Classes A, B, C, D, G, and M. 1  Classes A â C permit operation of motor vehicles based on GVW rating and must be renewed every 5 years. 2  Classes D and G are valid for operation of a single motor vehicle with a GVW rating of 26,000 lbs. or less.
Electrical Metallic Tubing (EMT) Electrical metallic tubing (EMT), also commonly called thin-wall, is a listed steel raceway of circular cross section, which is unthreaded, and nominally 10â² long. 20â² lengths are also available. Covered by Article 358 of the NEC, EMT is available in trade sizes 1/2 through 4.
Steel conduit has been in use as a âraceway systemâ for electrical conductors since the early 1900s. The wall thickness and strength of steel make metal conduit the wiring method recognized as providing the most mechanical protection to the enclosed conductors.