Wire and cable need to weave their way through a wide range of environments. From the walls of a home or office building to heavy-duty industrial or underground installations, conduits can protect wire and cable from nearly any threat. The right materials keep cables and wires safe from corrosion, impacts, sunlight, moisture and many other hazards that could impact performance or safety.
What Is a Conduit?
Electrical conduit is a plastic or metal tube that holds electrical wires or cables. It can be flexible or rigid and protects wires in a range of settings, including exposed or unfinished indoor areas or outdoor settings. To fit into diverse configurations and demands — including within concrete or underground — electrical conduit comes in many styles and sizes.
Wire conduit must terminate at an electrical box or another piece of equipment that serves the same purpose. Along with the electrical box and connectors, conduit is an important part of an electrical raceway. If it’s made of metal, the conduit can even take on the role of a grounding wire.
What Is Conduit Used for?
You can use conduit for different purposes, including:
- Meeting code requirements: Conduit is often required for specifications from the National Electrical Code (NEC) or local governments. Of course, you’ll need to meet these codes for new construction, but you may also need conduit to keep a structure up-to-date if existing materials become worn or damaged.
- Protecting wires from damage: Conduit can offer protection from fire, moisture, impact, chemicals and other threats like damage from rodents. Some are designed for specific purposes. Although wires and cables typically have some kind of insulation, conduit can offer much more protection.
- Adapting to design demands: Since electrical conduit adds insulation, you can use it to expand installation options. For example, rugged conduit can allow you to run wire in an exposed area that wouldn’t be suitable for the wire alone.
- Reducing interference: Conduit can even help minimize electromagnetic interference (EMI) for better-performing wire and cable.
- Cleaning up the area: If you have a lot of wires that are hard to manage, placing them in conduit can keep them organized and make them easier to work with. Plus, a smooth surface allows you to move them around, simplifying installation and potential maintenance needs in the future.
For many installations, conduit offers great all-around protection and versatility.
Types of Electrical Conduit
Electrical conduit comes in numerous styles, built for specific installations and demands. You’ll find an array of sizes and materials in both flexible and rigid designs. Metal conduit might use aluminum or steel, while plastic conduit could be made of polyvinyl chloride (PVC) or more advanced materials like polyamide systems. Some types of conduit, like electrical metal conduit, are technically considered tubes, so you’ll see a “T” in their acronyms.
Below are some popular styles of electrical conduit:
Electrical Metallic Conduit (EMT)
EMT is typically made of galvanized steel or aluminum, so it’s a rigid style of conduit. Still, the metal walls are thin, making electrical metallic conduit lightweight and easy to bend. It attaches to other components of the electrical raceway via compression fittings.
As a more attractive style of conduit and one that bends easily, EMT is often used for exposed indoor wiring. While it can be used outdoors, these installations require watertight fittings, and the conduit might not last very long. Other types of conduit usually offer more protection in these instances.
Electrical Non-Metallic Tubing (ENT)
ENT uses flexible plastic tubing to offer moisture and fire resistance, but like EMT, it can’t be used outdoors or in other exposed locations. It’s common in residential or commercial walls and within concrete structures. Electrical non-metallic tubing is flexible and uses glued fittings.
Flexible Metal Conduit (FMT)
As the name implies, flexible metal conduit bends easily. This quality comes from its spiral design. FMT is a heavy-duty option, typically made of galvanized steel with threaded fittings. It’s commonly used for wire runs with significant bending or those placed in exposed areas, such as wiring for water heaters or in attics.
Liquid-Tight Flexible Metal Conduit (LFMC)
Liquid-tight flexible metal conduit is similar to FMT but with an added plastic sheath to make it watertight. It’s often used for outdoor wiring, like connecting AC units and other outdoor equipment. Indoor settings that have high moisture levels can also benefit from LFMC.
While often used for similar applications, LFMC and FMT typically outperform PVC conduit. PVC conduit is affordable and watertight, making it suitable for above and underground applications. However, it isn’t very durable and doesn’t bend easily, so it works best on straight runs.
Although PVC’s low cost is a big selling point, FMT conduit can reduce costs in other ways, such as significantly reduced assembly times, application flexibility and extended product life span. Thanks to these qualities, many electricians now opt for FMT and LFMC in place of PVC electrical wire equipment.
Liquid-Tight Non-Metallic Flexible Conduit (LFNC)
LFNC-B — a commonly used type of non-metallic flexible conduit — has a flexible PVC wall embedded with rigid PVC enforcements. It can bend but still offers structure and a watertight build. LFNC-B provides moderate protection in wet, dry or oily settings. It’s also flame-resistant. This durable conduit is popular indoors and outdoors in industrial or moisture-heavy applications, like pools and heating, ventilation and air conditioning (HVAC) systems.
You can also find liquid-tight flexible electrical conduit made of polyamide rather than PVC, adding resistance against oil, benzine, acid and solvents and flames. Polyamide conduit can even self-extinguish, making it ideal for industrial machines, robotics and other demanding applications.
Rigid Metal Conduit (RMC)
Rigid metal conduit is one of the most heavy-duty conduit options. It has a thick wall, often made of galvanized steel, and uses threaded fittings. You’ll find it used to run cables through walls and support overhead utility service line connections. With its thick metal walls, RMC offers considerable impact and EMI protection.
RMC can be made of different metals and corrosion treatments. Galvanized steel is a popular choice that works well in industrial buildings, but other configurations can offer corrosion resistance in specific environments, such as those with chemical fumes or in coastal areas.
Intermediate Metal Conduit (IMC)
IMC is similar to RMC but thinner and lighter by about a third of the weight. It offers some middle ground between EMT and RMC. Made of rigid steel, IMC has corrosion-resistant coatings and can be threaded or non-threaded. It has a larger diameter on the inside and a smoother coating that makes it a bit easier to pull wires through compared to RMC. The NEC allows IMC to be used in the same applications as RMC, so it has mostly replaced RMC in both commercial and residential projects.
Fiber Optic Conduit
Fiber optic conduit protects and surrounds the individual strands of fiber optic cable. Fiber optic conduit offers greater protection for critical network communications in a wide range of tough environments, including underground installations that involve corrosive soil, temperature changes and accidental excavation.
This conduit is usually made of steel or another rugged metal and may incorporate PVC or fiberglass braiding. Because fiber optic cables transmit digital binary signals and not electrical currents, the conduit can be made of metal without creating shock hazards.
Food and Beverage Conduit
The food and beverage industry must meet strict sanitation requirements to avoid contamination. Without the right care, conduits and their fittings can house bacteria and other contaminants that could reach the processing line or otherwise taint the sterile environment. Sterilization processes can involve high-powered water jets, high heat and corrosive cleaning materials, any of which can wear away at coatings on the wiring or conduit.
The Food and Drug Administration (FDA) has guidelines and third-party testing requirements to help facilities avoid contamination from these sources. Conduits must be made of sanitary materials that are easy to clean and, in some places, safe for food contact. These standards come from organizations like the NEC, the Occupational Safety and Health Administration (OSHA), UL or EcoLab.
Food and beverage conduit and fittings are designed to meet these specifications and provide liquid-tight protection.
What Type of Wire Can You Run Through Conduit?
Conduit can support many types of wires and cables, but they typically use THHN or THWN wires. THHN refers to wires with thermoplastic insulation, high-heat resistance and a nylon coating, while THWN wires have thermoplastic insulation and heat and water resistance.
You’ll find THHN and THWN wires used on their own and within various cables, like Romex cables. While not common, you can run these cables through conduit. More commonly, individual THHN or THWN wires run through conduit.
If you’re using non-metallic cable, you’ll need a grounding wire, but metal conduit can also serve that purpose. Modern installations typically include a ground wire, but older constructions might use the conduit to ground the raceway.
How Do You Run Cable or Wire Through Conduit?
Pulling wire or cable through conduit can be challenging if the wiring gets caught somewhere along the path. If you’re working with conduit that already has wire inside it, you can attach the new wire to the old one and pull it through. For new installations or old ones with damaged wiring, this approach might not be an option. Instead, you’ll probably need to try one of the wire-pulling methods we’ve covered on our blog:
- The string method: If you have a short, straight piece of conduit, you can use the string method. This option involves pushing a rod with a string on it through your conduit and tying the electrical wire to the string. You then pull the rod through the conduit, bringing the string and wire with it.
- A conduit mouse: A conduit mouse or conduit piston is a special tool for pulling wire through conduit. With the help of a shop vacuum, the conduit mouse gets sucked through the conduit, bringing the attached wire along with it. This option works well for conduit with twists and turns but may not work well for particularly long stretches.
- The fishing weight method: If you can move your conduit vertically, the fishing weight method simply involves dropping a weight attached to your wire down through the conduit. This option only works for relatively straight conduit.
- The fish tape method: Fish tape is a common wiring tool that has a long, flat metal wire wrapped in a spool. For wire pulling, you’ll feed this tape through the conduit, attach it to the electrical wire on the other end of the conduit and pull the wire back through the conduit.
- The joint fish tape method: This joint fish tape strategy is similar to the regular fish tape method, but it can help you pull wire through conduit with 90-degree turns or existing wires. With the help of a partner, you’ll feed two spools of fish tape through either end of the conduit. You’ll hook them together in the middle of the conduit and pull so one spool of fish tape runs continuously through the conduit. Then, you can follow the regular fish tape method.
Be sure to read our guide on running conduit in exterior walls or underground if you’ll be working in those settings. Both of these installations are more complex than others, often requiring a contractor and specialized tools.
How to Choose the Right Type of Conduit
The right type of conduit for your project depends on various factors, such as:
- Environmental concerns: Consider what kind of threats your conduit will need to offer protection from, such as moisture, impacts, corrosion, sunlight and chemicals.
- Installation demands: Do you need your conduit to bend, be placed inside concrete or be buried underground? Make sure your conduit is suitable and rated for these environments.
- Cost: Weigh the benefits of certain types of wire conduit with your budget. In many cases, the NEC will dictate some aspects of your conduit choice, but you can still opt for certain variations. For example, a rigid metal conduit might offer more rugged protection, but if your application isn’t particularly vulnerable to heavy impacts or corrosion, an intermediate metal conduit might provide similar performance at a lower price.
- Assembly time: Some conduit is easier to work with and can speed up installation or assembly time. EMT, for instance, is easier to bend, and IMC is easier to pull wire through. Consider what benefits a certain type of conduit might offer and any advantages specific manufacturers provide.
- Variety: If you plan to order one type of conduit for multiple projects, look for something that can be used in different settings. For example, work that primarily involves exposed indoor wiring might benefit from general-purpose ENT, but you wouldn’t want to plan on using specialized fiber optic conduit for other installations.
Conduit is a necessary part of many electrical raceways, but in some cases, you might be better off with braided sleeves. Braided sleeves offer another type of protection and can help with cable organization. They contain braided fibers typically made of plastic or metal that protect against high heat, corrosion, abrasion, moisture, chemicals and EMI.
The open weave of the sleeve supports heat dissipation, moisture evaporation and flexibility while providing accessibility. Braided sleeves can even be designed to resist specific threats, like fire and damage from rodents.
Choosing the right kind of protection for your cables can be complex. If you’re not sure which type of conduit or cable sleeve is best for your application, the pros at AerosUSA can help.
Choose AerosUSA for Top-Tier Conduit
At AerosUSA, we know conduit is often the first layer of defense for wires and cables. That’s why we offer expert support and an array of conduits to fit whatever project comes your way. We’re committed to innovation and quality across our selection. From cost-cutting installation processes to longer-lasting materials, our cable and wire conduit and braided sleeves can help you keep wires and cables safe in even the toughest or most specialized settings.