EMT vs. PVC Conduit: A Beginner’s Guide to Common Raceways

In the debate of EMT vs. PVC conduit, the best choice hinges on the installation environment and performance requirements. Electrical Metallic Tubing (EMT), a thin-walled steel raceway, is the top choice for indoor commercial and industrial applications where high mechanical protection is crucial. Its metallic nature allows it to serve as a grounding conductor, simplifying some installations. In contrast, PVC (Polyvinyl Chloride) conduit, a plastic raceway system, excels in environments where corrosion resistance is paramount, such as in wet locations or for underground burial. While lighter and often less expensive, PVC conduit always requires a separate grounding conductor because it is non-conductive. The decision also impacts installation, as working with EMT conduit demands skill in conduit bending, whereas PVC is joined with solvent cement and requires expansion fittings for long runs. Both must be installed in compliance with the National Electrical Code (NEC), especially concerning conductor fill and support intervals.

What is a Conduit and Raceway System?

Before diving into the specifics of EMT vs. PVC, it’s important to understand the fundamental roles they play. In electrical work, a conduit definition is a tube or trough used to protect and route electrical wiring. A collection of conduit, fittings, boxes, and other components forms a raceway system. The primary goals of any raceway system are to shield conductors from physical damage, impact, moisture, and chemical vapors, while also simplifying future wiring changes. The National Electrical Code (NEC) provides extensive guidelines on the proper use and installation of all conduit types to ensure safety and reliability.

What is EMT Conduit? (Electrical Metallic Tubing)

Electrical Metallic Tubing, universally known as EMT, is a thin-walled, unthreaded steel raceway. It is typically galvanized to provide a degree of corrosion protection. Because of its construction, EMT is relatively lightweight compared to other metallic conduits like RMC or IMC, making it easier to handle and install.

Key Characteristics and Applications of EMT

• Mechanical Protection: EMT’s steel construction offers excellent mechanical protection against impact, making it ideal for exposed work in commercial buildings, industrial settings, and residential garages or basements.
• Grounding: Per NEC Article 250, EMT is permitted to function as an equipment grounding conductor, which can streamline installation by eliminating the need to pull a separate grounding wire. This is only valid if connected with appropriate, securely tightened fittings.
• Installation: EMT cannot be threaded; instead, sections are joined using compression or set-screw fittings. Installation requires proficiency in conduit bending to navigate corners and offsets. For electricians looking to improve this skill, learning how to bend EMT conduit is a valuable part of professional development.
• Limitations: Standard EMT is not intended for highly corrosive areas or for direct burial in earth unless it has supplementary corrosion protection and is installed with fittings listed for that purpose. It is generally not the first choice for wet locations unless appropriate weatherproof fittings are used.

What is PVC Conduit? (Polyvinyl Chloride)

Polyvinyl Chloride (PVC) conduit is a rigid, non-metallic raceway made from a durable and lightweight plastic. It is most recognized by its gray color, which distinguishes it from white PVC plumbing pipe. Electrical PVC is formulated for UV resistance and other properties required for electrical installations.

Key Characteristics and Applications of PVC

• Corrosion Resistance: PVC’s greatest strength is its immunity to rust, acids, and alkalis. This exceptional corrosion resistance makes it the standard choice for underground installations, concrete encasement, and in environments with chemical exposure, such as farms or industrial plants.
• Wet Locations: As it is completely waterproof when properly installed, PVC is ideal for any wet locations.
• Grounding: Because it is a plastic, PVC is non-conductive and can never be used as a grounding conductor. A separate equipment grounding conductor must always be installed inside PVC conduit.
• Installation: PVC sections are joined using a simple two-step process of applying primer and solvent cement, creating a permanent, watertight bond. Bends can be made using a heating tool to soften the plastic. For long, straight runs exposed to significant temperature swings, expansion fittings are required by the NEC to accommodate thermal expansion and contraction.
• Limitations: Standard Schedule 40 PVC offers less mechanical protection than EMT. In areas where it is exposed to potential physical damage, the thicker-walled Schedule 80 PVC is often required.

Head-to-Head Comparison: EMT vs. PVC Conduit

NEC Code Considerations for Conduit Installation

Whether you are a seasoned journeyman electrician or in the middle of your electrician training, strict adherence to the National Electrical Code (NEC) is non-negotiable. Properly applying these NEC rules for raceway systems is a hallmark of a professional electrician. Master conduit fill and bending with our NEC courses.

Conductor Fill and Calculations

One of the most critical aspects of conduit installation is calculating conductor fill (or conduit fill). The NEC limits the percentage of a conduit’s interior that can be filled with wires to prevent heat buildup and damage during pulling. Using a conduit fill chart or conduit fill calculator is essential for compliance. The general rules from NEC Chapter 9, Table 1 are 53% for one wire, 31% for two wires, and 40% for three or more wires. Here’s a simplified process for mastering conduit fill calculations:

1. Identify your conduit type and trade size (e.g., 1-inch EMT). Find its total available area for the number of conductors from NEC Chapter 9, Table 4.
2. Identify the gauge and insulation type of all wires you plan to install (e.g., 12 AWG THHN).
3. Look up the cross-sectional area of each individual wire in NEC Chapter 9, Table 5.
4. Multiply the area of each wire by the number of conductors of that size.
5. Sum the total areas of all conductors to get your total fill area.
6. Confirm that your total conductor area does not exceed the maximum fill area for your conduit as determined in Step 1.

Support Intervals

The NEC also mandates maximum support intervals to prevent conduit from sagging. For EMT, it must be securely strapped within 3 feet of every box or fitting and then at least every 10 feet along the run. PVC support requirements are stricter; it must also be supported within 3 feet of a box, but subsequent supports are typically every 3 feet for sizes up to 1-inch to prevent sagging due to its flexibility and thermal expansion. Always consult the current nec code book, specifically Table 352.30 for PVC, as these intervals can change.

Conduit Bodies and Fittings

Conduit bodies (e.g., LBs, LLs, Ts) are fittings used to provide access to conductors for pulling, splicing, and bending. They are an essential part of most complex raceway systems. All fittings, from couplings to conduit bodies, must be UL listed and approved for the specific type of conduit and environment (e.g., rated for wet locations if used outdoors).

Key Takeaways for Choosing the Right Conduit

• Environment is Everything: Use EMT for dry, indoor locations where physical damage is a concern. Use PVC for underground, outdoor, or corrosive applications.
• Grounding is Different: EMT can act as the equipment grounding conductor, while PVC always requires a separate ground wire.
• Don’t Overstuff: Always perform a conductor fill calculation based on NEC tables to ensure safety and compliance.
• Know Your Raceway Options: While EMT and PVC are common, it’s also important to understand the differences when choosing the correct raceway type for various applications.
• Installation Skills Vary: Conduit bending is a learned art for EMT, while PVC work requires proper cementing and planning for thermal expansion.

Primary Sources

• National Fire Protection Association (NFPA) for the official National Electrical Code (NEC)

Frequently Asked Questions (FAQ)

Can you mix EMT and PVC conduit in the same run?

Yes, you can transition between EMT and PVC, which is common when running a circuit from an indoor exposed area (EMT) to an outdoor or underground section (PVC). This requires using a proper transition fitting, such as a threaded male terminal adapter on the EMT side connected to a female PVC adapter. It is critical to maintain grounding continuity across the transition.

What is the main difference in installation for EMT vs PVC conduit?

The primary installation difference is the method of bending and joining. EMT requires a mechanical bender for turns and uses screw- or compression-type fittings. PVC is bent using a heat source and is joined with solvent cement for a permanent, waterproof seal.

Does PVC conduit provide enough mechanical protection for exposed work?

In areas not subject to significant physical damage, Schedule 40 PVC may be acceptable for exposed work. However, if the conduit is in a location where it could be hit (e.g., low on a garage wall), NEC Article 352 often requires the use of heavier-walled Schedule 80 PVC for better mechanical protection. Local codes may have specific rules on this.

Why is a conduit fill chart so important for both EMT and PVC?

A conduit fill chart, derived from the NEC, is crucial for safety. Overfilling a conduit prevents heat from dissipating, which can degrade wire insulation and create a fire hazard. It also makes pulling conductors extremely difficult and can cause abrasion and damage to the wires.