Machine Design

Safety Standard for Portable Generators

Consumer Product Safety Commission,

Underwriters Laboratories,

Underwriters Laboratories (UL) has published UL 2201, a standard for portable generators. The document, the first voluntary safety standard for portable generators sold in the U.S., covers units with internal-combustion engines that generate 15 kW or less, 250 V or less, and have ac output receptacles.

The Consumer Products Safety Commission (CPSC) estimates 10.6 million U.S. houses had portable generators in 2005, and the number has grown each year since 1999. Consumer generators are usually gasoline powered and generate 5 to 6 kW of electricity that can provide supplemental power during temporary outages.

The CPSC also reported 404 deaths from generator-related carbon-monoxide poisoning as well as additional deaths from other generator-related causes. A standard 5-kW generator in the basement of a relatively closed-up two-story home can generate fatal levels of CO on the second floor in 2.5 to 4 hr.

Experts from the CPSC and UL say consumers should always put generators outside the home where air can circulate on at least four sides of the unit.

Other generator-related risks include fire and electric shock.

“Portable generators are commonly used during and after storms,” points out Robert Williams, UL vice president of standards. “However, consumer-grade generators typically are not weatherproof, and owners risk electrocution or shock if they use these units in wet conditions. The industry needs to be able to manufacture and market portable generators that have been tested for foreseeable hazards.”

UL 2201 provides a framework under which UL can test generators and certify them safe for real-world conditions.

Other requirements include positioning guides for fuel tanks, protection against engine- generated heat, and provisions against fuel spilling into the engine compartment. The standard dictates that electrical parts must be insulated or inaccessible to users and they must be protected from short circuits, vibration, excessive heat, moisture, and flammable substances. All receptacles should be grounded, rated for at least 15 A, and weather resistant.

The standard also requires a CO-poisonwarning label. Other warnings on certified units tell users to read the manuals, let the engine cool before refueling, and avoid gasoline- ethanol blends with over 15% ethanol.

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