How to Install RGS Conduit: A Step-by-Step Professional Guide

Understanding RGS: Beyond the Basic Conduit Meaning

For licensed electricians, the term “conduit” encompasses a wide range of products, but Rigid Galvanized Steel (RGS) stands in a class of its own. When discussing conduit meaning in a professional context, RGS refers to a heavy-walled, threaded electrical raceway made of steel with a protective zinc coating. Governed by NEC Article 344, this type of raceway is recognized for providing the highest level of physical protection against impact and damage. The robust nature of RGS electrical conduit makes it the standard for industrial applications, outdoor installations, and areas where physical abuse is a significant concern. Its threaded design ensures a strong mechanical and electrical connection at every joint, which is critical for system integrity.

IMC vs RGS Conduit: Making the Right Choice

A common point of discussion in the field is the IMC vs RGS conduit debate. While both are rigid metal conduits, they have key differences. RGS has a thicker wall and is heavier than Intermediate Metal Conduit (IMC). This added thickness gives RGS superior strength and impact resistance. IMC, while still very durable, is lighter and has a slightly larger internal diameter, which can sometimes make wire pulling easier. The choice often comes down to the specific demands of the installation. For the most demanding environments, including many hazardous locations and areas subject to severe physical damage, RGS is the required and preferred choice. For many other commercial applications, IMC provides a compliant and more economical alternative.

Pre-Installation Planning: Tools, Materials, and Protection

A successful rigid metal conduit installation begins with proper preparation. Gathering the correct tools and materials beforehand prevents delays and ensures a code-compliant job. Pay special attention to the environment, as supplemental conduit corrosion protection may be necessary beyond the standard galvanization. For instance, wiring systems in corrosive environments requires specific materials and coatings.

• Essential Tools: Pipe cutter or band saw, level, tape measure, and a power or manual pipe threader for executing proper conduit threading techniques. For larger sizes, a hydraulic conduit bender is indispensable for creating smooth, accurate bends.
• Conduit & Fittings: Sticks of RGS conduit, couplings, factory elbows, and various conduit body types (e.g., LB, LL, LR, T, C) for navigating turns and providing access points.
• Enclosures and Supports: Straps, hangers, and enclosures like electrical pull boxes and junction boxes. For larger conductor management, you may also integrate the system with wireways or an electrical gutter.
• Specialty Fittings: For specific applications, you’ll need items like sealing fittings and explosion proof fittings for classified hazardous locations.

The Step-by-Step Guide on How to Install RGS Conduit

Executing a flawless RGS installation requires precision at every stage. Follow this professional process to ensure your work is safe, durable, and compliant.

1. Measure and Cut: Measure the required length of conduit between termination points or fittings. Use a pipe cutter, portable band saw, or hacksaw to make a straight, square cut. Accuracy here minimizes waste and ensures tight-fitting joints.
2. Perform Conduit Reaming and Deburring: This is a non-negotiable step. After cutting, the inside edge of the conduit will be sharp. Use a reaming tool or a deburring head to smooth this edge completely. Failing to perform proper conduit reaming and deburring can strip wire insulation during pulling, creating a serious shock or fire hazard.
3. Master Conduit Threading Techniques: Using a manual or power threader, cut NPT (National Pipe Taper) threads onto the end of the conduit. Apply generous amounts of cutting oil to ensure clean, sharp threads and to prolong the life of your dies. The threads must be clean and well-formed to ensure a solid mechanical connection and proper grounding path.
4. Execute Bending Rigid Conduit: For field bends, use a mechanical or hydraulic conduit bender. Follow the bender’s instructions carefully to avoid kinking or flattening the conduit, which is a violation of NEC 344.24. For complex layouts or back-to-back 90s, meticulous layout and math are essential.
5. Assemble and Secure Components: Thread the conduit into couplings, fittings, and hubs until it is wrench-tight. For enclosure entries, a proper threaded hub installation is key to maintaining the system’s integrity, especially for wet locations. Secure the conduit run according to conduit support requirements outlined in NEC 344.30, which generally requires support within 3 feet of each box and every 10 feet thereafter for most sizes.

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Advanced Considerations for RGS Systems

Beyond the basic installation, professional electricians must understand the critical roles RGS plays in specialized applications. These considerations separate a standard installation from an expert one.

Grounding and Bonding Conduit

One of the primary advantages of an RGS system is its ability to function as an equipment grounding conductor (EGC) per NEC 250.118. This is only effective if every connection is wrench-tight. Proper grounding and bonding conduit ensures a continuous, low-impedance path for fault current to travel back to the source, allowing the overcurrent protection device to operate quickly. Loose connections compromise this safety feature.

Hazardous Location Wiring Methods and Physical Protection

In classified areas (e.g., Class I, Division 1), RGS is one of the primary approved hazardous location wiring methods. When used with listed explosion proof fittings and sealing compounds, it contains explosions and prevents ignition of the surrounding atmosphere. This robust system provides far superior physical protection compared to other methods, a concept reinforced by NEC updates that emphasize protecting vulnerable cables from damage.

Service Entrance Conduit

Due to its strength and durability, RGS is frequently specified as the service entrance conduit. It provides maximum protection for service-entrance conductors as they run from the weatherhead down to the meter base and into the main service panel, safeguarding the most critical part of a building’s electrical system.

Related Resources from ExpertCE

• How has the 2023 NEC changed LFNC conduit use in corrosive environments?

Frequently Asked Questions

What are the main steps on how to install RGS conduit according to NEC Article 344?

The primary steps are: planning the run, accurately measuring and cutting the conduit, performing thorough conduit reaming and deburring to protect wires, using proper conduit threading techniques for strong connections, precisely bending rigid conduit as needed, and securing the system according to NEC conduit support requirements.

When are explosion proof fittings required for a rigid metal conduit installation?

Explosion proof fittings are required when RGS is used as one of the hazardous location wiring methods in areas classified by the NEC as hazardous (e.g., Class I, II, or III, Division 1 or 2). These fittings are designed to contain an internal explosion and prevent it from igniting flammable gases, vapors, or dust in the surrounding environment.

What are the primary differences in the IMC vs RGS conduit debate?

The main difference is wall thickness and weight. RGS has a thicker wall, making it heavier but also providing superior physical protection. IMC is lighter and has a slightly larger interior diameter, making it easier to handle and pull wire through. The choice depends on the level of physical protection required by the NEC and the specific job site conditions.

Why is grounding and bonding conduit so critical with RGS?

Properly grounding and bonding conduit is critical because the RGS raceway itself is permitted to serve as the equipment grounding conductor (EGC). This relies on every threaded connection being wrench-tight to create a continuous, low-impedance path for fault current. A compromised path could prevent a circuit breaker from tripping during a fault, creating a major safety hazard.