18 Questions
What is the primary function of a service disconnect?
To protect service entrance conductors from overcurrent
What is the main difference between a switchboard and a panelboard?
Switchboards are larger and handle larger amounts of electrical current, while panelboards are smaller and handle smaller amounts of current.
What is the typical size range for building transformers?
100 kVA to 1000 kVA
What is the primary function of a building transformer?
To change the voltage, current, and phase of electrical power for distribution within a building
Which of the following is a key component of a service entrance?
Service disconnect
What is the primary purpose of a panelboard in a building's electrical system?
To serve as a single unit for controlling light, heat, and power circuits
What is the primary function of service entrance conductors?
To carry power from the transformer to the building's service disconnects
What is the purpose of a service entrance?
To connect the utility-supplied wiring to the service disconnect
What is the function of a switchboard?
To distribute power within the building's electrical system
What is the purpose of a building transformer service entrance?
To step down the voltage from the utility for use within the building
Which component of the building's electrical service equipment is responsible for overcurrent protection?
Circuit breakers or fuses
What is the function of panelboards in a building's electrical system?
To distribute power within the building's electrical system
What is the purpose of an SPST (single pole single throw) switch?
To control a single lamp or group of lamps from one location
What is the purpose of an SPDT (single pole double throw) or three-way switch?
To control a single lamp from two different locations
What is the function of a disconnect (safety power switch)?
To isolate a circuit or equipment from the supply side
What is the purpose of a bus bar?
To serve as a common connection for two or more electrical circuits
What distinguishes a cable from a single conductor?
A cable contains multiple conductors bundled together with an outer sheathing
What are the standard ratings of disconnects in amperes?
30, 60, 100, 200, 400, 600, 800, 1200, 1400, 1600, and 1800
Study Notes
Building Electrical Service Equipment
- Building electrical service equipment includes service entrance conductors, service entrance, switchboards, panelboards, and building transformers.
Service Entrance Conductors
- Service entrance conductors carry power from the transformer through a metering device to the building's service disconnects.
- They can be overhead (service drop) or underground (service lateral).
Service Entrance
- Service entrance includes the components that connect the utility-supplied wiring to the service disconnect, excluding the utility's metering equipment.
- Service entrance equipment receives the service entrance conductors and includes metering equipment, main disconnect or switch gear, and overcurrent protection devices.
Switches
- SPST (single pole single throw) switch is used to control a single or group of lamps from one location.
- SPDT (single pole double throw) or three-way switch is used to control a single lamp from two different locations.
Disconnects
- Disconnect (Safety Power Switch) is a mechanical switching device used to isolate a circuit or equipment from the supply side.
- Standard ratings of disconnects in amperes include 30, 60, 100, 200, 400, 600, 800, 1200, 1400, 1600, and 1800.
Conductors
- Electrical conductors can be solid or stranded, and may be insulated or bare.
- Bus bars are electrical conductors that serve as a common connection for two or more electrical circuits.
- Cables contain more than one conductor bundled together in a factory assembly of wires.
Service Disconnect
- Service disconnect is a required part of the service entrance equipment that allows electrical service from the utility company to be switched off.
- It is a set of fuses or a circuit breaker that protects the service entrance conductors.
Switchboards and Panelboards
- Switchboard is a large cabinet or assembly of metal cabinets that connects disconnecting switches, overcurrent protection devices, and instruments.
- Panelboard is one or more metal cabinets that serve as a single unit, including buses, automatic overcurrent protection devices, and switches for controlling light, heat, and power circuits.
Building Transformers
- Building transformers are used to change voltage, current, and phase of electrical power nearby and within a building.
- Typical sizes of building transformers include 3, 6, 9, 15, 25, 30, 37.5, 45, 50, 75, 112.5, 150, 225, 300, 500, 750, 1000, 1500 kVA, and larger.
Test your knowledge of building electrical service equipment including service entrance conductors, switchboards, panelboards, and building transformer service. Learn about the components involved in generating electric power for buildings.
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