7 Types of Electrical Conduits - Application and Installation
How to Choose Between EMT, PVC and Other Electrical Conduits
Electrical conduits refer to an electrical system used to protect and provide the route of electrical wiring. Electrical conduits are made of metal, plastic, or fiber and could be rigid or flexible. Conduits must be installed by electricians following standard regulations, as those provided by the National Electrical Code (NEC). Here are seven of the most common used electrical conduits.
Galvanized Rigid Conduit or RMC
A conduit made from galvanized steel tubing is commonly referred as a rigid conduit.
The thickness of a galvanized rigid conduit protects the electrical wiring from being hit and allows it to be threaded. Galvanized rigid conduits are used by electricians in commercial and industrial applications normally available in 10 feet and 20 feet lengths. This type of electrical conduit is used above grade and has threads on both ends with a coupling on one end.
The installation of Rigid Steel Conduit (RSC) is covered by Article 344 of the National Electrical Code® (NEC®). The rigid metallic conduit can be treated to prevent corrosion by applying different coatings to the conduit. It is the heaviest-weight and thickest wall conduit available in trade sizes ½ through 6.
When to Use Electrical Metallic Tubing (EMT)?
Another example of a rigid electrical conduit is the EMT, also known as Electrical Metallic Tubing. An EMT conduit is made of steel; in some cases, aluminum is also used, cheaper than a galvanized rigid conduit and lighter than a GR conduit.
EMT is also a very popular material in commercial and industrial buildings because it can be bent to a specific radius and directions and it is thinner than RMC. During recent years, EMT conduits have become popular in residential construction as it provides an exterior corrosion resistance surface.
EMT is a listed steel raceway of circular cross section, which is unthreaded, and normally 10 feet long.
Electrical Non-Metallic Tubing Applications
Electrical nonmetallic tubing is another example of electrical conduit made of a thin-walled corrugated tubing, moisture-resistant and flame retardant. The non-metallic electrical conduit can be bent by hand and can be easily installed due to its flexible properties. However, fitting used to connect non-metallic tubing are rigid and cannot be bent. If you are looking for a faster installation and lower labor cost, this is the one to consider.
Flexible Metallic Conduit or Liquid-tight Flexible Metal Electrical Conduit (LFMC)
A flexible metallic conduit forms a hollow tube in which electrical wires are passed. It is highly recommended in dry areas. The Flexible Metallic Conduit also called greenfield of flex, does not maintain permanent bend and it can be used where EMT is impractical to use.
However, a liquid-tight flexible metal conduit is covered by a plastic waterproof coating. Its interior is very similar to the flexible metallic conduit. It is recommended for use in general wiring, wet or damp locations. It can also be used to direct burial; concrete embedded, and site lighting jobs.
Liquid-tight Flexible Nonmetallic Conduit
Liquid-tight Flexible Nonmetallic Conduit (LNFC) is another term for a number of flame resistant types of non-metallic tubing. This type of electrical conduit is recommended as a raceway for the installation of approved conductors with a nominal rating of 600 Volts or less for non-hazardous locations. The interiors of this electrical conduit may be corrugated or smooth.
Aluminum Electrical Conduits
An aluminum conduit is a rigid conduit commonly used in commercial and industrial applications. These types of electrical conduits are used to prevent corrosion and are the preferred conduit used in areas where large amounts of water and corrosion-prone areas. Aluminum cannot be directly embedded in concrete since the metal reacts with the alkalis in cement however it might be protected with additional coatings to prevent concrete from affecting the conduit.
It is normally used in concrete slabs or walls.
The Most Common of All Electrical Conduits
PVC is the lightest conduit material and usually the most affordable type of conduit. PVC pipes can vary in thickness depending on the uses and where the PVC will be installed. The PVC conduit resists moisture and corrosion but the tubing is non-conductive an extra grounding conductor must be passed into each conduit. PVC conduit has a higher thermal coefficient of expansion allowing the conduit to expand and contract. Be aware the installing PVC underground in multiple or parallel run configurations, mutual heating might cause problems on cable performance.