What does the suffix "KX" stamped on the side of an EA model thermostat signify?

The suffix "KX" stamped on the side of an EA model thermostat indicates that the thermostat is designed for pilot duty applications. Pilot duty thermostats are specifically intended to control devices that operate at a lower current and voltage, usually serving as control elements for other higher-power devices rather than driving a load directly. This feature is essential in settings where precise control is required, such as in food service equipment. The ability to manage pilot duty loads allows for efficient control without overloading the thermostat components.

The other options refer to different characteristics that don’t specifically relate to the "KX" designation. Power duty would imply a higher capacity for handling power loads, which is not the case here. High temperature range would indicate the ability to function at elevated temperatures, which is also not what "KX" signifies. Lastly, temperature sensor type would denote the specific kind of sensor used within the thermostat, which is unrelated to the pilot duty function denoted by the "KX" suffix.