Generac 9931 150A Service-Entrance Automatic Transfer Switch with Surge Protection (NEMA 3R)
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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
Not sure if this fits?
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. Ships via calculated freight — shipping shown at checkout (heavy/hazmat item). 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?+
Low cost ground shipping — calculated at checkout (batteries, transfer switches and oversized items). Most leave the warehouse in 2–4 business days.
What's the return policy?+
30-day returns on unused parts and accessories in original packaging.
Fast nationwide shipping
Low cost ground shipping — calculated at checkout. Most items leave the warehouse in 2–4 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.
Genuine Generac part
Sold and shipped as a genuine Generac OEM part from a factory-authorized dealer. 30-day returns on unused parts in original packaging.