Temp controller probe - what's the deal?

I bought this controller online, and installed it two days ago:
http://www.chicompany.net/freezer-c...3.html?zenid=b2eed32ecd44fcfaeb885413960985a8

I have a fully insulated fermentation chamber lined with 2" insulation foam and sealed with Great Stuff. Also, I'm using a re-wired A/C unit that turns the fan and compressor on whenever electricity it sent through the tail.

First, I put the probe in a 2L bottle of water and set it to 63F. It turned my A/C on for for a little bit, then shut off. Few hours later, ambient temp inside was 69F and the A/C was off.

Second, I taped the probe to the outside of my fermenting bucket and shielded it from any air movement. Came home 5 hours later, A/C was off and the ambient temp was again 68F - 69F.

Third, I left the probe out in the open near the bottom of the chamber and set the temp controller to 55F. 10 minutes later I check on it, A/C is still on, and the ambient temp is 64F (I have a digital thermometer inside the chamber). I turn the temp controller dial to re-set the temp at 60F, and it turns the A/C off...even though the temp inside is still 64F, not 60F.

Does it sound like a bad temp controller, or am I just using it wrong?

 

Did you make sure it was properly wired for cooling. (I know Chicompany says they are, but.....) What BTU air conditioner (main page says 8000 max).

I thought maybe the dial could be off temperature wise, but you checked for that. I'd see what other suggestions people have and if nothing fixes it, you might have a bad controller.

 

Thanks for the reply. My A/C is only 5350 BTU, so that shouldn't be an issue. Also, the controller has to be set for cooling otherwise it wouldn't turn on when I put my hand around it, or when I set it to something really low like 55F.

Maybe the dial really is off temp wise by 10^F or something. I'll set it to 53^F and see if that maintains a 63^F +- temperature. Good thought!

 

Would not be a big surprise for a cheap analog controller to be off calibration. My Johnson controller is 4 degrees off - not a big deal. Why not test it in a glass of ice water and then a some 100F water.

 

Before leaving home, when ambient was 63F, I turned it down to 50F and it kicked on. Stayed on until I set it to 55F, then kicked off. It looks like it is 10F off.

 

As long as the setup is consistent, you're fine. Just tape a reminder of the correction to the thermostat. Don't forget, the turn-on and turn-off temperatures are not the same. So, calibrate by leaving it set for a day, then make adjustments.

 

Thanks for all the advice. I came back after being out for a few hours and the chamber's ambient temp was a nice 61F. I'll probably set it a couple degrees higher, leave it a couple days, then put it back to 70F (well, 60F by the controller's dial) for it to condition.

Now the only question I have is, will keeping the chamber at 63^F for a few days for the sake of one actively fermenting beer do anything negative to the other two (and soon to be three) beers that have already passed active fermentation and are currently just clearing, etc?