Unit 9: Multi Family Dwelling Service Calculations Flashcards
Applying NEC® demand factors and load calculation methods to determine proper service size, feeder conductors, and overcurrent protection for multi-family residential buildings.
True or False:
Every panelboard circuit and circuit modification shall be legibly identified at the panelboard or adjacent to the panelboard.
TRUE
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Installation of direct-buried cables in an area that is subject to movement by frost or settlement shall be _____.
placed with “S” loops or adequate allowance for movement
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As a general rule, the disconnecting means for an air-conditioning or refrigerating equipment is required to have a rating of at least _____ of the nameplate rated-load current of the equipment.
115%
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Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to _____.
qualified persons only
What size copper THW conductors are required to supply a single-phase, 240- volt, 5 hp motor and a single-phase, 240-volt, 1kW, non-continuous non-motor load?
8 AWG
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When buried under a driveway of a dwelling, rigid metal conduit shall have a burial depth of _____.
6 inches
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Cable splices made and insulated by approved methods shall be permitted to be located within a cable tray, provided they are _____.
performed with only copper conductors
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Metallic surface-type cabinets for electrical equipment in damp or wet locations shall be mounted so there is at least _____ air space between the cabinet and the wall or other supporting surface.
1/4 in
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Given: An equipment disconnecting means is mounted at a height of 6 feet on a remote wall in an aircraft storage and maintenance hangar. The disconnect switch is 10 feet horizontally away from any aircraft fuel tanks. The disconnect switch is located in a/an _____ area.
unclassified
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The size of a wire-type equipment grounding conductor is most dependent upon _____.
available fault-current
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Busways shall be securely supported at intervals not exceeding _____ unless the raceway is otherwise designed and marked.
5 feet
Given: You are to install an underground 50 ft. run of Schedule 40 PVC conduit that will contain three (3) size 2 AWG THWN circuit conductors and one (1) size 8 AWG THWN equipment grounding conductor. In compliance with the NEC, what trade size PVC is required for this installation?
11⁄4 in.
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A single-phase, 125-volt, 15- or 20-ampere receptacle outlet shall be installed at each residential kitchen countertop and work surface that is at least _____ or wider.
12 inches
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The short-circuit and ground-fault protective device protecting an air conditioner motor-compressor on 15- or 20-ampere branch circuits shall have sufficient _____ to permit the motor-compressor and other motors to start and accelerate their loads.
time delay
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Factory assembled non-heating leads of heating cables, if any, of electric space heating cables shall be at least _____ in length.
7 feet
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At least one 15-volt, single-phase, 15- or 20-ampere-rated receptacle outlet is required to be installed within 18 in. of the top of a show window. No point along the top of the show window shall be further than _____ from a receptacle outlet.
6 feet
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Where junction or pull boxes enclose conductors of size 4 AWG or larger the boxes are to be sized by the raceway(s) entering the box and not by the size of the conductors contained in the box. Where splices, angle or U-pulls are made, the distance between each raceway entry in the box and opposite wall of the box shall not be less than _____ times the largest raceway in a row plus the sum of the additional raceways in the row.
six
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Circuit protection must be designed and capable of disconnecting motors and their controllers from the circuit. The disconnecting means of motors and their controllers shall open _____ supply conductor(s) of the circuit.
simultaneously all ungrounded phase
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A feeder tap less than 25 feet long does not require overcurrent protection at the tap if the ampacity of the tap conductor is at least _____ of the rating of the overcurrent device protecting the feeder conductor.
one-third
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As a general rule, overhead spans of open conductors and multiconductor cables, of not over 1000 volts, shall have a vertical clearance of not less than _____ above the roof surface of a building or structure.
81⁄2 feet
Given: A 75 kVA transformer will supply a 225-ampere rated panelboard with size 4/0 AWG THWN copper conductors. What size copper system bonding jumper is required for the transformer?
2 AWG
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In a Class I, Division 1 location, each conduit entry into an explosionproof enclosure shall have a conduit seal installed within _____ from the enclosure.
18 inches
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Each commercial building accessible to pedestrians shall have an outside electric sign circuit rated at least _____ that supplies no other load.
20 amperes
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As a general rule, overhead service conductors, installed as open conductors, must have a clearance of at least _____ laterally (to the side) from windows that are designed to be opened, doors, ladders, stairs and porches.
3 feet
