Hey guys, I have a saison in the ferm chamber right now set at 90F, and I have to continuously top off the airlock with vodka because every time the heating function cycles, the airlock sucks back into the wort. I think my issue lies in the fact that I have the temperature sensor insulated against the carboy so it's measuring the temp of the liquid and not the ambient temp of the ferm chamber. The heater stays on for a while until the wort warms up enough, but the ambient temp must get pretty high during that time, creating a pressure differential between the chamber and the headspace and forcing the suck back. My ferm chamber is just an old mini-fridge with a hair dryer set on low for my heat source (and obviously the fridge's cooling system as the cold source).
A few primary questions/observations:
1. I'm not entirely convinced that setting the temp sensor to read the chamber's ambient air will make a big difference here. There would still be a decent temperature/pressure gradient between chamber air and headspace air, and I imagine suck back would still occur. Does anyone have any familiarity with temp sensor placement and this issue?
2. I don't think I could just use a rubber stopper or piece of foil or something like people do when cold crashing, since I'm raising the temps during fermentation. I guess foil would potentially work, but then during the hot cycle it would just be pushing all that oxygen back in (although that's essentially what it's doing now...).
3. For people that don't experience this: do you use a different heat source? I bet a carboy belt would not cause the same problem but I'm trying to keep the ferm chamber system as cheap as possible and we had a spare hair dryer on hand.
4. Epiphany: If I put a piece of insulated foam to separate the neck of the carboy and airlock from the bulk of the carboy (and hair dryer), would that solve my problem?
Lend me your thoughts and personal solutions!