3 Objectives List the components of the service entrance. List service drop clearances specified in the NEC.List eight basic guidelines when locating a residential service entrance.Calculate the size of service entrance needed based on the power needs of the dwelling.Select proper conductors and components for the service entrance.
4 Objectives (cont.)Size and install conductors between the meter socket, main disconnect, and service panel.Provide proper grounding for a service entrance.Explain the purpose of a step-down transformer and indicate where it is used.
5 Service EntranceAll conductors, devices, and fittings that carry electricity from power company’s transformer to the consumerService entrance components:Service entrance conductorsMeter socket, pan, or enclosureService entrance panelGrounding systemFittings, fasteners, and hardware
6 Service Entrance Location Service drop—Overhead service entrance conductors(OSHA)
7 Service Entrance Location (cont.) Service lateral—Buried service entrance conductors(Goodheart-Willcox Publisher)
8 Selecting Service Entrance Location Underground service conductors installed in a straight lineService conductors should be kept as short as practical to minimize voltage dropService conductors must enter building as near as possible to the service panelService disconnect must be at or near point of entry
9 Selecting Service Entrance Location (cont.) Service panel must be located in a central and accessible areaService equipment must be protected from physical damage, water, and dustService equipment cannot be placed in bathrooms, storerooms, closets, or damp basements
10 Number of Services Generally, a structure can have only one service Some exceptions:To supply fire pump or emergency systemTo supply a large load demandLarge structuresService from a generator or solar photovoltaic sourceMultiple voltage/phase requirements
11 Service DisconnectsFor multiple-occupancy buildings, a maximum of six disconnects can be connected to a single service drop or lateral(Goodheart-Willcox Publisher)
13 Service Drop Service drop mast Insulator Service head Drip loop Meter socketMeter(Goodheart-Willcox Publisher)
14 Temporary Wiring Provides electrical power during construction (Goodheart-Willcox Publisher)
15 Temporary Wiring (cont.) Installation requirements:Locate in a safe placeKeep conductors overhead if possibleAll receptacles require GFCI protectionProtect wiring from physical damageLamps require protective coversWeatherproof housings required when exposed to weatherInspect frequently
16 Service DisconnectService equipment must include a disconnect that disconnects service from building’s wiring systemCommon types:Main disconnect switchMain circuit breaker in service panel
17 Service GroundingGrounded (neutral) service conductor connected to neutral bus bar in service panelNeutral bus bar is connected to grounding bus barGrounding bus bar is connected to grounding electrode
18 Grounding Electrode Conductor Connects grounding bus bar in service panel to grounding electrode(Goodheart-Willcox Publisher)