Article 250: Grounding And Bonding

Transcription

1 Part D: Code Book Questions Article 250: Grounding And Bonding 1.! A ground-fault is an unintentional, electrically conducting connection between an ungrounded! conductor of an electrical circuit and the normally non-current-carrying conductors, or! earth.! (a) metallic enclosures! (c) metallic equipment! (b) metallic raceways! (d) all of these 2.! Ground clamps, or other fittings shall be approved for general use without protection or shall be! protected.! (a)!by enclosing in wood! (c) by equivalent protective covering! (b) by enclosing in metal! (d) all of these 3.! Nonconductive coatings (such as paint, lacquer, and enamel) on equipment to be grounded shall! be removed from threads and other contact surfaces to.! (a) provide a water tight joint! (c) assure good electrical continuity! (b) provide a sealed joint! (d) lower inductance 4.! A.C. circuits of less than 50 volts shall be grounded under which of the following?! (a)!where supplied by transformers if the supply system exceeds 150 volts to ground.! (b)!where supplied by transformers if the transformer supply system is ungrounded.! (c)! Where installed as overhead conductors outside of buildings.! (d)!all of these 5.! Which of the following A.C. systems ( volts) need not be grounded?! (a) motion picture projection equipment!! (c) metal service raceways! (b) electrically operated cranes!! (d) industrial electric furnaces 6.! Circuits for electrical cranes operating in Class III locations over combustible fibers shall not! be.! (a) grounded! (c) spliced! (b) pulled in raceways! (d) THWN conductors

2 7.! Where an A.C. system operating at less than volts is grounded at any point, the grounded! conductor shall be run to each service.! (a) 300! (c) 1000! (b) 600! (d) ! The grounded service conductor shall not be smaller than the required.! (a) grounding electrode conductor! (c) ungrounded service conductor! (b) largest phase conductor! (d) largest equipment conductor 9.! When service entrance phase conductors are larger than 1100 kcmil copper, the bonding jumper! shall have an area not less than % of the area of the largest phase conductor.! (a) 6%! (c) 12-1/2%! (b) 10%! (d) 15% 10.!A bonding jumper shall be used to connect the equipment grounding conductors of the derived! system to the grounded conductor. This connection shall be made at.! (a)!any point on the separately derived system from the source to the first system disconnect! (b)!any point on the separately derived system from the source to the first overcurrent device! (c)! the source if the system has no disconnecting means or overcurrent device! (d)!all of these 11.!A grounding electrode conductor shall not be required for a system that supplies a and is! derived from a transformer not more than 1000 va, provided the system grounded conductor is! bonded to the transformer frame.! (a) Class I circuit! (c) Class III circuit! (b) Class II circuit! (d) all of these 12.!Which of the following conditions must be met for vehicle mounted generators used to supply! electrical tools on a construction site?! (a)!the frame of the generator is bonded to the vehicle frame! (b)!the generator supplies cord and plug connected equipment through receptacles mounted on!! the vehicle or on the generator! (c)! The non-current-carrying metal parts of equipment and the equipment grounding conductor!! terminals of the receptacles are bonded to the generator frame.! (d)!all of these

3 13.!Given: A metal underground water pipe is used as a grounding electrode and used to bond other! electrodes together. The grounding electrode conductor is connected to the water pipe on the! interior of the building. The connection of the grounding electrode conductor to the interior water! pipe shall be made a maximum of feet from the point where the water pipe enters the! building.! (a) 3! (c) 8! (b) 5! (d) !A metallic water system is used as a grounding means. Which of the following statements! is/are true?! (a)!must be bonded around the meter.! (b)!must bond around insulated joints.! (c)! Must be supplemented by an additional electrode.! (d)!all of these are true 15.!A bare #4 conductor may be concrete encased and serve as the grounding electrode when at least! feet in length.! (a) 10! (c)! 20! (b) 12! (d)!15 16.!Electrodes of pipe, or conduit, shall not be smaller than trade size.! (a) 1/2! (c) 3/4! (b) 5/8! (d) 1 17.!Electrodes of iron or steel shall have a diameter of at least.! (a) 1/2! (c) 1! (b) 3/4! (d) 5/8 18.!The number of square feet that each plate electrode should expose to the soil is.! (a) 4 square feet! (c) 2 square feet! (b) 3 square feet! (d) 1 square foot 19.!In using multiple grounding electrodes, they shall be separated one from the other at feet! distance apart.! (a) 6! (c) 10! (b) 8! (d) 12

4 20.!A ground ring encircling the building, in direct contact with the earth at a depth below earth! surface shall not be less than inches, consisting of at least 20 of bare copper not smaller than! #2 AWG.! (a) 24! (c) 36! (b) 30! (d) !The grounding electrode shall be installed such that of length is in contact with the soil.! (a) 6! (c) 7 6! (b) 7! (d) 8 22.!A single electrode consisting of a which does not have a resistance to ground of 25Ω or less! shall be augmented by one additional electrode.! (a) rod! (c) plate! (b) pipe! (d) any of these 23.!Where separate services supply a building and are required to be connected to a grounding! electrode, shall be used.! (a) multiple electrodes! (c) two electrodes! (b) the same grounding electrode! (d) paralleled electrodes 24.!Bonding together of all separate grounding electrodes will limit between them and between! their associated wiring systems.! (a) potential differences! (c) stray currents! (b) high frequencies! (d) arcing 25.!The grounding electrode conductor shall be and shall be installed in one continuous length! without a splice or joint.! (a) solid or stranded! (c) bare! (b) insulated or covered! (d) any of these 26.!Aluminum grounding conductors shall not be used where.! (a) within 18 of earth! (c) in direct contact with masonry! (b) subject to corrosive conditions! (d) any of these

5 27.! and larger grounding electrode conductors shall be protected where exposed to severe! physical damage.! (a) #8! (c) #4! (b) #6! (d) #2 28.!Grounding electrode conductors smaller than #6 shall be in.! (a) EMT! (c) rigid metal conduit! (b) IMC! (d) any of these 29.!The #4 solid copper conductor connecting the grounding electrode to the service has been! accidentally cut. Which of the following would be acceptable connectors for splicing this! conductor?! (a) split bolt connector!! (c) wire nut! (b) irrevesible compression sleeve connector!! (d) none of these are acceptable 30.!According to the Code, ferrous metal enclosures for grounding electrode conductors shall.! (a) not be permitted! (c) be in rigid conduit! (b) be electrically continuous! (d) none of these 31.!A single-family dwelling contains a 200 amp single-phase service panel supplied with #2/0 THW! conductors. The minimum size bonding jumper for this service is.! (a) #6 aluminum! (c) #4 aluminum! (b) #6 copper! (d) #4 copper 32.!A concrete encased or buried grounding electrode connection shall.! (a) be made accessible!! (c) be a minimum #4 bare! (b) be made only by exothermic welding!! (d) not be required to be accessible 33.!The grounding or bonding conductor shall be connected to the grounding electrode by, or! other listed means.! (a) exothermic welding! (c) listed pressure connectors! (b) listed lugs! (d) any of these 34.!Connections to grounding and bonding jumpers be made dependent on soldering.! (a) shall! (c) shall not! (b) may! (d) must

6 35.!Not more than one conductor shall be connected to the grounding electrode by a single clamp or! fitting unless the clamp or fitting is.! (a) cast bronze or brass! (c) in thickness! (b) listed for multiple conductors! (d) none of these 36.!Grounding of a metal raceway used to protect fluorescent is required if the raceway is feet! or over, or within reach of ground or grounded metal.! (a) 6! (c) 10! (b) 8! (d) !Short sections of metal enclosures, or raceways, used to protect from physical damage shall! not be required to be grounded.! (a) service conductors! (c) cable assemblies! (b) feeders! (d) none of these 38.!A metal elbow installed underground in a run of nonmetallic conduit is not required to be! grounded if it is isolated by a minimum cover of at least inches to any part of the elbow.! (a) 6! (c) 18! (b) 12! (d) !Which of the following shall be provided where necessary to assure electrical continuity and the! capacity to conduct safely any fault current likely to be imposed?! (a) Grounding! (c) Jumpers! (b) Bonding! (d) Shunts 40.!A #6 copper conductor with one end bonded to the service raceway or equipment and with! inches or more of the other end made accessible on the outside wall of the dwelling is an example! of the approved means for the external connection of a bonding, or grounding conductor to the! service raceway or equipment.! (a) 6! (c) 24! (b) 12! (d) !To ensure effective continuity between enclosures shall be removed from the conduit! threads.! (a) ends! (c) galvanize finish! (b) enamel! (d) aluminum

7 42.!Expansion joints and telescoping sections of raceway shall be made electrically continuous by! equipment or other means approved for the purpose.! (a) grounding conductors! (c) bonding jumpers! (b) grounded conductor! (d) none of these 43.!A bonding jumper shall be a, or similar suitable conductor.! (a) wire! (c) bus! (b) screw! (d) any of these 44.!Service bonding jumpers must be sized.! (a) according to the fuse size!! (c) 1/3 as large as the service conductor! (b) same as the largest service conductor!! (d) according to Table !The maximum length of a bonding jumper on the outside of a raceway is feet and shall be! routed with the raceway or enclosure.! (a) 3! (c) 8! (b) 6! (d) none of these 46.!The interior metal water piping system shall be bonded to the.! (a) grounded conductor at the service!! (c) service equipment enclosure! (b) grounding electrode conductor!! (d) any of these 47.!Non-current carrying metal parts of electrical equipment typically is kept feet (through air)! from lightning protection conductors?! (a) 3! (c) 8! (b) 6! (d) !Equipment installed and likely to become energized shall be grounded at which of the following! distances?! (a)!8 feet horizontal and 5 feet vertical of grounded metal objects! (b)!5 feet vertical and 5 feet horizontal of grounded metal objects! (c)! 8 feet vertical and 5 feet horizontal of grounded metal objects! (d)!8 feet vertical and 8 feet horizontal of grounded metal objects

8 49.!Exposed non-current carrying metal parts of fixed equipment must be grounded under all of the! following conditions except (by special permission).! (a)!where supplied by metal clad wiring! (b)!electrically heated appliances with the frames insulated from ground! (c)! where in electrical contact with metal! (d)!where located in damp locations 50.!Listed equipment protected by a system of double insulation, or its equivalent, shall not be! required to be grounded. Where such a system is employed, the equipment shall be.! (a) labeled! (c) distinctively marked! (b) approved! (d) identified 51.!An electrically operated organ shall have both the generator and motor frames grounded! or.! (a)!the generator and motor shall be effectively insulated from ground and from each other! (b)!the generator and motor shall be effectively insulated from ground! (c)! the generator shall be effectively insulated from ground and from the motor driving it! (d)!both the generator and motor shall have double insulation 52.!Which appliance, in a dwelling is not required to be grounded if insulated from ground?! (a) toaster! (c) blender! (b) can opener! (d) aquarium 53.!Where extensive metal in or on buildings may become energized and is subject to personal contact! will provide additional safety.! (a) adequate bonding and grounding! (c) suitable ground detectors! (b) bonding! (d) none of these 54.!A run of flexible metal conduit may be used as an equipment grounding conductor if the! conductors are protected at, not exceeding six feet in length.! (a) 20 amps or more! (c) 30 amps or more! (b) 20 amps or less! (d) 30 amps or less 55.!The grounding conductor shall be identified by.! (a) being bare! (c) a continuous green color with yellow stripes! (b) one continuous green color! (d) any of these

9 56.!The equipment grounding conductor in type NM cable for 15, 20 and 30 ampere branch! circuits.! (a)!may be at least one size smaller than the insulated circuit conductor! (b)!must be the same size as the insulated circuit conductors! (c)! is required only with aluminum cable! (d)!none of these 57.!Which of the following is not a true statement concerning an equipment grounding conductor?! (a)!equipment grounding conductors may be required to be larger than circuit conductors.! (b)!under certain conditions, equipment grounding conductors may be run in parallel.! (c)! Equipment grounding conductors shall be increased to compensate for voltage drop.! (d)!one equipment grounding conductor may serve multiple circuits. 58.!A/an shall be used to connect the grounding terminal of a grounding type receptacle to a! grounded box.! (a) neutral conductor! (c) equipment bonding jumper! (b) branch circuit! (d) bonding jumper main 59.!The arrangement of grounding connections shall be such that the disconnection or removal of a! from the box does not interfere with or interrupt the grounding continuity.!! (a) receptacle! (c) device! (b) luminaire (fixture)! (d) any of these 60.!A two-wire D.C. system supplying premises wiring and operating at less than 50 volts between! conductors shall.! (a) not be grounded! (c) not be permitted! (b) be grounded! (d) not be required to be grounded 61.!Fire protective signaling circuits shall be grounded, the only exception being D.C. power-limited! circuits having a maximum current of amperes.! (a) 0.300! (c) 0.030! (b) 1.5! (d) 2.34

10 62.!What size grounding conductor is required for a two-wire DC generator used in conjunction with! balancer sets to obtain neutrals for a 3-wire system equipped with overcurrent devices that will! disconnect the 3-wire system in case of excessive unbalancing of voltages or currents?! (a)!#10 solid copper minimum size! (b)!shall not be smaller than any system conductor! (c)! shall not be smaller than the neutral conductor! (d)!sized from Table !Secondary circuits of current and potential instrument transformers shall be grounded where the! primary windings are connected to circuits of volts or more to ground and, where on! switchboards, shall be grounded irrespective of voltage.! (a) 30! (c) 250! (b) 100! (d) !Cases or frames of current transformers, the primaries of which are not over 150 volts to ground! and which are used exclusively to supply current to meters.! (a) need to be grounded! (c) need to be insulated! (b) need to be isolated! (d) need not be grounded 65.!Mats of insulating rubber or other suitable floor insulation shall be provided for the operator! where the voltage to ground exceeds on live-front switchboards.! (a) 50! (c) 120! (b) 100! (d) !The grounding conductor for secondary circuits of instrument transformers and for instrument! cases shall not be smaller than #12.! (a) metal! (c) copper! (b) aluminum! (d) all of these 67.!The minimum insulation level for neutral conductors of solidly grounded systems shall be! volts.! (a) 600! (c) 1500! (b) 1000! (d) 2100

11 68.!The neutral of a solidly grounded neutral system shall be permitted to be grounded at more than! one point for.! (a)!transformers supplying conductors to a building or other structure! (b)!underground circuits where the neutral is exposed! (c)! overhead circuits installed outdoors! (d)!all of these 69.!The grounding electrode to which the portable or mobile equipment system neutral impedance is! connected shall be isolated from and separated in the ground by at least feet from any other! system or equipment grounding electrode.! (a) 6! (c) 12! (b) 10! (d) 20!! Article 280: Surge Arresters 70.!A surge arrester is a protective device for limiting surge voltages by or by passing surge! current.! (a) decreasing! (c) limiting! (b) discharging! (d) derating 71.!The rating of the surge arrester shall be the maximum continuous phase-to-ground power! frequency voltage available at the point application.! (a) equal to! (c) greater than! (b) less than! (d) equal to or greater than 72.!Metal oxide surge arrester ratings are based on the magnitude and duration of overvoltage at the! arrester location as affected by.! (a) switching surges! (c) phase-to-ground faults! (b) system grounding technique! (d) all of these 73.!Surge arresters shall be permitted to be located and shall be made inaccessible to! unqualified persons unless listed for installation in accessible location.! (a) indoors! (c) indoors or outdoors! (b) outdoors! (d) neither indoors or outdoors

12 74.!When installing a surge arrester at the service of less than 1000 volts, the grounding conductor! shall be connected to.! (a) the grounded service conductor!! (c) the grounding electrode for the service! (b) the grounding electrode conductor!! (d) all of these 75.!The conductor between a surge arrester and the line for installations operating at 1000 volts or! more may be.! (a) #6 copper! (c) #4 copper! (b) #6 aluminum! (d) any of these 76.!Surge arrester grounding conductors run in metal enclosures shall be.! (a) bare!! (c) bonded to both ends of such enclosure! (b) bonded on one end of the enclosure only! (d) insulated