Electrical System Design Want us to call you
The best distribution system is one that will, cost - effectively and safely, supply adequate electric service to both present and future probable loads - this section is included to aid in selecting, designing and installing such a system. The function of the electric power distribution system in a building or an installation site is to receive power at one or more supply points and to deliver it to the individual lamps, motors and all other electrically operated devices. The importance of the distribution system to the function of a building makes it almost imperative that the best system be designed and installed. In order to design the best distribution system, the system design engineer must have information concerning the loads and a knowledge of the various types of distribution systems that are applicable. The various categories of buildings have many specific design challenges, but certain basic principles are common to all. Such principles, if followed, will provide a soundly executed design.
(Example of electrical system diagram)
Codes and Standards
The National Electrical Code (NEC), NFPA Standard No. 70, is the most prevalent electrical code in the United States. The NEC, which is revised every three years, has no legal standing of its own, until it is adopted as law by a jurisdiction, which may be a city, county or state. Most jurisdictions adopt the NEC in its entirety; some adopt it with variations, usually more rigid, to suit local conditions and requirements. A few large cities, such as New York and Chicago, have their own electrical codes, basically similar to the NEC. The designer must determine which code applies in the area of a specific project.
The Occupational Safety and Health Act (OSHA) of 1970 sets uniform national requirements for safety in the workplace - anywhere that people are employed. Originally OSHA adopted the 1971 NEC as rules for electrical safety. As the NEC was amended every three years, the involved process for modifying a federal law such as OSHA made it impossible for the act to adopt each new code revision. To avoid this problem, the OSHA administration in 1981 adopted its own code, a condensed version of the NEC containing only those provisions considered related to occupational safety. OSHA was amended to adopt this code, based on NFPA Standard 70E, Part 1, which is now federal law.
The NEC is a minimum safety standard. Efficient and adequate design usually requires not just meeting, but often exceeding NEC requirements to provide an effective, reliable, economical electrical system. Many equipment standards have been established by the National Electrical Manufacturers’ Association (NEMA) and the American National Standards Institute (ANSI). Underwriters Laboratories (UL) has standards that equipment must meet before UL will list or label it. Most jurisdictions and OSHA require that where equipment listed as safe by a recognized laboratory is available, unlisted equipment may not be used. UL is by far the most widely accepted national laboratory, although Factory Mutual Insurance Company lists some equipment, and a number of other testing laboratories have been recognized and accepted.