Cooling Thermostat TMP-1, C.A.P. Sometimes gardeners just need a simple device to control the temperature of an area, and a Sentinel Cooling Thermostat is a perfect choice. Any cooling device that operates on 120 volts and 15 amps or less can be plugged into it to be turned on and off when the temperature changes. Its temperature probe can be placed 30 inches from the unit, and it reads temperatures from 51 to 115 degrees Fahrenheit.