Uneven Fermentation Chamber Heating


I’ve tried to search through other posts to solve this problem, but I can’t seem to quite get the answer I’m looking for. I was hoping someone might be able to help.

I’ve got a large chest freezer that I use in my garage for fermentation and conditioning bottles. It’s right around 20-23 cu. ft., so definitely pretty large. I’ll have somewhere between 1-4 carboys in there at a time, as well as often a few cases of bottles. Being here in MN, right now I need to be heating it as the garage gets easily into the 20’s at night. I have a two-stage temperature controller to help with those spring and fall months where it is often necessary to go back and forth between cooling and heating during the days.

For heating, I use a small personal space heater with a built-in fan. I believe it’s rated at 1200 W, which is certainly awfully large for this, but it’s what I had. Currently I have the temperature probe taped to a large bottle of water in an attempt to somewhat match the temperature of the beer without having to move it from carboy to carboy every time and because I have multiple carboys at a time, it seemed to make sense. I have the heater place on one end of the freezer, on the floor, and the probe set a foot or two away and the carboys behind that.

Anyways, the problem I seem to be having is that the heater puts out a ton of heat when it’s on, raising my temp to the setpoint. Then after it shuts off, because it put out so much heat while it was on, the temperature overshoots by up to 2 degrees. I don’t find this to be a huge concern, but it certainly isn’t ideal. I’m fairly certain my actual beer isn’t fluctuating this much, but I’d like to have the control do what I want. Also, this makes it less convenient to set both heating and cooling because if I put the setpoints as close together as I would like, then the cooling kicks in after it overshoots, which I definitely don’t want. Ideally I would have both heating and cooling with 2 degree differentials and have it heat from (for example) 58-60 F and cool from 61-59 F or maybe 62-50 F. But with this overshoot, I have to leave a wider gap, which takes away a lot of the convenience of having the two-stage controller.

Just wondering if anyone has seen similar problems and might have an idea to stabilize things a little more. I thought about using a light bulb in a paint can or something like that so that it would heat more slowly and have less overshoot, but I’m not sure how much that would help. Or maybe there is a better way to arrange things with such a large freezer space to more accurately control and even-out the temperature.

Thanks for your help.

You can buy a ceramic heat bulb to run with the temp controller and run a small 12v DC fan constantly to keep temp even.

The only thing I can think of is that the residual heat from the heater coils after shutting off is enough to heat another couple degrees. Maybe a small fan for continuous circulation in there would help a bit.

And welcome to the forum