mainbreaker

Mainbreaker, in electrical engineering and building infrastructure, refers to the main overcurrent protective device that controls power to an entire electrical panel or service equipment. It is the primary disconnect that can isolate all ungrounded conductors feeding the panel, providing a single point of shutdown for safety and maintenance. In residential systems, the mainbreaker is typically a large two-pole unit rated to common residential service levels (often 100, 125, 150, or 200 amps), though higher ratings are used in larger buildings.

Function and operation: The mainbreaker protects the service conductors from overcurrent and can be tripped automatically by fault currents or manually by the user. When opened, it cuts power to all branch circuits fed through the panel. In many installations, the mainbreaker is located at the top of a load center; some panels use a main-lug design plus a separate service disconnect elsewhere.

Types and configurations: Mainbreakers come in various sizes and configurations, including single-pole or double-pole designs depending on the service voltage. Some panels do not have a built-in mainbreaker and rely on a separate main disconnect at the service equipment or a utility-provided disconnect. The mainbreaker’s rating must match the service and the panel’s design, and it must be compatible with the panel’s bus structure and labeling.

Safety and standards: The mainbreaker is subject to electrical codes and standards (for example, requirements related to service disconnects and panelboard construction). It should be accessible, properly labeled, and maintained by qualified personnel. If a mainbreaker is damaged, overheating, or shows signs of wear, it should be replaced or repaired by a licensed electrician.