Generac RTSW400A3 400A 1ph-120/240V Service Rated Nema 3R Automatic Transfer Switch

Generac RTSW400A3 400A 1ph-120/240V Service Rated Nema 3R Automatic Transfer Switch Features:

Generac RTSW400A3 400A Automatic Transfer Switch Features:

The Generac RTSW400A3 400A Service-Rated Automatic Transfer Switch is a high-capacity, code-compliant solution designed for large single-phase standby generator systems. With its 400-amp rating and service-entrance status, it can serve as the main electrical disconnect where permissible under local code, simplifying your electrical setup while delivering full load capability. It’s built to sense utility outages and transfer your home load seamlessly to generator power, then return to the grid automatically when voltage returns.

Equipped with integrated load management, this switch can control up to four HVAC circuits (24 VAC) without extra hardware. That lets you prioritize essential loads and potentially use a smaller generator without sacrificing performance. Built to last, it comes in a NEMA 3R aluminum enclosure that protects internal components against rain, snow, ice, and debris. Its heavy-duty contactor is engineered for rugged performance and frequent switching.

All of the timing, sensing, and control logic is handled at the generator side, which means the switch itself remains mechanically focused and simpler to install. Open-transition switching ensures utility power is fully disconnected before generator power is applied, minimizing risk and wear. A 5-year limited warranty provides long-term peace of mind for homeowners demanding reliability under heavy loads.

Key Features

• 400 Amp service-rated automatic transfer switch (single-phase, 120/240V)

• Service entrance rated — can act as main disconnect where allowed by code

• Integrated load management: supports up to 4 HVAC loads without additional modules

• NEMA 3R aluminum enclosure for indoor or outdoor use; resists weather and environmental exposure

• Heavy-duty Generac contactor built for frequent switching and high load demands

• Open transition switching to separate utility vs generator power safely

• All switching timing, sensing, and control handled by compatible generator controllers

• Withstand Rating: 22,000 Amps L-F (fault rating)

• Lug capacity: #4 up to 250 MCM conductors

• 5-year limited warranty

RTSW400A3 Specifications Sheet
RTSW400A3 Owner's Manual
RTSW400A3 Warranty