Need help stabilizing chest freezer temperature

[HopDevil7]

Hi all. Long time reader, first time poster.

Background:
I recently purchased a chest freezer off craigslist to use as a fermentation chamber. This time of year in PA, my basement temperature is ~59-60 degrees (F). My goal is to stabilize a temperature ~68F. I purchased an inkbird and a thermowell which is submerged in a one gallon carboy set inside the chest freezer (please see attached pictures).

Issue: I cannot stabilize/control the temperature for the life of me. I have 2 degrees differential set both ways (heat/cool) and the heater turns off when the initial goal of 68 degrees is achieved. Then, it approaches 70 degrees (no heat/cool source activated) so the chest freezer turns on, gets up to 71-72 degrees and then begins to drop sharply to 65-66 degrees triggering the heat source to turn on. Repeat.. on/off/on/off etc.

Equipment I am using:
Temperature Controller: Inkbird Itc-308
https://www.amazon.com/dp/B011296704/?tag=skimlinks_replacement-20

Cooling Source: ~14.6 cubic feet Gibson Chest Freezer

Heat Source: Lasko #100 MyHeat Personal Ceramic Heater (200 watt)
https://www.amazon.com/dp/B003XDTWN2/?tag=skimlinks_replacement-20

Question: What can I do to get this thing stabilized before using for brewing? My initial thought is that my tiny space heater (200 watt) is still too powerful causing the water temp to rise another ~3 degrees after the 68 degree temp is reached (thus causing subsequent heat/cool/heat/cool cycles)

 

[aspiffymofo]

There isn't a lot of thermal mass to buffer that heater in your ferm chamber. It will be better once you put a full 5 gallons in there.

200W might be high for a heater (I think I'm using a heater mat that's less than 50W. You could also try the lightbulb in a coffee can trick for a heater and experiment with different power levels that way.

 

[TallDan]

The gallon jug is your problem. Measure Air temperature instead.

It takes much longer to heat and cool that jug, and by the time you hit target temp in the jug, the air temperature has gone beyond the target.

 

[beermanpete]

The compressor runs until the thermostat turns it off. Due to the longtime constant of the carboy full of water the air in compartment will get much colder than the water before the compressor shuts off. Also, there is some compressed freon in the system that will continue chilling the compartment until the system equalizes. It would likely work better to measure the air temperature and work out an offset to account for any temperature gradient in the wort due to the fermentation temperature rise.

 

[CGVT]

Edit: re read original post.

Take carboy and fill it with water, put your probe directly on the side of your carboy and insulate it from the air with bubble wrap.

Let it run for about a day and see if it stabilizes. If so, do the same with your fermenting beer. It will settle at your set temp.

 

[HopDevil7]

Thanks all for the advice. Any concerns with the power of the 200 watt space heater? I was thinking of downgrading to a 50-100 watt bulb or heat wrap and/or running a computer fan at all times to increase circulation.

 

[Doed]

Thanks all for the advice. Any concerns with the power of the 200 watt space heater? I was thinking of downgrading to a 50-100 watt bulb or heat wrap and/or running a computer fan at all times to increase circulation.

Run the fan all the time, that will help to keep things stable and help with condensation...a little.

I have a 1500 watt hair dryer in my chest freezer for heat so i don't think your personal heater is a big deal.

 

[PADave]

I have practically the same exact set up, and can hold 1 degree. When fermenting, tape the probe to the fermenter, insulate with some bubble wrap. Put lots of jugs of water where you got room, will act as a heat sink. I use a heating pad, under the jugs of water, for a heat source, very gentle heat, and about the safest option. But when fermenting, your heat source shouldn't even kick on, the yeast will be producing plenty of heat of their own. Only time my heat kicks on is after fermentation is done and I want to raise the temp to let the yeast clean up. Get a small fan, to circulate the air. And lastly, get a dehumidifier to suck up the moisture.

heating pad:
https://www.amazon.com/gp/product/B01CO9BDOG/?tag=skimlinks_replacement-20

fan:
https://www.amazon.com/gp/product/B009OXTWZI/?tag=skimlinks_replacement-20

dehumidifier:
https://www.amazon.com/gp/product/B000H0XFD2/?tag=skimlinks_replacement-20

 

[JONNYROTTEN]

Forget the jug.
Use the thermowell/stopper on carboy/bucket.
After brew day put primary in freezer with probe hanging in the air overnight,this will balance out the wort temp to the set temp on controller.
THEN put probe in the themowell to moniter temp the next day.
If you put the probe in a themowell directly after brew day with even a 2 deg temp difference the fridge will run for hours before it balances out.
If you have an early brew day check the temp before going to bed.
This is one of the benefits of a themowell. You can swap between air and wort temp by simply pulling it out of the themowell instead of dealing with straps and bubble wrap.

 

[HopDevil7]

I have practically the same exact set up, and can hold 1 degree. When fermenting, tape the probe to the fermenter, insulate with some bubble wrap. Put lots of jugs of water where you got room, will act as a heat sink. I use a heating pad, under the jugs of water, for a heat source, very gentle heat, and about the safest option. But when fermenting, your heat source shouldn't even kick on, the yeast will be producing plenty of heat of their own. Only time my heat kicks on is after fermentation is done and I want to raise the temp to let the yeast clean up. Get a small fan, to circulate the air. And lastly, get a dehumidifier to suck up the moisture.

heating pad:
https://www.amazon.com/gp/product/B01CO9BDOG/?tag=skimlinks_replacement-20

fan:
https://www.amazon.com/gp/product/B009OXTWZI/?tag=skimlinks_replacement-20

dehumidifier:
https://www.amazon.com/gp/product/B000H0XFD2/?tag=skimlinks_replacement-20

Thanks again all - I took several pieces of advice and was able to get this thing stabilized. I added a mini-fan which I plan to have circulating at all times. I wasn't really comfortable with the 200 watt space heater so I switched to a 24 watt heat mat mounted to the inner wall. I realize I was probably OK with the heater, but this just seemed a bit more conservative. I filled the chest freezer with carboys filled with water and cases of beer currently bottle conditioning to add some thermal mass.

TLDR version - she's ready..

 

[PADave]

Just curious, what yeast are you fermenting with that you want to be at 68? Looks like you got things down now. Part of your problem initially was trying to hold temp in an empty freezer. Air has nowhere near the thermal mass of a liquid.

 

[Rockn_M]

I use the reptile pad and it works great! When your fermenting just tape the temp probe to your fermentation container with a coozie or something to insulate and you'll have a great setup.

 

[jrcrilly]

I use the same controller and heater as described in your first post to control a 15cf freezer with no issues (always less than a degree from setpoint). I believe your problem is that the thermowell is exposed to far too much ambient air. As suggested above, tape the sensor to the vessel. That works every time.

 

[HopDevil7]

Just curious, what yeast are you fermenting with that you want to be at 68? Looks like you got things down now. Part of your problem initially was trying to hold temp in an empty freezer. Air has nowhere near the thermal mass of a liquid.

68 was more or less a "test" temperature I chose just to prove I could effectively stabilize the temperature in the chest freezer (in a 58 degree basement) prior to introducing 9 gallons of recently bottled beer in the process of priming (brewed in a closet). Many on here suggested a bottle conditioning temperature right around ~70 degrees. Additionally, I will be brewing a milk stout this weekend. The 68 number was based on this quick google search yielding:

"Normal ale fermentation temperatures range from 68 to 72 °F (20 to 22 °C)"

https://byo.com/bock/item/1869-controlling-fermentation-temperature-techniques

You are 100% right - the lack of thermal mass coupled with the thermowell submerged in the single one gallon container was causing the chaos. The 200 watt heater was probably not ideal either in this particular situation, but I later learned even the 200 watt heater did fine after the chest freezer was 75% filled

 

[HopDevil7]

I use the reptile pad and it works great! When your fermenting just tape the temp probe to your fermentation container with a coozie or something to insulate and you'll have a great setup.

I love it so far! Mine is 24 watts, any idea what yours is?

 

[HopDevil7]

I use the same controller and heater as described in your first post to control a 15cf freezer with no issues (always less than a degree from setpoint). I believe your problem is that the thermowell is exposed to far too much ambient air. As suggested above, tape the sensor to the vessel. That works every time.

You are correct - the lack of thermal mass seemed to be a critical component as well. I invested in the 24 watt reptile heat pad and it has been fantastic. What I like about it is it is a very gradual raise in temp. Not too fast, not too slow, and not having to worry about blowing hot air directly on any one particular carboy.

I did test it again with the 200 watt heater once there was a lot of thermal mass in the chest freezer and it seemed fine so the moral of the story is the heater wasn't the main/an issue.

 

[Rockn_M]

I love it so far! Mine is 24 watts, any idea what yours is?

Mine is 16W but it doesn't too cold for much more.

 

[IslandLizard]

The 68 number was based on this quick google search yielding:

"Normal ale fermentation temperatures range from 68 to 72 °F (20 to 22 °C)"

That alone tells you Google doesn't know **** about brewing beer.

Anyway, ales can be successfully fermented anywhere from 55 to 95F depending on the yeast and the beer desired. The majority probably between 62 and 72, where fermenting towards the lower end of a yeast's range tends to yield cleaner beer, generally.

I usually start out around 65F, but again, the actual temperature used depends largely on the yeast in use and the character desired. The first few days to a week, until around 70% of the beer has fermented, are the most determinative.