What Are Different Types of Flexible Electrical Conduit?

Different Types of Flexible Electrical Conduit

Flexible conduit is described as a raceway for electrical conductors or wiring. Material, assembly and use are described in the NEC. Here are the most common types of flexible electrical conduit.

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1. Flexible Metal Conduit (FMC)

This type of electrical conduit is lightweight, durable and easy to install. This flexible metal conduit is made of a helically wound strip of metal (galvanized steel or aluminum) that provides strength and flexibility while protecting wire. It is recommended for concealed or exposed dry areas. It bends easily to fit around corners and obstacles, making it suitable for surface-mounted installations. For options available from ANAMET Electrical, Inc. see FMC Conduit.

Some of the common applications include:

• Industrial and commercial settings: This conduit is used in buildings, electric motor connection, elevators, escalators and chair lifts, where wiring is not exposed to water.
• Residential settings: They can be commonly used in homes, especially for wiring appliances like washers, dryers, refrigerators, heaters and air conditioners.

2. Liquid Tight Flexible Metal Conduit (LFMC)

As the name implies, this is one of the flexible electrical conduit types that work exceptionally well in wet environments. It has a metal core with an extruded thermoplastic cover to make a liquid tight conduit. Galvanized steel is often used for the stripwound core with an integral bonding wire. However, NEC approved stainless steel in the stripwound core in when installed with a separate grounding conductor or bonding jumper.

A variety of thermoplastic materials are approved by UL for conduit jackets. These thermoplastic jackets have heat-, cold-, corrosion-, prolonged UV- and static electricity-resistant properties.

The following are some common applications for LFMC conduit:

• Outdoor and underground installations: Liquid-tight conduit is suitable for areas that may be exposed to moisture or water, such as irrigation systems, air conditioners or outdoor lighting. UL listed conduit suitable for burial in the earth or in concrete is marked with DIR BURIAL or DIRECT BURIAL. For more information, see What is Direct Burial?
• Hazardous locations: Since they offer protection against moisture and corrosion, UL listed, liquid tight conduit is approved for use in Class I Div. 2 Hazardous Locations exposed wiring might cause danger.

3. Liquid Tight Flexible Non-Metallic Conduit (LFNC)

As the name implies, this is one of the flexible electrical conduit types that works exceptionally well in wet environments. It is PVC extruded as liquid tight conduit.

There are two varieties of LFNC, Types A and B. Two layers of flexible PVC sandwich a layer of continuous nylon knit cord in LFNC Type A. Type B is a continuous coil of PVC in a smooth PVC jacket. For more information about the differences between these LFNC Types available from ANAMET Electrical, Inc., see LFNC Types.

The following are some common applications for this type of conduit:

• Outdoor and underground installations: Liquid tight non-metallic conduit is suitable for areas that may be exposed to moisture or water, such as irrigation systems, air conditioners or outdoor lighting.
• Hazardous locations: Since they also offer protection against moisture and corrosion, UL listed liquid tight conduit is approved for use in Class I Div. 2 Hazardous Locations exposed wiring might cause danger.
• Jacket options: Halogen Free and fire resistant jackets are available for conduit installation in hot, confined work spaces.

Choose the Right Conduit Size

Consider electrical conduit size to keep connection easy.

• UL listed flexible conduit is available from ANAMET Electrical in diameters from &#; inch to 2 inches.
• Choose conduit and fittings that suit the application, so the conduit can be connected to a power panel or junction box through standard knockout holes.

A rule of thumb is for three or more wires to fill 40% or less of the conduit volume, to allow for wire fishing and flexibility. More wires or cable make conduit rigid and hard to bend.

Contact Anamet Electrical Inc. For  All Your Flexible Conduit Needs

At Anamet Electrical Inc., we offer a wide range of flexible electrical conduit types to meet your needs. Our products are designed to connect and protect electrical wiring easily and effectively. Contact us today for more information.

How is a flexible conduit made? What are the tests it must undergo to ensure tightness and strength? How is a flexible conduit system built? This article is a mini-guide to flexible conduit system, where you can find all the information you need to learn about them. 

Browse the dedicated section to discover all the electrical cable conduit available in our catalog. 

Flexible conduit system: all the details

Let&#;s start with a conduit  system, and let&#;s review it with the help of an explanatory figure. 

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What is it? It is a closed wiring system consisting of fittings for protecting and managing cables in electrical or communication systems, allowing them to be inserted and/or replaced but not to be inserted laterally.

Figure 1a: flexible conduit | Figure 1b: flexible conduit with plastic recovery (composite conduits) | Figure 1c: non-metallic flexible conduit

Conduit  (1): a part of a closed wiring system with a circular cross-section for cables in electrical or communication installations, allowing their insertion and/or replacement. 

Conduit  fitting (2): a device designed to join or end one or more components of a conduit system or to change its direction 

Composite conduit (3) and/or conduit fitting (1): Pipe conduit or fitting including both metallic and non-metallic materials

Non-metallic conduit (plastic pipe) (4) and/or pipe fitting (plastic fitting): pipe or conduit fitting consisting only of a non-metallic material and without metallic components. 

Flexible conduit (1,3): a conduit that can be bent by hand with reasonably light effort and intended to be bent throughout its lifespan

Reference standards: EN IEC -1, IEC -1

Basic construction of  a flexible metal conduit system

The profile of a flexible conduit is formed by a spiral shape passing through the axis with equal space through a reinforced template. Flexible conduits are manufactured in galvanized steel, AISI 304 or AISI 316L stainless steel, bronze, and other materials. 

This table summarizes the typical characteristics of flexible conduit compared with the specific features of our flexible conduit. 

Flexible conduits available in market Vs Euro flexible conduit

Tests for flexible conduit according to EN IEC standards

There are several tests to assess the quality of a flexible conduit and its features. In particular, it is necessary to determine:

• Mechanical properties: different types of tests are used (for example tensile, compression, impact, bending, tests, and more) to determine the mechanical features of the material by applying an external force.

• Electrical properties: current or voltage is applied to test the basic elements such as electrical continuity, bonding test, electrical insulation strength, and resistance.

• External influences: tests are carried out for protection against water and dust. Due to water, ferrous metals become corrosive when exposed to weather agents, and thus a corrosion test is required as well. Learn more about the IP rating protection against weather agents or dust and water. 

Quality control on Euro flexible conduit

At Euro , our quality control department carries routine in-house testing for flexible conduit according to EN IEC .

Figure 3: compression test setup | Figure 4: tensile test setup

Compression testing for Euro flexible conduit

The test samples are positioned on a flat steel support, and an intermediate steel piece, as shown in Figure 3, is placed at the center of the sample. A continuously increasing compressive force is applied to the intermediate piece, reaching the values shown in Table 1 within 30 seconds. After the force (according to the classification) has been applied for (60 ± 2) seconds, the outer diameter of the sample is measured where flattening occurred without removing the force. The difference between the initial outer diameter and the diameter of the flattened sample must not exceed 25% of the initial outer diameter measured before the test.

The force and the intermediate piece are then removed, and 60 seconds after removal, the outer diameter of the sample is measured again where flattened. The difference between the initial diameter and the diameter of the flattened sample must not exceed 10% of the outer diameter as measured before the test. After the test, the specimens must not show visible cracks without further magnification.

Tensile test for Euro flexible conduit

A pipe sample and two end fittings are assembled according to the manufacturer&#;s instructions so that the total length (L) is about 300 mm.

The assembly is subjected to continuous and increasing tensile force for 30 to 40 seconds up to the value specified in Table 1. After 2 min ± 10 s the force is removed. If elongation occurs, the manufacturer shall provide instructions to assist in a safe installation. For conduit systems where the tensile strength is not stated, the tensile strength of the joint must meet the requirements of the applicable tests. After testing, the end fittings must remain properly assembled to the pipe, and there must be no visible damage.

Download this report for more information on conduit classification coding, and do not hesitate to contact us for more information. 

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