Which safety device is used to detect overheating in an HVAC unit?

The limit switch is a critical safety device in HVAC systems that plays a vital role in detecting overheating. It is designed to monitor the temperature within the system and will automatically shut down the unit if it senses that the temperature exceeds a predetermined threshold. This action helps prevent potential damage to the HVAC components or even catastrophic failures resulting from overheating.

When the air handler, furnace, or other heating elements begin to overheat, the limit switch acts quickly to interrupt the operation of the system, ensuring that temperatures remain within safe operational limits. This proactive measure is essential for protecting the equipment and maintaining safety for both the system and the occupants of the space.

While the other options also serve important functions within an HVAC system, they do not specifically focus on the role of overheating detection. A fuse primarily protects against overcurrent situations but does not monitor temperature. A capacitor is used to store energy and assist in starting or running motors but does not have a temperature-monitoring capability. A thermostat, on the other hand, regulates temperature settings for comfort control but is not directly involved in detecting overheating as a safety feature. Thus, the limit switch stands out as the correct choice for its dedicated purpose in preventing overheating.