chapter 4

• Service Entrance


  That portion of the supply conductors which extends from the street main duct or transformer to the service or switchboard of the building supply
• National Electrical Code (NEC) definition of Service Entrance

  The conductor and equipment for delivering energy from the electricity supply system to the wiring system of the premises served
• Types of Service Entrance

  • Overhead service
  • Underground service
• Overhead Service Entrance


  • Common type of service wire installed by electric power supply companies for industrial, commercial, and residential houses
  • Service drop connected from nearest utility pole to building service entrance point, entering through weatherhead down to electric power meter
• Underground Service Entrance


  • Raceway (conduit) extending from building to property line where it is tapped to the main
  • Cable recommended is the OSE type (Underground Service Entrance) cable
  • Low voltage cable not advisable for installation in concrete enveloped raceway, except when service equipment is not at the point where underground run meets the building
• Electric Meter


  • Generally installed outside building at property line wall or electric post for ready access to meter reader, making it more difficult to tamper or install jumpers
  • For multi-door services, use of master metering is preferred with battery of meters installed in central meter room or reserved space to facilitate meter reading
• Main


  Feeder interior wiring extending from the service switch, generator bus, or converter bus, to the main distribution center or electric service equipment
• Grounding (per NEC)


  • Establishes a zero voltage point in the system
  • Grounded line of a circuit should not be broken nor fused to maintain a solid and uninterrupted connection to the ground
  • Established ground automatically becomes the reference for all voltage in the system
• Branch Circuit


  • Technical term for the House Wiring Installation
  • House wiring varies in sizes depending upon the kind of load it is to serve
  • Load refers to the electricity drawn or consumed by lighting fixtures, appliances, equipment etc.