Types of Metal Conduit

Rigid Metal Conduit (RMC)

  • Heavy-duty galvanized steel tubing with threaded fittings.
  • Suitable for outdoor installations, providing protection and structural support.
  • Available in 10- and 20-foot lengths with threads on both ends.

Galvanized Rigid Conduit (GRC)

  • Galvanized steel tubing with a thick wall for maximum protection.
  • Approved for all interior and exterior applications.
  • Requires threaded fittings and is more expensive than other types of conduit.

Intermediate Metal Conduit (IMC)

  • Thinner and lighter-weight version of RMC.
  • Suitable for all interior and exterior applications.
  • Easier to work with than RMC and is more common in new construction.

Other Types of Conduit

Electrical Metallic Tubing (EMT)

  • Thin-wall conduit made of galvanized steel or aluminum.
  • Commonly used for exposed indoor wiring runs.
  • Installed with couplings and fittings secured with setscrews or compression-type fasteners.
  • Not threaded like RMC and IMC.

Flexible Metal Conduit (FMC)

  • Also known as “Greenfield.”
  • Flexible spiral construction for snaking through walls and structures.
  • Used for short runs and connecting to motors or fixed appliances.
  • Standard FMC is for dry indoor locations, while LFMC is watertight for outdoor applications.

Liquid-tight Flexible Metal Conduit (LFMC)

  • FMC with a plastic coating and sealed fittings.
  • Used in wet or corrosive environments and with outdoor equipment.

Rigid PVC Conduit

  • Similar to plastic plumbing pipe, installed with glued plastic fittings.
  • Can be bent after heating in a portable heater box.
  • Suitable for direct burial and corrosive environments.

Conclusion

The selection of conduit type depends on the specific application, environment, and code requirements. Metal conduits, such as RMC, GRC, and IMC, provide robust protection and are suitable for various installations. EMT is commonly used for exposed indoor wiring, while FMC and LFMC offer flexibility and watertightness. Rigid PVC conduit is ideal for direct burial and corrosive environments. Proper installation and adherence to code regulations are crucial for the safety and functionality of electrical systems.

Key Facts

  1. Types of Metal Conduit:
    • Rigid Metal Conduit (RMC): Thick-walled threaded tubing made of coated steel, stainless steel, or aluminum.
    • Galvanized Rigid Conduit (GRC): Galvanized steel tubing with a thick wall, providing maximum protection.
    • Intermediate Metal Conduit (IMC): Thinner and lighter-weight version of RMC, suitable for various applications.
  2. Other Types of Conduit:
    • Electrical Metallic Tubing (EMT): Thin-wall conduit made of galvanized steel or aluminum, commonly used for exposed indoor wiring runs.
    • Flexible Metal Conduit (FMC): Flexible spiral construction, used for short runs and snaking through walls.
    • Liquid-tight Flexible Metal Conduit (LFMC): FMC with a plastic coating, used with sealed fittings for watertight applications.
    • Rigid PVC Conduit: Similar to plastic plumbing pipe, installed with glued plastic fittings, suitable for direct burial and corrosive environments.

References

FAQs

What is the most common type of metal conduit?

  • Galvanized rigid conduit (GRC) is the most common type of metal conduit, known for its durability and protection.

What are the different types of metal conduit?

  • The main types of metal conduit include rigid metal conduit (RMC), galvanized rigid conduit (GRC), and intermediate metal conduit (IMC).

What is the difference between RMC, GRC, and IMC?

  • RMC is heavy-duty and suitable for outdoor installations, GRC offers maximum protection and is approved for all applications, while IMC is thinner and lighter, making it easier to work with.

What is electrical metallic tubing (EMT)?

  • EMT is a thin-wall conduit made of galvanized steel or aluminum, commonly used for exposed indoor wiring runs.

What is flexible metal conduit (FMC)?

  • FMC, also known as “Greenfield,” is a flexible spiral conduit used for short runs and connecting to motors or fixed appliances.

What is liquid-tight flexible metal conduit (LFMC)?

  • LFMC is a type of FMC with a plastic coating and sealed fittings, designed for wet or corrosive environments and outdoor applications.

When should I use metal conduit?

  • Metal conduit is recommended for outdoor installations, exposed locations, and areas where protection from physical damage or electromagnetic interference is required.

What are the advantages of using metal conduit?

  • Metal conduit provides excellent protection against impact, moisture, and chemical vapors, and it can also be used as a grounding conductor.