I am building a fermentation chamber and I was wondering if there is a way to have two zones but only use one cooler?

My thinking is have two of everything except the cooler. So there would be controller 1 heat 1 and a relay, then controller 2 heat 2 and the same relay. The relay would be plugged into the cooler. If either chamber was to hot the cooler would come on for both if that brought the other chamber down to cold then the heater would come on for just that chamber. Would this work or am I thinking it?

  • 2
    how big of temperature difference do you plan on having between the zones?
    – jsolarski
    Commented May 12, 2015 at 17:08

2 Answers 2


Although it would be wasteful of electricity, you could have two temperature zones in a single freezer with the higher temperature confined to a single carboy and the lower temperature dominating the remainder of the refrigerated space.

Put one controller on the freezer's plug and place its temperature probe on one side of the chest's interior. Set this controller to your lower temperature.

Put the other controller on the plug for a carboy heater belt and wrap the belt around the carboy you want at the higher temperature. Set that controller to the higher temperature and put its probe inside the carboy, near the center of the wort. Wrap the carboy and belt in a fire-retardant blanket to insulate them, keeping as much of the belt's heat inside the carboy as possible. Put that carboy, belt, insulation and all in the freezer, as far from the other controller's temperature probe as possible.

Put your cold-loving wort in one or more carboys and place them in remaining empty space in your freezer.

Over time, the freezer will attain the colder temperature which will chill all of the contained wort, including the contents of the belted carboy. The probe in the belted carboy will detect the undesirably low temperature and turn on the belt to heat the carboy. A little of that heat will escape the insulation and reach the colder probe, causing it to turn on the freezer to lower the undesirably warm temperature. A tug of war would proceed from there, wasting electricity, but keeping both sections of the freezers at or near their desired temperatures.

  • 2
    Thanks I'll just keep an eye out for a second mini fridge and build two chambers.
    – Michael
    Commented May 14, 2015 at 15:15

My concern would be that if you're going to construct this in a way to circulate the cool air, you will also be circulating the warm air. I don't see how you'd be able to make two zones that share cooling (or heating) elements that can remain effectively independent.

I suppose you could construct it a little like a refrigerator. Plan on chamber 1 always being colder, and sharing cold air with chamber 2. But that would run into problems if you needed raise the temperature in chamber 1. I would definitely not build the chamber to share a heater or cooler, unless I planned on keeping the chambers the same, or nearly the same temperature.

As to the controllers, I think that could work. I'd wonder what would happen if the controllers requested contradictory temp changes though. A lot would come down to your construction again and how the chambers share hot and cold.

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