What does the cad cell detect on an oil burner to ensure safe operation?

• A. Supply Voltage
• B. Ambient Temperature
• C. Flame
• D. Combustion Air Flow

Answer: (C)

The cad cell is a flame sensor. It sits in the burner’s safety circuit and responds to the flame’s radiant energy. When the flame is present, the cad cell conducts enough current for the control to know the burner is lit. If the flame goes out, the current falls and the control shuts off the fuel to prevent unburned oil from accumulating. This is its job: verify that a flame is actually present. It isn’t measuring supply voltage, ambient temperature, or combustion air flow, which are handled by other parts of the system.