Chest freezer fermentation chamber

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.

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.

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 1-2º 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.

I don't think a 4º 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 3º over the set point.

I don't think your current setup is capable of maintaining temps within 1º
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.

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

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.

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.

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

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.

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.

Hi all, in my setup I hesitate to even tape the probe to the carboy. This is because the temp of the beer is going to lag behind the air temp in the freezer. So if you want to hit 70F in the carboy for a German Hef, if you have the probe attached to the carboy, the air temp in the freezer could drop as low as 65F or lower before the carboy cools down. Then, the air will still be cold and the carboy will continue to cool beyond where you want it. The best approach is to try to control air temp inside the freezer and either use a thermal well or a temp tape (fish tank thermometer) to find out what the differential is between your beer in the carboy and the air temp. Then adjust the set point accordingly. This will keep your beer from over heating or over cooling after freezer goes off. For this method, probe placement is important. If you have it too high in the air over the floor of the freezer, the freezer will be too cold. The set point will turn off the freezer and the walls will remain very cold and continue cooling the air, which will then continue cooling your beer. But, if you put the probe too close to the floor of the freezer, then the controller will turn the freezer off before the air has a chance to cool down. I set my probe about 2 inches from the floor. If I have my set point at 68, my beer is about 70ish. Also, the air at the top of the freezer is 70 and the air at the bottom of the freezer is 66, leaving the air in the middle the perfect 68. In live in SoCal where right now we're having over 100 temps, the freezer only cycles a couple times an hour.

Calman2k, You may be over analyzing this, the process your describing is used successfully by quite a few of us.