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Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
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D4F
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Joined: 15 Mar 2012
Posts: 2,036
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Sun Mar 25, 2012, 1:52pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

I found the article on PID temperature reading vs. brew water temperature done by Auber in 2007.  Good read for Gaggia SBDU owners.

Click Here (www.afonic.org)

The conclusion is that it takes at least 4 minutes between double shots for the brew water to get back to within 2 C stabile start and it takes 20 minutes to stabilize from cold start.  The study was to help correlate PID setting to brew temperature.  There can be a 10C or 18F drop in water temperature by the end of a double.

This may not be news to most since the study was 2007.  I now wonder how that knowledge works with the attempts to speed the process.  It was also mentioned in the article that PID temperatures can stabilize before water temperature.  PID temperatures should be 99c - 107c or 210f  - 225f.

We can see PID or external thermometer temperatures of the tank, but those can appear stable while water is still heating.  So, the following question.  If you want to speed the process of heating brew water back to starting temperature and approximately, recovery time, what will that mean to tank or PID temperatures?  Perhaps AndyPanda can give some data here as he has been most able to accomplish stable water temperature.  Flicking on and off the steam switch will certainly give wide swings in the tank external temperatures with a fair lag in the water, because of mass and cold incoming.  Heat input must be supplied about 50% of the brew cycle time if enough calories are to be input to match the cooling of incoming water and radiant loss.  So, what does that look like at the thermometer?  I may not be aggressive enough at adding heat because the PID reading, RTD at the brew stat site, gives large temps and I do not want to boil the water while brewing.

 
D4F also at
http://www.gaggiausersgroup.com/
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AndyPanda
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AndyPanda
Joined: 12 Jul 2010
Posts: 769
Location: San Francisco Bay Area
Expertise: I love coffee

Espresso: Olympia Cremina, Various...
Grinder: Mazzer Major, Fiorenzato,...
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Roaster: BreadMachine/HeatGun
Posted Sun Mar 25, 2012, 7:38pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

It is going to depend a lot on where you place the temp probe.  I deliberately put my probe as far from the heating elements as I could .... still I would expect the heat conducts through the aluminum to my probe faster than it does to the water.

I also know that the cabinet (metal cabinet vs plastic) makes a difference to warm up time --- people have been saying 20 minutes for ages and it is sacrilegious in this forum to suggest faster warm up times - but on a plastic cabinet (or with the boiler insulated from the stainless case of the classic) I can get stable temps in 5 minutes of warm up time.  So I already think the study you linked is for a particular test case and not gospel for all Gaggias or techniques for warmup (such as getting up to steam temp and flushing that super hot water through the group and PF).

Recovery time ... how do you treat your PF after the first shot?  Do you knock the puck out and quickly wipe out any remaining grinds and put the PF right back into the group to stay warm?  Or do you rinse the PF/basket under the group?  Or do you (gasp) rinse it in the sink with cool water?  There are so many variables in technique that to give a number for recovery between shots would only apply to that specific routine.

I have a bottomless PF with very little mass --- I still keep it warm but I have measured that it doesn't really suck much heat away from the group when I lock it in (it only contacts metal-to-metal in two small areas of the ears - the rest of the contact is with the gasket).  But someone with a heavy brass spouted PF might get completely different results and need to heat all that PF mass back up to temp depending on how much they let it cool between shots - and how much they flush from the boiler between shots for cleaning the shower screen or for rinsing/heating up the PF again.

Lately I've been using the very old Gaggia with the larger boiler - it takes longer to get it up to heat - but I don't have to do anything during the shot.
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,036
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Sun Mar 25, 2012, 8:13pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

AndyPanda Said:

It is going to depend a lot on where you place the temp probe.  I deliberately put my probe as far from the heating elements as I could .... still I would expect the heat conducts through the aluminum to my probe faster than it does to the water.

Posted March 25, 2012 link

I understood this, but you recently described your method of hitting the steam switch before brewing, and then on and off.  Your temperature swings would be less than those of us who put the sensor in the brew stat position.  You still would have a good point of referrence for the rest of us.  I may need larger swings of temp at the brew stat to equate to the top of the boiler, but you have proven your method with brew water temps.  I thought that the recent info that you posted here was on a unit similar to the Classic.  For all of us who are trying to use your method, or similar with a PID, just looking for temperature swings.

 
D4F also at
http://www.gaggiausersgroup.com/
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AndyPanda
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AndyPanda
Joined: 12 Jul 2010
Posts: 769
Location: San Francisco Bay Area
Expertise: I love coffee

Espresso: Olympia Cremina, Various...
Grinder: Mazzer Major, Fiorenzato,...
Vac Pot: vintage Corey
Drip: AeroPress
Roaster: BreadMachine/HeatGun
Posted Sun Mar 25, 2012, 10:01pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

The recent info was on the machine similar to the Classic (and on the Classic itself).  

But since then (the past couple of days) I worked on another Old White Coffee with steam knob on front - and just thought I toss out the fact that on the older machine, with a much larger boiler, I don't even have to do anything at all other than get the thing up to temp to begin with.   I guess I tossed that out as a way of saying that even though my method with the Classic works really well for me, it is still a routine that requires some understanding and discipline to pull off (which I enjoy, but others may find to be tedious).  And it is so much easier when you actually have the larger volume of hot water.

I think it would be really interesting to design the additional features into a PID so it would anticipate the shot (well delay the pump until the heating elements have started to energize) and then heat enough for the incoming flow.  OR the preheating coil of copper tubing (and variations thereof) is interesting too -- or adding a thermoblock between the pump and boiler.  All interesting methods.

BTW ... I gave a test to my idea of unplugging one of the two heaters on the Classic.  I didn't spend enough time with it, but I found that the temps my thermometer was reading kept rising during my shots, even with just half the heating power but the taste of the shot made me think that the temps of the water were actually too cool.  I really need to test this more carefully (I had a busy weekend and only had a few minutes to experiment) -- but my initial results didn't encourage me.  I think it would be a lot better to leave both heaters connected but modulate the power to them so the whole boiler heats more evenly rather than just heating the one side.
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D4F
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Joined: 15 Mar 2012
Posts: 2,036
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Mon Mar 26, 2012, 8:35am
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

Seems like the heater could come on with a timed preinfusion and then programmed to keekp the temperature close.  I guess it would take some programming to make it work at various set or starting temperatures.  I sould guess that the higher temperature that the boiler is set, the more heat is lost to the surroundings, thus more "on" cycle to keep the temperatuer up.  Still, it seems that with direct computer plotting, and equipment like the quoted linked Auber study prior, that a program could be generated to get close.  It could start with the brew switch and run with the shot, or if advantageous, start with a preinfusion, similar to your method.

Other than the concept, above me.

Also a great link to AndyPanda's temperature method

Posted Mon Mar 5, 2012, 8:41am
Subject: Re: Need advice on Gaggia machine purchase
http://coffeegeek.com/forums/espresso/machines/569101?Page=3

 
D4F also at
http://www.gaggiausersgroup.com/
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AndyPanda
Senior Member
AndyPanda
Joined: 12 Jul 2010
Posts: 769
Location: San Francisco Bay Area
Expertise: I love coffee

Espresso: Olympia Cremina, Various...
Grinder: Mazzer Major, Fiorenzato,...
Vac Pot: vintage Corey
Drip: AeroPress
Roaster: BreadMachine/HeatGun
Posted Mon Mar 26, 2012, 8:46am
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

Hey ... would you test something out for me please?   I don't have a PID so I can't test this myself.

Ideally you would do this without having your PID set to force the heater on for the entire pull.  Just a standard PID that will try to hold your set temp whether the pump is on or not.

Try hitting the steam switch for 4-5 seconds and then off and then start the pull and see if the PID can then keep up with the shot without letting the temp drop too much at first.  You might try steam for 3 seconds or 6 seconds instead.

One other thing I try .... this only works with a 3-way valve machine .... I will hit the steam switch and the pump with the steam valve closed .... you hear the pump loud for a few seconds, as it fills up the empty space at the top of the boiler, then the pump loads up and starts trickling through the OPV back to the water reservoir.  This is just to make sure the boiler is completely filled.  It usually takes a few seconds after this to get the boiler back up to temp if much water was pumped in - but this just makes sure that the boiler is close to full so you don't start your shot and immediately pump a lot of cold water into the boiler before anything even starts to flow out the grouphead.

I'd be really interested to hear if your PID can hold the temp better during the shot if you do the 4-5 second manual heater on just before you start the shot. (just letting the PID try to hold temps normally - without any special tie in to the brew switch since "I think" that would take the heat too high)
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D4F
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Joined: 15 Mar 2012
Posts: 2,036
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Mon Mar 26, 2012, 5:20pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

I actually had the same thought in the beginning.  I learned the steam switch trick on my old Delonghi, so I transitioned that to the Gaggia.  I was doing that before the PID.  The PID was added and helps the beginning stability and temperature selection, only.  The PID portion ot the device uses only blips of power in its selected range, and that is not near 50% as I understand.  It will not maintain the temperature during brew after helping with a several second head start.  That is why I switched to the alarm function with a higher set point.  I am forcing the PID to run in "on and off" mode, not PID mode and I am still having trouble keeping up with the incoming water.  That is why I am trying to get an idea how much your headstart jumps the temperature.  I may need to set the alarm "on and off" higher.  My sensor at the brew t-stat gets about 240 before starting back down.  That is very fast, and the rise well over set, or overshoot.  I suppose as long as you do not get steam, you do not know where the water temperature actually is.

I have not seen the internals of the digital thermometer, a picture would be interesting.  I cannot quite visualize what you have for wiring.

 
D4F also at
http://www.gaggiausersgroup.com/
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AndyPanda
Senior Member
AndyPanda
Joined: 12 Jul 2010
Posts: 769
Location: San Francisco Bay Area
Expertise: I love coffee

Espresso: Olympia Cremina, Various...
Grinder: Mazzer Major, Fiorenzato,...
Vac Pot: vintage Corey
Drip: AeroPress
Roaster: BreadMachine/HeatGun
Posted Mon Mar 26, 2012, 6:18pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

D4F Said:

I have not seen the internals of the digital thermometer, a picture would be interesting.  I cannot quite visualize what you have for wiring.

Posted March 26, 2012 link


Here is another post ... on page 2 and 3 are pictures of my thermometer setup except it doesn't show the inside where it attaches to the boiler ... inside I have a small piece of wood (let's call it a Popsicle stick - but it's actually a saxophone reed) glued to the side of the boiler to hold the TC bead against the boiler - a little hollow in the boiler side of the wood for the bead and some heat sink compound where the bead is and glue on the edges of the wood so the wood sticks to the boiler side.  Hope that gives you a visual since I don't have a picture of that part.
http://coffeegeek.com/forums/espresso/machines/569101
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,036
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Tue Mar 27, 2012, 11:37am
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

Great pictures to illustrate the device, just what I needed.  Do you know what the sensor is?  A thermocouple bead, and what type?  Probably does not matter except for curiosity.  Are you using one of these to "over the lip?"  I know that over the lip is described, and you do it, but it looks like there is an automatic crush of the wiring.

 
D4F also at
http://www.gaggiausersgroup.com/
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AndyPanda
Senior Member
AndyPanda
Joined: 12 Jul 2010
Posts: 769
Location: San Francisco Bay Area
Expertise: I love coffee

Espresso: Olympia Cremina, Various...
Grinder: Mazzer Major, Fiorenzato,...
Vac Pot: vintage Corey
Drip: AeroPress
Roaster: BreadMachine/HeatGun
Posted Tue Mar 27, 2012, 5:27pm
Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
 

I don't use this thermometer for over the lip (you talking about the PF?) because it is a $10 thermometer and not nearly as fast reading as my better TC.  (I think you need a very fast reading TC to get the brew temp because the water cools so damn fast when it hits the air).

I don't know what kind it is ... it is just a bead on the end.  But my standard TC (K type?  I don't really know what the types are) is one where if the bead or wire breaks, I can simply twist the ends together into a tight little knot and clip it short and it reads "almost" as good as the original bead did.  But the little cheap $10 one doesn't work at all if you break the bead and twist the wires together.  Plus the wires feel more stiff/brittle than normal wire (almost like guitar strings) -- so your guess is as good as mine what kind of TC it is.

Someone suggested (was it in this thread or another one) using the black rubber crema enhancer disk.  I've done this in the past and it worked pretty well but it is messy.  The advantage is you can use plain old water  (no wasted coffee) and get some ideas of temps while water is flowing (splattering).  But if you have coffee you don't mind wasting ... grinding, tamping like normal and setting the bead on top of the puck (some say the bead should be down inside the puck - I don't really know - I've tried it both ways - hate wasting the coffee) you can get a more real life flowing shot.
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