Understanding UL Safety and Performance Requirements for Generator Systems
Introduction to UL Standards for Standby Generators
Underwriters Laboratories (UL) is a respected agency that establishes safety and efficacy standards for a wide range of industrial and consumer equipment. Their mission is “to promote safe, secure and sustainable living and working environments for people by the application of science, hazard-based safety engineering and data acumen.” UL standards are recognized across industries for ensuring public safety and product reliability. When it comes to standby generators, UL standards play a vital role in protecting users and facilities by enforcing rigorous design, testing, and manufacturing requirements.
Peace of Mind with UL Listed Equipment
UL standards focus on the generator unit as a whole, rather than just individual components. This holistic approach includes critical aspects such as fuel systems, hazardous component guarding, labeling, raw material quality, corrosion protection, fabrication standards for enclosures, assembly standards like torque specifications, and the use of UL recognized components. Manufacturers adhering to UL standards must conduct comprehensive tests for uniform quality and durability before generators leave their facilities. These measures ensure a high level of safety and reliability, providing users with peace of mind when operating UL listed standby generators.
Key UL Standards for Standby Generators
Fuel Tanks
- UL 142 – Standards for Base Tanks:
- UL 142 applies to typical sub-base fuel tanks, requiring a double-walled design for added protection. The standard addresses allowed tank heights and capacities, permissible functional connections, necessary stub-ups, and testing limits. Tanks must be production tested to 3 psi and prototype tested to 15 psi to ensure leak resistance and durability.
- UL 2085 – Standards for Protected Tanks:
- UL 2085 covers “Convalt” style tanks, which must be constructed from steel, feature a ¼” polystyrene layer, a 30 mil polyethylene geo membrane, and 6 feet of concrete. Steel reinforcement in the center of the tank walls is required, along with a 2-hour fire rating. These robust tanks are engineered to withstand severe impacts and prevent leaks, even under extreme conditions.
Transfer Switch Equipment
- UL 1008 – Transfer Equipment:
- This standard governs transfer equipment rated up to 600V and 6000A, detailing operational and short circuit requirements to ensure safe and reliable switching between power sources.
- UL 891 – Dead-Front Switchboards:
- UL 891 applies to dead-front switchboards rated for 600 volts or less, which may feature front access or both front and rear access. These switchboards are commonly used for generator paralleling and must meet requirements for insulated case circuit breakers.
- UL 1558 – Metal-Enclosed Switchgear:
- This standard covers metal-enclosed low-voltage power circuit breaker switchgear rated at 600 volts or less. It specifies the need for metal barriers between sections, complete compartment isolation, and power circuit breakers for enhanced safety.
Stationary Engine Generator Assemblies
- UL 2200 – Engine Generator Assemblies:
- UL 2200 encompasses standards for engine generators, including safe operation limits, permitted stationary locations, and allowable ordinary locations. It applies to generators rated at 600 volts or less, ensuring safe installation and operation.
Testing Requirements for UL Listed Generators
UL standards require comprehensive testing to guarantee uniform quality and durability of generators and associated equipment. Key tests include:
- Temperature Tests: Conducted on the engine, alternator, surfaces, and controls to verify safe operation under various conditions.
- Alternator Tests: Such as dielectric withstand and harmonic distortion tests to ensure electrical safety and performance.
- Enclosure Tests: Including salt spray and impact testing to assess corrosion resistance and physical durability.
- Air Flow Tests: Blocked inlet and ignitable fuel spill tests to confirm safe ventilation and prevent fire hazards. Note: Second party enclosures must be submitted and tested as a system to receive UL 2200 verification.
- Rain Tests: Simulate water spray at a 30-degree angle to the enclosure surface to ensure no water leakage into electrical boxes.
- Parallel Testing: Specific parameters for paralleling generators can be found in UL 2200, ensuring safe and effective operation when multiple generators are used together.
Conclusion
UL standards for standby generators are designed to maximize safety, reliability, and performance. By requiring rigorous design, construction, and testing protocols, UL helps ensure that generators and their supporting equipment perform reliably under demanding conditions. When choosing standby generators, look for UL listed equipment to benefit from the highest safety and quality standards in the industry.
