Test-Room Performance of Line-Voltage Thermostat

The line-voltage thermostat is the room thernostat most commonly used with in-space electric heaters. It may be used to control a radiant, natural convection, or fan-type heater rated up to 5 kW. The characteristics of the heater effect the thermostat performance and the resultant control of room temperature. This paper presents test data from an investigation of ten different makes and models of thermostats used to control six different in-space heating systems in a specially constructed test room. Test results are reported in terns of air temperature distribution, temperature swing, and cycling rate. The test results indicate that the thermostat operates as an ambient modulated thermal timer that cycles due to the intemal I2R losses in the switch. A graphic representation is presented to explain the excessive droop characteristic observed.