By stopping your unit from going on and off (short-cycling) so much, a time delay relay keeps it from wearing out prematurely. A time delay relay is also the perfect accessory for families that have children who like to play with the thermostat. No matter how often you change the setting on the heat/cool switch or the fan on/auto switch, you can't burn out your compressor. This is because the time delay relay won't turn your system on for 3-5 minutes after the last thermostat adjustment has been made.