800A Main Circuit Breaker 480Y/277V 3PH 4W NEMA 3R

Yes. In a 480Y/277V wye system, 277V is derived directly from the line-to-neutral connection. Each of the three phases measures 277V relative to the neutral conductor. This means a single 480Y/277V service can simultaneously supply 480V three-phase loads and 277V single-phase loads — such as fluorescent or LED lighting — without requiring a separate transformer.

An 800A main circuit breaker at 480Y/277V serves as the primary overcurrent protection and disconnecting means for a three-phase, four-wire service entrance. It controls and protects the entire downstream distribution system, making it ideal for large commercial buildings, industrial facilities, and utility interconnection points that require high-capacity, code-compliant power control.

NEMA 3R designates an outdoor-rated enclosure designed to protect internal components from rain, sleet, and ice formation. For an 800A main circuit breaker, a NEMA 3R rating means the unit can be safely installed in exterior locations — such as on building exteriors or in partially sheltered utility yards — without risk of weather-related damage or compromised performance.

A code-compliant assembly should carry UL 891 certification for low-voltage switchgear construction and be EUSERC approved for utility interconnection. It should also meet UBC, CBC, and IBC seismic zone requirements. DEI Power's 800A 480Y/277V NEMA 3R assemblies satisfy all of these standards and are built with genuine Siemens components as an approved OEM.

NEMA 1 enclosures are rated for indoor use only, protecting against contact with internal parts and limited dust ingress. NEMA 3R enclosures add weatherproofing for outdoor installation, guarding against rain, sleet, and ice. For any 800A main circuit breaker that will be mounted outdoors or in unconditioned utility spaces, a NEMA 3R enclosure is required to maintain safety and performance.

Yes. Because service entrance equipment must meet specific utility requirements, DEI Power builds each 800A 480Y/277V NEMA 3R assembly to approved utility specifications. Customers are encouraged to contact a DEI Power specialist directly to discuss project requirements, confirm configuration details, and receive an accurate quote before order placement.