Which component of a rotary cup oil burner detects a primary air failure?

• A. Regulator
• B. Vaporstat
• C. Combustion chamber
• D. Ignition electrode

Answer: (B)

In a rotary cup oil burner, the vaporstat is a critical component designed to monitor and detect the flow of fuel vapor. When there is a primary air failure, meaning that the required amount of air for proper combustion is insufficient, the vaporstat can sense the resulting changes in pressure or vapor flow. If the primary air supply diminishes, the vaporstat will activate a safety mechanism to either alert the operator or shut down the burner to prevent inefficient combustion or potentially dangerous operating conditions.

The other components do not directly monitor the primary air flow. The regulator controls the fuel pressure, the combustion chamber is where the combustion occurs, and the ignition electrode is responsible for igniting the fuel. None of these play a role in detecting air failures, which is why the vaporstat is the correct answer in this context.