What does a cad cell do on an oil-fired furnace?

A cad cell, or cadmium sulfide cell, is a crucial component in an oil-fired furnace that plays a vital role in flame detection. It operates by sensing the light produced by the flame during combustion. When the flame is present and functioning properly, the cad cell generates a small amount of electrical current that signals to the furnace control system that the burner is ignited. If the flame goes out or fails to ignite, the lack of light will result in the cad cell not producing the necessary current, which prompts the system to shut down the burner to prevent the accumulation of unburned fuel, reducing the risk of fire or explosion.

This flame-sensing function is integral for safety and operational reliability, as it ensures that fuel is only supplied when a flame is present, allowing for efficient combustion and minimizing emissions. Other options, while related to the overall functioning of an oil burner, do not accurately describe the specific function of a cad cell.