Electrical-Design-Principles for engineering pptx

Electrical-Design-Principles for engineering pptx

1. [ ELECTRICAL DESIGN PRINCIPLES ] ( Engineering Utilities 1 )

2. [ TOPICS ] BRANCH CIRCUIT REQUIREMENT DEVICE AND EQUIPMENT REQUIREMENT ELECTRICAL MATERIAL REQUIREMENT CONDUCTOR REQUIREMENT CABLE, RACEWAY, ENCLOSURE REQUIREMENTS

3. [ BRANCH CIRCUIT REQUIREMENTS ] TYPES OF BRANCH CIRCUIT Individual General Purpose Appliance Multiwire Life Safety Critical

4. individual branch circuit Serves one receptacle or piece of equipment such as for a range, clothes dryer, large copy machine, or other piece of machinery.

5. general purpose branch circuit Supplies two or more receptacles or outlets for lighting and appliances

6. appliance branch circuit Supplies to one or more outlets for the purpose of connecting appliance

7. multiwire branch circuit consisting of two or more undergrounded (hot) conductor having a voltage between them and a common neutral (grounded) conductor that is shared between the undergrounded conductors such as in a 120/240 V three-wire circuit.

8. life safety branch circuit an emergency system of feeders and branch circuit that provides adequate power to patients and personnel. It must automatically connect to an alternate power source such as a generator when the normal power source is interrupted.

9. critical branch circuit an emergency system of feeders and branch circuit intended to provide power to task illumination, special power circuits, and selected receptacles serving areas and functions related to patient care. It must automatically connect to an alternate power source such as a generator when the normal power source is interrupted.

10. [ Device and equipment requirements ] switches must be selected to match the load they control. A panelboard like enclosure called lighting control panel is used in large lighting installations that require many switches. Receptacles must be selected to match the appliance or equipment they serve. Normally, switches are mounted approximately 48 inches (1.2 meters) above finished floor ( aff ), convenience receptacles at 16 inches(0.4 meters) aff and convenience receptacles in bathrooms and restrooms at 44 inches (1.1 meter) aff , unless otherwise specified.

11. [ CONDUCTOR REQUIREMENTS ] Copper and aluminum are the most common conductor materials used in building electrical wiring, although other materials can be used. As a general rule, solid copper conductors are used in small conductor sizes (up to about 8 AWG) because safety issues associated with aluminum are avoided and weight and cost are not significantly affected.

12. [ CONDUCTOR REQUIREMENTS ]

13. [ CABLE, RACEWAY, ENCLOSURES REQUIREMENTS ] All building wiring must be enclosed in a cable, conduit, wireway, or raceway. During installation, conductors are snaked through conduit or tubing, are laid in a wireway, or are contained in cables and secured to structural framing. Care must be exercised in placing conductors, as conductors and insulation can be easily damaged.

14. [ CABLE , RACEWAY, ENCLOSURES REQUIREMENTS ] For example, if a conductor is pulled through a tight conduit, it can stretch. Deformation caused by stretching reduces the cross-sectional area of the wire, thereby reducing its ampacity. This creates an unsafe condition because the conductor can overheat.

15. [ CABLE, RACEWAY , ENCLOSURES REQUIREMENTS ] Conductors that are run through a raceway must have sufficient open-air space to prevent overheating. The number of current-carrying conductors that can run through a raceway is limited by code.

16. [ CABLE, RACEWAY , ENCLOSURE REQUIREMENTS ]

17. [ CABLE, RACEWAY, ENCLOSURES REQUIREMENTS ] All electrical connections must be made in a protective enclosure such as a panelboard, junction, or device box, fixture, or appliance. Every switch, outlet, and connection must be contained in an electrical box and every lighting fixture must be mounted on a box.

18. [ CABLE, RACEWAY, ENCLOSURES REQUIREMENTS ] There are no requirements that specify that a certain type of electrical box be installed for a specific purpose. The typical trade practice is to install octagonal and round boxes for lighting outlets and to install rectangular and square boxes for switches and receptacle outlets.

19. [ CABLE, RACEWAY, ENCLOSURE REQUIREMENTS ]

20. [ ELECTRICAL DESIGN PRINCIPLES ] ( Engineering Utilities 1 ) END