Classification of Electrical Conduits and Fittings in a Construction Project

Abstract

Building wiring is the electrical wiring and related devices such as meters, switches and light fittings used in buildings or other structures. Electrical wiring uses insulated conductors. Wires and cables are rated by the circuit voltage, temperature and environmental conditions (moisture, sunlight, oil, chemicals) in which they can be used, and their maximum current. Wiring safety codes vary by country and the International Electro-technical Commission (IEC) is attempting to standardize wiring amongst member countries. Color codes are used to distinguish line, neutral and earth (ground) wires[1]. Electrical conduits refer to an electrical system used to protect and provide the route of electrical wiring. Electrical conduits are made of plastic, metal or fiber and could be flexible or rigid. An electrical conduit is a tube used to protect and route electrical wiring in a building or non-building structure. Electrical conduit may be made of fired clay, metal, plastic or fiber. Most conduits are rigid, but flexible conduit is used mostly for some purposes[2]. Conduit is generally installed by electricians at the site of installation of electrical equipment. Its form, use and installation details are often specified by wiring regulations, such as the US National Electrical Code (NEC) and other building codes[3]. Electrical conduit provides very good protection to enclosed conductors from impact, moisture, and chemical vapors. Varying numbers, sizes, and types of conductors can be pulled into a conduit, which simplifies design and construction compared to multiple runs of cables or the expense of customized composite cable. Wiring systems in buildings may be subject to frequent alterations. Frequent wiring changes are simpler and safer through the use of electrical conduit, as the existing conductors can be withdrawn and new conductors are installed, with little disruption along the path of the conduit. A conduit system can be made waterproof or submersible. Sensitive circuits can be shield by using metal conduit from electromagnetic interference, and also can prevent emission of such interference from enclosed power cables. When installed with proper sealing fittings, a conduit will not permit the flow of flammable gases and vapors, which provides protection from fire and explosion hazard in areas handling volatile substances. Some types of conduit are approved for direct encasement in concrete. This is frequently used in commercial buildings to allow electrical and communication outlets to be installed in the middle of large open areas[4]. For example, retail display cases and open-office areas use floor-mounted conduit boxes to connect power and communications cables. Both plastic and metal conduit can be bent at the job site to allow a neat installation without unnecessary numbers of manufactured fittings. This is particularly advantageous when following irregular or curved building profiles. Special equipment is used to bend the conduit without kinking or denting it. The cost of conduit installation is higher than any other wiring methods it is due to the cost of labor and materials. In applications such as residential construction, the high degree of physical damage protection may not be required, so the expense of conduit is not warranted. Conductors installed within conduit cannot dissipate heat as readily as those installed in open wiring, so the current capacity of each conductor must be reduced (derated) if many are installed in one conduit. It is impractical, and prohibited by wiring regulations, to have more than 360 degrees of total bends in a run of conduit, so special outlet fittings must be provided to allow conductors to be installed without damage in such runs.