Multi-Purpose Fermentation Chamber

While there are tons of designs for fermentation chambers to be found, this build incorporates smart design, a clean look, and repurposed equipment to create a unique system.

DISCLAIMER: WE ARE WORKING WITH 115V. IF YOU ARE NOT COMFORTABLE WITH YOUR ABILITIES, CONSULT AN ELECTRICIAN OR SOMEONE WHO IS.

Looking back on my early years of homebrewing I can quickly recall the one improvement I made to my brewing process that took my beer from “meh” to “ooh, I didn’t make enough of this one . . .”

This wasn’t a particularly complicated or expensive upgrade either. As a matter of fact, I had picked it out of my neighbor’s curbside offerings one evening after work. If it wasn’t for the note left which simply read “Works,” I probably would have passed by this opportunity and who knows, my homebrewery may have never reached its full potential.

Prior to that find, I tried every option out there to keep a steady temperature for my yeast buddies. A giant bucket of water with ice packs, in the tub with wet towels, close to the radiator, far from the radiator, in the closet . . . you name it. They all seemed to reduce the swings in temperature, but they left much to be desired. On top of that, the house I was living in was drafty and in the wintertime I’d have a hard time keeping fermentation temperatures in the mid-60s °F (~18 °C). Placing the fermenter near the radiator to maintain fermentation temperatures or for a diacetyl rest would help, but some mornings I’d often find my wort temperature had plummeted after the heat had shut down overnight. I’d have my fingers crossed that the temperature plunge didn’t shut down my yeast leaving me with an under-attenuated beer.

Sadly, that first refrigerator didn’t survive a house move I made, but shortly after parting ways I came across another similar opportunity when a friend was cleaning out a relative’s house. I had several modifications I wanted to make to provide me with a truly controlled environment.

I had several key objectives for this build. My primary goals were to create a fermentation chamber that was capable of simultaneously controlling both heating and cooling (dual stage), was multi-functional space, could be easily kept clean, and lacked wires running amok in the chamber. I had several secondary goals too. First was that I wanted to over-ride the thermostatic control in the fridge, not simply cut power to the whole unit like many fermentation controllers do when turning on and off. Also using my BCS-460 unit as a controller would allow me to maintain specific temperatures with targeted and timed increases and decreases in temperature during warmer and colder months. Finally I wanted my BCS-460 unit to control both my HERMS brewhouse and cellar. So this fermentation chamber needed to be controlled by a modular unit.

By overriding the thermostatic controls of the fridge, my BCS-460 tells the fridge when to kick on and off. For heating, I used a Ferm-Wrap™ unit that I installed into the air circulation duct located in the back of the fridge. This allows air to pass over the heating element, increasing its efficacy. By over-riding the fridge’s thermostatic controller, other components like the interior light and fan have power even when the cooling unit is not turned on.

And by keeping this chamber as a storage place for vital brewing supplies and parts that are often needed quickly during a brewing session, allows it to be multi-functional for my needs. Optimizing work space is often underappreciated, and difficult to maintain at times, but does help set the stage for an efficient brew session.

Build a Multi-purpose Fermentation Chamber

Materials

• (2) 25-amp solid state relays (SSR)
• Heat shrink butt splice connectors
• Heat shrink spade connectors
• 3 male aviation cable connectors with an appropriate number of female connector panel mounts
• 24” AWG 12 THHN stranded wire for heating and cooling
• AWG 18 THHN stranded wire for signal wire from BCS
• PVC or aluminum housing for relays
• Ferm-Wrap™ heating wrap
• Upright refrigerator/freezer with room for fermenters
• BCS-460 (or other PID temperature control device, there are manyto choose from e.g.. BrewPi/STC-1000)

Step by Step

1. SOURCE THE FRIDGE

The foundation of this build is the refrigerator or freezer (which is what I use here), so before getting into this build decide on the specifications that you’re after and start hunting. The primary consideration that needs to be made is the interior layout. Fitting a fermenter or two is the obvious criteria so be sure you know the dimensions of your fermenters. I was looking for something that had removable glass shelves. Wire rack style shelves are hard to keep clean and offer a tippy surface for small items. I’ve also found that a good deal of older upright freezers have the cooling coils built right into the shelving, making them impossible to remove without ruining the unit. Steer away from those. Check Craigslist, classifieds, or a great option is Habitat for Humanity’s ReStore. The one by my house almost always has working refrigerators/freezers in stock for reasonable prices.

2. BRING THE HEAT

With the cooling covered, I moved onto the heating side of the build. I had been using the FermWrap™ carboy heater for a couple of years at that point and was happy with the output as well as the thin, clean construction. To maintain my clean design mantra, I needed to find a location for the FermWrap™ that provides good heat transport as well as being out of the way. Luckily, in my freezer there was a false interior wall cavity/duct that drew warmer air from the top of the freezer down and across the cooling coils in the lower section. A perfect location for moving air around the interior. It also was conveniently located next to a wire chase way that enabled me to run wiring into the chamber without having to drill into the walls. I used aluminum tape to adhere the FermWrap™ to the inside of the back wall using my fingers and a long, curved stick.

3. LEARN YOUR WIRING

Perhaps the most critical part of this build is understanding what each wire’s role is in the operation of the refrigerator. Since we are, in effect, high-jacking the controls of the unit, knowing where to properly tie into the system is crucial. To start, I tracked down the wiring diagram for my particular model. Some appliances provide the wiring diagram conveniently on the back where the UL sticker is located. If no details are provided there, find the model number and start with the manufacturer’s website as the information from them is likely to be the most accurate.  I made sure to cross reference the diagram to my unit to confirm its accuracy and then traced each wire and labeled it to reduce the risk of cutting into the wrong wire. For this unit, I wanted to replace the built-in thermostat control with my own controller and avoid interrupting the operation of the door light, fan, or defrosting mechanism. To do that I simply located the wires running to and from the thermostat, cut them to leave as much excess wire as possible for splicing into later.

4. MAKE IT SMART

This starts with installing a set of temperature probes that will send instructions back to the controller. My goal was to get three temperature probes to monitor the ambient air within the chamber as well as two individual fermenters. I wanted a clean look, avoiding having wires sticking out of the door and ruining the fridge’s seal. The wire chase that I used for the heating pad supply line was in an ideal location for the temperature sensors. My hot-side brewing system is controlled using a BCS-460 Brewing Control System. I have straight mount 2-wire sensors that have been fitted with male 2-pin aviation electrical connector plugs. This allows quick and secure connections to my control panel. I wired in a set of mating female panel mount connectors to the back panel of the chamber. This allows me to move sensors around for accuracy and calibration checks or for easy replacement should a sensor fail.

5. FOCUS ON CONTROL

The BCS-460 has six individual outputs that can be switched on or off, with the guidance of as many as four temperature sensors. To programmatically control the cooling or heating the BCS outputs need to be wired to a relay, typically a solid-state relay (SSR), which acts as a switch to whatever is connected to it. When the temperature sensor tells the BCS that a change in temperature is needed, the BCS sends voltage to the appropriate output on the unit, which triggers the SSR to close the circuit turning the refrigerator or heater on. As this fermenter chamber can heat and cool, two solid-state relays — one controlling the cooling process and one the heating process — is required. A very similar setup can be achieved by using a dual-stage temperature controller (i.e. Ranco ETC-211000 controller, UNI-STAT, or similar), which has the relays built into the unit. But those devices will shut power to the whole chamber down, not just the cooling/heating.

6. WIRE IT UP

Now that all the wires for the cooling, heating, and temperature sensors are labeled and run to a central location, it’s time to make the final connections. I wired the SSR control units into a PVC junction box located on my workbench. I mounted the SSRs into the enclosure, cut two pairs of appropriately-sized lengths of wire and labelled each pair with a colored tape to mark the heating (red) and cooling (blue) leads. Then crimped a spade connector and butt connector on each end of each wire and connected one of these wires to each of the SSR terminals on the switched-side. Working on one circuit at a time, I wired the appropriate cooling or heating signal wire, which triggers the relay on and off, from the BCS output to the + input side of the corresponding SSR. The grounds (-) of the input side of the SSRs are wired together and run back to the ground on the BCS unit to complete the circuit. The BCS is capable of temperature control using a sophisticated PID-control feature but I found that using the hysteresis control with a value of 1 °F (0.55 °C) to be plenty sufficient at maintaining temperature and not cycling the refrigerator on and off too much, which can shorten its life-span.