A New NEMA Standard for Room Thermostat Test Equipment

This new equipment standard replaces one published in 1948. Significant improvements in the new equipment include a larger test chamber more suitable for testing line voltage electric heat thermostats and a chamber that operates in normal room ambient rather than 40°F. The equipment consists of an insulated test chamber in which air flow across a thermostat test wall is maintained at 30 ft/min. Adjacent to the chamber is an instrument panel which contains the appropriate control systems. These controls record, program, and provide electrical loads for testing specified thermostat characteristics. During performance testing, the test chamber air temperature is automatically increased or decreased at preselected rates upon demand of the test thermostat. Thermostat characteristics observed during testing are 1) operating differential- difference in temperature between cut-in and cut-out of the thermostat, 2) cycle rate-number of full cycles per hour, and 3) effective operating droop-difference in cut-in points when operating at 20 and 80 percent duty cycle. The results of the new equipment provide a uniform method of testing room thermostats and therefore consistent means for comparing one thermostat performance to another under many different conditions.