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Old 08-09-2012, 11:46 PM   #1
High5Brewing
 
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I've been a member here for a little while, but never really posted. Reading many of the comments and questions on here has been extremely helpful!

Now on to my question...

I have a chest freezer that I use for fermentation temperature control. I use one Johnson temp controller to operate it for cooling, and one connected to a hair dryer to heat it when needed. My problem is that the heating and the cooling seem to overshoot their temperature ranges so the temp is constantly fluctuating between a few degrees. For example, I am currently trying to ferment at 65. The cooling controller is set at 66 with a differential of 1. The heating controller is set at 65, also with a differential of 1. The chest freezer will kick on...stop at 65, but then the temp creeps down to 63 after a bit, so the hair dryer will kick on. It stops at 66 but then the heat will slowing creep up to 67 and the chest freezer comes back on...and the cycle continues.

I have the temp probes taped to the outside of the carboy with a towel taped around it, so the temp reading should be fairly accurate to what is in the carboy.

Will this temp fluctuation affect my beer negatively? I guess I'm looking for suggestions from anyone that either has experience with this or has a chest freezer setup for fermenting. What do you use for a heat source?

Thank you to everyone that posts on here...I wouldn't be brewing as well without all of your input.

 
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Old 08-10-2012, 12:52 AM   #2
duboman
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I don't have a ferm chamber but it's my understanding the controller needs to be hooked up so it overrides the thermostat of the freezer and you should use a thermowell for the probe that is actually in the vessel so the inside ambient temp doesn't throw anything off.
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Old 08-10-2012, 01:56 AM   #3
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For mine I use only one controller. The chest freezer is in the garage. I set the controller to cut out at the set point, and when the temp creeps back up the compressor kicks back on and cools to the set point. The temp will get 1-2 colder than the set point but I think it just averages out.

For the winter months I set up the controller to heating, again to cut out at the set point. I use a reptile tank heating element that screws into a desk lamp.

I would suggest just using one controller set to cool, and let the temps average out, also when you tape the probe to the bucket put some bubble wrap on the outside of it so the air temp doesn't effect it as much.
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Old 08-10-2012, 02:32 AM   #4
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I don't think a 4 swing is going to hurt your beer.
I have a refrigerated fermentation chamber, but I do not use a heat source. Mine is programmed to turn on if the temp rises more that 3 over the set point.

I don't think your current setup is capable of maintaining temps within 1
IF this is something you feel you need my suggestion would be to replace the two controllers you are currently using with a single, dual mode controller (like the STC-1000)
AND purchase a thermowell for the temp probe so you are measuring the temperature of the liquid and not the container.

 
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Old 08-10-2012, 02:34 AM   #5
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I'm assuming you are fermenting at a volume of at least 5 gal?

Given the mass of the wort I honestly wouldn't worry much of a 2-3 degree fluctuation...is it PERFECT? No, but will it make a good beer go bad? No.

The ambient temperature may fluctuate, but understand the actual temperature of the beer takes much more time to change.

I agree with a previous poster: a thermowell is a sound investment. It will give one of the most direct temperature readings of your beer without being directly invasive.

However, good on you for trying to fine tune your fermentation conditions! If its an easy fix, go for it. Otherwise, pour another pint.

Cheers
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Old 08-10-2012, 02:41 AM   #6
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If you have room use a water bath in the freezer to buffer the shock. I use a Rubbermaid tote filled with water, the carboy sits in that. The 2-4 degree temp swings don't effect the water it evens out to what your looking for.

 
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Old 08-10-2012, 03:14 AM   #7
High5Brewing
 
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Schecter - yes, 5 gallon batches...sometimes 10 split among 2 carboys.

Thanks for the tips everyone. I like the idea of a thermowell, but not sure how I feel about having one more thing to worry about sanitization with. From what I've heard/read taping to the outside with bubble wrap/towels gets you really close to the actual temp in the fermentor. I think I'll try it without the heating side for a while. I just figured it would be good to have since i live in Indiana, and the temperature even in the garage can change significantly day to day.

 
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Old 08-10-2012, 03:27 AM   #8
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But c'mon...it's a GREAT excuse to expand upon your brewing gear!

I'm sure the brewing gods will smite me, but between you and me...

...(as long as you're getting no off flavors, your beer tastes great, and you're having fun...I think you're doing just fine. Take the simple advice given by the other great members here, and if needed expand upon the other advice and perhaps purchase a thermowell for more precise temperature readings).

There's always more batches to learn from. And if a beer ever goes bad, remember, marinated pork chops always taste good with a decent sear...

Cheers
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Old 08-10-2012, 07:01 AM   #9
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I have to disagree with the thermowell idea. The thermowell will give you even larger temp variences. Think about it, what takes longer to cool, the wort in the center of the carboy? Or the outside edge? By the time the wort at the center of the carboy reaches 66 degrees the outer edge may be at 60 or even lower. I use the probe taped to the outer edge and can hold my temp to within 1 degree. In my opinion this is the best method.

 
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Old 08-10-2012, 01:14 PM   #10
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I have found the best results with my temperature probe mounted on the outside of the carboy and covered with bubble wrap or other insulation. I have the heating cycle set to come on at 2 degrees below my desired temperature and go off 1 degree below. The cooling is set to come on 2 degrees above my temperature and go off 1 degree above. This gives me a 4 degree maximum swing while keeping the heating and cooling from fighting each other. After the freezer shuts off the cooling continues from the cold walls of the freezer until the temperature has dropped about another degree. When the heater shuts off the temperature rises very little as the heater doesn't have much warm mass to keep radiating heat. I keep air circulating all of the time.

This is sitting in my garage and the freezer runs only a 4-5 minutes about 6 times per day in the summer. In the winter the heater runs 10-15 minutes every hour or two.

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