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.
An additional benefit of using steel conduit is that the NEC recognizes a properly installed metal conduit system as an equipment grounding conductor. Three basic types of steel conduit are in use today: rigid metal conduit, intermediate metal conduit, and electrical metallic tubing. Let's take a closer look at the features of each type. Rigid metal conduit â RMC (ferrous metal).