UL 2561 for Factory-Built 1400-Degree Chimneys

The Importance of UL Listings

We’re proud of our strict adherence to UL standards — a commitment that has helped us set the standard for safety and protection. Products that meet UL standards have attained the highest echelon of rigor and met accepted industry goals: the UL mark is the single most accepted certification mark in the United States, appearing on 22 billion products annually. There are more than 1,500 different UL standards, and each number represents a different application and level of protection. See our earlier article for a complete understanding of UL listings and their importance.

The dangers of using products that have not qualified for a UL listing are real and well-documented. Fires confined to chimneys, flues or fuel burners account for 77% of residential building heating fires, according to the U.S. Fire Administration. Many of these are caused by using products that are not adequately tested or built to withstand their application demands. The unfortunate result of these fires is not only structural damage but also injuries. About 10 fatalities a year are directly caused by chimney fires.

UL 2561: The UL Standard for Safety for Factory-Built Chimneys Where Flue-Gas Temperatures Do Not Exceed 1,400 F

The UL 2561 Generator Exhaust System standard covers a factory-built chimney intended for “venting gas, liquid, and solid-fuel-fired appliances in which the maximum continuous flue-gas temperatures do not exceed 1,400 F (760 C)” under continuous operating conditions. This includes building heating appliances and other low-heat appliances. This certification is relevant to the entire chimney system, which may consist of multiple sections, a chimney cap, lateral supports, a thimble and flashing assembly if needed. These chimneys must be installed in accordance with the Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, NFPA 211.

UL 2561 Generator Exhaust System Testing and Requirements

All factory-built chimneys that meet UL 2561 Generator Exhaust System requirements undergo three main tests, in this order: a thermal shock test of 1,800 F (980 C), a continuous flue gas temperature test of 1,400 F (760 C), and a 10-minute flue gas Temperature Test of 1,800 F (980 C). Upon the conclusion of these tests, it must be determined that no part of the chimney has shown damage or been permanently distorted so that it doesn’t work as intended, including its protective coating, any finish on metal parts, including no burning or scaling, and no cracking, disintegration or spalling of any ceramic materials “to the extent that serviceability of any part of an assembly has been impaired.”

Additional result requirements include the following:

• The effectiveness of insulating material has not been reduced
• The insulating material shall remain in its intended position
• The thermal conductivity of the insulating material shall not be increased
• The thermal insulation shall not show evidence of softening, melting or other evidence of malfunction or deterioration.

There are many additional requirements and testing procedures for a product to meet the UL 2561 Generator Exhaust System listing. For example, “Chimney sections are to be mounted vertically on a vibration table, first inverted for one hour and then mounted in the intended installation position for one hour.” Receiving a fire rating isn’t easy. Because of its demands, many companies aren’t committed to earning them. At Schebler, we are. We understand such ratings aren’t merely an honor; they’re a necessity.

The Certainty of UL Listed Safety

UL is steadfast in its commitment to ensuring that products bearing its mark continue to perform at acceptable levels. As a result, UL Solutions performs quarterly inspections, appearing at a facility unannounced to examine parts, conduct tests, measure dimensions and even check product labels for accuracy. If UL uncovers a violation, it can completely halt production of that product.

At Schebler, we’re proud to have been UL certified since 1994 and have never received a single major violation. This certainty is one of the key reasons we’re the unquestioned leader in providing the finest prefabricated chimney and exhaust systems.

Contact us to learn more.