Generac 9931 150A Service-Entrance Automatic Transfer Switch with Surge Protection (NEMA 3R)
warranty
dealer
support
At a glance
- Amperage
- 150A
- Voltage/Phase
- 120/240V, single-phase
- Service Entrance Rated
- Yes (with utility service circuit breaker)
- Enclosure
- NEMA 3R aluminum, powder-coated (indoor/outdoor)
- Surge Protection
- Factory-installed whole-house SPD; 50 kA per phase, 20 kA nominal discharge, 200 kA SCCR, UL 1449 4th Edition Listed
- Transition Type
- Open transition, automatic
- Withstand Rating
- 22,000 amps
- Lug Range
- 250 MCM - #6
- Listings
- ETL Listed (ETLus); SPD UL 1449 4th Edition Listed
- Dimensions
- 26.8 in H (30.0 in overall) x 13.5 in W x 6.3 in D
- Weight
- 30.0 lbs (13.6 kg)
- Warranty
- 5-year limited warranty
Why this generator
- Service-entrance rated 150A automatic transfer switch with built-in utility service disconnect breaker — doubles as your main service disconnect
- Factory-installed whole-home surge protection (50 kA per phase, UL 1449 4th Edition Listed) shields both your home and your Generac generator from damaging surges
- Rugged NEMA 3R powder-coated aluminum enclosure rated for indoor or outdoor installation
- Heavy-duty 22,000A withstand-rated Generac contactor with open-transition automatic transfer at 120/240V single-phase
- Pre-wired with built-in whole-house load management (load shedding) so a right-sized generator can cover the entire home
- Fast-mount hanging system speeds installation, backed by Generac's 5-year limited warranty
Everything you need to know
Generac 9931 150a service-entrance automatic transfer switch with surge protection (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.