My fermentation system uses an aquarium heater that goes as low as 67* F, which I have in a large tub in my basement. I place either my plastic or glass fermenters in the tub, fill the H2O to just below the level of the beer, and turn the heater on. With my basement temps this time of year in the upper 50’s I can keep my fermentation at a steady 67*. Also by using water instead of air to heat my fermenter I am able to keep my internal fermentation temperature within 1/2* of my H2O as shown by my thermowell. The drawback to this system is that I cant ferment in the 63-65* range. I havent found a heater that has a low end below 67*. So I recently bought one of the cheap Chinese temp controllers on ebay, unfortunately they can only be set in degrees celsius, which means if I set my low at 17c (62.6f) and my high at 18c (64.4f) my fermentation system will cycle up and down 1.8f every hour or two. Is this 1.8 fluctuation during active fermentation going to somehow stress my yeast, cause off flavors, or stall fermentation? Or should I stick with my original heater that gives me a steady but higher temp?
I think that 1.8* would be inconsequential. Just from active internal fermentation I believe the temps swing more than that. As long as they don’t swing above the temps recommended I would not worry.
If a 1.8 temp swing was enough to mess up a beer, there would be no home brewers. When a beer ferments, it will heat up a few degrees during the most active part of fermentation. People say as much as 5-10 degrees. Then when it slows down, it will cool back down to ambient temp. A 1.8 degree swing is not an issue what so ever.
I am aware of the temp range/swing duing the entire fermentation period, but was concerned about a 1.8*fluctuation temp swing every hour or so due to my controller turning the heat on at 62.6, and off at 64.4, cooling off, and repeating again in an hour or so later, for the entire fermentation period.
Nope, the yeast will be just as happy. And the volume of the beer will buffer temp swings so the actual temp shift is probably like 0.5*.