Flexible conduits are essential components in electrical installations, providing versatile solutions for protecting electrical wires from physical damage, moisture and other environmental hazards.

Their ability to bend and adapt makes them easy to install in tight or complex spaces, making them suitable for routing electrical work in an assortment of commercial applications.

Four types are commonly used:

• Flexible Metallic Conduit (FMC).
• Liquidtight Flexible Non-Metallic Conduit (LTNFC).
• Liquidtight Flexible Metal Conduit (LTFMC).

Each has its own advantages and optimal applications. We discuss each below.

Flexible Metallic Conduit (FMC)

Main Advantages

Flexible Metallic Conduit (FMC) offers improved static flexibility, which allows for tighter bends in hard-to-reach areas. Advantages include its durability, with metal construction providing robust protection, and its versatility, which makes it suitable for various indoor applications without needing liquidtight features.

Safety Considerations

Safety is a critical factor in electrical installations, and FMC provides several safety benefits, such as:

• Fire Resistance: FMC’s lack of jacketing reduces the risk of producing smoke or fumes if a fire occurs.
• Grounding Capabilities: FMC provides excellent grounding capabilities for maintaining electrical safety and preventing faults.

Optimal Applications

FMC provides essential protection for electrical wiring in various settings, including buildings where liquidtight protection is unnecessary and installations near machinery with tight bends.

Liquidtight Flexible Non-Metallic Conduit (LTNFC)

Main Advantages

Liquidtight Flexible Non-Metallic Conduit (LTNFC) offers superior protection against water, making it ideal for environments exposed to moisture. LTNFC’s water-resistant properties are achieved through its construction and liquidtight fittings, which ensure the electrical wires remain protected from water ingress.

Material Composition

Manufacturers create LTNFC using a combination of flexible PVC and rigid PVC materials, which offer several benefits:

• Flexibility: The flexible PVC component allows LTNFC to bend and adapt to various installation environments.
• Durability: The rigid PVC component adds strength and durability, ensuring long-term protection for electrical wiring.
• Water Resistance: The combination of materials ensures that LNFC is both flexible and capable of preventing water ingress.

Use Cases

LNFC excels in applications where moisture exposure is a concern, including:

• HVAC Applications: Used in HVAC systems to protect wiring.
• Exposed Outdoor Areas: Commonly used in outdoor environments where non-metallic conduits are preferred for their resistance to corrosion and water.
• Repetitive Flexing: Non-metallic conduits are less likely to fatigue and fail compared to metallic conduits, making them suitable for applications involving frequent movement.

Liquidtight Flexible Metal Conduit (LTFMC)

Main Advantages

Liquidtight Flexible Metal Conduit (LTFMC) combines the flexibility of metal with liquidtight protection. Constructed with a hot-dip galvanized (HDG) steel core, it provides mechanical protection, and liquidtight fittings prevent moisture from entering the conduit.

Flexibility vs. Protection

LFMC strikes a balance between flexibility and protection. The minimum bend radius of LTFMC is determined by trade size and UL or CSA requirements, ensuring that the conduit can be installed in various environments while maintaining its protective qualities.

Comparative Advantages

LFMC is particularly well-suited for applications requiring flexibility and robust protection. Scenarios where LTFMC is preferred over LTNFC include:

• Industrial Environments: LFMC provides enhanced protection against physical damage, making it ideal for industrial settings with higher risk factors.
• Areas with Greater Need for Physical Protection: LTFMC is more durable than LTNFC in situations where physical impact is a concern.
• Applications Requiring Both Flexibility and LiquidTight Features: LFMC offers the best of both worlds, combining flexibility with liquidtight protection.

Codes and Compliance

Various codes and standards govern the use of flexible conduits, which impact the choice of conduit in different projects.

For example, UL-listed LTFMC products may be required in hazardous locations as specified by the National Electrical Code (NEC). Compliance with these standards ensures safety and reliability in electrical installations.

UL vs. Non-UL Conduits

When selecting flexible conduits, it’s essential to consider whether UL listing is required. UL-listed conduits, such as UL360 for LTFMC in the USA, meet specific regulatory standards that detail construction, material and performance requirements.

While non-UL conduits do not meet these specific criteria, they are still constructed with attention to quality and sizing to ensure compatibility with standard connectors.

Consicerations

When selecting and installing flexible liquidtight conduit, contractors should gather detailed information about the application and installation area. Key factors to consider include:

• Listed Component Requirements: Determine if UL-listed components are necessary for the project.
• Working Temperatures: Ensure the conduit can withstand the operating temperatures of the environment.
• Material Requirements: Choose materials that provide the necessary protection and durability.
• Trade Size: Select the appropriate trade size for the conduit to ensure proper fit and function.
• Indoor or Outdoor Location: Consider the environmental exposure and choose conduits accordingly.
• UV Resistance: Ensure the conduit can withstand exposure to sunlight if used outdoors.
• Corrosive Environments: Select conduits that can resist corrosion in harsh environments.
• Hazardous Location Status: Verify if the installation area is classified as a hazardous location and select conduits that meet the required standards.
• Flame Retardant Properties: Choose conduits with flame-retardant properties if fire safety is a concern.

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