I wouldnt. I just check the fermometer on my carboy and adjust the temperatur controller accordingly. My fermentor can hold 4 carboys so individual monitoring is not an option.
With a normal temperature controller, you do not want the probe to read the temperature of the wort. Most controllers do a 3F range. Suppose you want your fermentation at 65F. If your probe measures wort temperature, the unit will cycle on when your wort is 65F and will stay on until your wort gets to 62F, then shut off. Then your wort will gradually rise in temperature back to 65F and it will repeat. All you are doing is introducing a fluctuating wort temperature - the bad news. The good news is that it is fluctuating near your optimal temperature.
The flip side is hanging the probe in the air. If you set the temperature at 65F, it will cycle on at an air temp of 65F and off when the air temp gets to 62F. In the time the air temperature changes those 3 degrees, the wort temperature does not change much at all. Temperature stability is one thing you want, but there is now a disconnect between your wort temperature and air temperature (at high activity, the wort temperature can be up to 8F higher than your air temperature and at the end it equalizes). So now you have stability (good) but the stability may be around a temperature you do not want (bad).
There are two solutions. If you want a stable wort temperature, then you want a probe to measure the wort and activate the compressor to start when the wort deviates by a small amount, say 0.1 or 0.2F, not 3F. Keep in mind that the surrounding air temperature may change several degrees to effect this change, so your compressor will not be constantly cycling on and off. The second solution is to estimate the normal air temperture to wort temperature differential during fermentation and adjust your air temperature accordingly. For example, assume you know that your wort will be 5F higher than the air temperature for the first day after fermentation starts, 3F higher for the next 3 days, and 1F higher until fermentation ends. Set your temperature at 5F low on day 0, raise it 2F on day 1 after fermentation starts, then raise it 2F on day 4. In the mean time, monitor the actual wort temperature to verify that your temperature changing schedule is accurate and adjust if necessary.
I do the poor man's version on option two now. I start with the fermenter in a bucket of water 4 inches deep with a towel draped over the top and dunked in the water (max cooling). After a few days, I take off the towel so I just have the cool water at the bottom of the fermenter (some cooling). After about 5 days, I set the carboy on the cool floor (minimal cooling). I check my temperature a few times a day (more the first few days), and it has been very stable since I started doing this.
If you want precise ferment temps, an electronic controller would be best so you can set the differential to 1F, not 3. If you put the probe on the fermenter and slightly insulate it from the air, a setpoint of 68 will kick the compressor on at 69 and off at 67. Not too bad.
There are pros and cons with all the different placement options.
If you want precise ferment temps, an electronic controller would be best so you can set the differential to 1F, not 3. If you put the probe on the fermenter and slightly insulate it from the air, a setpoint of 68 will kick the compressor on at 69 and off at 67. Not too bad.
There are pros and cons with all the different placement options.
This is how I do it. The compressor runs longer but not as often. Do any of the commercial controllers have the ability to have finer then 1 degree F? And if they did what would the wear and tear on your compressor be?
If I could do 1F, then I would probably do it this way too. I think truly you want is to limit wort fluctuation to around 0.1F to 0.2F, but with your method, you are probably getting this. The probe is mostly insulated, but not completely. The compressor kicks on and drops the air temp around, say 8 degrees, but since the probe is insulated agains the carboy, it only drops 1 degree and the wort only drops 0.1 degree and then the compressor shuts off. Perfect.
I just have the plain analog controller for my freezer conversion that I used for fermentation in the 50s and it is a 3F range, so I don't think I could do this. But if I ever go to a dedicated fermentation chamber I will have to consider it. Which controller are you using with the 1F range?
It's a sanitary stainless tube that goes through your stopper and into the center of the wort allowing you to slide your temp probe in. It reads the middle temp of the wort.
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