How to build a temperature-controlled closet or pantry

Precise temperature control during fermentation is a critical aspect of brewing high quality beer but it can be challenging to achieve, especially in warm climates where cold tap water is not available. BREWHA's Water, Beer and Wort Chiller is an excellent chiller that is perfect for regulating fermentation by running cold water through the 3-in-1 or 4-in-1 fermenter jacket. Some brewers, however, may want to regulate temperature through a cold room. This article was written by BREWHA customer Jim from Tulsa, OK, and describes why he repurposed a small closet in his house to make a cold room and provides instructions on how he did it.

I have thoroughly enjoyed reading the posts on Home Brew Talk about the 3-in-1. However the way others have been keeping fermentation temperatures under control just didn’t appeal to me, for one reason, the temperature seemed to fluctuate too much. So I have gone in another direction—I decided to cool a room to the desired temperature so the liquid will take longer to change temperature and will tend to stay steady.

A few years back I read about a device called a “CoolBot”. It allows one to turn an ordinary room into a walk in cooler using a window type A/C unit. As you know they are fairly cheap¸ easy to install, and work well in small spaces. The CoolBot tricks the A/C, by heating the A/C’s Temperature probe thus making the unit work much harder. The folks at “Store It Cold” state that the CoolBot can maintain temperatures as low as 38F in a 7’ x 12’F room. Restaurants, flower shops, etc. have been using them for years.

I am very lucky, as I have a small walk in pantry next to my kitchen. One wall is shared with my garage. So I turned my 4.5’x 5.5’ pantry into a walk in cooler, perfect for maintaining fermentation temperatures in the 3-in-1. It has an added bonus, it allows me to cellar my coveted stash of bottled brews I have collected from all over the US.

First I installed the window A/C unit high into the wall, venting into the garage. Then I installed a drain tube for condensation that would be collecting in the bottom of the A/C unit, ran power to a GFI protected electrical outlet, and covered the walls, ceiling and door with 1” foam core insulation.

Installing the Coolbot was a snap. There are three temperature probes and a power cord.

  1. Remove the front cover of the A/C unit.
  2. Place the icing probe into the cooling fins of the unit. This probe shuts down the A/C in the event the cooling fins get iced over. The A/C will turn back on once the probe senses the absence of ice on the cooling fins.
  3. The heating probe, it is placed to touch the A/C’s own temperature sensor and wrapped in aluminum foil. This probe is the one that tricks the A/C into cooling the room to your desired temperature.
  4. The last probe is the coolers ambient temperature and just hangs down.
  5. Power up the CoolBot.
  6. Program your desired temperature.

The CoolBot has worked flawlessly keeping the fermentation temperature steady. The room temperature may fluctuate a degree or two up or down. But because of the large volume of liquid in the 3-in-1, once the desired temp is reached it tends to stay there. I filled the water jacket as an insulator, which I think also helps keep temperature steady. I believe the water in the jacket behaves the same as the beer inside the vessel when cold crashing. I keep a vent tube on the water jacket at all times as I do not want to take the chance of creating a vacuum causing the jacket to deform.

You will notice in the photo to the left that I have the heat temperature probe placed into a bottle. I have found the temperature stays steady when the air from the A/C is not blowing on it. The room is so small that without the bottle, the air hits the opposite wall and bounces back, affecting the temperature reading.

I want to make one more change to the CoolBot which will be to lengthen the room sensor cable, making it possible to fit the sensor into the thermowell of the 3-in-1. I believe I will be able to keep the yeast activity temperature spike under control. I am not sure if this is necessary, but something I have been thinking about.

Now it’s time for a beer……Cheers


  • Well I have checked the Temp after a day and a half of running. The lowest it would get was 44 F.
    The two problems I have, is my room shares a wall with my garage which gets hot as you can imagine, here in Oklahoma. And my door is a hallow apartment style door. As for the BTU I cant remember the size.
    I would suggest checking the Cool Bot web site for the recommended size unit. I think another layer of insulation and a properly insulated door would go a long way to making my setup work for logering.
    I hope the info helps.

  • I have not tried to brew a loger yet. But I have just set my Cool Bot to 37f to see how low I can get the temp in the room. I will get back to you soon to answer the questions.

  • I am wondering what size AC unit Jim from Tulsa is using for his cooling pantry setup? I was using a 5,000 BTU unit and do not know if it can reach layering temperature. – Ron in Charlotte.

    Ron H

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