Jonathan and several other blog readers have been asking for this post for some time now. For those of you who don’t care about fermentation temperature controls this is going to be really boring (I’ve warned you). For those that do, hopefully my experiences can provide a nice blueprint for building something similar.
The goal of this project was to create a way to provide customized and stable fermentation temperatures for our beer. There are many great examples of converted chest freezers out there but we had a few unique requirements including:
- House our 2 sweet Blichmann conical fermenters
- Provide both heating and cooling capabilities so we could leave the whole setup in Jeff’s garage year round
- Easy access so we’d be able to take samplings for gravity readings
Our starting point was a freezer we found off Craigslist about two years ago. It has served us quite well, but the main issue with using it as is was that it wasn’t tall enough to fit a conical fermenter and the lip for the motor prevented us from fitting two in there. We began researching options for extending the freezer and there are many detailed tutorials from people who’ve built great “collars” that extend the height of the freezer. The key issue in our situation was the fact that if we increased the height too much we’d risk being unable to lift the conical fermenters over the lip and into the unit (at one point I actually exported a pulley/hoist system for this but it proved impractical the more I thought about it). After a few days of research I decided our best shot was to create a collar that could collapse on both sides and a platform on the bottom that would allow the fermenters to sit level with each other and high enough that they could be easily accessed.
Our next challenge was temperature control and humidity. Since chest freezers are built to be below freezing (duh) they typically experience a good deal of moisture and then ultimately condensation. The solution we’re currently testing for this is a plug-in humidifier. It cost about $20 from Ace Hardware and seems to be doing a decent job so long as we remember to plug it in every week or two (for it to “recharge”). For temperature control we wanted both heating and cooling. I had seen an example here of a dual stage controller but unfortunately we had a bit of a tough time locating one online. We finally ended up buying it from here and it seems to be some other more official part that someone has wired themselves (notice the very professionally looking “stage 1” and “stage 2” notations). For the cooling needs, obviously the freezer is what we use, but for the heating element we have been using a 150 Watt infrared heat bulb. I found this at the pet store and thus far it seems to work really well at heating up the the freezer. Granted we don’t have the most intense Georgia winters but due to the fact that it’s a closed and sealed space we didn’t have any issues with it retaining the precise temperature (except for the time that we forgot to plug it in!).
For the overall construction I used 2x6s and 2x10s. I glued 3/4″ foam board to the wood for an added level of sealing and insulation. As you can see from the pictures I used weather proofing foam/tape and weather stripping to give it a full, tight, leak resistant seal on the seams of the collapsible sides.
Honestly at this point there is nothing I’d change about the design yet. I’ve contemplated added some small fans inside to help circulated the heat (or cold) when either stage is operating but I’m not sure if that would be very useful (it seems like the temperature inside stays very consistent). We do have a sweet temperature/humidity sensor and plan to install that at some point for additional testing/monitoring. Eventually I’m interested in building a 2nd fermentation chamber off of this one somewhat similar to this. The 2nd chamber could potentially be where we place beers for additional aging or for bottle/keg conditioning when we need it. We’ll see.