So I have taken an old fridge with the freezer on the top and am in the process of converting it into a kegerator. I have cut out a large hole in the center divider of the fridge and freezer to basically turn the unit into a freezer...I still have the original wiring and thermostat running the fridge at the moment but I was thinking about hooking up my Johnson A419 to the fridge. Would that be better to do and set the temp probe into a glass of water to read the temp? Also, I purchased a 120V computer fan that I intended on hooking up into the light wiring of the fridge so that that the fan helps pull the cold air down into where the kegs are sitting. Is this recommended or will the fan produce too much heat and then defeat the point of what I was trying to achieve? Lastly, I was planning on hooking up the faucets to the front of the freezer door instead the door on the fridge so that I do not have liquid lines moving and in the way when I need to open the fridge door. Please feel free to throw in some suggestions. Thank you @billandsuz @IceAce
Your mods, including the fan, are fine. No need for an external Johnson controller. The thermal mass of the kegs will keep the beer temp from straying too far from the midpoint of the notoriously wide range of the built-in thermostat. If you were using it as a fermentation box, that would be different. For serving, you'll be fine.
You might not need the fan at all. Cold air is heavy and will fall to the bottom. Think of the open top ice cream freezer/display at the grocery. They don't even have a cover and as long as the product is below the cold zone it stays frozen. The heat generated from the fan would be insignificant. I believe the A419 probe is not water proof. Lines in the freezer box? Well, when the compressor is on the blowing air will be much less than 38, closer to 0. And even though it only takes a few minutes to get the box to 38, the 0 degree air in the freezer box might be enough to freeze the 3/16" lines. There is very little liquid in the line. Maybe it will be fine. Good luck.
Only reason why I thought of the fan was to simply add some effiency, (if that's even possible) since the fan will not be generating cold air, simply recirculating it. I was curious about placing the original temperature probe in water since the temperature won't fluctuate as much. However, that may be a bad thing as well. Since air temperature may be significantly warmer? I have the electronic assembly that controls the fridge still attached and have it resting towards the bottom of the fridge since the temperature probe is on it. I currently do not have the computer fan running in there and the air temperature is reading 36 degrees and the setting on the fridge is at 2.5!! So I guess my plan worked. I wonder if I have decreased the lifespan of the compressor by doing what I did? Regardless, I'm not trying to freeze, so it may not be too bad. I planned on insulating the inside of the fridge even more to try and be more efficient since my fridge is in a really hot Texas heat garage.
You'll actually be creating a problem here. With this setup, the compressor will not turn on (or off) until the liquid temperature reaches the extremes of the thermostat. Granted, you'll be using a much smaller quantity of water than a keg of beer, but this is more likely to result in a perceivable swing in beer temperature. Controlling the liquid temperature corrects a change in the liquid temperature, while controlling the air temperature prevents a change in the liquid temperature. That said, if you envision opening the door frequently, this will reduce the cycling of the compressor somewhat, which is a good thing. As to your mods decreasing the lifespan of the compressor, consider that it was designed to achieve freezing temperatures in the freezer box. You've actually lessened the load it was designed to carry.
