Article 350

Liquidtight Flexible Metal Conduit: Type LFMC

Part I. General

1. Scope. This article covers the use, installation, and construction specifications for liquidtight flexible metal conduit (LFMC) and associated fittings.
2. Definition.

Liquidtight Flexible Metal Conduit (LFMC). A raceway of circular cross section having an outer liquidtight, nonmetallic, sunlight-resistant jacket over an inner flexible metal core with associated couplings, connectors, and fittings for the installa‐ tion of electric conductors.

350.6 Listing Requirements. LFMC and associated fittings shall be listed.

ARTICLE 350 — LIQUIDTIGHT FLEXIBLE METAL CONDUIT: TYPE LFMC 350.120

Part II. Installation

350.10 Uses Permitted. LFMC shall be permitted to be used in exposed or concealed locations as follows:

1. Where conditions of installation, operation, or mainte‐ nance require flexibility or protection from liquids, vapors, or solids
2. In hazardous (classified) locations where specifically permitted by Chapter 5
3. For direct burial where listed and marked for the purpose

350.12 Uses Not Permitted. LFMC shall not be used as follows:

1. Where subject to physical damage
2. Where any combination of ambient and conductor temperature produces an operating temperature in excess of that for which the material is approved

350.20 Size.

1. Minimum. LFMC smaller than metric designator 16 (trade size 1∕2) shall not be used.Exception: LFMC of metric designator 12 (trade size 3∕8) shall be permit‐ ted as covered in 348.20(A).
2. Maximum. The maximum size of LFMC shall be metric designator 103 (trade size 4).

Informational Note: See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions.

350.22 Number of Conductors or Cables.

1. Metric Designators 16 through 103 (Trade Sizes 1∕2 through 4). The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
2. Metric Designator 12 (Trade Size 3∕8). The number of conductors shall not exceed that permitted in Table 348.22, “Fittings Outside Conduit” columns.

350.24 Bends — How Made. Bends in conduit shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Bends shall be permitted to be made manually without auxiliary equipment. The radius of the curve to the centerline of any bend shall not be less than required in Table 2, Chapter 9 using the column “Other Bends.”

350.26 Bends — Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes.

N

350.28 Trimming. All cut ends of conduit shall be trimmed inside and outside to remove rough edges.

350.30 Securing and Supporting. LFMC shall be securely fastened in place and supported in accordance with 350.30(A) and (B).

1. Securely Fastened. LFMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each
   box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (41∕2 ft). Where used, cable ties shall be listed and be identified for securement and support.Exception No. 1: Where LFMC is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical.Exception No. 2: Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following:
   1. 900 mm (3 ft) for metric designators 16 through 35 (trade sizes1∕2 through 11∕4)
   2. 1200 mm (4 ft) for metric designators 41 through 53 (trade sizes 11∕2 through 2)
   3. 1500 mm (5 ft) for metric designators 63 (trade size 21∕2) and larger
   Exception No. 3: Lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap conductors to luminaires, as permitted in 410.117(C).Exception No. 4: Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessi‐ ble ceiling to luminaire(s) or other equipment. For the purposes of 350.30, listed LFMC fittings shall be permitted as a means of secure‐ ment and support.
2. Supports. Horizontal runs of LFMC supported by open‐ ings through framing members at intervals not greater than

1.4 m (41∕2 ft) and securely fastened within 300 mm (12 in.) of termination points shall be permitted.

350.42 Couplings and Connectors. Only fittings listed for use with LFMC shall be used. Angle connectors shall not be concealed. Straight LFMC fittings shall be permitted for direct burial where marked.

350.56 Splices and Taps. Splices and taps shall be made in accordance with 300.15.

350.60 Grounding and Bonding. If used to connect equip‐ ment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equip‐ ment that requires movement after installation, an equipment grounding conductor shall be installed.

Where flexibility is not required after installation, LFMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(6).

Where required or installed, equipment grounding conduc‐ tors shall be installed in accordance with 250.134(B).

Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102.

Informational Note: See 501.30(B), 502.30(B), 503.30(B), 505.25(B), and 506.25(B) for types of equipment grounding conductors.

Part III. Construction Specifications

350.120 Marking. LFMC shall be marked according to 110.21. The trade size and other information required by the listing shall also be marked on the conduit. Conduit suitable for direct burial shall be so marked.

352.1 ARTICLE 352 — RIGID POLYVINYL CHLORIDE CONDUIT: TYPE PVC