Getting an AC unit to run down to fermenting temps

[OHIOSTEVE]

If this is common knowledge or has been posted before I apologize. I have been trying to figure out how to cool my fermentation room down to the high 50's or even lower by using just a window AC unit. I was perusing the net and found this idea and was wondering if the brain trust here thinks it will work. I have an EBAY 2 stage temperature controller wired to a receptacle. One side heat the other cooling. The heat side did a perfect job all winter long. I am thinking about plugging a night light into the cold side, then attaching the bulb of the night light to the thermostat wire of the AC unit( the copper probe wire) That way when it is time to cool the room, the ebay conroller kicks electricity to the cooling side and the light comes on and the AC reads that it is 80+ degrees and kicks on. When my EBAY controller probe reads that the beer is cool enough the light will kick off and the AC unit will then be reading the ambient temp which SHOULD almost immediately turn it off. I also plan on keeping a fan on the AC to keep it from freezing up.
Ok why will this not work?

 

[mjmac85]

Can you place the ac thermometer in a different room?

 

[tektonjp]

Easy enough to test. Try it and let us know.

 

[raouliii]

Couldn't you bypass the AC thermostat and use your external 2 stage controller?

 

[mjmac85]

Yes but in this case if he wants it down to 65 degrees will the ac unit even turn on at 65 degrees? If not you need to trick it into thinking it is hotter than what it is.

 

[JKoravos]

Bypass the thermostat and the compressor will run until it dies or freezes the coil, whichever comes first. In low humidity conditions I've had my AC cool my fermentation chamber below 0°F.

The best option is to actually wire your controller into the AC in replacement of the thermostat, that way the AC fan continues to run when the compressor shuts down, which helps prevent icing on the coils. It's even better if your controller has a duty cycle setting so the compressor will turn off every so often regardless of whether the temperature setting is telling it to keep running.

 

[david_42]

I've seen this done with house thermostats back when setback stats cost half-a-car.

Bypassing the built-in thermostat is better, but not always possible. Is the A/C thermostat analog or digital.

 

[OHIOSTEVE]

I will probably use an old analog one that we had in the bedroom. I am not savvy enough electrically to wire the thermostat direct or anything like that so I thought this would be a quick easy fix, and I only need it to get down into the 50's so freezing up shouldn't be an issue.

 

[JKoravos]

Freezing will be an issue even at 50F if you have a humid atmosphere. The coils run below freezing regardless of what your set temperature is.

 

[OHIOSTEVE]

Ok< I have the AC installed and I can get the compressor to kick on and off by heating up the temp probe so this is gonna work.....not counting the possibility of the coils freezing up which I will deal with if it happens....now the issue is that being an analog AC the unit runs and blows air constantly. even if the heat side of the temp controller is on, the AC is still running because only the light bulb is plugged into the controller and the AC is plugged into the wall outlet. Could I plug both the AC unit and the light bulb into the cool side so the unit turns on and off with the bulb rather than running all the time and kicking the compressor on and off with the bulb? OR is this even an issue? ...

 

[mcl]

I just adjusted the thermostat "adjustment" screw. I then plug my AC unit into the outlet that is hooked up to the Ebay controller. I have tested mine down to about 42 degrees.

 

[OHIOSTEVE]

I just adjusted the thermostat "adjustment" screw. I then plug my AC unit into the outlet that is hooked up to the Ebay controller. I have tested mine down to about 42 degrees.

I have no idea how to do that

 

[OHIOSTEVE]

OK, the coils freezing up aside as it is still a possibility...it works. I plugged a small power strip into the cold side of the temp controller. Plugged a night light and the AC into the strip. ( this part is ghetto and will be replaced by a more asthetic idea) I stuck the night light in one end of a beer can..the thermostat probe from the AC in the other end and wrapped it all up with insulation. When I heated the temp controller probe with my body heat, the cooling light of the temp controller came on, and the night light and the AC kicked on. After running about 30 seconds, the compressor on the AC kicked on even though it is cold in the room right now.

 

[OHIOSTEVE]

it is working so far. Started a batch of skeeter pee on the counter top a few days back and racked it to a carboy today and stuck it in the ferment room and stuck the probe to the side of the carboy. It was initially 24degrees C and the light and the AC kicked on. it ran the temp of the skeeter pee down to 19 degrees and shut off.

 

[jpalarchio]

It's been done before, should work.

http://forum.northernbrewer.com/viewtopic.php?f=26&t=101991&p=904190#p904190

 

[OHIOSTEVE]

It's been done before, should work.

http://forum.northernbrewer.com/viewtopic.php?f=26&t=101991&p=904190#p904190

That is basically what I did except I enclosed the bulb and the thermister wire together. I wish I had used a digitl AC because they will shut completely off. This analog one will continue to run but just kick the compressor off.Thats why I had to plug both the light and the AC into the ebay controller.