Dead a/c in fermentation chamber

[MikeSzwaya]

Hi all-

I just finished a fermentation chamber for my conical. It's pretty tight - fully caulked, 2" pink foam board, and spray foam for gaps. The cooling system is basically a new 5,000 BTU Frigidaire fra052xt7 controlled by a Ranco controller with the temperature probe in a thermowell. The chamber dimensions are 2'x'2.5'x'3' (15 cu. ft.). Pretty small.

I brewed a lager Wednesday and cooled down to about 63°. I set the Ranco at 55° with the A/C on High Cool & the max. setting. BTW, the temperature in my garage was in the mid to low 50's. Mt goal was to drop the beer to the mid-40's, pitch-n-aerate, and then ferment around 50 (Narziss).

The next morning (Thursday), 10 hours later, it was at 60°. I set a thermometer in the chamber to see what the air temperature is. I got home Thursday (now 24 hours later) and the beer was at 56° while the chamber itself was around 45°. I stuck a thermometer in the outlet air of the A/C and it was also in the mid 40's. It just didn't seem that cold.

From searching old posts on fermentation chambers and air conditioners, I was assuming that the air in the chamber would drop pretty hard, near 35-ish. I thought it wouldn't take *that* long to drop 11 gal of beer 8 degrees. But, I also read - somewhere - that A/C's don't work that well when it's cold out.

So I'm wondering, with ambient garage temperatures in the upper 40's to low 50's, am I asking too much of this A/C unit? Or is it not working correctly (if so, I need to return it sooner than later). Would I need one of those Coolbot's to force the temperature lower?

 

[Homercidal]

That sounds kind of low for an A/C to me. I think most people are fermenting Ale, in the low 60s with A/C units. Might be struggling to reach that temp.

 

[kladue]

Did you bypass the compressor controls or just switch power on/off with the controller. Unit may not fire up with low ambient temperatures or the cold side is shutting down on freeze up.

 

[MikeSzwaya]

That sounds kind of low for an A/C to me. I think most people are fermenting Ale, in the low 60s with A/C units. Might be struggling to reach that temp.

I'm not sure why not. The Coolbot people are claiming they can get homemade walk-in coolers down to 38-42 with an A/C.

Did you bypass the compressor controls or just switch power on/off with the controller. Unit may not fire up with low ambient temperatures or the cold side is shutting down on freeze up.

I did not bypass. I simply plugged the A/C into the Ranco outlet and am letting it turn the A/C on and off. I'm a little naive on how A/C's run. I assumed that if I set it on Max and turn it on, it will always discharge cold air. Will the unit not pump out cold air if the temperature is too low?

 

[jordanpace]

Yeah, make sure you bypassed the sensor in the AC or it will not fire up when temp is under 60 (depends the model).

 

[jmferris]

Will the unit not pump out cold air if the temperature is too low?

Having worked some time in the hotel business for a stint out of college, I am intimately familiar with a problem that is similar to this. Running an A/C too long on the maximum setting with the lowest temperature can sometimes lead to any condensation in the unit actually freezing up and blowing air that was either not as cold as it should be, or sometimes even hot.

Perhaps you can try backing off from the maximum settings a bit to see if it makes an improvement? You should be able to tell after a couple of hours if the air blowing out is colder or not. Not saying that this is ultimately your problem, but cranking an A/C to 11 is not always advisable, depending on the unit.

 

[integrator]

I was going to say take it off Max also...

 

[Homercidal]

I have a roof mounted AC unit at work, and it feeds several rooms. I only need the server closet cold in the winter. But the thing runs so much due to the thermostat being outside the room. It would ice up the unit and then there was NO cooling.

Now the thermostat is in the room and it runs less and is not icing up, and the temps are where I want them. I think you can run them too hard.

 

[3 Dog Brew]

I built one of these just recently and I can point out two things that may help you.

First, you need to bypass the thermistor that regulates the temperature of the unit. On mine, I picked up a unit that had a dial for the temperature control (rather than a digital control). Inside the front panel is a wiring diagram that showed me which to spade lugs to short together to bypass the temperature control. If you are uncomfortable doing this, then by all means, get someone who knows electricity and circuits to help you or formulate plan "B".

Second, I already had another fan (two actually) to recirculate the air inside the chamber when the A/C was off. I had to redirect the air from the fan to blow directly on the A/C coils to keep them from freezing the condensation from the air. Twice the unit locked up on me when the coils froze up and then the A/C fan couldn't pull enough air to defrost them. Lastly, make sure you have a drainage line for the accumulated condensation.

 

[hamiltont]

I have the same setup, pic attached. In the pic if you look inside the louvers on the side of the AC you can see a piece of copper tubing running diagonally. That used to be located in the front of the unit behind the filter. It senses the room temp and shuts the AC down ~60F. Carefully reroute it to the outside where it's always above 60F. I can get mine down to 32F ambient is a few minutes. Cheers!!!