The Resideo L4006E1125 High Limit Aquastat is a temperature control device designed for hydronic HVAC systems, including boilers and water heaters. It operates by monitoring water temperature and interrupting the burner circuit when the set limit, adjustable between 100°F and 200°F, is reached, preventing overheating. Commonly used in residential and commercial heating equipment, it enhances system safety and reliability. Its precise control helps maintain optimal operating conditions, reduces energy consumption, and protects components from thermal stress, extending the overall lifespan of the heating system.