Unit 6: Voltage Drop Calculations Flashcards
Learn to compute voltage drop values, assess efficiency losses, and select appropriate wire sizes to ensure compliance. (25 cards)
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Given: The lightning protection system ground terminals shall be bonded to the building or structure grounding electrode system. The bonding shall be _________ and to all raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode.
bonded at both ends
What is the required function of Type AC cable in ensuring electrical safety?
fault current
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A totally enclosed ac motor located in a Class I, Division 1 location shall _________.
be supplied with pipe ventilation
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Color coding shall be permitted to identify intrinsically safe conductors where they are colored _________ and where no other conductors of the same color are used.
light blue
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Mandatory rules of the NEC® are those that identify actions that are specifically required or prohibited, are characterized by the use of the terms _________.
shall or shall not
A surge arrestor is required on each ungrounded conductor of an industrial facility that experiences severe thunderstorms. If the electrical system is a 4-wire, wye connected grounded system, how many surge arrestors shall be required?
three
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As per the NEC®, a _________ location may be temporarily subject to dampness and wetness, as in the case of a building under construction.
dry
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Under what conditions are high-impedance grounded neutral systems permitted for 3-phase AC systems ranging from 480 volts to 1,000 volts?
- the conditions of maintenance ensure that only qualified persons service the installation
- ground detectors are installed on the electrical system
- line-to-neutral loads are not served
What minimum size THWN copper conductors are required to supply a continuous-duty, 25 hp, 208 volt, 3-phase motor, where the motor is on the end of a short conduit run that contains only three conductors, at an ambient temperature of 115°F?
1 AWG
25 hp motor FLC = 74.8 amperes x 125% = 93.5 amperes (before correcting)
93.5 amps ÷.73 (temperature correction) = 124.6 amperes
NOTE: The wire size needs to be increased due to the elevated ambient temperature. Therefore, Size 1 AWG THWN conductors with an ampacity of 130 amperes should be selected from Table 310.16.
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Floor duct installed in the concrete floor of an aircraft hangar shall be classified as a _________ location.
Class I, Division 1
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Generally, where installed on the outside of a raceway, the length of the equipment bonding jumper shall not exceed _________ and shall be routed with the raceway.
6 feet
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Unless otherwise permitted by the local authority having jurisdiction, Type AC cable shall be secured within _________ of every box, cabinet, or fitting and at intervals not exceeding 4½ ft. where installed on or across framing members.
12 in.
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Energized electrical equipment operating at 120-volts to ground with exposed live parts on one side and a concrete block tile wall on the other side of the working space, is Condition _________.
two
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Where corrosion protection is necessary and rigid metal conduit (RMC) or intermediate metal conduit (IMC) is threaded in the field, the threads shall be coated with a/an _________, _________, and _________ material compound.
approved, electrically conductive, corrosion-resistant
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In general, flexible metal conduit (FMC) shall be securely fastened in place
and supported by an approved means at intervals not exceeding _________.
4½ feet
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The accessible portions of abandoned supply circuits and interconnecting cables for information technology equipment, or any systems in an information technology equipment room, shall be _________.
removed unless contained in a metal raceway
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Disregarding exceptions, the maximum distance permitted for seven (7) current-carrying Type NM cables to be bundled together without requiring the ampacity of the conductors to be reduced is _________.
24 in.
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For other than dwelling units, all single-phase, 125-volt, 15- and 20- ampere receptacle outlets shall be calculated at not less than _________ for each single or for each multiple receptacle mounted on one yoke.
180 VA
Where underground installed service conductors emerge from grade and are exposed to physical damage, which of the following listed raceways are not approved for such use?
a. Rigid metal conduit
b. Schedule 80 PVC
c. Schedule 40 PVC
d. RTRC-XW
c. Schedule 40 PVC
Fill in the blank:
One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved, is defined in the NEC® as a/an _________ person.
qualified
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Cable splices made and insulated by approved methods are permitted to be located within a cable tray, provided they are _________.
accessible
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Transformers containing oil or a liquid that will burn where located in Class I, Division 1 locations shall be _________.
installed in vaults only
Given: A retail department store having dimensions of 100 ft. by 300 ft. is supplied by a 208Y/120-volt, three-phase electrical system. What is the general lighting demand load, in VA, on the ungrounded (phase) serviceentrance conductors?
57,000 VA
Refer to the previous question and determine the minimum required number of single-phase, 120-volt, 20-ampere branch circuits to be provided for the general lighting load.
24
120 volts x 20 amperes = 2,400 VA (one circuit)
57,000 VA (demand) ÷2,400 VA (one circuit) = 23.75 =
24 circuits
