Would it be possible and effective, without causing undue stress to the keezer, to temperature control a second insulated chamber? I would like to be able to control fermentation temps and/or run casked ale (during the summer) at around 50°F. The Keezer is set around 1°C and is fairly large (fits 4 kegs, hump space contains bottles & CO2).

I'm mainly concerned with the fact that you're moving air, not heat per se. Is there a better way to do this (without spending a lot of money)?

  • 2
    I'm considering a reservoir of water in the keezer and a pump (controlled by a thermostat) that runs water through a coil in the second chamber. Whenever I get around to building it, I'll let you know if it works.
    – jcs
    Jun 14, 2013 at 23:48

4 Answers 4


Just had a cool idea, ya know the flapped contraption that connects the outflow tube from your dryer to the outside of your house? What if you connected a temp probe to your secondary temp control box and ran the powered end to a fan in your keezer, and put that fan in front of a similar flapped device that would allow your cold (or warm) air to flow into the secondary box when activated but then shut when the air flow stops? I think the concept is there but would be fun to play with!

I have learned from my own fermentation chamber build that airflow is critical. Originally I just attached a small fridge to a box and quickly realized the air needs to be moved around for it to be effective (think of a walk in cooler, you always get hit with a blast from the fan!), that might be obvious for some but it was an afterthought/duh moment for me.

Good luck Slacker man, sounds like a fun project!


You're moving air, and the air can be cooled or heated to form the basis of energy transfer between the two chambers. So the system will work at some basic level.

However, it may not transfer much energy between the chambers in relation to the efficiency and energy used. If the chambers are adjacent, then it might work, but if they are separated and you have ventilation air hoses connecting them, then you'll need a decent fan to overcome the static pressure.

The Volumetric Heat Capacity is the amount of energy stored per unit volume per degree. For air, it's about 0.001, and for water it's 4.17. So, for the same volume and temperature increase, water will absorb over 4000 times as much energy - this makes it a much more efficient carrier. When using air, it will absorb a little energy and quickly rise in temperature to match it's surroundings, stopping the heat exchange early. This can be overcome by using a more powerful fan, but then this implies more cost.

So, water carries more energy per increase in temperature. But water is not an ideal medium here, since there is a real chance of freezing. Mixing in 30% glycol/glycerine will reduce the freezing point to well below the freezing point of water. Of course, the downside with water is the additional hardware required - tube, pump etc.

Given that your goal is to make a simple way to chill a second chamber to 10°C from a 1°C source, then I think you can probably stick with using air. Just be sure to have both in and out feeds between the chambers to get the best airflow.


The guys making BrewBit did exactly what you are asking. Check out the first half of the "Dual Probes" video on their kickstarter page or on YouTube Pretty nice system they built.


There are a lot of projects like this, a quick search on homebrewtalk and I found this.

Maybe there are other/better methods out there, but this is a fairly easy build. So long as the secondary chamber doesn't have too much dead space, you're fine, and since you'll be custom building it that shouldn't be an issue. Just have a think about what will go in that chamber (soda kegs or carboys? etc) and build it to fit that particular shape with not a lot of overhead.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.