Temperature Probe

For those that use a ranco or Johnson control in your kegerators, where do you keep you temperature probe? I know just leaving it hang in the kegerators is “bad” because the temperature can fluctuate easily. I’ve been taking my to the side of a keg, but I wanted to hear some other suggestions.

Are the probes water proof? Can I put a container of water in there and just let it sit in the water? The water temp should move that quickly if in say a milk jug.


Actually “just hanging it in the air” is the best. That’s the way fridges work. Set your differential to 3-4 degF and enjoy.

Putting it into another liquid just delays its effects.

Putting it into another liquid just delays its effects.[/quote]

Which I thought was the goal? By having it in a medium that stays stable when you open and close to door or lid keeps the fridge from cycling, put it more closely approximates the beer temps inside

In control theory you want your controller to be as close as possible to the medium being controlled. Delays increase the variation in the (beer) temperature. Depending on your controller differential you can place it 1. on or in your keg (you will want a very fine temperature differential - less than 1 degF), 2. in the air (which is cooling the keg) a differential of 3-4 degF is standard, or 3. in something else further from the beer (in temperature spread speak).

We don’t open the keg fridge all that much anyway. But if you do open the fridge, the air temperature will rise. And this increased air temperature will increase the beer temperature. It will also eventually increase the liquid temperature in the other liquid. So do you want to chill the air/keg right away or wait until the other liquid has warmed? Better to do it right qway. It optimizes/decreases the sways/variations in the keg temperature. If you wait for the 2nd liquid to rise (what differential?), the beer will begin to warm and it will take longer to chill.

Mine is strapped to the side of my keg with a piece of foam insulation over it. Simplest way to measure the temperature of the beer instead of the air. All the carbonation calculations are based on beer temps, not surrounding air temps which can fluctuate widely. If you keep your probe directly on the keg you can have a much smaller differential setting on your controller.

i have mine wrapped up in a cloth napkin and taped. i’m thinking this will buffer extremes. so far, so good, but it’s hardly a scientific endeavor.

Excessive on/off cycling of equipment will shorten its life. Unless the equipment has some sort of delay software built into its control function, putting the bare thermocouple out there is not a good thing. Insulating the thermocouple in either an insulating blanket or in a large thermal mass is preferred.

I have the thermocouple for my fermentation chamber buried in a foam block that is taped to the outside of my fermenter. The thermocouple is right up against the fermenter wall, but is shielded from the ambient cool air blast in the chamber. The thermocouple controls a fan that blows air into the chamber from the freezer compartment.

That’s the way refrigerators work. Check out your regular fridge.

Placing the sensor directly against the beer is good (especially for fermenting beer), but the differential is probably more than just hanging the sensor in the air. No reason it would short-cycle.