Generac RTSW300A3 300A Service-Entrance Automatic Transfer Switch (NEMA 3R)
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At a glance
- Amperage
- 300A
- Voltage/Phase
- 120/240V single-phase
- Service Entrance Rated
- Yes
- Enclosure
- NEMA 3R aluminum (indoor/outdoor)
- Transition Type
- Open transition (automatic)
- Withstand Rating
- 22,000A
- Listings
- ETL Listed
- Lug Range
- 600 MCM - #4 or (2) 1/0 - 250 MCM
- Dimensions
- 42.9 in H x 16.7 in W x 10.0 in D
- Weight
- 140 lbs (63.5 kg)
- Warranty
- 5-year limited
Why this generator
- Service entrance rated 300A Smart Switch that doubles as your main utility disconnect, eliminating the need for a separate service disconnect
- Integrated Smart A/C Module manages up to four HVAC loads with no additional hardware, expandable to eight more loads with Smart Management Modules
- Rugged NEMA 3R aluminum enclosure with baked powder-coat finish, rated for indoor or outdoor installation
- Heavy-duty ETL-recognized Generac contactor with a 22,000A withstand rating, built for years of reliable transfers
- Designed for Generac single-phase generators with Evolution or Nexus controllers, which handle all timing, sensing, and exercise functions
- Backed by Generac's 5-year limited warranty
Everything you need to know
Generac RTSW300A3 300a service-entrance automatic transfer switch (NEMA 3R enclosure). 120/240V single-phase, designed to pair with Generac air-cooled home standby generators.
Genuine Generac unit from a factory-authorized dealer. Free shipping to the lower 48. Professional installation available in NC & SC.
Frequently asked questions
Is this a genuine OEM part?+
Yes — sold and shipped as a genuine Generac part from a factory-authorized dealer.
Will it fit my unit?+
Check your model and year — message us with that info and we'll confirm fit before you order.
How fast does it ship?+
Free shipping to the lower 48. Most accessories and parts ship within 2–4 business days.
What's the return policy?+
30-day returns on unused parts and accessories in original packaging.
Free curbside shipping
Liftgate delivery to the lower 48. Most orders leave the warehouse in 3–5 business days.
Install help, no upsell
We size, spec, and connect you with a vetted local installer — or talk your contractor through it for free.
Real Cummins warranty
Full 5-year / 2,000-hour limited warranty — registered and supported through Cummins directly.