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-   -   Using fermentation chamber? (http://www.homebrewtalk.com/f11/using-fermentation-chamber-378397/)

whoaru99 01-03-2013 11:49 PM

Using fermentation chamber?
I have a small chest freezer turned into a fermentation/lagering chamber. Do you just set the bucket/better bottle/carboy et al directly on the bottom of the freezer or put something under it...like a piece of foam board insulation or whatever?

b-boy 01-03-2013 11:52 PM

I just put it on the bottom of the freezer.

aiptasia 01-03-2013 11:53 PM

Just stick it directly in there. Make sure to tape the sensor of your temperature controller to the side of the fermenting container (carbouy, bucket, whatever). As the beer ferments, it's going to rise in temperature above the ambient temperature inside the freezer itself. Duct tape, I love it. :)

whoaru99 01-04-2013 03:34 AM

1 Attachment(s)
Here is my test setup.

At ~2 o'clock is a thermocouple for the temp control and one of the same for a datalogger setup to track the chamber air temp.

At ~4 o'clock is a fine wire thermocouple stuck to the bucket and covered with three layers of Reflectix double reflective insulation, also into the datalogger.

In the top is an immersion thermocouple that's in the water to about the same level as the external thin wire thermocouple, to the datalogger as well.

The thermocouple system is outputting the three channels to the datalogger once per second (1Hz is as slow as it goes). The temp control is set to 50F, with 5F hysteresis (+/-2.5F).

Started with the 5gal water in the bucket at 70F and the freezer temp at 50F, and am going to look at the data in about 18 hours (or ~24 hours after I flipped the switch on it all).

whoaru99 01-04-2013 11:45 AM

Point of the question, since I did't really say, was wondering if some sort of insulating pad under the container would provide more or less uniform temperature in the container.

maida7 01-04-2013 01:34 PM

I doubt it makes a difference

whoaru99 01-05-2013 04:13 AM

1 Attachment(s)
It may not affect uniformity, per se. If anything, maybe it'd probably slow the rate of cooling or warming

FWIW, here's the result of the data logging...the graph is a composite of two because I stopped the logging after ~23 hours to have a look at the data, then restarted it which started a new log file and I didn't take the time to attempt to append them.

As you see, the 5gal of ~71F water took roughly 33 hours to attain approximately the 50F setpoint. There was still about 1F difference between the pail temps and the average air temp in the freezer. The surface temp of the bucket and the immersion probe tracked very closely...they're essentially overlaid on each other in the sloped line. If there was fermentation going on don't know if that would still hold true. Also clear is the increasing amount of "off" to "on" time of the freezer as the pail temp got closer to the setpoint temp.

The two vertical lines toward the left are because I unplugged the thermcouples a couple times to do some curiosity checks with a thermocouple adapter and multimeter.

VladOfTrub 01-06-2013 12:52 AM

That's a very nice graph. The data is beneficial. It looks like you put about 2 months wear and tear on the compressor of the family meat pop freezer in 24 hours. I know that you are in the R & D stage. But, you may want to adjust the controller to change the cycling time of the compressor. With proper adjustments, you probably could have shortened the pull down time, without over shooting and kept the compressor running longer. Stop and go kills a compressor. The problem is that a meat freezer refrigeration system isn't designed the way a true ferm chamber system is designed. What you have, is a low cost freezer condensor, coupled to a very accurate electronic controller. Forcing the condensor to operate outside of it's design temps and pressures. The compressor never ran long enough to fill the evaporator with saturated refrigerant. A BTU is a pound of water up or down one degree, until change of state. You had about 40 pounds of water at 71 degrees, pulled down to 50 in 33 hours. You had a load of 840 BTUs pulled down in 33 hours. That isn't too good. In essence, you only needed to use the amount of power needed to run a 200 watt light bulb. You used way more energy than that everytime the compressor cycled. Due to the controller settings. The BTU output of the refrigeration system wasn't utilized efficiently. A true ferm chamber uses a balancing act between heaters and the refrigeration system to maintain close temperatures. Among other design features, that a 200 dollar meat freezer doesn't have.

whoaru99 01-06-2013 03:41 AM

I am open to suggestions on the temp controller settings.

Bear in mind the temp controller and thermocouple datalogging systems are separate. Since I'm using a just the On/Off control of an Auber PID, afaik, all I have available to change is the setpoint and hysteresis.

Considering the swings in freezer ambient air temp didn't cause any oscillation in the water temp at all, it would seem that more hysteresis wouldn't hurt anything from that perspective.

b-boy 01-06-2013 06:27 PM


Originally Posted by whoaru99 (Post 4745493)
Point of the question, since I did't really say, was wondering if some sort of insulating pad under the container would provide more or less uniform temperature in the container.

I did try using plywood for a base, but it wicked up a lot of moisture. I didn't want mold to start growing. I think a piece of plastic would work. I thought about using some plastic trellis from Lowes. It will lift the carboy off the bottom, but still let air circulate.

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