Immersion Lid Temperature Controller

For the past few years I’ve been doing small batch brew-in-a-bag (BIAB); brewing 2.5 gallons (9.5 L) of delicious beer at a time, in my kitchen, by my lonesome. Something was missing in my homebrew life, and that was the social aspect of brewing with friends. Determined to start up a monthly collaborative “experimental brew” at my place, I began amassing oodles of excellent gear for a ¾-barrel BIAB system.

With the goal of being able to easily fill a 25-gallon (95-L) oak barrels in a single batch, I bought the Speidel 120L (31.7 gallon) HDPE fermenter. I tricked it out with some neat after-market gear (thermowell, etc.) and then began looking for cooling solutions — after all, we all know how important fermentation temperature control is!

Like many folks, I typically use a small fridge to control temperatures during fermentations, which works great, but the beastly 120L fermenter would not fit into any fridge I own. My first temperature control attempt was a set of two cooling jackets chained together, where the cooling jackets wrap around the fermenter and cold water is pumped through them. I found that trying to chill an HDPE fermenter from the outside with relatively small jackets was not going to work as well as I had planned. I had an especially difficult time lowering the temperature inside the fermenter at high kräusen. That quasi-fail led me to my next cooling solution.

I’d seen that some of the popular fermenter manufacturers make relatively costly drop-in immersion chilling setups for their conical fermenters. I knew I had to attempt to do this, so I began researching how I could create an immersion chilling system for my fermenter. I’m by no means a “handy” man, but I was able to put together a very nice custom system that actually works amazingly well, and was much less costly than an off-the-shelf system.

For my system, I used a low-cost 50 foot (15 m) stainless steel immersion chiller (3/8-inch stainless steel tubing) and cut the stainless tubing at the bend. I then attached a set of Brew Hardware’s TRUE Weldless Bulkhead with 3/8-inch compression fittings to the ends of the tubing. The end of the bulkhead that attaches to the chiller is a 3/8-inch compression fitting, while the other end of the bulkhead contains ½-inch NPT threads. After installing the fittings, I mounted them through drilled out holes in the fermenter lid and attached some Blichmann QuickConnector ½-inch NPT X ½-inch straight barb fittings. I then put a submersible pump in a cooler with ice water, and ran ½-inch vinyl tubing from the pump to the inlet of the chiller coil. A ½-inch tube is run from the chiller outlet back into the cooler. I leak tested the system and moved it into “production.”

I use a temperature controller to monitor the liquid temperature within the fermenter. When the temperature reaches a set value, the controller turns on the pump and flushes ice water through the immersed coil. Once the temperature is lowered, the pump is turned off. The natural “stirring” action of the fermenting wort helps the cooling process.

How well does it cool? I took 25 gallons (95 L) from 73 °F to 66 °F (23 °C to 19 °C) in under ten minutes during extremely active fermentation. If you can keep the water in the cooler cold, then you will have great success. For future iterations, I think I may put the cooling water in a bucket inside a small chest freezer. This may reduce the need to manually swap out ice bottles and cubes. Also note that you could fill the reservoir with warm water if you wanted to heat up the fermenter.

The concepts and techniques in this project will work in a variety of fermenters. The Speidel 60L (15.8 gallon) fermenter uses the same lid as the 120L, and is a good candidate for this project, as is nearly any bucket fermenter with a large lid. There are many places online where you can get stainless coils of various sizes, just make sure you get a coil that will fit through the fermenter opening and is tall enough to be submerged in liquid during your ferment.

For more cool brewing action and excitement, visit me on Instagram @aaronritchiebrewing and RitchieBrewing on YouTube.