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31 Cards in this Set
- Front
- Back
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Components in a building electrical system are divided into three categories - what are they?
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1. wiring and raceways
2. power-handling equipment 3. utilization equipment (1227) |
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What is included in the first category of building electrical equipment "wiring and raceways"?
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"...conductors and raceways of all types;" (1227)
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What is included in the second category of building electrical components "power-handling equipment"?
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"...transformers, switchboards, panelboards, large switches, and circuit breakers;" (1227)
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What is included in the third category of building electrical components "utilization equipment"?
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"...actual utilization equipment such as lighting, motors, controls, and wiring devices." (1227)
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What is NEC and what does it do?
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The National Electric Code of the NFPA (National Fire Protection Association)
defines the fundamental safety measures that must be followed in the selection, construction, and installation of all electrical equipment." (1227) |
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Why should you use only UL approved materials?
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Underwriters Laboratory (UL) is the single agency that sets the minimum standard of "intrinsic electrical safety for electrical equipment" (1228)
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Why does the selection of electrical materials involve economic consideration?
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"...usually many brands and types of equipment that will fulfill the construction needs are available. In such cases, economic factors often decide the issue." (1228)
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What is the voltage rating of an electrical equipment?
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"...the maximum voltage that can safely be applied to the unit continuously.
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How is voltage rating determined?
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"by the type and quantity of insulation used and the physical spacing between electrically energized parts." (1230)
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What is the current rating of an electrical equipment?
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"...determined by the maximum operating termperature at which its components can operate at full load. That in turn depends on the type of insulation used... the actual criterion ... is the maximum permissible operating termperature of its insulation (and other components)." (1230)
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How is electrical equipment rated?
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"...for the normal service it is intended to perform... may be in
voltage, current, duty, horsepower, kW, kVA, temperatures, enclosure, and so on." (1230) |
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What are the two types of interior electrical systems and what are their purposes?
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1. electrical power system - to distribute electrical energy.
2. electrical signal or communication system - to transmit information. (1230) |
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What are the principal types of interior wiring systems in use today?
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1. exposed insulated cables
2. insulated cables in open raceways 3. insulated conductors in closed raceways (1230) |
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What is the difference between CABLE and WIRE?
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"By convention, a single insulated conductor No. 6 AWG or larger, or several conductors of any size assembled into a single unit, are referred to as CABLE.
Single conductors No. 8 AWG and smaller are called WIRE." (1231) |
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What are the three possible raceway positions in a building structure?
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"1. Buried in the structure...
2. Attached to the structure... 3. Part of the structure..." (1231) |
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What components are covered by "Combined Conductor and Enclosure"?
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"...all types of factory-prepared and factory-constructed integral assemblies of conductor and enclosure." (1231)
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What is AMPACITY?"
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"Conductor current-carrying capacity" (1231)
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What determines ampacity?
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"...the maximum safe operating temperature of the insulation." (1231)
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In a given environment (open-air, buried, enclosed), what factors determine ampacity?
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"...ampacity increases with increasing conductor size AND
with maximum permissible insulation temperature." (1231) |
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What is the relationship between heat dissipation from a conductor and its allowable ampacity?
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the greater the heat dissipation, the greater the allowable ampacity. (1231)
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What is the ambient temperature on which ampacity tables are based?
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30 degrees C (86 degrees F) (1231)
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How is electrical insulation rated?
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"Insulation is rated by voltage." (1232)
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What is the rating for ordinary building wiring?
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"300 or 600V." (1232)
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What are the advantages of aluminum conductors over copper?
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1. weight
2. lower installation cost |
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Where does copper show a good economy?
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"... in small- and medium-sized cable, because weight is not a problem and the smaller conduit required for the smaller copper conductors generally makes the combined installation cheaper." (1232)
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What is NEC type AC armored cable aka BX?
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"It is an assembly of insulated wires, bound together and enclosed in a protective armor made of a spiral-wound interlocking strip of steel tape." (1234)
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What is MC cable?
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metallic clad
similar to BX but wider application - can be used "exposed or concealed and in cable trays, and, when covered with a moisture-impervious jacket, in wet and outdoor locations as well." (1234) |
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Describe NEC types NM and NMC cable aka Romex.
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Non Metallic - plastic outer jacket.
"restricted to small buildings - that is, residential and other structures not exceeding three floors above grade. Easier to handle than AC but more susceptible to damage. (1234) |
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What does building wire consist of?
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a copper conductor covered with insulation/jacket. (1235)
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What is a busway (busduct)?
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"... an assembly of copper or aluminum bars in a rigid metallic housing..." (1235)
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From an economic standpoint, In what two situations is it preferable to use a busduct (busway)?
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1. "when it is necessary to carry large amount of current (power) and"
2. "when it is necessary to tap onto an electrical power conductor at frequent intervals..." (1235) |
