Chapter 10 Raceway Systems 149 Copyright Goodheart-Willcox Co., Inc. 10.4 Intermediate Metal Conduit Intermediate metal conduit (IMC) is a heavy- duty rigid metal conduit that is thicker than EMT but thinner and lighter than RMC. It is permitted for use in all atmospheric condi- tions and in all types of occupancies, including all uses where RMC is permitted. It is sold in 10′ lengths and in 1/2″ to 4″ ″ diameters, with or ″ without threads. The internal diameter (ID) of IMC is larger than that of the equivalent trade size (nominal size) of RMC therefore, there is more room for pulling wires and calculating conduit fill. fi Like RMC, IMC is joined with threaded fit- tings and can serve as an equipment ground when installed with proper fittings and tight connections. Cutting, threading, and install- ing IMC are the same as with RMC. Because IMC can be used interchangeably with RMC and weighs about one-third less, it has replaced RMC in many applications. Intermediate Metal Conduit: Type IMC — Article 342 Locations s All Al lo wed Dry Wet Corrosive Maximum Mounting Distance 3′ 10′ Courtesy of RIDGID®. RIDGID® is the registered trademark of RIDGID, Inc. Figure 10-15. Threading RMC requires a pipe vise (stand-type vise shown here) and a threader. Portable Chain Vise Manual Pipe Threader PRO TIP IMC M C and RMC Trade Size and n d Color Codes Straight S lengths of RMC C and IMC are typically sold with a threaded coupling c (IMC may have an integral coupling) ng on one end and a threada d protector cap on n the other end. The caps s are a color-coded for fo easy reference to the t tr ade size of the conduit co diameter. The trade d size is the nomin na l dimension (not the actu t ua l dimen- sion) and n d often is given without ut the “inch” symbo b ol . For example, a nomina n al 1″ conduit is trade ad size 1. The color codes e s are different for R RM C and IMC: • Blue: RMC, trade sizes z e 1, 2, 3, 4, 5, and 6 • Black: RMC, trade d e sizes 1/2, 1 1/2, 2 1/2, and 3 1/2 • Red: RMC, trade tr sizes 3/4 and 1 1/4 • Orange: : IMC, I trade sizes 1, 2, 3, and 4 • Yellow: w IMC, trade sizes 1/2, 1 1/2, 2 1/2, and d 3 3 1/2 • Green: Gr IMC, trade sizes 3/4 and 1 1/4.