What is the significance of the cad cell in an oil furnace safety mechanism?

The cad cell plays a critical role in the safety mechanism of an oil furnace by confirming the presence of a flame. This component is a light-sensing device that detects infrared light emitted by a flame. If the flame goes out or fails to ignite, the cad cell will not sense the light, prompting the system to shut down the burner to prevent the release of unburned fuel into the combustion chamber. This function enhances safety by ensuring that the furnace only operates when there is a proper flame, thereby preventing potential hazards such as fire hazards or the build-up of dangerous gases.

In contrast, the other options relate to different functions or aspects of furnace operation. Preventing overheating primarily involves other safety devices like high-limit switches. Adjusting fuel delivery is managed by the fuel pump and control systems based on demand, and locking the furnace operation typically involves mechanical or electrical safeguards that prevent operation under certain conditions, which is not the primary role of the cad cell. Therefore, confirming flame presence is the essential function of the cad cell, making it a vital part of the oil furnace’s safety system.