So, with an ambient room temp of say 40F, a 40-watt bulb should keep my refrigerator at ale fermentation temp?Yes, leave the temp controller active, the fridge thermostat will probably not go UP to 60!
I understand that direct light on the carboy is to be avoided, but what about indirect, light that is reflected off the insides of the refrigerator, onto the carboy?
Using the coffee can method very little light escapes and it's all reflected incandescent so no UV problems. At 40deg ambient, my 25watt bulb works well. Any colder than that and I need to switch to the 40. With the 2 stage I will just leave the 40 in. It heats sooo slowly that the freezer can easily overpower it when the temp gets above setpoint. Just avoid the temptation to peek inside. All that warm air leaves the building quickly.