HomeRoast Digest


Topic: Sunbeam Vac pot tuning: a simple solution (7 msgs / 230 lines)
1) From: Dan
I got one recently and after adjusting the high and low thermostats got it to work well. But the upper globe had a very high temperature. (Don't ask me if the thermometer was correct etc etc-- it was and was double checked.)
The simple repeatable solution that I initially hated, but now like was to just put two ice cubes in the upper globe along with the coffee. (I always use 6 cups of water and 2.6 oz of coffee.) Icecubes are always the same temperature (tap water isn't), the same size and available. The result is water at 200-203 F each time in the upper globe and very nice coffee.
dan
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2) From: Doug Hoople
Nice work, Dan, and an ingenious solution!
Doug
On Mon, Apr 5, 2010 at 5:39 PM, Dan  wrote:
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3) From: Phil Palmintere
"...  Icecubes are always the same temperature ...  dan
I'm not sure why you say icecubes are always the same temperature.
--phil
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4) From: Allon Stern
On Apr 6, 2010, at 12:49 AM, Phil Palmintere wrote:
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Maybe his point is that the ice cubes from his freezer are a consistent temperature, versus the tap water which varies between winter and summer. I didn't read that as stating that there is a law of nature that ice cubes are always some particular temperature.
-
allon
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5) From: Phil Palmintere
Hi Allon,
I wasn't thinking about it as a law of nature -- more of a statistical
issue.
If I understand it correctly, a consumer frost-free freezer achieves its
"frost-free-ness" (to make up some words here) by actually heating the
freezer lines of the freezer compartment to above 0 degrees C about every 6
hours to melt the frost off... and that the payload of the freezer goes
through similar although not quite as dramatic freeze/thaw cycles to keep
the frost off them.
Thus, an ice cube's actual temperature, while still below 0 degrees C, might
undergo swings of 20 degrees every 6 hours or so.
And that's assuming the door to the freezer is always closed.  In my house,
it is being opened often to retrieve or store contents, which adds to the
variability of the temp of the ice cube.
In contrast, if the main water supply to most homes goes through miles of
underground pipe, the surrounding earth is a pretty big heat sink to cause
the water to reach a quite consistent temperature when delivered to the tap
(after you've opened the tap & let it run for a minute).
However, off-list someone politely pointed out to me that while the
temperature of the ice cube might indeed vary by 20 or more degrees in a
residential environment, at the end of the day the energy "absorbed" by the
phase change from solid to liquid (melting the ice) is so much higher than
the energy absorbed by first warming the ice from, say, -20 degrees C to 0
degrees C that the only thing that really matters in the real world is the
melting.
So, I guess the initial temperature of the ice cube is pretty much
irrelevant.   
--Phil
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6) From: raymanowen
You say " The result is water at 200-203 F each time in the upper globe and
very nice coffee."
I am sorely tempted to ignore the political scene, international terrorism
and posit that the temperature was not the "200-203 F" you imagine. That's
1.5% precision- Not with a meat thermometer that can't be calibrated or read
that closely and improperly installed.  A frangible device, poorly installed
with toxic contents sounds like a sequel to Poe's *The Pit and the Pendulum*
.
Without instigating quarrels, flaming, etc,- if the result already is "very
nice coffee," what more do you want?  For a certainty, if you keep tinkering
your results will change.  Some better, some worse.  Keep notes.  Small
increments in grind size, along with time and the mythical temperature
control make the brew.
Ice can exist at 30F, 20F, -20F, -40 with little effect on the =
ice bath
temperature. Ice absorbs most heat when it melts. (32 ice --> 32 wate=
r).
It's a stable temperature regulator only at 32 F. There is no regulation=
 at
any other temperature,
You would never use a precise Hg thermometer around food stuff, but note
that for basic research use, the proper calibration check procedure is to
fully immerse the thermometer body in the heated medium (water or oil) and
compare the 10% FS and 90%FS readings for  and Full Scale, against a
mercury standard thermometer. Most physical devices are non-linear and
useless at the extreme ends of their scales
Unless your thermometer is thus calibration-checked along with that of a
separate technician, the two can never duplicate each other's results, Most
people using cheap (<$100) thermometers or a bad installation, couldn't tell
the difference between 200F and 203F, if their life depended upon it.=
  If
the coffee already rates as "very nice," and you can repeat it stop talking
and start enjoying.
If you don't know anything about parallax scale errors, a digital
thermocouple readout probably won't help, given a poor initial installation.
How many grad students wanted us to instrument their projects with new
thermocouples, connectors and lead wire "for accuracy," for free. Beggy
choosers.
Cheers, Mabuhay -RayO, aka Opa!
Got Grinder?
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7) From: Ryan M. Ward
"Ice can exist at 30F, 20F, -20F, -40 with little effect on the=
 ice bath
temperature. Ice absorbs most heat when it melts. (32 ice --> 32 wate=
r).
It's a stable temperature regulator only at 32 F. There is no regulation=
 at
any other temperature,"RayO brings up a very good point here that I didn't =
even think to mention. It is a weird fact of nature(well, not that weird, t=
here are stranger facts of nature), that although water can take on any tem=
perature between melting point and boiling point- and ice can take on any t=
emperature between absolute zero and 0 Celsius, ice water, once it has reac=
hed a uniform temperature- is always 0 degrees Celsius(32 F, sorry- I exclu=
sively use Celsius and Kelvin temperature scales in life, I honestly never =
use Fahrenheit and don't know Fahrenheit temperatures very well, the one ex=
ception to this rule being that I steam my milk to 150 F, when I worked as =
a Barista, I was trained using Fahrenheit). =
This is why thermometers and thermocouple readers are calibrated with ice w=
ater that has been allowed to sit for 10 minutes- its pretty reliable. =
In fact, all the way up until the 50's the Celsius temperature scale used t=
o be defined in terms of the melting and boiling points of water(0 is melti=
ng, 100 is boiling) at standard atmospheric pressure. =
 =
-- =
Ryan M. Ward
*Note: This email was sent from a computer running Ubuntu Linux 9.10 (Karmi=
c Koala)http://www.ubuntu.com**Note: This signature was placed here by me and is not automatically-gener=
ated-annoying-end-of-email-spam placed here by anyone other than myself. I =
am a Linux nut and am doing my part to support open source software and the=
 Linux and Ubuntu communities by getting the word out with each email I sen=
d, I encourage you to do the same.
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