Freezer Fermentation Chamber Question

With the ambient temperature in my house being around 65-75 (Haven't turned on the AC yet) I purchased a freezer and an STC-1000. It all seems to work fine if I want to maintain an air temperature in the freezer.

I placed 5 gallons of warm water (75 degrees) inside and placed the probe against the bucket, placed a folded kitchen cloth on the outside, and tapped it up. The freezer kicked on immediately and kicked off when the probe read 20C. When I measured the temperature of the water with a lab thermometer, it reads closer to 31C. I tried a thin layer of bubblewrap underneath the cloth with similar results.

Is there a better way to insulate the probe to ensure it reads the wort temperature? Any thoughts on drilling a hole in the lid for the probe? Mainly, what effects would that have on the plastic probe and the risk of infection?

I drilled a hole in a white labs yeast vial, filled with water and put probe in it. I then took a block if wood and drilled a hole in it large enough to hold the yeast vial and insulate it from the freezer a bit. My probe reads +/- 1 degree f of my fermenter/keg temp.

It will take a little while for the large mass of wort/beer to equal out to the small vial so that may be what you're finding too. Cooling your wort down to fermentation temp prior to pitching can help you achieve steady temps faster.

Thanks, steady temperatures are what I'm looking for. This water was several degrees higher when I put it in and has taken longer than I expected to drop to the desired temperature. Given that fluids resist temperature change, I'm fairly confident in the setup's ability to maintain a healthy fermentation environment. However, I'm curious as to how quickly temperatures change.

For example, if I place 5 gallons of wort at 65f into a freezer that's also 65f and then immediately pitch yeast that's known to increase the temp by 5 degrees, how quickly will the yeast raise the wort temperature? From what I've seen in this setup so far, I'm certain it won't be as quick as the freezer cools the wort.