Generac 9931 150A 1ph-120/240V Service Rated Nema 3R Automatic Transfer Switch with Integrated SPD Features:
Generac 9931 150A Service-Rated Automatic Transfer Switch with Surge Protection (1Ø, 120/240V)
The Generac 9931 150 Amp Service-Rated Automatic Transfer Switch with Integrated Surge Protection is designed for higher-demand standby power systems that require both reliable load management and advanced electrical protection. Built for use with Generac generators utilizing Evolution™ and Power Zone™ 200 controllers, this switch continuously monitors incoming utility power and automatically transfers your electrical load to generator power during an outage. Once utility power stabilizes, it seamlessly returns your system to normal operation without interruption.
What sets this model apart is its integrated whole-house surge protection device (SPD), providing an added layer of defense against damaging power surges and transient voltage events. Instead of relying on a separate surge protection unit, this switch incorporates protection directly into the system, helping safeguard sensitive electronics, appliances, and critical equipment. The SPD utilizes thermally protected metal oxide varistors (MOVs) to manage high-energy surges while reducing the risk of overheating or failure.
Designed for efficiency and code compliance, this transfer switch is service entrance rated and includes an integrated utility service circuit breaker, allowing it to function as the primary disconnect point for the electrical system. Its 150-amp capacity makes it well-suited for larger homes or light commercial applications where additional electrical load capacity is required. The open transition design ensures safe switching between power sources, while all sensing, timing, and transfer operations are controlled directly by the generator for precise, coordinated performance.
Built to perform in demanding environments, the Generac 9931 features a NEMA 3R aluminum enclosure with a durable powder-coated finish, offering protection against weather and environmental exposure. The fast-mount hanging system simplifies installation, while the heavy-duty contactor ensures long-term reliability. With manual operation capability and a 5-year limited warranty, this unit delivers a complete, high-capacity solution for both automatic power transfer and surge protection.
Key Features
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150 Amp service-rated automatic transfer switch with integrated surge protection
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120/240V single-phase (1Ø) configuration
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Built-in whole-house surge protection device (SPD) for added electrical protection
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SPD utilizes thermally protected MOV technology for surge suppression
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Service entrance rated with integrated utility service circuit breaker
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Open transition transfer design for safe switching between power sources
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Compatible with Generac Evolution™ and Power Zone™ 200 controllers
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Generator-controlled timing, sensing, and transfer operation
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Adjustable voltage pickup and drop-out settings for optimized performance
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Heavy-duty Generac contactor for long-term durability
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NEMA 3R aluminum enclosure for indoor/outdoor installation
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Powder-coated finish for corrosion and weather resistance
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Fast-mount system for simplified installation
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Manual operation capability without power applied
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ETL listed with up to 22,000A withstand rating (150A model)
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Integrated SPD rated up to 50 kA surge current capacity per phase
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5-year limited warranty
