutes, it will go into a cool brew head and PF. Not news as the info can be found in other places. A picture or demonstration is worth a thousand words, and perhaps it explains why I got some sour shots when I did not have 20 minutes and convinced myself that the PID stable temperature meant machine and brew head stable.
Posted Fri Apr 6, 2012, 11:43am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Waiting for warmup is easiest ... but if you are in a hurry here is something you can try:
Heat it up to steam temps and flush some of that super hot water through your PF into your waiting cup - that warms up the PF and your cup. You can let it cool back down near brew temps and heat it up to steam temp a second time and flush through PF again if you want. I can usually get a decent temp with only 5-10 minutes of warmup if I'm in a hurry ... but it certainly is easier to turn it on 30 minutes before I want the shot.
D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Fri Apr 6, 2012, 12:06pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
I tried similar, but then I do not know where I am temperature wise. I guess the answer is keeping a sensor mounted on the brew head or PF. When I try to push the time, I occasionally end up sour or bitter. You may have been doing this long enough to have the feel, no substitute for experience. I find timing less critical if I am not having espresso/americano. A little milk and sugar or honey covers a lot for me.
Posted Fri Apr 6, 2012, 6:15pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
You wouldn't know where you were temp wise if you wanted to pull a shot a few seconds after doing that heatup routine ... but that wasn't what I was suggesting. I meant get the PF and group heated up in 5 minutes (instead of 20) and then let your PID idle for a few minutes and you should be exactly at the same temp the PID usually holds it. You just got the PF warmed up with hot water early on so it doesn't take so long ... once that's warmed up the PID should settle your machine back into constant temps in a couple of minutes.
Posted Fri Apr 6, 2012, 11:19pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Glad to hear I'm not the only one using the steam function to heat up my machine more quickly...
As for temp probe locations, I've tried different locations on the boiler and have found the brew stat location to work the best with a PID. In fact, I have two PID's and two RTD's on my machine as a result of playing with locations and left them on as it's nice to see overall stability of temps in the boiler for both brew and steam...
D4F Senior Member Joined: 15 Mar 2012 Posts: 1,223 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Sat Apr 7, 2012, 6:25pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Interesting thoughts on speeding up the process. I timed letting the PID run it to stable with the second sensor, a K thermocouple pushed between the PF ear and group head. I may have picked one of the slowest spot to stabilize. In reality, my machine is by the sink with an Instahot. I often warm the PF that way. I will show my ignorance in that I have only looked at a parts diagram, not opened the machine, but the brass group and then PF seem slow to warm even when water is put through. The aluminum boiler and elements are little mass and up top, so brewing will bring down some heat, but also add some cold water. Interesting, the thermocouple did not show much upswing in temperature when I hit brew. I then realized that the brew water goes through the stainless basket and out, little contact with the brass, especially the top of the PF which is wrapped in stainless with basket in. It seems like a little mass is trying to heat a lot of mass and not quite steam the water. I know that a boiler temperature of 240 for a short time does not flash the water, I already do that. It seems that the PF has enough mass to significantly affect the shot, though the basket is shielding the other way then. I probably did not test well, as I am new to using and placing the thermocouples. What I did find is that if I want to shorten the stabilization time, then I need to stand there and run the machine instead of getting ready. I am not sure that I benefit much. I also realize that this is where experience pays and those who speed the process are probably much more efficient than I. It would be interesting to see numbers of how long it takes to get a stable PF temperature using the speed method. I am thinking that it is the last to stabilize, other than brew water if brew water is doing much flushing, thus measuring that.
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