Introduction
Running electrical wiring can be a daunting task for many homeowners. While metal conduits provide protection and neatness, threading Romex cables through them brings some safety concerns. In this guide, I will walk you through the complete process to run exposed Romex through metal conduits safely.
Choosing the Right Materials
Selecting the Correct Size Metal Conduit
- The conduit should be at least 1/2 inch larger than the Romex cable to allow easy pulling without damage.
- For a standard 12/2 Romex cable, a 3/4 inch conduit would be suitable. Going larger by another 1/4 inch provides extra space.
- The conduit must be made of ferrous metal like steel or aluminum for proper grounding. Non-metallic conduits do not provide a ground path.
Picking the Right Romex Wire
- Use only standard NM-B cable with THHN conductors for exposed installations.
- 12 AWG is adequate for 15 amp circuits, while 10 AWG can handle 20 amps.
- The cable jacket must be marked with "Sunlight Resistant" for outdoor installations.
Gathering Other Supplies
- Conduit straps to securely mount the conduit.
- Wire lubricant to reduce friction when pulling the cables.
- Conduit bodies and junction boxes to make wire splices accessible.
Planning the Installation Route
- Lay out the exact path before installing the conduit to avoid kinks and bends below the allowed radius.
- Route the conduit along walls/ceilings to keep it out of the way. Avoid burying conduits in concrete slabs.
- Install pull boxes if there are multiple bends or the run exceeds 100 feet.
Mounting the Conduit
- Use appropriate conduit straps to firmly fasten the conduit in place.
- Maintain 1/4 inch clearance from combustible surfaces.
- Ground the conduit properly as it acts as the grounding path. Connect to nearby grounded junction boxes or use grounding locknuts.
Pulling and Splicing the Romex
- Apply a thin coat of wire lubricant on the conductors to minimize friction.
- Carefully pull the cables through the conduit without kinking or damaging the jackets.
- Leave 12-18 inches of extra cable at boxes for splices and future maintenance.
- Use watertight wire connectors to join Romex cables in junction boxes.
Safety Best Practices
- Always switch OFF the power supply at the breaker before working.
- Install proper conduit seals at outdoor ends to prevent moisture ingress.
- Use separate neutral and ground wires instead of shared grounding.
- Label all wire runs clearly for future identification.
Conclusion
Running Romex through metal conduits takes careful planning and execution. Following the safety guidelines listed here regarding sizing, mounting, pulling, and splicing ensures a safe, trouble-free installation. Proper grounding and sealing techniques are especially vital for outdoor applications. Paying close attention to the details at every step leads to a professional looking and code compliant project.