What component is responsible for the ignition in a direct spark ignition system?

In a direct spark ignition system, the component specifically responsible for the ignition process is the spark electrode. This part generates a spark that ignites the air-fuel mixture within the combustion chamber of the furnace. The spark electrode creates a high-voltage electrical discharge, which leads to the ignition of the gas when it is released in the presence of oxygen.

The functionality of the spark electrode is essential for the system's operation because it initiates the combustion process, enabling the gas furnace to begin heating. This method of ignition is crucial in many modern gas appliances, providing a reliable and efficient way to light the burner without the need for pilots or flame sensors found in other ignition systems. The other components mentioned, such as thermocouples, hot surface igniters, and Venturis, have different roles in the furnace's operation, but it is the spark electrode that carries out the critical task of igniting the fuel.