**There are three temperatures listed on the interface. There is the water temperature, and the two surface temperatures of each heater. Watch for about ten (10) minutes to make sure neither heater gets more than 3-5 degrees Fahrenheit hotter than the water temperature. | **There are three temperatures listed on the interface. There is the water temperature, and the two surface temperatures of each heater. Watch for about ten (10) minutes to make sure neither heater gets more than 3-5 degrees Fahrenheit hotter than the water temperature. |