The thermostat is set up and running well for days and then starts to let temp drop 20 degrees less than set point. A daily occurrence not associated with the heater shutting down due to overheating or other malfunction....tried with multiple heaters. I am scrapping it.

ACF Greenhouses: I’m sorry to hear you received a defective thermostat. We have not heard of any other customers having issues with theirs and will be happy to replace it with a new one.