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HOMEBREW Digest #5113
HOMEBREW Digest #5113 Sun 24 December 2006
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
Re: fermentation temp ("Michael O'Donnell")
re: fermentation temp. (3rbecks)
Controlling Fermentation Refrigerator Temperature - Part 1 (Fred L Johnson)
Controlling Fermentation Refrigerator Temperature - Part 2 (Fred L Johnson)
Don't know where to buy pills? ("Advertise I. Spirally")
Three Philosphers ("David Craft")
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Date: Fri, 22 Dec 2006 22:06:01 -0800
From: "Michael O'Donnell" <odonnell at msi.ucsb.edu>
Subject: Re: fermentation temp
Jeff is wondering about putting a temp probe in the wort... I've never
done this, but instead, I take my temp probe, place it against the side
of my fermenter (a corny keg) put a piece of neoprene foam on the
outside of it and duct tape it in place. I haven't done enough
experimenting to see whether this keeps the temp close to the wort, but
when I do the same thing on my serving fridge, I definitely get less
frequent compressor action, and the temp seems to swing more slowly.
Incidentally, since this is one of the rare days when a bunch of spam
slipped through the cracks, I'd like to take the chance to raise a glass
to Pat and the other janitors for the fantastic job they do keeping this
list up, running and mostly spam-free. You guys are great, thanks!
moose o'donnell
santa barbara, CA
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Date: Sat, 23 Dec 2006 06:42:09 -0600
From: <3rbecks at sbcglobal.net>
Subject: re: fermentation temp.
Jeff, I use exactly that type of set up. B3 (I believe) has a 2 hole
stopper that has a stainless thermowell attached to one of the holes that is
about 18 inches long. I run the Ranco probe in the thermowell and control
the refrigerator from the actual wort temperature. I set the temperature
differential at 1 degree. About the only draw back to this set up is that
when the wort temperature rises above the set point (usually during the
early stages of fermentation), the refrigerator will run hard for a while
and it will overshoot the set point by a degree or two. It's due to the
thermal mass of the 6 gallons of wort, I suppose. At the beginning of
fermentation, I usually try to chill the wort below the set point because
I've found that if I leave it three or four degrees above the set point that
the over shoot is much greater.
This method is not perfect, but I feel that it's more accurate than my
previous method of controlling the temperature by regulating the air
temperature inside the refrigerator. I felt that the old way involved too
much guesswork, as I didn't really know the actual temperature of the
fermenting wort.
Rob Beck
Kansas City
Listening to someone who brews his own beer is like listening to a religious
fanatic talk about the day he saw the light.
- Ross Murray, Montreal Gazette, 1991
------------------------------
Date: Sat, 23 Dec 2006 09:28:49 -0500
From: Fred L Johnson <FLJohnson52 at nc.rr.com>
Subject: Controlling Fermentation Refrigerator Temperature - Part 1
There has been some discussion recently regarding where would be the
best location to place the temperature probe when regulating the
temperature of a refrigerator for fermenting. Some have suggested to
control the air temperature of the refrigerator, some have suggested
the wort itself by using a thermowell in the fermentor, others
recommend putting the probe on the surface of the fermentor and have
indicated that this would not work well on plastic because of its poor
conductivity. Some has suggested controlling the air temperature but
setting it to some temperature lower than the target fermenation
temperature to compensate for heat that is generated during the
fermentation. I would like to consider these various methods and would
like to hear other's thoughts on this. The following are mine.
All of the following assumes that the ambient air temperature outside
the refrigerator is considerably warmer than the target fermentation
temperature.
Let's first consider using a thermowell in the wort to regulate the
refrigerator. For example, we wish to ferment at 67 F and have
precooled the refrigerator to 67 F, but the wort is currently at 70 F.
The refrigerator immediately will begin cooling the chamber and will
continue until the wort reaches 67 F, which may take significant time,
depending upon the volume (mass) of the wort. The chamber could cool to
a very low temperature by the time the wort reaches 67 F. The wort will
then continue to cool well below the set point because the chamber
temperature is so low. The chamber will begin to warm at a rate that
depends upon the effectiveness of the refrigerator's insulation, and
the wort temperature will continue to decrease below the set point
until the air and wort reach the same temperature. The refrigerator
will continue to warm and will not turn on again until the wort warms
up to the switch-on point (e.g., 2 degrees above the set point). As
occurred during the cooling phase, the thermal mass of the wort will
cause the wort temperature to lag behind the chamber temperature. When
the wort temperature rises to the switch-on point, the chamber
temperature will be somewhat higher than the wort temperature. The
refrigerator will then begin cooling, and the on/off cycling of the
refrigerator will continue, with wort and chamber temperature swings
getting progressively smaller with each cycle until the temperature
swing is within the differential of the swith-on/swith-off points.
End of part 1.
Fred L Johnson
Apex, North Carolina, USA
------------------------------
Date: Sat, 23 Dec 2006 09:28:57 -0500
From: Fred L Johnson <FJohnson54 at nc.rr.com>
Subject: Controlling Fermentation Refrigerator Temperature - Part 2
Let's now consider placing the temperature controlling probe in the air
within the refrigerator chamber. As before, we've preconditioned the
chamber to be at the target fermentation temperature of 67 F, and the
wort is currently 70 F. When the wort first goes in the refrigerator,
the refrigerator may not come on at all or only very briefly because
the air temperature wouldn't change much. The wort will gradually cool
to the set temperature, and the refrigerator will cycle on and off at
about the same rate as it did just before the wort was initially
introduced. The chamber temperature will fluctuate little, e.g., +/- 2
F (depending upon the differential that is set), compared to the
example when the probe was monitoring wort temperature.
Neither of these two examples have included the effect of heat
generated by the fermentation, so let's consider that now. The problem
is created when the heat generated in the wort is not instantly
transferred to the air surrounding the fermentor. In the thermowell
scenario, when heat begins to accumulate in the wort, the refrigerator
will begin cooling, and this will occur sooner than in the case when
the probe is monitoring the chamber temperature. Having the probe in
the wort will more effectively minimize the rise in wort temperature.
However, at the time the refrigerator turns off, the chamber
temperature will again be much cooler than the wort temperature, and
the wort will tend to cool further, perhaps well below the set point.
The heat of the fermentation will work against this and will minimize
the degree to which the wort will chill.
The entire problem at hand is the result of non-instantaneous transfer
of heat between the wort and the chamber. The better the conduction of
heat between the two, the less will be the differential between the two
in either scenario. Stirring the wort during fermentation would also
help conceivably.
It seems to me that the best way to minimize temperature fluctuations
of the wort would be to:
1) use a very highly conducting fermentor--stainless steel would be the
best among the fermentors that are commonly available (glass, plastic,
steel), but silver would be the Cadillac. ;-)
2) pitch only when the wort is at the target fermentation temperature,
and
3) control chamber temperature, with the initial setting at the target
fermentation temperature, but continually lower the set point over time
during fermentation to offset heat generated by the wort and then
continually raise the set point over time as the rate of heat
generation decreases until the target fermentation temperature is
reached.
One would need to empirically determine how fast to lower the chamber
set temperature during active fermentation and thereafter how fast to
raise it as fermentation subsides. This would have to be done by
monitoring both the wort and chamber temperatures continually and by
experimentally (trial-and-error) changing the chamber temperature set
point throughout fermentation.
Comments and counter points are encouraged!
Is there anyone out there with a couple of YSI temperature controllers
and a spare computer to collect the data in my neighborhood? This would
be a fun and pretty easy experiment.
Fred L Johnson
Apex, North Carolina, USA
------------------------------
Date: Sun, 24 Dec 2006 06:20:12 -0500
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Date: Sun, 24 Dec 2006 12:42:33 -0500
From: "David Craft" <Chsyhkr at bellsouth.net>
Subject: Three Philosphers
Greetings,
On this Christmas Eve I am looking for Three Wise Men to help me conjure up
some Three Philosphers Ale.
I have made sour beers, cherry beers, and Belgian Strong Dark Ale, but am
wondering what best brings all this together into this wonderful beer??
Thoughts?
David Craft
Battleground Brewers Guild
Greensboro, NC
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End of HOMEBREW Digest #5113, 12/24/06
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