Which Johnson Controls unit...

I uses the digital model (A419). The main reason I use digital and not analog is that the A419's probe fits into typical thermowells. The analog probe doesn't.

 

I use the A19AAT-2C on my keezer, works just fine. I don't know how fine-tuned/accurate the analog model is, but it serves its purpose well in my application. For fermentation control, I have a minifridge w/ an insulated chamber attached in an uninsulated outbuilding, so in the spring and fall I need to worry about both cooling and heating during warm days and chilly nights. So I have to use a dual-stage controller, went with a Ranco. If I only needed to cool, I would have probably gone with the cheaper Johnson for that. Perhaps do a test run overnight...dial in the setpoint, leave a glass of water in the fridge, and then measure with a calibrated thermometer to see if what's on the dial of the Johnson is what the actual temp in the fridge holds at.

 

I use the johnson analog model because I only need to cool and it goes in a multi-bucket freezer. I keep it set to where it keeps the thermometer at 64-66F. Where it's set I can't actually read the dial, lol, because I'm going blind and the numbers are too small/the room is too dark. So I just kept tweaking it till it was keeping the freezer at the temp I wanted.

 

I use the analog in my keezer. It works for me. Once you set it up, you will never think about it again.

 

You cant use the A19AAT-2C because the differential is too large and your temperture swings will get too high. Go with a controller that allows you to adjust the differential. However, DO stick with a "differential" controller. Do not be tempted to use a PID controller for refrigeration. While they are excellant for heating (I use PID for RIMS controller) they cannot be used for refrigeration because compressors resond very poorly to be turned off and on rapidly. Most will just lag and refuse to cooperate. Look into Love and Ranco controllers.

 

That's a good one because it has two relays - a relay for controlling refrigerator and one for a heater. So if you put it in a garage in the winter, you can set it to turn on a heating device (heating pad/brewbelt or light-bulb-in-paint-can) when it gets really cold.

[Edit: and as you can see, you can set the differential between 1 and 30 degrees so you can avoid large temperature swings that a 5 degree differntial would cause - A 2 degree differential is pretty good setting refrigerators. 1 might be too low and cause the frige to turn on and off too often.]

 

I'm not saying that. A refrigerator cant warm itself if left outside in the cold. If the weather is cold and the temperature gets down to Zero, eventually the inside of the freezer will be cooled by the ambient temperature. Make sense? If you keep it indoors that isn't a problem.

 

That's correct.

 

I have two Ranco ETC 111000 controllers (single stage) that have worked well. They can be programmed to heat or cool (but not both at the same time). For cooling you set a min temp and a differential (say 6). If you set 60 with a 6 diff the controller will cut on the fridge at 66 and cut it off at 60. For heating just shift the differential: Heating at 60 with 6 diff would have the heater cut on at 54 and off at 60. I have used mine for cooling only, but it is easy to shift to the heat mode.

Before you spring for a two stage, consider how many times you need to add heat and cold in the same day.

It is very important to keep a respectable differential as described by Wicked when in the cooling mode. Normally I am around 6, but in the summer may have to go to 8-10. This is not a problem to keep your wort at a constant temp.

I see no reason you could not put the temp probe into a thermowell housing. Almost as accurate is a thermometer in a bottle of water which mirrors the temp of the wort.

You can get the single stage Ranco from eBay for about 50 bucks (unwired). Wiring is easy, check youtube for some pretty decent instructions and to see how others use this model.

 

Depends on what you're using it for. For fermentation, you'd want a small differential. 2 degrees seems about right on a homebrew level. For serving, with the large thermal mass of 5 gallons of beer (that doesn't produce its own heat like fermenting wort), 5 degrees is perfectly suitable.

 

Here's how to wire and program a Ranco (programming starts at 10:30):

 

That's true. I use a A19AAT-2C controller (5 degree differential) for serving. But even for fermenting you shouldn't go too low on the differential. I was saying that 2 degrees is usually a good range for a fridge/freezer - as in a range to keep it safe from over-cycling.

 

You can call me Ray.
And you can called me Jay.
But you doesn't has to call me Johnson.

 

This thread doesn't look TOO old so here's my question. Everything else is straight forward, however when it comes to my options of installing the actual temperature probe in the fridge, I'm a little weary. Did you guys/gals just snake the probe through the fridge door and mount it somewhere in the fridge? That seems like the only viable option I'm seeing, but I wanted to make sure there is not a better one before i actually unwind this copper cable.

Thanks,
Josh

 

I snake the Ranco wire through the door and into a thermowell that is in the fermenting liquid. The door will still seal just fine.
Annoyingly the fit is so tight that I cannot get the probe into one of my three thermowells.