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Old 10-19-2012, 04:36 PM   #11
zeg
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One thing that can help with this is to try to couple the temperature of the fermenter as tightly as you can to the thermometer that's driving the thermostat. I usually ferment in a refrigerator, with a wired thermometer probe taped to the side of my Better Bottle and a thermometer strip near the bottom. From my observation, I believe the strip thermometer reflects predominantly the beer temperature, while the thermometer probe is heavily influenced by the air temperature.

What I find is that, when the refrigerator is going, the beer temperature can be 15 to 20 degrees higher than the ambient, and can hold this for a long time. This is simply because there's a whole lot more thermal mass in the beer than in the air in the fridge. Once the compressor cycles off, the ambient very quickly equilibrates with the fermenter and the two temperatures match. So in this case, there's no need to worry about the difference. The "ambient" is small enough that it's dominated by the fermenter. If I ran the compressor based on the beer temperature, it would probably save some on/off cycles, but that's about it.

If you're in a room, though, the fermenter makes almost no difference to the room temperature. It may raise the temperatures in its immediate vicinity, but it's going to take a long time for that to propagate out. As a result, the thermostat won't react to the fermenter temperature, as you've observed.

So, IMO, the most effective thing to do is to restrict the volume you're trying to heat/cool so that you can tie it very tightly to the temperature you're trying to control. Turning the room down to 50F because you're trying to cool a 5 gallon fermenter is a bit wasteful...



 
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Old 10-19-2012, 04:47 PM   #12
Matt3989
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A thermowell attached to your stopper is really the best way, it gives a very accurate temp of the middle of the beer, i find those stick on strips to be a pretty terrible indicator typically



 
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Old 10-19-2012, 04:54 PM   #13
johngaltsmotor
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In my fermenter fridge I run a computer fan blowing at the carboy to improve heat transfer from the beer to the air. It's an easy way to keep things (more) equal. Plus keeping the fridge full of other things with mass (I store my Corny's full of sanitizer in there) so it doesn't cycle as often to cool the air. It's amazing how much insulation you can get from stationary air.

 
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Old 10-19-2012, 04:58 PM   #14
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Yet another reason why I use a ghetto water bath.

I can take the temp of the water and know it's almost the same as the fermenting beer. Water temp doesn't fluctuate nearly as much as air temp and is easily adjusted with frozen water bottles or swapping out some of the water with hot water.

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Old 10-19-2012, 05:11 PM   #15
OHIOSTEVE
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I have an actual room I built to ferment in. I have an ebay temp controller hooked to a heater and an AC. The AC side works perfectly if I attach the probe to the side of the carboy. I removed the front cover of the AC and pulled the thermistor wire out and put it into a tube with a light bulb in the other end. The controller turns on the bulb and the AC that way the sensor on the AC is fooled by the heat of the bulb and it will run down lower...how low I have no idea as I have had no need to test it yet.... However the heater side shuts off trying to raise the thermal mass of the beer. There is a safety switch I do not know how to bypass that will not allow it to run long enouigh to drop the temp low enough. My solution was to just hang the probe in the air. It works to keep the ambient at whatever temp i want it at. I set the ambient at 60 thinking a 4-5 degree difference would be about it.. this has shown me that there is a big difference in the ferment temp compared to ambient temp. This is good enough for me for now but like I said it would be pretty cool to be able to adjust temps remotely....
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Old 10-19-2012, 05:18 PM   #16
OHIOSTEVE
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http://www.gottabemobile.com/2011/08...-a-smartphone/

gotta be a way to make something like this work
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Old 10-19-2012, 06:44 PM   #17
zeg
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Probably possible. Though I think you'd be better off properly closing your control loop so that you can just set the temperature you want and trust the system to keep you there.

 
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Old 10-19-2012, 08:23 PM   #18
OHIOSTEVE
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i have no idea what that even means...see told ya I was dumb
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I started brewing 69 days ago, 35 gal so far. SWMBO hasnt complained yet! Better than the hookers, gambling, and crack I used to do, I guess.
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Old 10-20-2012, 02:54 AM   #19
zeg
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Sorry... The control "loop" here is the connection (however it's made) between the heater/cooler and the temperature of the beer that you're trying to control. It's a loop in the sense that you (somehow) measure the temperature of the beer, then apply heat or cooling, which then changes the temperature of the beer, which you measure, and react.

Currently, you have what I'd call a loose loop---you are not directly measuring what you are trying to control, so your system can't regulate the temperature very effectively. It sounds to me like you are trying to compensate for this by "inserting yourself" into that loop. There's not anything wrong with that. It's often easier to put a human in the loop than to develop a robust automatic solution. I actually do it with my refrigerator for fermentation. In my case, I set an outlet timer to turn the fridge on and off the right amount to keep the temperature where I want it. It sounds like your system is already more sophisticated than mine!

The downside is that it's a lot of work and, in the end, isn't very precise anyway. Thus, if I were in your shoes, I would try to fix it the "right" way. When I say "tighten the control loop," I mean I think you should sort out your heater issue so that you can stick your thermometer right on the beer and directly monitor the temperature you're trying to regulate.

I wouldn't really advocate overriding the safety on your heater, that might be there for a reason... But you could, in principle, find a way to limit how long it is asked to run in one go. If the beer hasn't reached the temperature target, switch off for a short time, then turn it back on. This isn't necessarily an easy thing to rig up, though. But it's just an idea.

 
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Old 10-20-2012, 03:33 AM   #20
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Thanks zeg...I understand now. yes I had it set up just like you are saying but the heater is an issue. I may need to invest in a bigger heater or find someone versed enough in electronics to by pass the safety switch safely.. I thought about a ferm wrap but right now I have 6-7 brews in there in different stages of fermentation. I usually monitor the newest brew that will be the most active. I may make a thermowell that goes down in the bung and drop the probe in that and see if that is any better.. thanks for the tips.


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