Johnson Controls Temperature Controller - probe placement question

I have the Johnson Controls Digital Temperature Controller installed inside a commercial cooler.

Previously I have taped my probe of my johnson probe to the side of my commercial cooler. I have a wireless thermometer, and I can usually see a stable temp (usually a little less than my set temperature on the controller, but not higher).

Recently I saw someone who tapes the probe directly to the side of the carboy.

I tried this, and now an hour later my ambient temperature monitor inside the cooler is reporting a much higher temp- 77F. The controller still reports 65F due to the probe being taped to the cold carboy.

Any recommendations on which method would be better for temperature control?

If you want to know the temperature of the wort/beer in the carboy, tape it directly to the carboy. Most of the time, when a recipe says to ferment at a certain temperature, it is for the temperature of the actual liquid. If you have the temperature probe dangling in the air, then you are only getting the ambient temperature.

And if you have it taped to the inside of the cooler, then you are only getting the temperature of the inside wall of the cooler, which may not be the same as the wort/beer.

I dont know about a commmercial cooler but my Johnston A419 probe is plumber puttyed to the ale pail in my chest freezer and reads consistent with ambient if the door isnt opended too much and fermentation isnt really active.

if you have a spot try putting it in a little cup of water to control the liquid temp and not the air temp..
Edit: LVBEN is right and i forgot to mention you can account for the fermentation temps by lowering thr setpoint by 5-7 degrees

LVBen said:

If you want to know the temperature of the wort/beer in the carboy, tape it directly to the carboy. Most of the time, when a recipe says to ferment at a certain temperature, it is for the temperature of the actual liquid. If you have the temperature probe dangling in the air, then you are only getting the ambient temperature.

And if you have it taped to the inside of the cooler, then you are only getting the temperature of the inside of the cooler, which may not be the same as the wort/beer.

Click to expand...

Truth

LVBen said:

If you want to know the temperature of the wort/beer in the carboy, tape it directly to the carboy. Most of the time, when a recipe says to ferment at a certain temperature, it is for the temperature of the actual liquid. If you have the temperature probe dangling in the air, then you are only getting the ambient temperature.

And if you have it taped to the inside of the cooler, then you are only getting the temperature of the inside wall of the cooler, which may not be the same as the wort/beer.

Click to expand...

Tape can be affected by air temp swings unless insulated. Plumbers Putty insulates and sticks in one shot.

Remember that fermenting wort produces a lot of heat, I tape to the carboy to control the temp of the wort. The temp in the chamber might be lower or higher depending on what's happeninbg, but you'll be guaranteed that your wort is at the right temp.

At first I just left my probe hanging in the fridge. Now I tape it to the carboy covered by some bubble wrap for insulation. I notice a difference with the temp, how stable it was and how often the fridge ran. Now when I open the door to check fermentation the compressor doesn't kick in.

Thanks everybody!

I like the plumbers putty idea and I will put it to use.