Chapter 10 Raceway Systems 151 Copyright Goodheart-Willcox Co., Inc. because the conduit itself serves as the equipment grounding conductor. When RMC is properly installed, with fittings that maintain a continuous ground throughout the system, a separate equip- ment grounding conductor is not required. Carlon, Lamson & Sessions Figure 10-13. Electrical nonmetallic tubing is a corrugated plastic tube that is easy to handle and install. Electrical nonmetallic tubing (ENT) Connector Nonmetallic box Rigid Metal Conduit: Type RMC — Article 344 Locations Allowed Dry Wet Corrosive Maximum Mounting Distance 3′ 10′ Electrical Nonmetallic Tubing: Type ENT — Article 362 Locations Allowed Dry Wet Corrosive Maximum Mounting Distance 3″ 3′ be performed according to the manufacturer’s instructions. See Figure 10-13. There are some restrictions and limitations on the use of ENT: • Not for use around hazardous material • Cannot be left exposed, with some exceptions • Not to be used as supportive means • Not permitted for direct burial application • Not for voltage exceeding 600 V. 10.3 Rigid Metal Conduit Rigid metal conduit (RMC) is galvanized and somewhat similar to water pipe. It is used for both indoor and outdoor applications. The conduit is smooth on its interior and exterior surfaces. It can be cut, threaded, reamed, and bent as neces- sary for proper installation. All connections are made with threaded fi ttings. See Figure 10-14. Also called “heavy-wall conduit,” RMC has thick walls and offers excellent protection for wires. Small sizes can be bent by hand with diffi culty, and larger sizes must be machine-bent. RMC is the original conduit, used before thin- wall (EMT) and similar but lighter-weight inter- mediate metal conduit, or IMC. In residential installations, RMC may be used for mast heads and other exposed outdoor applications. It is sold in 10′ lengths and in diameters of 1/2″ through 6″. To cut RMC with a pipe cutter, follow the cut- ting procedure used with EMT conduit. RMC must be firmly connected to items such as electrical outlet boxes and panels with a threaded locknut and bushing. This solid connection is necessary