---
aliases:
  - nec-356
title: "Article 356 Liquidtight Flexible Nonmetallic Conduit: Type LFNC"
tags:
  - authorship/other
  - exclude-from-word-count
  - topic/construction/electrical
  - type/media/reference
---
# Article 356 Liquidtight Flexible Nonmetallic Conduit: Type LFNC

## Part I. General

### 356.1 Scope.

This article covers the use, installation, and construction specifications for liquidtight flexible nonmetallic conduit (LFNC) and associated fittings.

### 356.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Liquidtight Flexible Nonmetallic Conduit (LFNC).

A raceway of circular cross section of various types as follows:

* (1) A smooth seamless inner core and cover bonded together and having one or more reinforcement layers between the core and covers, designated as Type LFNC-A

* (2) A smooth inner surface with integral reinforcement within the raceway wall, designated as Type LFNC-B

* (3) A corrugated internal and external surface without integral reinforcement within the raceway wall, designated as Type LFNC-C

> [!info] Informational Note:
> FNMC is an alternative designation for LFNC.

### 356.6 Listing Requirements.

LFNC and associated fittings shall be listed.

## Part II. Installation

### 356.10 Uses Permitted.

LFNC shall be permitted to be used in exposed or concealed locations for the following purposes:

* (1) Where flexibility is required for installation, operation, or maintenance.

* (2) Where protection of the contained conductors is required from vapors, machine oils, liquids, or solids.

* (3) For outdoor locations where listed and marked as suitable for the purpose.

* (4) For direct burial where listed and marked for the purpose.

* (5) Type LFNC shall be permitted to be installed in lengths longer than 1.8 m (6 ft) where secured in accordance with 356.30.

* (6) Type LFNC-B as a listed manufactured prewired assembly, metric designator 16 through 27 (trade size 1/2 through 1) conduit.

* (7) For encasement in concrete where listed for direct burial and installed in compliance with 356.42.

* (8) Conductors or cables rated at a temperature rating of LFNC conduit shall be permitted to be installed in LFNC, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the LFNC.

> [!info] Informational Note:
> Extreme cold can cause some types of nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact.

### 356.12 Uses Not Permitted.

LFNC shall not be used as follows:

* (1) Where subject to physical damage

* (2) Where any combination of ambient and conductor temperatures is in excess of that for which it is listed

* (3) In lengths longer than 1.8 m (6 ft), except as permitted by 356.10(5) or where a longer length is approved as essential for a required degree of flexibility

* (4) In any hazardous (classified) location, except as permitted by other articles in this Code

### 356.20 Size.

#### 356.20(A) Minimum.

LFNC smaller than metric designator 16 (trade size 1/2) shall not be used unless permitted in 356.20(A)(1) or (A)(2) for metric designator 12 (trade size 3/8).

* (1) For enclosing the leads of motors as permitted in 430.245(B)

* (2) In lengths not exceeding 1.8 m (6 ft) as part of a listed assembly for tap connections to luminaires as required in 410.117(C), or for utilization equipment

#### 356.20(B) Maximum.

LFNC larger than metric designator 103 (trade size 4) shall not be used.

> [!info] 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.

### 356.22 Number of Conductors.

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.

### 356.24 Bends --- How Made.

Bends in conduit shall be so made that the conduit is not damaged and the internal diameter of the conduit is not 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 shown in Table 2, Chapter 9 using the column "Other Bends."

### 356.26 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.

### 356.28 Trimming.

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

### 356.30 Securing and Supporting.

Type LFNC shall be securely fastened and supported in accordance with one of the following:

* (1) Where installed in lengths exceeding 1.8 m (6 ft), the conduit shall be securely fastened at intervals not exceeding 900 mm (3 ft) and within 300 mm (12 in.) on each side of every outlet box, junction box, cabinet, or fitting. Where used, cable ties shall be listed for the application and for securing and supporting.

* (2) Securing or supporting of the conduit shall not be required where it is fished, installed in lengths not exceeding 900 mm (3 ft) at terminals where flexibility is required, or installed in lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap conductors to luminaires permitted in 410.117(C).

* (3) Horizontal runs of LFNC supported by openings through framing members at intervals not exceeding 900 mm (3 ft) and securely fastened within 300 mm (12 in.) of termination points shall be permitted.

* (4) Securing or supporting of LFNC shall not be required where installed in lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment. For the purpose of 356.30, listed liquidtight flexible nonmetallic conduit fittings shall be permitted as a means of support.

### 356.42 Couplings and Connectors.

Only fittings listed for use with LFNC shall be used. Angle connectors shall not be used for concealed raceway installations. Straight

LFNC fittings are permitted for direct burial or encasement in concrete.

### 356.56 Splices and Taps.

Splices and taps shall be made in accordance with 300.15.

### 356.60 Grounding.

Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit.

> [!important] Exception No. 1:
> As permitted in 250.134, Exception No. 2, for dc circuits and 250.134, Exception No. 1, for separately run equipment grounding conductors.

> [!important] Exception No. 2:
> Where the grounded conductor is used to ground equipment as permitted in 250.142.

## Part III. Construction Specifications

### 356.100 Construction.

LFNC-B as a prewired manufactured assembly shall be provided in continuous lengths capable of being shipped in a coil, reel, or carton without damage.

### 356.120 Marking.

LFNC shall be marked at least every 600 mm (2 ft) in accordance with 110.21. The marking shall include a type designation in accordance with 356.2 and the trade size. Conduit that is intended for outdoor use or direct burial shall be marked.

The type, size, and quantity of conductors used in prewired manufactured assemblies shall be identified by means of a printed tag or label attached to each end of the manufactured assembly and either the carton, coil, or reel. The enclosed conductors shall be marked in accordance with 310.8.
