The Carrier HH12ZB250 auto limit switch is a temperature-sensitive safety control designed to protect HVAC equipment from overheating. It automatically opens at 250°F to interrupt the circuit and closes at 210°F to restore operation once safe temperatures are reached. Commonly used in furnaces, air handlers, and heating systems, it ensures proper thermal regulation. This switch enhances equipment safety, prevents damage from excessive heat, improves system reliability, and supports consistent performance while reducing maintenance needs and operational risks.