While its core objective – protecting wiring – has remained the same for decades, many advancements have been made when it comes to electrical conduit. Aspects such as the materials used, the manufacturing process and even the installation of conduit have benefited from new technology and new ideas being implemented. Here is a look at the various types of conduit that are available from suppliers like Champion Fiberglass and why you should consider many factors when selecting the conduit for your job.
Conduit materials
There are two groups of conduit: Metal and Non-metal. These are then split into separate branches.
Metal conduit
- Electrical Metallic Tubing (EMT) is usually manufactured from coated steel and is more commonly used in residential applications. An aluminium variant is available and better suited where conduit needs to be surrounded by concrete.
- Intermediate Metal Conduit (IMC) is lighter than RMC but does the same job. It comes in threaded and unthreaded variants, but there is a downside: The walls are thinner, which means the chance of bends and dents is higher.
- Galvanised Rigid Steel (GRC) is more commonly used in larger industrial and commercial applications such as factories and shopping malls. As GRC can be installed outdoors, it has added ultraviolet protection, as well as protection against electromagnetic interference, which is important for shielding cables in it.
- Rigid Metal Conduit (RMC) is usually made from heavy steel, that has been galvanised, or a lighter aluminium. Due to the former’s weight, strong threaded fittings are required to fix the conduit in position.
Non-metal conduit
- Electrical Non-metallic Tubing (ENT) is traditionally corrugated with a thin wall that is protected against flames. It should be installed in walls where it is cool. ENT is also more flexible than other conduits and can be bent by hand to be shaped around any obstacles in its path.
- Fibreglass Conduit (RTRC - rein-forced thermosetting resin conduit) is manufactured using resin and fibreglass matts that are cured in an oven. This type of conduit is resistant to high temperatures and is the least corrosion-prone conduit. It is one of the cheaper types of conduit available and is lightweight thanks to the materials used.
- PVC Conduit has poor protection against ultraviolet light and has the highest percentage of expansion and contraction in varying weather conditions. It comes in numerous wall thicknesses, making it a favourite with contractors who may need to use various sizes on a project. It can be bent on-site with the correct equipment, but there may be issues should the environment it is installed in become too hot.
- Rigid Non-metallic Conduit (RNC) is smooth walled and usually manufactured from high-density polyethylene, polyvinyl chloride (PVC) or fibreglass. It is best used underground and features a high level of resistance to corrosion.
Points to ponder
There are several factors to consider when choosing conduit, namely:
- Accessibility once installed
- Conductivity
- Corrosion resistance
- Cost
- Distance between expansion joints
- Durability
- Fault resistance
- Fire resistance
- Memory
- Replacement
- Temperature range
- Toxicity
- Weight
