The main function of a time delay relay is to stop your unit from short-cycling or going on and off frequently. As a result, your unit stays away from wearing out prematurely. Many families have children who naturally like to play with the thermostat. A time delay relay is the greatest savior for them as it saves your compressor from burning out irrespective of how frequently you change the setting on the heat/cool switch or the fan on/auto switch. This is because no matter what, the time delay relay will not allow your system to get turned on for 3-5 minutes after the last thermostat adjustment is made.