Molly Ayala
Electrical conduit is a metal or plastic pipe that routes electrical wires in an installation while protecting the electrical cables from damage in an exposed area. Conduits are available in rigid or flexible forms and are used in exposed locations such as exterior wall surfaces, crawl spaces, attics, basements, and outdoors. They are also used in unfinished areas like basements, crawl spaces, and attics, and in surface-mounted installations outdoors. Conduits are classified by wall thickness, mechanical stiffness, and material used to make the tubing.
| Characteristics | Values |
|---|---|
| Definition | A raceway used to house and protect electrical wires within a building or structure |
| Types | Metal conduit, non-metal conduit, RMC, IMC, GRC, FMC, ENT, EMT, FMT, LFMC, PVC, LSZH |
| Uses | To protect electrical wires or cables from damage, fire, moisture, impact, chemicals, rodents, electromagnetic interference |
| Installation | Installed in exposed locations such as exterior wall surfaces, crawlspaces, attics, basements, and the outdoors |
| Compliance | Must follow the National Electrical Code (NEC) guidelines and all applicable local code regulations |
| Materials | Metal, plastic, steel, aluminium, PVC, polyamide systems |
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What You'll Learn
Conduit vs cable
Conduit and cable are two different methods of installing electrical wiring. A conduit is a hollow tube through which wires are pulled during installation. It is a metal or plastic pipe that routes electrical wires while protecting them from damage in exposed areas. Conduits can be rigid or flexible and are used in unfinished areas like basements, crawl spaces, and attics, as well as in surface-mounted installations outdoors.
On the other hand, a cable is a group of wires encased inside a flexible protective sheathing. The most common type of cable used in home wiring is non-metallic (NM) or Romex cable. Cable differs from conduit in that it is a single unit, whereas conduit is a separate pipe that houses wires.
There are several types of conduits available, including:
- Rigid Metal Conduit (RMC): Thick-walled tubing usually made of coated steel, stainless steel, or aluminum. It is designed to protect wires and connectors from electromagnetic interference and corrosion.
- Galvanized Rigid Conduit (GRC): Galvanized steel tubing with thick walls, often used in commercial and industrial construction.
- Intermediate Metal Conduit (IMC): A thinner and lighter version of RMC, made of steel tubing. It is commonly preferred in construction due to its ease of use and comparable protection.
- Electrical Metallic Conduit (EMT): Rigid, thin-walled metal conduit typically made of galvanized steel. It is easy to bend and best used indoors or outdoors with watertight fittings.
- Flexible Metal Conduit (FMC): Made by coiling self-interlocked steel or aluminum strips, it is used in dry areas where a non-flexible conduit is impractical but metallic strength is required.
- LSZH Conduit: A new type of plastic wire conduit that produces less smoke and is halogen-free, making it safer than PVC conduits.
Conduits are often required to meet specifications from the National Electrical Code (NEC) or local governments, especially in new construction or when updating existing structures. They offer enhanced protection from fire, moisture, impact, chemicals, and damage from rodents. Conduits can also help minimize electromagnetic interference and expand installation options by adding insulation.
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Conduit types and materials
Electrical conduits are tubes or enclosures that protect electrical wiring and provide a route for individual electrical wiring conductors. They are typically required where wiring is exposed or at risk of damage. Conduits can be made of metal or plastic and are either rigid or flexible.
Rigid metal conduit (RMC)
RMC is a thick-walled tubing typically made of stainless steel, coated steel, or aluminium. It is strong and offers solid protection but is expensive in terms of materials and labour. RMC is typically used outdoors to provide protection from damage and can also provide structural support for electrical cables, panels, and other equipment.
Galvanized rigid conduit (GRC)
GRC is made from steel and is traditionally found in industrial and commercial applications. It has impressive impact resistance, UV stability, and the ability to protect from electromagnetic interference (EMI). However, its heavy weight and poor field handling make it expensive to install and susceptible to corrosion.
Intermediate metal conduit (IMC)
IMC is a thinner, lighter version of RMC. It is commonly preferred in construction as it is easier to work with and offers the same level of protection as RMC. It has a thicker, galvanized wall, making it suitable for outdoor applications.
Electrical metallic tubing (EMT)
EMT is made from galvanized steel or aluminium and is a more economical and thinner-walled option than other conduits. It is rigid but can be bent with a simple tool called a conduit bender. It is commonly used for exposed indoor wiring in residential and light commercial construction.
Flexible metal conduit (FMC)
FMC is made by coiling self-interlocked steel or aluminium strips to form a hollow tube for electrical cables. It is available in standard or reduced wall thickness. FMC is common in dry areas where installing a non-flexible conduit would be impractical, but metallic strength is still needed.
Polyvinyl chloride (PVC) conduit
PVC conduit is the most common type of non-metallic conduit. It is similar to plastic plumbing pipe and is installed with plastic fittings that are glued in place. It can be bent after being heated in a portable heater box. PVC conduit is resistant to moisture and corrosion but is not recommended for use in areas with direct sunlight exposure as the material can break down over time.
Liquid-tight flexible metal conduit (LFMC)
LFMC is a flexible metal conduit with a plastic coating, used with sealed fittings to make it watertight. It is commonly used with outdoor equipment, such as air conditioner units.
Other types of conduit
Other types of conduit include electrical nonmetallic tubing (ENT), which is flexible corrugated plastic tubing that is moisture-resistant and flame-retardant, and fiberglass conduit, which can be substituted for steel in most industrial applications due to its extreme corrosion resistance and UV stability.
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Conduit installation locations
Conduits are commonly installed along the exterior surface of walls, in crawl spaces, attics, and basements. They can also be used in dry areas where it would be impractical to install non-flexible conduit, such as with flexible metallic conduits (FMC).
In the United States, the National Electrical Code (NEC) serves as the benchmark for safe electrical design and installation across all 50 states. It is important to refer to the NEC, local, and engineering guidelines to determine the specific requirements and codes applicable to your project.
For example, the NEC requires installing a hanger within three feet of each box and every ten feet thereafter for surface-mounted installations. However, in a basement or garage environment where the conduit is exposed and susceptible to physical damage, it is recommended to place the first hanger within two feet of the box and every six feet thereafter.
Additionally, certain types of conduits may be installed in damp or wet locations, while others, such as BX wiring or AC wiring, are restricted from being used in such conditions per electrical code (NEC 320.12).
Overall, it is important to carefully select the appropriate conduit type and refer to the relevant guidelines and local regulations to determine the suitable installation locations for your specific project.
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Conduit installation guidelines
Planning and Permits
Before beginning any conduit installation project, it is essential to carefully plan the installation, taking into account the specific requirements and constraints of the project. This includes determining the type of conduit to be used, the routing of the conduit, and any necessary fittings or connections. It is also important to review the National Electrical Code (NEC) guidelines, local code regulations, and any applicable engineering guidelines to ensure compliance with safety standards and obtain any necessary permits.
Choosing the Right Conduit
Electrical conduits come in a variety of materials, including metal and plastic, and can be rigid or flexible. The choice of conduit depends on the specific application, the environment in which it will be installed, and any relevant electrical codes or restrictions. For example, flexible conduits are often used to connect to motors or other devices where isolation from vibration is important or where an excessive number of fittings would be required for rigid connections. Rigid metal conduits (RMC), on the other hand, are typically used for structural piping that houses the wiring for a building's connection to utility service lines.
Installation Process
The installation process will vary depending on the type of conduit being installed. In general, it is important to follow the manufacturer's instructions and industry best practices for the specific type of conduit being installed. This includes using compatible fittings such as elbows, couplings, connectors, and electrical boxes made of similar materials. For metal conduits, proper grounding is essential to ensure electrical safety. It is also important to consider the wall thickness, mechanical stiffness, and material of the conduit, as these factors can impact the installation process and the overall performance of the conduit.
Inspection and Maintenance
Once the conduit is installed, it is important to inspect the work to ensure it meets the relevant codes and standards. This may include visual inspections, testing, and verification by a qualified electrician or inspector. Ongoing maintenance and inspections are also important to identify any potential issues and ensure the conduit remains in good condition over its lifespan.
Safety Considerations
Working with electrical systems can be dangerous, so it is important to prioritize safety throughout the installation process. This includes properly training all personnel involved, using appropriate personal protective equipment (PPE), and following safe work practices when working with live wires or in potentially hazardous environments. It is generally recommended that conduit installation be left to professional electricians who have the necessary training and experience to safely complete the work.
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Conduit bodies
There are six common conduit body types:
- LR conduit bodies form an L-shape that allows the electrician to adjust the raceway's orientation by 90 degrees. They accept electrical wire through a conduit hub at the top, then direct it out through a second conduit hub on the right.
- LL conduit bodies form an L-shape and redirect conduits on the same plane.
- LB conduit bodies form a right angle and include two conduit hubs. The access point is on the back of the body, on the opposite side of the cover.
- T-shaped conduit bodies have two conduit hubs that mirror each other and one that points at a 90-degree angle from the other two.
- X-shaped conduit bodies have four conduit hubs.
- Straight conduit bodies have no bend and direct wires in a single direction.
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Frequently asked questions
An electrical conduit is a metal or plastic pipe that routes electrical wires in an installation while protecting the electrical cables from damage in an exposed area.
Electrical conduits can be made of materials such as PVC, galvanized steel, stainless steel, coated steel, or aluminum.
There are seven common types of electrical conduits, each with a unique application. They are divided into two main categories: metal conduits and non-metal conduits. Some examples include rigid metal conduit (RMC), electrical metallic tubing (EMT), flexible metallic conduit (FMC), and intermediate metal conduit (IMC).
Electrical conduits are used to protect electrical wires and cables from damage in exposed or unfinished areas, such as exterior walls, crawl spaces, attics, basements, and outdoor locations. They can also be used to organize wires and reduce electromagnetic interference.
Yes, all electrical conduit installations must follow the National Electrical Code (NEC) guidelines, local codes, and engineering specifications. These regulations ensure safe electrical design and installation.
