Which materials are commonly used in modern hot surface ignitors (HSIs)?

Hot surface ignitors (HSIs) are critical components in modern gas heating appliances, playing a key role in igniting the burner. The correct choice highlights that silicon carbide and silicon nitride are commonly used materials for manufacturing these ignitors due to their favorable properties.

Silicon carbide is highly resistant to thermal shock and can withstand high temperatures, making it ideal for ignition applications where rapid heating and cooling occur. Its excellent conductivity allows it to reach the necessary temperatures to ignite gas quickly and efficiently. Silicon nitride, on the other hand, offers improved durability and thermal stability, further enhancing the performance and longevity of the ignitor. These materials can endure the extreme conditions of a furnace environment, enabling reliable ignition cycles.

In contrast, the other options consist of materials that do not possess the same level of thermal resistance or efficiency required for HSIs. Chrome and copper may not handle temperature fluctuations as effectively, while aluminum and ceramet have limitations regarding heat tolerance. Graphite and steel also lack the necessary characteristics for optimal performance in high-temperature applications necessary for reliable fuel ignition. Thus, silicon carbide and silicon nitride are the superior choices for hot surface ignitors in modern HVAC systems.