Intermediate
Metal
Conduit — (IMC)
The product was developed in the 1970s. Intermediate Metal Conduit (IMC) is a lighter-weight, thinner wall alternative to rigid steel conduit. Covered under Article 342 in the NEC®, IMC is a listed threaded steel raceway of circular cross section with a coupling which can be either a standard straight-tapped conduit coupling or the integral type. Threads on the uncoupled end are covered by industry color-coded thread protectors which protect the threads, keep them clean and sharp, and aid in trade size recognition. IMC is available in trade sizes 1/2 through 4. Thread protectors for trade sizes 1, 2, 3, 4, are color-coded orange; trade sizes 1/2, 1 1/2, 2 1/2, 3 1/2 are yellow; and trade sizes 3/4 and 1 1/4 are green. The nominal finished length of IMC with coupling is 10 feet.
IMC has a reduced wall thickness, when compared to RSC, and weighs about one-third less than RSC. The outside has a galvanized coating for corrosion protection and the inside has an approved organic corrosion-resistant coating. IMC is interchangeable with galvanized rigid steel conduit. Both have threads with a 3/4-inch per foot taper, use the same couplings and fittings; have the same support requirements; and are permitted to be used in the same locations.
