Freezer settings for fermentation

I have a 7 cu ft freezer and recently got a temperature control module for it, so now I can make lagers (yay)!

The freezer has a dial on the side that goes from 1 to 7 to control the temperature of the freezer. The owners manual recommends setting it to 4 unless you needed it cooler or warmer.

When using the freezer with an external temperature control module, does it make any difference what setting I put the dial on the freezer? Should I put it on coldest, highest, stay in the middle, or does it really not matter since the temperature control module will be doing its thing?

 

I reckon it doesn't matter. It's only going to go as low as you want it to anyways.

 

Unless it's one of the Igloo units - which are really more chest-fridge than chest-freezer - the thermostat range is likely between "Below Freezing" to "Way WAY Below Freezing".

That's how my recent vintage Frigidaire 13cf works...in which case you can set it to 1, 7, or anywhere in between and your external controller will still own the show in the range we use for producing beer...

Cheers!

 

Well...mine is going 10 degrees or more colder than the temp setting...any ideas?

 

A temperature probe dangling in an empty chest freezer is going to see the "over-shoot" that occurs when the compressor shuts off - with the evaporator loop full of dense vapor. That vapor will still expand and draw "heat" out of the food compartment, hence the over-shoot.

Otoh, if the probe was thermally-coupled to an FV and insulated from the air, it would show a much less "active" temperature curve as the thermal mass of the FV will dampen out the on/off spikes.

This temperature plot was just taken from my keezer. The squarish blue curve is the compressor turning on and off, the purple curve is the beer temperature, and the yellow and green curves are the air temperature at the top and bottom of the compartment.



You can see the air temperature swings rather wildly with the compressor, and continues to fall after the compressor shuts off, but the beer probe curve is actually quite smooth. That's the curve you care about and should be metering...

Cheers!

 

Slightly off topic but @day_trippr. How do you take these multi point temp measurements and store them ?

 

I cobbled together a temperature logger for the RaspberryPi I could get to from anywhere without depending on a subscription service.
Full write-up starts here...

http://www.homebrewtalk.com/showthread.php?t=469523

Cheers!

 

I use a Brews By Smith Fermentation Kit to control the temperature in my 7 cubic foot chest freezer and it works flawlessly.

I turned my chest freezer's built in controller to the 'minimum' setting to reduce the chances of overshooting the cooling cycle. Using a thermowell allows me to read the temperature of the fermenting beer, which is the most stable and reliable method of reading the true fermentation temperature.

The key thing I found out is that having two 6.5 gallon plastic fermentors inside the chest freezer provides the most accurate temperature control. With a single fermentor inside the chest freezer I noticed a larger temperature swing than I did when having two fermentors inside it.

For the heating cycle I placed the two square foot 32 Watt Fermwrap surface area heater underneath both fermentors. This combined with the freezer's 'minimum' cooling setting, has proved to be very effective in slowly raising the temperature and maintaining a 0.5F temperature swing in either direction.

 

I tried putting the probe down into a pitcher of water but that didn't seem to help much. Will try it with two 6.5 gallon fermenters of water in there to see if that may do it.

 

Is your freezer constantly 10 degrees colder than the temp setting, or is it swinging from above the temp setting, to that much below?

 

Had it set at 52 degrees and it was going down to 38 with the probe in open air in the freezer. Was going to 41 with the probe in a pitcher of water in there.

Put two 6.5 gallon fermenters with water in there, and put the probe next to a can of coke with 2 coozies wrapped around the can and probe. With a temp set at 52, it got to 50.6 and is at 50.9 now. I think everything is good now. When I brew, I will put the probe against the fermenter and wrap and tape it, and I think I should be good to go.

Appreciate the help guys!

 

When you're trying to apply steady temperature control to a vessel containing an exothermic reaction, that Coke can of water will tell you precisely nothing that you need to know.

Attach your temperature probe to your FV - whether using a thermowell, or strapping it to the side with a thick insulator over it.
Then your controller will be able to control what you actually care about - the beer....

Cheers!

 

This was all just me testing to see if the controller worked before I brewed.

My 1st attempt was just the probe in open air and it got way too cold. I adjusted the compressor delay and put the probe in a pitcher of water, but it was still being influenced my the ambient air temp in the freezer.

The coke can was just a test to figure out if the temperature controller worked. It appears it does, so when I brew I will attach the probe to the fermenter and insulate it with some foam rubber or something.