Florida brewing: swamp cooler temp fluctuations

The momentary drop to 50 is not a big problem . . . it would takes several hours to change the temp of 5(?) gallons of liquid enough to harm your yeast. To get a better feel, put your thermometer in a 750 bottle filled with water and immerse that in the cooling water beside your primary. You will be surprised how slowly it reacts to water temp changes, your primary is even slower.

Brewing in Florida without a ferm fridge is tough. People have a hard time understanding room temp is 78+ and evaporate cooling is almost nonexistent. You are pretty much forced to use ice to control temps. But the tricky part is your primary is making heat when fermentation starts. Ideally you want to start your wort 1 or 2 degrees below fermentation temp. But as those yeast get busy they will raise the wort temp 4-6 degrees, which needs to be controlled. Then as fermentation decreases this will drop off. After all is done you want to raise the temp a few degrees for a diacetyl rest. In theory this can be accomplished with frozen water, but you'll be busy. I gave up and got the fridge.

EDIT: Just saw where you stated you had a 1 gallon batch . . . still no worries here, the yeasties may have felt the slightest shiver, but I would predict no damage.

 

Well, this coincides with a related topic that I just posted, and I can tell you that dropping my primary temp low enough, and long enough, for slush to form in the bottom of the bucket in the middle of fermentation has not harmed the yeast. I pulled the bucket out of the freezer, warmed it back up to where the liquid was roughly at my target ferment temp of 64, and fermentation went right on going as if nothing happened. Cold may make your yeast go dormant, and I'm guessing enough cold over a long enough period of time may do permanent damage, but dropping it to 50 for however long it is you spent at work should not prevent your fermentation from completing.

I don't know that there won't be any off flavors, but it won't go bad.