Can You Put Romex in Metal Conduit?

Installing Romex (nonmetallic sheathed) cable in a metal conduit, especially when connecting to a panel, is a task that must adhere to specific codes and standards. The National Electrical Code (NEC) outlines clear guidelines for this process, particularly under section 312.5(C). This article aims to elucidate the requirements and exceptions for such installations, ensuring compliance and safety.

NEC 312.5(C): General Requirement for Cable Termination

The NEC’s one-sentence rule under 312.5(C) states: “Each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.” This foundational rule emphasizes securing cables to prevent strain and ensure a stable connection.

Can You Run Romex In Conduit?

Romex in Metal Conduit

Yes, Romex (nonmetallic sheathed cable) can be run in a conduit, but there are specific considerations and guidelines to follow. It’s important to understand the context and reasons for doing so:

  1. Protection: Romex can be run in conduit for added protection against physical damage, especially in exposed or hazardous locations. For instance, running Romex in a conduit along the surface of a garage wall can protect it from being damaged.
  2. Conduit Sizing: When running Romex in conduit, choosing the right size of conduit is essential to avoid overcrowding and overheating. The National Electrical Code (NEC) provides guidelines on conduit fill, which should be followed to ensure safety and compliance.
  3. Transitioning from Exposed to Hidden Areas: In some cases, Romex may need to be run through conduit for a short distance, such as when transitioning from an exposed area to a wall cavity or through a floor.
  4. Local Codes and Regulations: Always check local building codes and regulations, as they may have specific requirements or restrictions regarding running Romex in conduit.
  5. Not Typically Necessary Inside Walls: In typical residential construction, where wiring is run inside walls, through attics, or in other protected spaces, running Romex in conduit is not necessary and not usually practiced, as the sheathing of Romex provides adequate protection in these environments.
  6. Ease of Pulling Wires: Pulling Romex through the conduit can be more challenging than individual THHN wires, especially around bends and long runs, due to its stiffness and the friction of the sheathing.

While running Romex in conduit is technically possible, it should be done carefully considering the reasons, NEC guidelines, and local codes. The decision should be based on the specific needs of the installation and the environment where the wiring is run.

Conditions for Romex Cable Entry into Panelboards

When installing Romex into panelboards, the National Electrical Code (NEC) provides specific conditions that must be met. These conditions ensure safety, reliability, and ease of maintenance in electrical systems.

This article segment delves into these key conditions, clearly understanding how to properly and safely integrate Romex cables into panelboards. Electricians and DIY enthusiasts must know these guidelines to ensure their installations comply with NEC standards and provide a secure electrical environment.

Let’s explore these conditions in detail to understand how to approach Romex cable installations in panelboards.

  1. Raceway Length: Romex cables can enter the top of a service-mounted panelboard through a nonflexible raceway. The length of this raceway must be at least 18 inches but not more than 10 feet.
  2. Securing Cables: Securing the Romex cable within 12 inches of the raceway’s outer end is mandatory.
  3. Raceway Positioning: The raceway must extend directly above the panelboard without penetrating the structural ceiling.
  4. Fittings Requirement: Fittings are required at both ends of the raceway to protect the cables from abrasion. These fittings must remain accessible after installation.
  5. Raceway Sealing: The raceway needs to be sealed at its outer end to prevent environmental damage to the cables.
  6. Cable Sheath Continuity: The cable sheath should be continuous inside the raceway and extend into the panelboard beyond the fitting by at least 1/4 inch.
  7. Raceway Securing: The raceway must be secured in accordance with the wiring method requirements applicable to it.
  8. Wire Fill Calculation: The wire fill table in Chapter 9 of the NEC must be used to prevent cable overfill in the raceway.

Determining Cable Capacity in Conduits

When calculating how many cables can fit in a 2-inch conduit, it’s important to refer to Note 9 to Table 1 in Chapter 9 of the NEC. This note requires that multiconductor cables be treated as a single conductor. For cables with oval or elliptical cross-sections, the cross-sectional area is calculated based on the major diameter to determine an equivalent circle diameter.

Complying with NEC 312.5(C) for Romex cable installation in metal conduits is critical for your electrical work’s safety and legality. Understanding and adhering to these specific requirements and conditions ensures that your installation is up to code, secure, and reliable. When in doubt, consulting with a licensed electrician or referring to the latest NEC manual can provide additional guidance and clarification.

Mas Broto

Written by: Mas Broto

Mas Broto is a small business owner with 30 years experience in the real estate industry. He is the founder and editor of, the most comprehensive free home improvement website on the planet!