An electrical conduit is a type of durable tubing or a similar enclosure that covers up and protects electrical wiring. This conduit is usually needed when the wiring will be installed in an exposed position where without the conduit it can be damaged. There are several types of electrical conduits, including the rigid nonmetallic conduit and flexible conduits.
Here are several types of electrical conduits with info as to how they’re used:
Rigid Nonmetallic Conduit (RNC)
There are several subtypes of these, and the most notable is probably the reinforced thermosetting resin conduit (RTRC). This is also known as the fiberglass conduit. It’s strong and lightweight, and it’s used for a wide variety of indoor and outdoor applications, such as bridge and underground installations. Due to its light weight, it comes with lower labor costs.
Rigid Metal Conduit (RMC)
This is galvanized steel tubing with threaded fittings, and it’s mainly for heavy-duty uses. Usually, it’s for outdoor applications to provide the electrical wiring protection from potential damage. It can also deliver structural support for various types of equipment, including electrical cables and panels.
Intermediate Metal Conduit (IMC)
This is similar to RMC, except that it’s thinner and it weighs less. It’s rated to work for all applications for which RMC is designed. In fact, it’s more common to use this now for new construction projects because it’s lighter and therefore easier to work with than RMC.
Electrical Metallic Tubing (EMT)
This is another type of rigid conduit for electrical wiring. It can be made from lightweight yet strong aluminum, though usually it’s made from galvanized steel. The other name for this conduit is thin-wall conduit because it’s lightweight due to its thinness, and that’s obvious when compared to RMC. This may be rigid, but you can use a conduit bender to bend this. The tubing is also not threaded like RMC, and instead it’s secured with a setscrew or a fastener.
You see this type of conduit in exposed indoor wiring, especially in light commercial and residential construction. It can be used for exposed outdoor applications, but you will need special watertight fittings to protect the wiring from rain and snow.
Electrical Non-Metallic Tubing (ENT)
This is a corrugated type of plastic tubing that’s flexible, flame-retardant, and resistant to moisture. You can bend this quite easily, and you can install it with glued plastic fittings or snap-lock fittings. Some people tend to call this the “smurf tube” because a popular brand of this ENT comes in a blue color.
The ENT cannot be exposed like EMT due to the inherent lack of strength of the plastic non-metallic tubing. That’s why it’s mostly installed inside the walls, including metal-frame walls, wood-frame walls, and inside concrete blocks.
Flexible Metal Conduit (FMC)
This is also known as the Greenfield, which is the name of the FMC inventor. It’s designed in a spiral shape that makes it more flexible, so it can bend and snake through structures such as walls. The most common use of FMC is in dry indoor locations and it’s only for shorter distances. You may see it run between a wall box and a fixed or motor appliance like a garbage disposal unit.
Liquid-tight Flexible Metal Conduit (LFMC)
This is a subtype of FMC, and it has a plastic coating with sealed fittings. This makes it watertight, and suitable for outdoor applications such as for outdoor equipment like air conditioners.
Rigid PVC Conduit
This is similar to plastic plumbing pipes, and you install it by gluing plastic fittings in place. You can heat it in a portable heater box to bend it. Gluing together the conduit tubing and the fittings make it watertight so it can be used for outdoor applications. The use of PVC allows for underground installation, and it also works for corrosive settings.