I set up an Auberins controller to a smaller top mount refrigerator for my fermentation fridge. The controller can turn the fridge on and off and also a 100-300 watt heart source. I bought a 100 watt ceramic heat bulb used in reptile cages to do this, but after a quick test it seems that this takes a long time to heat up and cool down. I’m thinking this will cause an erratic temperature cycle. Will this work or should I just use a standard reflector bulb? Thoughts please.

i have used a small space heater with a fan which helps circulate hot air but you can not have the heater blowing directly on the fermentation vessel because the sides will become superheated before the entire temp reaches the cut off temperature. Not sure of the wattage on those things but i am guessing its over 300.

Drugstore heating pad strapped to the fermenter does the trick for me.

I found some 12' wide heat tape that works awesome and was cheap. THey sell it to put in reptile displays but it works awesome.

It's been my experience that you typically only need either heat or cooling at any one time. When the fermentation is active, you still may need cooling even when the ambient temperatures are low. OTOH, you may have to add heat as the fermentation wanes when the temps are relatively mild. You would have to set your trip points wide enough so that the heater isn't triggering the cooling to come on. If you go to a standard bulb (less watts) it will extend the heating times, but the swings should be gradual.

I've had good luck using a 50 watt bulb on all the time when the temps are 20-40 and the controller operating the fridge. My fridge is in an insulated but unheated building.

40 watt bulb in a chest freezer located in an attached garage. I don't see big swings, even when temps have been in the single digits in TX recently.