Conduit Fill Chart: How Many Wires Can Fit Into EMT, PVC, IMC, and RMC Conduits

As the backbone of modern electrical installations, conduits play a crucial role in safely routing and protecting electrical wiring across residential, commercial, and industrial applications.

Selecting the appropriate conduit size and type is essential to ensure optimal performance and compliance with safety standards.

Published: May 9, 2023.

Conduit Fill Chart

A conduit fill chart serves as a vital tool for engineers, electricians, and contractors, helping them navigate the complexities of electrical installations while adhering to the guidelines set forth by the National Electrical Code (NEC) and local building codes.

The following conduit fill chart lists how many conductors/wires (THHN, THWN, and THWN-2 wires) can fit into EMT, PVC, IMC, and RMC conduits and should be used as a reference only:

How To Read Conduit Fill Chart?

For example, if you want to find the answer to the following question, "How many #10 THHN in 3/4 EMT?" that means: How many 10 AWG (gauge 10) THHN wires can fit into 3/4 inches EMT wire conduit?

So if we check the "10 AWG" column and find the "3/4 inches EMT" row, we can find a value of "10" - that means that ten (10) gauge 10 wires can fit into a 3/4" EMT conduit.

Again, this chart is for reference purposes only.

What are EMT conduits?

EMT, or Electrical Metallic Tubing, is a type of conduit used to protect and route electrical wiring in various residential, commercial, and industrial applications. EMT conduit is made from thin-walled steel or aluminum, providing a lightweight, durable, and cost-effective solution for safely housing electrical wires.

EMT conduit is often preferred for its ease of installation, as it can be easily bent, shaped, and cut on-site to accommodate different routing needs. The thin-walled design and smooth interior surface of EMT conduits allow for easier wire pulling, reducing the risk of damage to the electrical conductors during installation. EMT conduits are typically secured with compression or set-screw connectors and couplings, ensuring a secure and stable connection.

While EMT conduits provide adequate protection for electrical wiring, they are not suitable for all environments. They are primarily intended for use in dry locations, as they do not have inherent corrosion resistance or watertight properties. In wet or corrosive environments, alternative conduit types, such as PVC-coated or rigid metal conduits, may be more appropriate.

It is crucial to adhere to the National Electrical Code (NEC) and local building codes when selecting and installing EMT conduits or any other conduit type to ensure the safety, compliance, and optimal performance of the electrical system.

What Are PVC Conduits?

PVC conduits, or Polyvinyl Chloride conduits, are a type of non-metallic conduit system used to protect and route electrical wiring in a variety of residential, commercial, and industrial applications. PVC conduits are made from a rigid, lightweight plastic material that offers several advantages over traditional metallic conduits.

Some key features and benefits of PVC conduits include:

• Corrosion Resistance: PVC conduits are inherently resistant to rust and corrosion, making them suitable for use in damp, wet, or corrosive environments where metallic conduits may not be appropriate. This resistance to corrosion ensures a longer service life and reduced maintenance costs.
• Electrical Insulation: As a non-conductive material, PVC provides an additional layer of electrical insulation, reducing the risk of electrical shock or short-circuiting.
• Easy Installation: PVC conduits are lightweight and easy to cut, making them simpler to install compared to metallic conduits. They can be joined using solvent cement, which creates a secure, watertight connection.
• Cost-Effective: PVC conduits are typically more affordable than their metallic counterparts, offering a cost-effective solution for electrical installations while maintaining safety and durability.
• Chemical Resistance: PVC conduits offer resistance to a wide range of chemicals, including acids, alkalis, and salts, making them suitable for use in environments with potential chemical exposure.
• Versatility: PVC conduits are available in various sizes, shapes, and configurations, including rigid PVC conduit (Schedule 40 and Schedule 80) and flexible PVC conduit, providing options for different project requirements and preferences.

However, it is essential to consider PVC conduits' limitations, such as lower heat resistance compared to metallic conduits and the potential for distortion under high temperatures. As with any conduit type, adhering to the National Electrical Code (NEC) and local building codes is crucial to ensure the safety, compliance, and optimal performance of the electrical system - this cannot be emphasized enough ...

What Are IMC Conduits?

IMC (Intermediate Metal Conduit) is a type of rigid metallic conduit used to protect and route electrical wiring in various residential, commercial, and industrial applications. IMC conduits are made from steel or aluminum, with walls that are thinner than those of Rigid Metal Conduit (RMC) but thicker than those of Electrical Metallic Tubing (EMT).

IMC conduits offer several advantages over other conduit types, including:

• Durability: IMC conduits are strong and resistant to physical damage, providing reliable protection for electrical wiring in demanding environments or locations with a higher risk of impact.
• Corrosion Resistance: IMC conduits are often coated with a galvanized finish, which increases their resistance to rust and corrosion. This makes them suitable for use in both indoor and outdoor applications, as well as in damp or wet environments.
• Lightweight: The intermediate wall thickness of IMC conduits makes them lighter than RMC conduits, which can lead to easier handling and installation.
• Easy Installation: IMC conduits can be easily cut, bent, and joined using threaded couplings or compression fittings, ensuring a secure and stable connection.
• Cost-Effective: IMC conduits tend to be more affordable than RMC conduits, offering a cost-effective solution that balances strength and durability with lower material and installation costs.

It is important to consider that IMC conduits, like other metallic conduit types, do not provide inherent electrical insulation. As such, proper grounding and bonding practices must be followed to ensure safety and compliance with the National Electrical Code (NEC) and local building codes.

What Are RMC Conduits?

RMC (Rigid Metal Conduit) is a type of heavy-duty metallic conduit used to protect and route electrical wiring in a variety of residential, commercial, and industrial applications. RMC conduits are typically made from galvanized steel, stainless steel, or aluminum and feature thick walls that offer robust protection for electrical wires.

RMC conduits provide several advantages over other conduit types, including:

• Durability: RMC conduits are extremely strong and resistant to physical damage, providing excellent protection for electrical wiring in demanding environments or locations with a higher risk of impact.
• Corrosion Resistance: RMC conduits are often coated with a galvanized or other protective finish, which increases their resistance to rust and corrosion. This makes them suitable for use in both indoor and outdoor applications, as well as in damp or wet environments.
• Grounding: Due to their metallic construction, RMC conduits can serve as an equipment grounding conductor when properly installed and bonded, ensuring a safe electrical system.
• Fire Resistance: RMC conduits offer inherent fire resistance due to their metallic composition, helping to contain and prevent the spread of fire in the event of an electrical fault.
• Versatility: RMC conduits are available in various sizes and configurations, providing options for different project requirements and preferences.

However, there are some drawbacks to using RMC conduits, such as their heavier weight and higher material and installation costs compared to other conduit types like EMT or IMC. Additionally, cutting, bending, and threading RMC conduits can be more labor-intensive than working with lighter alternatives.

When selecting and installing RMC conduits, it is essential to adhere to the National Electrical Code (NEC) and local building codes to ensure the safety, compliance, and optimal performance of the electrical system.

What Are GRC conduits?

GRC (Galvanized Rigid Conduit) is a type of heavy-duty metallic conduit used to protect and route electrical wiring in various residential, commercial, and industrial applications. GRC conduits are made from steel, featuring thick walls that offer robust protection for electrical wires. The steel conduit is galvanized, which means it is coated with a layer of zinc to provide enhanced resistance to rust and corrosion.

In many ways, GRC and RMC conduits behave the same and have the same features, except that GRC conduits feature an additional zinc layer for improved corrosion and rust resistance.

GRC conduits offer several advantages over other conduit types, including:

• Durability: GRC conduits are extremely strong and resistant to physical damage, providing excellent protection for electrical wiring in demanding environments or locations with a higher risk of impact.
• Corrosion Resistance: The galvanized coating on GRC conduits increases their resistance to rust and corrosion, making them suitable for use in both indoor and outdoor applications, as well as in damp or wet environments.
• Grounding: Due to their metallic construction, GRC conduits can serve as an equipment grounding conductor when properly installed and bonded, ensuring a safe electrical system.
• Fire Resistance: GRC conduits offer inherent fire resistance due to their metallic composition, helping to contain and prevent the spread of fire in the event of an electrical fault.
• Versatility: GRC conduits are available in various sizes and configurations, providing options for different project requirements and preferences.

However, there are some drawbacks to using GRC conduits, such as their heavier weight and higher material and installation costs compared to other conduit types like EMT, PVC, or IMC. Additionally, cutting, bending, and threading GRC conduits can be more labor-intensive than working with lighter alternatives.

When selecting and installing GRC conduits, it is essential to adhere to the National Electrical Code (NEC) and local building codes to ensure the safety, compliance, and optimal performance of the electrical system.

What Are GALV Conduits?

GALV conduits, short for galvanized conduits, refer to metallic conduits that have been coated with a protective layer of zinc to enhance their resistance to rust and corrosion. The term "galvanized" does not describe a specific type of conduit but rather refers to the zinc coating applied to the exterior surface of the conduit to improve its durability and longevity.

Galvanized conduits can be found in various types of metallic conduit systems, including Rigid Metal Conduit (RMC), Intermediate Metal Conduit (IMC), and Electrical Metallic Tubing (EMT). These conduits are commonly used in residential, commercial, and industrial electrical installations to protect and route wiring.

However, very often, GALV and GRC conduits labels are used interchangeably, which sometimes can lead to confusion and errors; be very careful when checking conduit fill ratings for GALV and RMC conduits - in most cases they are equal to RMC conduit fill values. Again, "in most cases" ...

Some key features and benefits of GALV conduits include:

• Corrosion Resistance: The zinc coating on galvanized conduits provides enhanced resistance to rust and corrosion, making them suitable for both indoor and outdoor applications, as well as damp or wet environments.
• Durability: The metallic construction of galvanized conduits offers robust protection for electrical wiring, guarding against physical damage and impact.
• Grounding: Galvanized conduits can serve as an equipment grounding conductor when properly installed and bonded, ensuring a safe electrical system.
• Fire Resistance: Galvanized conduits offer inherent fire resistance due to their metallic composition, helping to contain and prevent the spread of fire in the event of an electrical fault.
• Versatility: Galvanized conduits are available in various sizes, shapes, and configurations, providing options for different project requirements and preferences.

It is important to adhere to the National Electrical Code (NEC) and local building codes when selecting and installing galvanized conduits to ensure safety, compliance, and optimal performance of the electrical system.

What is Ampacity Derating In Conduit?

Ampacity derating in conduit refers to the process of reducing the current-carrying capacity (ampacity) of electrical conductors when specific conditions exist that could potentially increase the temperature of the wires and lead to overheating. These conditions usually involve the number of conductors within a conduit, the ambient temperature, or a combination of both factors.

Overheating can damage insulation, reduce the service life of conductors, and increase the risk of electrical fires. To address these concerns, the National Electrical Code (NEC) has established guidelines for ampacity derating, which require adjustments to the conductor's maximum current-carrying capacity under specific circumstances.

• Number of Conductors: When multiple conductors are bundled together in a conduit, their ability to dissipate heat decreases. As a result, the temperature inside the conduit can rise, leading to potential overheating. The NEC requires derating the ampacity of conductors when more than three current-carrying conductors are installed in a single conduit to account for this potential heat buildup.
• Ambient Temperature: The ampacity of a conductor is generally rated at a specific ambient temperature, typically 30°C (86°F). When the ambient temperature is higher than the rated temperature, the conductor's resistance increases, generating more heat and reducing its current-carrying capacity. The NEC provides correction factors for adjusting the ampacity of conductors based on the ambient temperature to prevent overheating in higher-temperature environments.

It is crucial to follow the NEC guidelines for ampacity derating when designing and installing electrical systems, as proper derating ensures the safety and longevity of the conductors, insulation, and the entire electrical installation.

Few Final Words

Selecting the correct conduit type and size is crucial, whether working with EMT, PVC, IMC, RMC, GRC, or GALV conduits.

Proper use of a conduit fill chart ensures that electrical wiring is not overcrowded, reducing the risk of overheating, short-circuiting, and other potential hazards.

Ultimately, understanding and utilizing conduit fill charts promotes best practices in the electrical industry, contributing to the successful completion of residential, commercial, and industrial projects that meet or exceed safety and performance standards.