Fermentation chamber getting too cool

I'm setting up a fermentation chamber with an A419 control unit and a new GE chest freezer (7 cubic foot) The freezer is set on it's warmest setting.

The issue I'm having is that even though the control turns on and off at the correct temperatures, the freezer continues to cool even after the control unit shuts it off (which duh, I guess I should have known that) , so the temp in the chamber is dropping 10 degrees cooler than what I want and sitting there for quite a while. Has anybody else had this problem?

So right now the set point is at 40, with a 2 degree differential. So it kicks on at the point I expect, and shuts off at 38. But the temp in the freezer continues to drop after that and according to the display on the control goes all the way down to 30 before stabilizing and coming back up.

Also it seems like sometimes the control is starting up the freezer before the differential temp if reached. Not every time, but I've seen it doing that at least twice now. Anybody know what's up with that.

Anybody have any tips on how to smooth this out a little?

 

This is fairly common when using a temp controller. The thermal mass of the freezer (walls, floor, etc.) will naturally be colder than the air in the unit. Once the air reaches the desired temp, the unit will shut off. The walls will then continue to cool the air. In my ferm chamber (upright freezer), I just compensate a bit (set the unit a tad higher).

Are you running a fan in your unit? This should help to even out the temperatures.

 

Nope, no fan hooked up as yet. (That's a good idea though) What I did do was raise the set point a couple degrees higher than what I really want it to be, and tightened down the differential to 1 and it seems to be staying pretty tight to where I want it. Maybe it's just going to be a matter of playing with it to find the closest scenario to what I want.

Thank for the input dutch.

 

A fan will help with your issue. Before I had a fan in my keezer the temp would drop around 3C below setpoint. With the fan the drop is less than 1C.

 

Good to know, thanks Chris.

 

I originally posted this answer where you asked the question in another thread.....

If the freezer is empty, try it with some thermal mass and check to see if the liquid temperature is close to where you want it. There will probably be some residual cooling from the cold evaporator coil after the compressor shuts off. I think someone already mentioned a fan to help move the air around inside - I put one in mine and it seems to help.

 

Thanks junkster. I didn't your answer on the other post. But that is good info.

 

I keep my controller probe in about 2 cups of water, it seems to do a much better job than having it in air.

+1 on the fan