Unit 6: Voltage Drop Calculations Flashcards
Identify voltage drop thresholds, calculate conductor sizes based on distance and resistance, and apply solutions to minimize power loss.
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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
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Type AC cable shall provide an adequate path for ________.
fault current
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A totally enclosed ac motor located in a Class I, Division 1 location shall ________.
be supplied with positive air 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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High-impedance grounded neutral systems shall be permitted for 3-phase ac systems of 480-volts to 1,000 volts where ________.
all of these conditions are met
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Where the overcurrent protection specified is not sufficient for the starting current of an airconditioner motor-compressor, the rating or setting shall be permitted to be increased, but shall not exceed ________ of the motor rated-load current or branch circuit selection.
225%
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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 (2)
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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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A metal junction box to be installed will contain the following conductors:
- three - size 6 AWG ungrounded conductors
- three - size 6 AWG grounded conductors
- one size 8 AWG grounding conductor
- three - size 12 AWG ungrounded conductors
- three - size 12 AWG grounded conductors
- one - size 12 AWG grounding conductor
The junction box is required to have a volume of at LEAST ________.
4 ½ 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
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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) service entrance conductors?
57,000 VA
100 ft. x 300 ft. = 30,000 sq. ft. x 1.9 (Table 220.12) = 57,000 VA
demand load
Comment: The Note directly below Table 220.12 clarifies the 125% multiplier for a continuous load as specified in 210.20(A) is included when using the unit loads in this table for calculating the minimum lighting load for a specified non- dwelling occupancy.
However, the Informational Note below 220.12 tells us the unit values given in Table 220.12 are based on minimum load conditions and may not provide sufficient capacity for the installation contemplated.
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
