Fermentation chamber heating

The only way to make this work is to have all carboys with the same fermentation schedule (i.e. same wort/yeast, pitch rate, desired temp). It would be nice to say you could have three totally different beers fermenting with different yeast and all maintaining a different optimum temp. But, that ain't gonna happen. In my photo above I have two different beers conditioning at the same temp (by design). If you really need to have multiple carboys fermenting/conditioning/aging with each at a unique temp you'll need multiple ferm chambers. Personally I drew the line at two ferm fridges. . . someone more enthusiastic might have three or four.

All you can control is the air temp surrounding the carboys. It's not unusual for a primary to have a +6 degree temp increase during active fermentation. Over time this drops, but the yeasties get to pick the time. As a brewer you get to make the wort . . . those little yeast-buggers really do make the beer . . .compromising their happiness will compromise your beer.

 

In that case, what @PortLargo said in the post above this one is right on. I think ambient temp is all you can reasonably control. (Or if they are identical batches, measure one and assume the second is close enough.)

But if you can managed to firmly attach one probe to two carboys (and insulate against ambient temp influencing the reading), my hat is off to you!

 

I agree. With multiple fermenters and one chamber, it can never be perfect. Under the heated air scanario (temp probe on a carboy, using heated air to regulate carboy temp) and multiple carboys fermenting, all carboys would need to be on the same schedule. I have two "identical" fermenters going right now, and one is fermenting more actively than the other. I think one has more wort but each got the same amount of yeast.

But to try to get back to the question, I think best case for how to measure temp (for the controller) is a thermowell, followed by measuring the the carboy temp, with controlling air temp being the least desirable.

For heat input, the ideal case is a completely uniform (around the carboy), gentle heat source. It's not desirable to make sudden changes in temperature, so a heat source that can only push the temp up slowly means that you don't need a PID controller to avoid big overshoots.

But if one was to start fermenting a batch today, and start another two weeks from now, they probably couldn't be in the same chamber and get optimal fermentation.

 

For fermentation buckets, I have used a floating fish tank heater attached to a temperature controller with the probe attached to the side of the bucket and covered with insulation.

 

Here's an example of a submersible heater, although I got mine for about $30.

https://www.amazon.ca/SUNSUN-JRB-25...6053800&sr=8-10&keywords=aquarium+heater+400w