Johnson Penn A19AAT Thermostat

Putting together a fermenter. I have an A19AAT thermostat sitting in a 15 cu ft freezer chest. I have been playing with this for hours now and have tried suggestions based on other posts (in water, suspended, etc.).

I seem to have a 10 degree variance between the thermostat setting and the internal temp of the chest. Set at 76F to get the internal temp to 66F. Has anyone else had this issue? Can you calibrate these things? I'm concerned because if it's defective, than I know I'm going to come in and see a bunch of frozen buckets one day...

 

You're going to get pretty big swings in the internal air temp if the chest freezer. That's normal. Air temp changes very rapidly when the compressor kicks on.

A better test would be attaching the probe to a carboy/bucket/fermenter of choice full of water. THEN see what kind of variances you get. Liquid temps change much slower than the air in the freezer.