What is UL 797?

UL 797, also known as Electrical Metallic Tubing (EMT), is a set of safety standards established by Underwriters Laboratories (UL) for electrical conduit systems. This standard specifies requirements for the materials, construction, and performance of EMT used in electrical installations.

Materials and Construction

UL 797 requires EMT to be made of hot-dipped galvanized steel or stainless steel. These materials provide durability, corrosion resistance, and structural integrity to the conduit system. The steel tubing is manufactured using a process called electric resistance welding, which ensures consistent and reliable joint strength.

EMT is available in various sizes, typically ranging from 1/2 inch to 4 inches in diameter. It comes in standard lengths of 10 feet and can be easily bent or cut to fit specific installation requirements. The conduit is characterized by its smooth exterior finish, allowing easy pulling and pushing of wires through the pipe.

Performance and Compliance

UL 797 sets strict performance requirements for EMT to ensure its suitability for electrical installations. The conduit must have adequate mechanical protection against damage and be able to withstand the normal stresses encountered during installation and use.

EMT undergoes rigorous testing to verify its compliance with UL 797 standards. These tests include examinations of dimensions, tensile strength, galvanizing coating, and impact resistance. Additionally, the conduit is subjected to a bending test to assess its flexibility and the ability to maintain the continuity of an electrical path even when bent at different angles.

Benefits and Applications

UL 797 certified EMT is widely used in residential, commercial, and industrial settings. Its popularity stems from several advantages it offers. Firstly, EMT provides excellent protection for electrical wires against mechanical damage, moisture, and chemical exposure. Secondly, its smooth interior surface helps reduce friction during wire pulling, thereby reducing installation time and effort.

Furthermore, EMT is lightweight and easy to handle, making it a preferred choice for electricians. Its flexibility allows for quick and hassle-free routing around obstacles. Additionally, the ability to connect easily with fittings and accessories ensures a secure and reliable electrical conduit system.

In conclusion, UL 797 sets the benchmark for quality and performance of Electrical Metallic Tubing used in electrical installations. Adhering to these standards ensures the safety and reliability of the conduit system and provides peace of mind for both electricians and end-users.