Glycol Chiller Part II

open fermenter also know as a garbage can

In Part 1, we took a dive into how I engineered a DIY glycol chiller—a way to keep my fermenters cool without emptying my wallet. From repurposing an air conditioner to using a temperature controller and a humble light bulb to trick the system, the build is all about thinking outside the box and making sure my beer stays in that perfect fermentation temperature zone. But keeping the glycol chilled is only half the battle. Here in Part 2, let me show you how I circulate that cold glycol to maintain the ideal fermentation temperatures and make sure everything stays on track during the hot months. Let's get that cold fluid where it really counts.

Now that we’ve got a reliable reservoir of sub-zero glycol humming along in our Igloo cooler, it’s time to move that cold power where it counts: the fermenters. At the center of this operation is what I like to call the Command Module

—a black utility box fitted with three ST-1000 temperature controllers and corresponding electrical outlets. Each controller is assigned to a fermenter, with its own dedicated temperature probe immersed in the beer. Actually, the probe is not immersed, it's duct taped to the inside of the garbage can and then a food grade liner (bag) is placed into the garbage can so that the fermenting beer doesn't touch the plastic. But the sensor is in indirect contact with the beer through the plastic liner. Power flows in from a 110v line at the base, while the three sensor cables feed in from the fermenters, giving the controllers real-time temperature data.

Each outlet is split into two zones: the top socket handles cooling, and the bottom socket handles heating. When a controller senses the beer creeping above the set temp, it energizes the top outlet—simultaneously activating a pump and opening a solenoid valve. That’s the magic moment: glycol is unleashed, rushing through a garden hose coiled around a garbage can fermenter, drawing out the excess heat and returning to the glycol reservoir. If the beer drops below target? The bottom socket kicks on a heating pad tucked beneath the can, gently nudging the temperature back up.

It’s a tightly orchestrated dance of sensors, solenoids, and controlled chaos—all in the name of perfect fermentation.

Fermenter with water heater insulation

So yes—at first glance, and second for that matter, the whole setup might look like something cobbled together in a backwoods lawmower shed. It’s not shiny, it’s not stainless, and it sure won’t be winning any design awards. But what it is—is effective. This system controls fermentation temperatures with surprising precision, all at a fraction of the cost of the sleek, space-age hardware you’ll currently find in your online homebrew outlet. Case in point? I was able to crash cool my last India Pale Lager down to 40°F overnight—no sweat, no drama. Just clever engineering on a budget.

Cheers!