Chapter 10 Raceway Systems 151 Copyright Goodheart-Willcox Co., Inc. Goodheart-Willcox Publisher Figure 10-17. Follow these steps to make permanent, watertight PVC attachments. Rigid Polyvinyl Chloride Conduit: Type PVC — Article 352 Locations Allowed Al lo Dry Wet Corrosive Maximum Mounting Distance 3′ See Table 352.30( 2. 30 (B ) Section 225.27 requires conduit run under- 7 ground to be sealed at joints prior to its entering a building. The seal is to prevent the intrusion of gasses or moisture into the building. The conduit may be sealed with a putty-like sealing compound or with an approved sealing bush- ing, depending on the AHJ’s requirements. 10.6 Flexible Metal Conduit Flexible metal conduit (FMC) is a spiral-wrapped metal conduit similar to the outer armor in AC (armored cable), Figure 10-18. It is often called Greenfield fi after its inventor, Harry Greenfield.fi FMC is routed and attached as if it were nonfl flex- ible conduit, but it has the advantage of being bent without using tools. There are special cou- plings, locknuts, and bushings for attaching FMC. After the conduit is installed, the wire is fi shed through as with other types of conduit. fi Frequently, FMC is used with EMT or rigid conduit. It is substituted where bends are needed. Instead of making complicated bends and angles in EMT or rigid conduit, a section of FMC can be inserted. There are special bush- ings, locknuts, and couplings to connect FMC to the other forms of conduit. There are also length limits as stated in the NEC. Joining PVC Step 1. Apply primer to the inside of the fitting. Step 2. Apply primer to the outside of the conduit. Step 3. Apply glue to the inside of the fitting. Apply glue to the outside of the conduit. Step 5. Push the conduit into the fitting. Turn the conduit 1/4 turn to spread the glue evenly. Step 6. This is a cutaway view of the completed assembly.