Keezer Temperature Control/Probe Placement

[Arminius757]

Hello everyone!
So I just got done constructing my fermentation freezer/keezer. Basically, I have a STC1000 running the freezer to keep it at a constant temperature. The issue that I am facing is probe placement so that I can keep the freezer at a constant temperature without major cycling. Originally, I had the probe place in a 1 pint mason jar filled with water. This meant that the freezer would kick in about every hour to hour and a half for about 20 mins. I have read that using water isnt the best idea though, so I tried taping the sensor to a piece of insulation to the side of the fridge. This, however, cause the freezer to kick in every 15 mins for about 5 mins at a time. I am worried that I am over working my freezer. Should I return to using the water instead? Or Should I keep the shorter, but more frequent cycles going?
Overall, I have an STC1000 running the fridge and a brewpi system controlling fermentation. Keeping the fridge at an ambient temperature of about 40 and using heat tape, I can get 4 gallons of water to 65-70 degrees.
I just want to save my freezer for as long as I can. Where shoudl I put my probe to get could cycles? Or is it ok to use water in my case?

Thanks!

 

[day_trippr]

Major problem is the totally empty chest freezer. Tough to tame.
Once you get some thermal mass in there things get simpler.

The worst thing to do is couple the sensor to the freezer wall.
Second worst is to use some arbitrarily small vessel of water as a thermal reference when you're actually trying to manage the temperature of a much larger vessel of import.

So, fwiw, what I've done for years is pin the temperature sensor under a ~4" square chunk of inch-thick closed cell foam using a velcro strap around the carboy.

This way the controller is controlling wort temperature, the sensor has a high degree of thermal isolation from the "ambient" temperature inside the freezer, and there's a five+ gallon thermal mass that isn't going to move in a hurry.

Cuts the cycling down in a hurry...

Cheers!

 

[EcuPirate07]

I use a bottle of water with the prob inside. If you are just trying to keep beer cold that's the way to go IMO. For fermentation it's a different story. You want accurate wort temps then.

Also longer running time is better than shorter cycles, clicking on and off more often is going to wear out faster.

 

[Arminius757]

Ok do if I anchor it about half way up my keg with some tape and a good layer of insulation I should create a large enough heat sink to keep the fridge from swinging widely?

 

[jlindborg]

I have a foam koozy with the bottom cut out that I've wrapped around a can of beer (top and bottom of the can are exposed). I have the thermostat probe wedged between the koozy and the can. It seems to do a good job at reducing the cycling.