BUILDING ELECTRICAL DESIGN PRINCIPLES

• Design of an electrical system involves applying the standards written into the building code.
• An electrical code specifies the minimum provisions necessary for protecting people and property from the improper use of electricity and electrical equipment.
• An approved product meets minimum safety standards as determined by extensive testing by an independent testing company or organization.
• Underwriters Laboratory, Inc. (UL) is a not-for-profit product safety testing and certification organization.
• National Electrical Manufacturing Association (NEMA) is the leading trade association in the United States representing the interests of electrical manufacturers.
• Most municipalities have ordinances (local laws) that require that any person who wishes to engage in the business of installing electrical systems must be licensed (usually by the state or province).
• Electrical construction drawings show the layout and design of an electrical installation.
• The following construction drawings and details are generally required: Complete plans and specifications of all electrical work, Labeling criteria of all electrical equipment, Lighting floor plan(s) including electrical circuits indicating conduit and wiring sizes, Power floor plans including electrical circuits indicating conduit and wiring sizes, equipment, and disconnect switches, Exit sign/means of egress lighting location and power supply, Panelboard schedule, Lighting fixture schedule, Electrical connections, Electrical wiring devices, Circuit and motor disconnects, Hangers and support
• Grounding conductor links ground to the metal frames or housings of appliances and motors and the metal boxes containing outlets and switches.
• System grounding is that part of a building electrical system that provides protection against electrical shock, lightning, and fires.
• Measured voltage at an outlet or connection is called the line voltage.
• If needed, the grounding conductor can safely carry current to ground in the event of a lightning strike or in cases of damage or defect in the circuiting, appliances, devices, or equipment.
• A grounded conductor is considered to be a current carrying conductor because it serves as a return path back to the circuit’s power source.
• The highest voltage to which a wiring device can be exposed is known as the maximum voltage.
• There are slight variations in utilization voltage.
• Grounding is required to protect building occupants and electrical equipment.
• A neutral conductor cannot by definition serve a single 120 V circuit because it has only one ungrounded conductor.
• A duplex receptacle that is the wall-mounted receptacle common in most homes and offices is designed to handle a maximum voltage of 250 V, but is intended for use on a 240 V circuit, where the line voltage is likely about 230 V.
• Wiring devices such as switches, receptacles, relays and conductors, and electrical equipment are manufactured to endure voltages slightly higher than the utilization voltage.
• The equipment-grounding conductor is a bare conductor or a green-colored, insulated conductor that connects (bonds) the outlet boxes, metallic raceways, other enclosures and frames on motors, appliances, and other electrical equipment.
• Grounding conductor does not normally carry current.
• A neutral conductor performs the function of a grounded conductor for at least two ungrounded (hot) conductors that have sources from different voltage phases, such as on a multiwire branch circuit, multiwire feeder, and the electrical service.
• The grounded conductors are necessary to complete an electrical circuit.
• Equipment grounding refers to a grounding conductor or grounding path that connects the noncurrent-carrying metal components of equipment.
• A grounded conductor in a single-phase branch serves as the grounded leg of the circuit by connecting the ungrounded (hot) conductor to ground.
• Grounding an electrical system begins with a ground, an electrode in direct contact with the earth itself.
• The grounding conductor is a continuous conductor that connects the ground to the neutral bus bar and the grounding conductor bus bar in the service equipment/main panelboard.
• A neutral conductor is a grounded conductor that is shared between two or more ungrounded conductors.
• Appliances and equipment connected to the 240 V building system voltages are designed for 230 V.
• A grounded (neutral) conductor is required to complete a single phase circuit by connecting the ungrounded (hot) conductor to ground.
• A voltage drop occurs as current flows from the service equipment through the branch circuit conductors to the outlet (point of use in the building).
• The neutral conductor is a grounded conductor that serves more than one circuit.
• On a 240 V system, approximately 230 V is available at the outlet of the branch circuit and not the 240 V available at the service equipment.
• Both conductors complete the circuit(s) by connecting it to ground and, as a result, are treated as current carrying conductors.
• The 400 Y/230 Volt, Alternating Current, Three-Phase, Four-Wire System (400 Y/230 V AC, 3Ø-4W) is an electrical service found in small commercial buildings (e.g., office buildings and schools) and high-rise buildings where single-phase motors (motors above about 1/2 horsepower) and equipment such as large air conditioners are used.
• The 240 V system is used in the first electrical services to buildings and is used to serve outbuildings and farm buildings because its use is limited to buildings with loads up to 12000 VA (50 A).
• System voltage is the target voltage entering the service panel.
• A minimum of two types of conductors is required to deliver alternating current in a building electrical system: the ungrounded conductor and the neutral conductor.
• Higher voltage is more dangerous.
• Small transformers located in electrical rooms or closets in the building step down the voltage from 480 V to 240 V for small equipment and convenience outlets.