Brew temperature offset for Erics thermometer

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rorym31
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#1: Post by rorym31 »

erics wrote:It is not so much that a machine is a double boiler (DB) but that in the majority of DB's out there, the brew water comes from a heat exchanger in the steam boiler. There exists lots of variables out there but starting a shot when the grouphead reads 197 F produces a 200 F delivery to the coffee.

I worked on a Vibiemme DB (a mix between Version 3 & 4) about a week ago and found that a TRUE brew boiler temp of ~ 225-226 F produced 200 F shots using a thermofilter. Grouphead temp was ~196-197 prior to shot initiation and all I did was a cursory 1 sec (or less) screen flush. Old habits die hard. :)
Hey Eric,

I have just purchased one of your thermometers to be used on my Rocket R58 V2 after struggling for a while with my boilers offset temp. After a bit of playing/practice with my warming flush routine I am now getting stable readings during the pour, with only a slight variance of 0.5F-1F, once the shot has come up to temperature.

My only question would be if there was an offset between the thermometer reading and the temperature of water actually hitting the puck? For example, lets say I wanted to achieve a temperature at the puck of 200F. What temperature should I be looking for on the thermometer and at what time during the pour?

Hope you can help!

Thanks,
Rory


...split from Brew temperature... again! by moderator...

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erics
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#2: Post by erics »

I have read your previous post as regards temperatures and assure you that a double boiler (DB) machine requires simply a cursory screen flush of 1-2 seconds prior to actually initiating the shot . . . leaning towards 1 second.

In your other post, you detailed a flush of about 6 ounces, grind & puck prep, and then another two ounce flush. YIKES!!! A major purpose behind a DB machine is to avoid this business of flushing. It is difficult to say what "most users" do but I believe that most prepare their drink of choice and leave the Portafilter in the machine until it is time for another . . . hence the cursory screen flush prior to brewing another.

The PID in the Rocket machine you have has a "built-in" offset of ZERO. They provide a table of brew boiler temperature that can be translated to a temperature of water presented to the coffee. Certainly this was accomplished after lots of testing on their (Rocket's) part. Brewing a shot in the manner I have described should produce results similar to the graph below:



Do you have a copy of the thermometer user's/installation manual ?? If not, it is available in my FTP site below my sig.
Skål,

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

rorym31 (original poster)
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#3: Post by rorym31 (original poster) »

erics wrote:I have read your previous post as regards temperatures and assure you that a double boiler (DB) machine requires simply a cursory screen flush of 1-2 seconds prior to actually initiating the shot . . . leaning towards 1 second.

In your other post, you detailed a flush of about 6 ounces, grind & puck prep, and then another two ounce flush. YIKES!!! A major purpose behind a DB machine is to avoid this business of flushing. It is difficult to say what "most users" do but I believe that most prepare their drink of choice and leave the Portafilter in the machine until it is time for another . . . hence the cursory screen flush prior to brewing another.

The PID in the Rocket machine you have has a "built-in" offset of ZERO. They provide a table of brew boiler temperature that can be translated to a temperature of water presented to the coffee. Certainly this was accomplished after lots of testing on their (Rocket's) part. Brewing a shot in the manner I have described should produce results similar to the graph below:

<image>

Do you have a copy of the thermometer user's/installation manual ?? If not, it is available in my FTP site below my sig.
Hey Erics - Thanks for this! Yeah I am new to dual boilers so my flush routine was embarrassingly off at first. I'll keep going with the 1-2 second flush...

The table I have in the booklet provided with the machine says that a boiler temp off 228F will provide a puck temp of 203.8F but yet I'm experiencing a temperature reading on your thermometer of 202F with a PID/Brew boiler temp of 230F. Which is leading me to believe that the chart is not accurate for this machine...or am I over analysing it? Should I not be seeing a higher temperature on the thermometer as per you graph?

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erics
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#4: Post by erics »

Thermometers sold by me to individuals have a small calibration tag attached (as detailed in the manual). All thermometers leave my house reading absolutely no more than +/- 1.50 degrees than what they should have read.

Water temperature presented to the coffee and grouphead temperature are different as detailed in the manual. One important fact to keep in mind is that changes in boiler temp obviously effect grouphead temp due to the thermosyphon action. The greater the magnitude in change increases the time it takes for the grouphead to react. For example, a one degree change might acclimate itself in a few minutes whereas a five degree change would take about 20 minutes. Any boiler temp change occurs within a few minutes at most. Grouphead temperature (which the thermometer reads) "rules the roost".

How did you acquire the thermometer?
Skål,

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

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erics
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#5: Post by erics »

The table I have in the booklet provided with the machine says that a boiler temp off 228F will provide a puck temp of 203.8F but yet I'm experiencing a temperature reading on your thermometer of 202F with a PID/Brew boiler temp of 230F. Which is leading me to believe that the chart is not accurate for this machine...or am I over analysing it?
I believe you need to put a little bit of faith in the numbers that Rocket has published. To simply verify those numbers would be a 24 hour task and, even then, one would need to know the calibration procedures, if any, that were employed.
Skål,

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

rorym31 (original poster)
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#6: Post by rorym31 (original poster) »

erics wrote:Thermometers sold by me to individuals have a small calibration tag attached (as detailed in the manual). All thermometers leave my house reading absolutely no more than +/- 1.50 degrees than what they should have read.

Water temperature presented to the coffee and grouphead temperature are different as detailed in the manual. One important fact to keep in mind is that changes in boiler temp obviously effect grouphead temp due to the thermosyphon action. The greater the magnitude in change increases the time it takes for the grouphead to react. For example, a one degree change might acclimate itself in a few minutes whereas a five degree change would take about 20 minutes. Any boiler temp change occurs within a few minutes at most. Grouphead temperature (which the thermometer reads) "rules the roost".

How did you acquire the thermometer?
I bought the thermometer from Chris' Coffee. It didn't come with a tag or manual...

I have kept my PID/Boiler temp at 230F since I have been using your thermometer. The thermometer has been reading 202F (give or take 0.5F-1F) since I have been using the new flush routine but I'm wondering with this reading what temperature would be actually hitting the puck.

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erics
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#7: Post by erics »

I bought the thermometer from Chris' Coffee. It didn't come with a tag or manual...
The manual is readily available from the CC website or from the link I previously advised. It does not come with a tag (from CC) because hours of tech time were expended to users who did not read the manual and were therefore unaware of what the tag numbers signified. All of this is explained in the manual.
Skål,

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

rorym31 (original poster)
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#8: Post by rorym31 (original poster) replying to erics »

Ok great, thanks Erics. Sorry if you feel I have wasted your time.

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#9: Post by erics »

You are certainly not wasting my time BUT you may be masking a problem. Best of all, you need not brew any espresso to POSSIBLY solve.

Check the grouphead region for scale as per this: Checking an E61 Espresso Machine for Scale . Clean/descale the grouphead interior and mushroom with white vinegar. Rinse thoroughly.

Set the PID to 223 F and let the machine be at idle with the Portafilter in place for an hour. What does the thermometer read?
Skål,

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

rorym31 (original poster)
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#10: Post by rorym31 (original poster) replying to erics »

Thanks Erics. I have checked the grouphead for scale but it all seems good. I've attached some images that I took of the mushroom and its chamber just in case you can see something I don't.

After leaving the machine at idle for an hour with a PID temp of 222F (The Rocket PID only has 222F or 224F as options) my thermometer read 190.6F.



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