1 Scope

1.1 These requirements cover steel electrical intermediate metal conduit (IMC), nipples, elbows, and couplings. This conduit is provided in trade sizes 1/2 – 6 (63 – 155), for use as a metal raceway for the installation of wires and cables in accordance with the NFPA 70^®, National Electrical Code^® (NEC^®). The values in parentheses are metric designators of conduit.

NFPA 70^®, National Electrical Code^®, and NEC^® are registered trademarks of the National Fire Protection Association, Quincy, MA.

1.2 Steel intermediate metal conduit is provided both internally and externally with an acceptable level of corrosion resistance in normally corrosive environments. Reference 1 for details regarding protective coatings.

Summary of Topics

This new Fifth Edition of ANSI/UL 1242 dated November 3, 2025 includes the following changes in requirements:

– Correction of Typographical Error in SI Unit in 6.2.1.

– Guidance on How to Determine Surface Treatment Thickness to Apply Exemption in 6.2.1.

– Addition of 5 and 6 Trade Size Intermediate Metal Conduits; 1.1, 5.3, Table 7.1, Table 8.1, Table 9.1, Table 18.1, and Table 19.1.

– Updates to Section 3, Referenced Publications, and Revisions of Several Referenced Standards; 8.1, 11.1, 13.1.1, 13.2.1, 14.2.4.4, 15.3, and 16.2.