Plenum fan and limit controls mount into the wall of a plenum and control when the blower fan is turned on and off. They feature a temperature probe that inserts through a hole in the plenum and measures the temperature of the furnace airstream. Depending on their configuration, they can have fixed or adjustable trigger temperatures.

Surface mount limit controls provide fail-safe controls for temperatures above the safety limit. They operate using temperature-sensitive metals that change shape and disconnect the connected circuit when the trigger temperature is reached. They are installed on flat surfaces using two mounting holes and fasteners to hold them in place. Depending on their configuration, their trigger temperature can be fixed or adjusted, and their reset can be manual or automatic. They are commonly used as protection devices to turn systems on or off when temperatures exceed or drop below their setpoint.

These fan controls mount to flat surfaces and operate fans based on surrounding air temperature. When the air temperature is cooled sufficiently, they stop the fan to ensure it only runs when needed to improve overall system efficiency.

Flame rollout limit controls are installed into a furnace or combustion heater and turn the system off when flames are detected outside the combustion area. This prevents furnace runaway and flames from spreading beyond the combustion area.