Thermocube sells plug adapters for turning on heaters and fans at preset temperatures. The plug adapters are $12.99 at Ace Hardware and Tractor Supply or can be ordered direct from Thermocube. I heated and cooled my Greenhouse last year with the cubes.

TC-22 Turns On at 120°F/49°C and Off at 100°F/38°C
TC-3 Turns On at 35°F/2°C and Off at 45°F/7°C

I used the TC-3 Thermocube to keep my plants from freezing. I plugged the cube into an extension cord and positioned it at floor level, since the floor is usually 10°F to 15°F colder than at bench height. Since there are two plugs in the cube I plugged in my 1200W heater and a box fan behind it to circulate the heat. When the floor temperature got down to 35°F the heater and fan tuned on and brought the heat up to 45°F or 60°F at bench height. I had a full greenhouse in February when night-time temps reached 5°F, and I never lost a plant from freezing.

I use exhaust fans for cooling located at the peak, so I plugged them into the TC-22 Cube and positioned it at the peak of the roof where it is the hottest. When the temperate reaches 120F (about 90F at bench height) the fan turns on, and turns off at 100F (about 70F at bench height).

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