The National Electrical Code (NEC 2002) provides guidance for electrical contractors and electricians, but it is really intended for use by governmental agencies that have legal jurisdiction over electrical installations and authorized electrical and insurance inspectors. The many mandatory chapters include Chapter 2, “Wiring and Protection,” Chapter 3, “Wiring Methods and Materials,” and Chapter 4, …
NEC 2002, Article 314, “Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Manholes,” requires that wire connections or cable splices be contained inside approved metal or plastic boxes. This provision is intended to shield wood building framing members or other adjacent flammable objects from electrical sparks should the wiring be defective. Boxes also …
CONDUIT BODIES AND COVERS Conduit bodies are tubular hardware units with openings at each end to admit EMC conduit and cavities that are large enough to give the installer access to the ends of wires or cables so they can be pulled out and easily be redirected if necessary. These bodies are available in different …
Indoor metal and nonmetallic conduit can keep dust and moisture out of wiring and protect it from mechanical abrasion. Short sections can protect wiring close to the floor used to power washing machines and clothes dryers in damp basements. These sections must be anchored to masonry walls where there are no wood studs for supporting …
INSULATED WIRE CODING The wire manufacturers’wire markings give: Wire gauge Maximum voltage rating Insulation code (R for thermoset, T for thermoplastic, X for cross-linked polyethylene thermoset) Maximum temperature code (H for 75°C, HH for 90°C, nothing for 60°C) Abbreviation for sheath if present (e.g., N for nylon) The identification codes for wires with thermoplastic insulation …
The NEC requires that ground-fault circuit interrupters (GFCI CIRCUIT BREAKERS ) be installed in many different rooms and locations in both public and private buildings. They are now required in bathrooms, kitchens, appliance rooms or spaces, and garages. In addition, they are required in basements, near swimming pools, hot tubs, or fountains, and in outdoor …
Miniature circuit breakers perform the dual functions of a switch and a fuse. They can open a circuit for safety or maintenance reasons simply by switching their toggle levers to the OFF position. As substitutes for fuses, they provide automatic circuit protection and need not be replaced after a dangerous overcurrent has passed or a …
Although overhead distribution system is losing favor in residential areas, it is still widely used in many parts of the country, particularly in towns and rural areas. Nevertheless, overhead distribution still has many economic and technical advantage Old or faulty transformers on existing poles can easily be replaced and new transformers can be added on …
A well-designed underground distribution systems must provide for anticipated load growth that can be accommodated economically. This means that provisions must be made to furnish electrical service to new as well as existing customers. Both overhead and underground distribution systems have existed in large metropolitan areas for many years, but underground distribution was rarely used …
The secondary distribution system is that part of the electrical power system between the primary system and the customer’s service entrance. This system includes distribution transformers, secondary circuits (secondary mains), customer services (consumer drops), and watthour meters to measure customer power consumption. Secondary voltages are provided by distribution transformers that are connected to the primary …