Installing Electrical Conduit Systems

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1-4 Flexible Metallic and Nonmetallic Conduit

Flexible metallic conduit (Figure 1-4) is similar in appearance to metallic armored cable, but they are unlike them because flexible metallic conduit is not preinstalled with conductors. In flexible metallic conduit, conductors must be pulled through the conduit after it is installed. Flexible metallic conduit is generally used where some type of movement or vibration may be present, such as wiring motors. Article 350 in the NEC covers flexible metallic conduit.

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Figure 1-4. Flexible metallic conduit

Flexible metallic conduit comes in two types, aluminum and steel. The available size of flexible metallic conduit depends on the type. The sizes may vary depending on the manufacturer. The NEC states that flexible metallic conduit will not be smaller than 3/8 inch and not larger than 4 inches (Table 1-1, page 1-4). Flexible metallic and nonmetallic conduit is available for use in wet areas.

**Table 1-1. Flexible metallic conduit sizes**
Steel (Inches)	Aluminum (Inches)
3/8	3/8
1/2	1/2
3/4	3/4
1	1
1 1/4	1 1/4
1 1/2	1 1/2
2	2
2 1/2	2 1/2
3	3
3 1/2	N/A
4	N/A

Editor: David L. Heiserman
Publisher: SweetHaven Publishing Services