Best way to rig up 2 fermenters in 1 fridge for basic control of stable temps

Hi All,

I’ve recently set up this project to control temps in a fridge. I was lucky enough to have everything barring the fridge and heater to build a legacy build for the cost of a project box and thrermowell and it’s working beautifully… At the time the website was a little confusing as it still referenced the arduino despite the project having moved on so I googled around and threw.

I’ve now got my head around where the project is at the moment and am pretty excited about where it’s headed. Elco and the team have done a great job and i’m looking forward to building a full home brewery setup around the new platform when it’s available again and I’ve decided on the end game.

Anyway onto my query. I’ve been lucky enough to be offered a very large 6’+ upright fridge for £20 and although i’ve not seen it yet am confident I can get 2 x fermentation vessels in there one above the other. I’m planning to add a 2nd uno off the same pi (i’ve got that side of things covered I think) for the time being but will likely replace all of that once multi chamber is launched and I get started on the brewery.

I’m wondering how best folks think to wire sensors etc for this setup as it’s currently an unsupported deployment? I was hoping someone may have done something similar. I’m thinking have one of the beers with a thermowell and a chamber temp sensor as normal and that should at least keep both beers pretty stable at the set temp even if not spot on. It’s a lot better that the 8-12° my garage sits at at the moment. I’m not too worried about ramping temps or crash cooling at this stage and could always move a brew to my other chamber for this.

I’d also wondered about keeping the fridge permanently under my target temp and using heat mats under each beer with a second sensor with an arduino and brewpi process for each beer but not sure if this would work at all and it’s obviously pretty inefficient as the heat/cool would fight.

Are there any other options i’m missing with this setup or any pointers for which beer to monitor. heater will be tubular and at the bottom. Any thoughts much appreciated.


I would control one beer as normal and put the room temperature sensor in the second beer.
All of your control will be based on the first beer and the second beer is along for the ride, but they should behave pretty similar.

i have a 1 fridge, 2 fermenter setup… i have a “wall” type sensor in each fermenter, a chamber sensor, and a room temperature sensor…

in this arrangement there will be one “active beer”, and the other beer will be along for the ride… the main pain is swapping cabling between the active sensor, and the subsequent reconfiguring of brewpi

it is important to note that the main characteristics of the beer will be generated in active fermentation, so the remainder of the time in the chamber is ok at the less than ideal temperature of following the trend required for another beer… with ale yeast the range between two different yeasts is still fairly comparable, so the swings are often within the range and are slowed by the thermal mass of the volume of beer

i’ve found the setup, as pictured below, to produce excellent beer

I would assign the room temperature sensor to the beer that is along for the ride. Then you do not have to swap the cables, only the sensor functions in device manager.
This is quick to do:

  • Set function to None for both, do not refresh list. Reassign functions.