The Carrier HH12ZZ205 limit switch is a temperature-activated safety device designed to protect HVAC systems from overheating. It opens at 205°F to interrupt electrical flow and closes at 165°F to restore operation once temperatures drop to a safe level. Commonly used in furnaces, air handlers, and heating equipment, it helps maintain proper thermal control. This switch enhances system safety, prevents heat-related damage, improves operational reliability, and supports consistent performance while reducing maintenance requirements and extending equipment lifespan