Electrical Supply: What are Metal Conduits?
Electrical conduit provides a route for electrical wiring. It also protects enclosed conductors, from impact, moisture, and chemical vapors. It’s commonly made of metal, plastic or fiber and can be flexible or rigid. Electricians should follow the standard regulations provided by the National Electrical Code (NEC).
What are the Types of Metal Conduits?
Metal conduit serves to shield sensitive circuits from electromagnetic interference. It also prevents interference that may be due to enclosed power cables. Here are some of the most common types of metal conduits.
Steel Conduit: Steel is the most popular metal conduit used since the early 1900’s. It provides the most mechanical protection to the enclosed conductors. When properly installed, steel can be an equipment grounding conductor, as per the regulatory of NEC.
Steel can be used as a rigid metal conduit, an intermediate metal conduit, electrical metal tubing, flexible metal conduit and liquid-tight flexible metal conduit. Read on for more information on these types of conduits.
Rigid Metal Conduit: RMC (ferrous metal) is a listed threaded raceway of circular cross-section with a coupling. It can be used as either a standard straight tapped conduit coupling or the integral type. RMC can have a primary coating of zinc or zinc combined with an organic coating or a nonmetallic coating such as PVC. These coatings serve to protect against corrosion. It is the heaviest weight and thickest wall steel conduit.
Intermediate Metal Conduit: IMC (ferrous metal): This type of metal conduit was developed in the 70’s. It is listed threaded steel raceway of a circular cross-section with either a straight tapped conduit coupling or an integral type. It has a thinner wall than RMC and weighs about one third less. The outside has a zinc-based coating and the inside has an approved organic corrosion-resistant coating.
Electric Metallic Tubing: EMT (ferrous metal) This is also commonly thin-walled, and a listed steel raceway of circular, which is unthreaded and normally 10 feet long. The outside corrosion protection is zinc-based and the inside features an approved corrosion-resistant organic coating.
Flexible Metal Conduit: Typically made with high grade, galvanized, low carbon steel, a flexible metal conduit. It is made with an interlocking system and is corrosion resistant. It is available in two different wall thicknesses, with the thicker, flexible metal being a full wall and the thinner wall product being a reduced wall. The full wall is more robust and specified were extra mechanical protection is called for. The reduced wall is available in high grade galvanized steel and an aluminum alloy strip of uniform gauge for excellent strength and durability.
Liquid-tight Flexible Metal Conduit (LFMC): This is a liquid-tight, flexible metal conduit covered by a plastic waterproof coating. It has an interior that is very similar to the flexible metal conduit. It is recommended in jobs for general wiring in damp and wet locations, including direct burial, concrete embedding, and site lighting jobs.
Steel conduit is typically used for protection of electrical conductor and wiring systems. It facilitates the insertion and extraction of conductors and wiring. It is used in every application where electrical conduit and wiring is present, including commercial, retail and residential buildings, manufacturing and other industrial facilities, healthcare and educational institutions and a wide variety of indoor, outdoor and underground applications, even where corrosive and hazardous conditions exist.
Aluminum Conduits: Aluminum conduits are another popular type of metal conduit. Typically less expensive and lighter in weight than their steel counterparts, these are used in commercial and industrial applications and can prevent corrosion. They are preferred in areas where there are large amounts of water and corrosion is likely. Aluminum cannot be directly embedded in concrete since the metal reacts with the alkali in the cement, but it may be protected with an additional coating so it can be used in concrete slabs or walls.
Aluminum is available in both rigid and flexible configurations. It is a useful alloy for Electrical Metallic Tubing (EMT) where it protects wiring that runs in a variety of electrical installations. It also comes in handy as a popular material in commercial buildings due to its ability to be bent on-site to meet specific radius and directions. It is also used in commercial industrial buildings.
Being familiar with the different types of metal conduits can help you identify what type will you need for your electrical applications, such as the best ways to protect and route the electrical wiring in a building or structure. Good luck finding the most reliable and efficient way to provide protection and electrical safety in the structures you may be working with.