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Holt, Electricians Exam Prep, Unit 6
Conductor Insulation Properties: Table _____ of the NEC provides information on conductor properties such as permitted use, maximum operating temperature and other insulation details. - 310.104(a) TW can be described as thermoplastic insulation, suitable for dry or wet locations with a maximum operating temperature of 60 degrees C(True/False) - True TFFN can be described as stranded fixture wire with thermoplastic insulation, nylon cover. (True/False) - True The ampacity of a conductor is listed in table _____ under the condition of no more than three current carrying conductors bundled together in raceway, cable or earth an ambient temperature of 86 degrees F. - 310.15(b)(16) The ampacities listed in Table 310.15(b)(16) are based on temperature alone and do not take _____ into account. - Voltage drop Voltage drop considerations are for ________ and not for safety; therefore, sizing conductors for voltage drop is not a Code requirement. - Efficiency of operation The smallest size conductor permitted by the NEC for branch circuits, feeders or services is _____ copper or _____ aluminum. - No. 14, No. 12 When selecting a conductor for a circuit, always select the conductors not smaller than the _______ of the equipment. - Terminal ratings
(110-14(c)(1) ) Equipment rated at 100 ampere or less shall have the conductor sized no smaller than _____ degrees C unless the terminals are marked otherwise. - 60 (110-14(c)(1) )What size THHN conductor is required for a 50 ampere circuit, listed for use at 60 degrees C? - No. 6 What size THHN conductor is required for a 50 ampere circuit, listed for use at 75 degrees C? - No. 8 (110-14(c)(2) )Terminals for equipment rated over 100 ampere and pressure connector terminals for conductors larger than No. 1 shall have the conductor sized according to the _____ temperature rating listed in Table 310.15(B)(16) - 75 degree What size THHN conductor is required to supply a 225 ampere feeder? - 4/ Parallel conductors (electrically joined at both ends) permit a smaller ________ per ampere. This can result in a significant cost savings for circuits over 300 amperes. - Cross-sectional area What size 75 degree C conductors are required for a 600 ampere service that has a calculated demand load of 550 amperre? - 1250 kcmil What size conductors(2) would be required in one raceway (nipple) for a 600 ampere service? The calculated demand load is 550 ampere. - 300 kcmil
130 ampere If the overcurrent protection device is over 800 ampere, the circuit conductor ampacity must not be ____ than the rating of the overcurrent protection device. - Less Air Conditioning: An air conditioner nameplate indicates the minimum circuit ampacity of 43 ampere and maximum fuse size of 60 ampere. What is the minimum size branch circuit conductor and the maximum size overcurrent protection device?(422.13) - No. 8, 60 ampere Water Heater: What size conductor and protection device is required for a 4500 VA, 240 Volt water heater(422.11(e)? - #10AWG, 30 Amps Motor: What size branch circuit conductor and short-circuit protection is required for a 2 horsepower (12 ampere) motor rated 230 volts?(240-6(a), 430-52(b)) - no. 14, 30 ampere Ambient temperature Derating Factor: Conductor ampacity adjustment does not apply if the different ambient is 10 feet or less and does not exceed -___ percent of the total length of the conductor.(310-15(a)(2)exception - 10 What is the ampacity of No. 12 THHN when installed in a walk in cooler that has an ambient temperature of 50 degrees F? (310.15(B)(2)(a) - 34.5 ampere What is the ampacity of No. 6 THHN when installed on a roof that has an ambient temperature of 60 degrees C?(310.15(B)(2)(a) - 53.25 ampere Conductor Size: What size conductor is required to supply a 40 ampere load? The conductors pass through a room where the ambient temperature s 100 degrees F. (310.15(B)(2)(a) -
No. 8 THHN To find the correction factor for situation where four or more current carrying conductors are bundled together, consult Table _____. - 310.15(B)(2)(a) Conductor bundle ampacity adjustment does ot apply to conductors that are in a conduit that does not exceed _____ inches in length. - 24 What is the ampacity of four current-carrying No. 10 THHN conductors installed in a raceway or cable? - 32 ampere A raceway contains four current-carrying conductors. What size conductor is required to supply a 40 ampere non-continuous load? - No. 8 THHN If the ambient temperature is different than 86 degrees F (30 degrees C) AND there are more than three conductors in a conduit or cable, You must multiply by both the temperature correction factor and the bundle adjustment factor(True/False) - True What is the ampacity of four current-carrying No. 8 THHN conductors installed in ambient temperature of 100 degrees F? - 40 ampere The grounded neutral of a balanced 3-wire delta circuit or balance 4 wire wye circuit (is)(is not) considered a current carrying conductor. - Is not The grounded neutral of a balanced 3 wire wye circuit (is)(is not) considered a current carrying conductor. - Is
Terminal Rating(110-14(c)(1): Equipment terminals rated 100 amperes or less (circuit breakers, fuses, etc.) and pressure connector terminals for No. 14 through No. 1 conductors shall have the conductor sized according to _____ degree temperature rating as listed in Table 310.15(a)(16) - 60 Terminal Rating(110-14(C)(1): What is the minimum size THHN conductor that is permitted to terminate on a 70 ampere circuit breaker or fuse? Be sure to comply with the requirements of Section 110-14(c)(1) - 4 Terminal Rating(110-14(C)(1): What size THHN conductor is required for a 70 ampere branch circuit if the circuit breaker and equipment is listed for 75 degrees C terminals and the load does not exceed 65 ampere? - No. 6 Terminal Rating(110-14(C)(1): Terminals for equipment rated over 100 ampere and pressure connector terminals for conductors larger than No. 1 shall have the conductor sized according to 75 degree C temperature rating as listed in Table 310-15(a)(16)(True/False) - True Terminal Rating(110-14(C)(1): What size THHN conductor is required for an air-conditioning unit if the nameplate requires a conductor ampacity of 34 ampere? Terminals of all the equipment and circuit breakers are rated 75 degrees C. - No. 10 Terminal Rating(110-14(C)(1): What is the minimum size THHN conductor required for a 150 ampere circuit breaker or fuse? Be sure to comply with the requirements of Section 110-14(C)(2). - No. 1/ Terminal Rating: In general, THHN (90 degrees C) conductor ampacities cannot be used when sizing conductors; but when more than three current-carrying conductors are bundled together, or if the ambient temperature is greater than 86 degrees F, the allowable conductor ampacity must be decreased. THHN offers the opportunity of having a greater ampacity for conductor derating purposes, thereby permitting the same conductor to be used without having to increase the conductor size.(True/False) - True
Terminal Rating(110-14(C)(1):What size conductor is required to supply a 190 ampere load in a dry location? Terminals are rated 75 degrees C. - No. 3/ Conductors in Parallel(310-10(H)(1) : Phase and grounded (Neutral) conductors sized No. 1 AWG and larger are permitted to be connected in parallel. - False Conductors in Paralle(310-10(H)(2) l:To ensure that the currents are evenly distributed between the parallel conductors, each conductor within a parallel set must be installed in the same type of raceway(metallic or nonmetallic) and must be the same length, material, circular mils, insulation type, and must terminate in the same method.(True/False) - True Conductors in Paralle (310-10(H)(3)l: Paralleling of conductors is done by sets.(True/False) - True Conductors in Parallel: (310-10(H)(1) When an electric relay (coil) is energized, the initial current can be very high, causing significant voltage drop. The reduced voltage at the coil (because of voltage drop) can cause the coils contacts to chatter (open and close like a buzzer) or not close at all. Paralleling of control wiring conductors is often necessary and permitted by the NEC to reduce the effects of voltage drop for long control runs.(True/False) - True Conductors in Parallel: (310-10(H)(5)(250-122(F) When equipment grounding conductors are installed in parallel, each raceway must have a full-size equipment grounding conductor sized according to the overcurrent protection device rating of that circuit.(True/False) - True Conductors in Parallel(310-10(H)(5): All parallel equipment grounding conductors are required to be a minimum No. 1/0.(True/False) - False Conductors in Parallel(310-10(H)(1)(Table 250-122): What size equipment grounding conductor is required in each raceway for an 800 ampere, 500 kcmil feeder parallel in two raceways? - No. 1/
(240-3)(310-15(A)(16)What size conductor (75 degrees C) is required for a 70 ampere breaker that supplies a 70 ampere load? - No. 4 (310-10 and 310-15) The temperature rating of a conductor is the maximum operating temperature the conductor insulation can withstand (without serious damage) over a prolonged period of time. The conductor allowable ampacities, ambient temperature correction factors, and correction factors all provide guidance for adjusting the conductor's ampacities for the different conditions.(True/False)
- True (Table 310-15(a)(16)): The ampacities in Table 310-15(a)(16) apply ony when the ambient temperature is 40 C and there are no more than two current-carrying conductors bundled together. If the ambient temperature is not 40 C or there are more than two current-carrying conductors in a raceway, the allowable ampacities must be adjusted to reflect the ampacity under the condition of use.(True/False) - False (Table 310-15(a)(16)):What is the ampacity of No. 8 THHN conductors when installed in a walk in cooler if the ambient temperature is 50F? - 57 amperes (Table 310-15(a)(16)): What size conductor is required to feed a 16 ampere load when the conductors are in an ambient temperature of 100F? The circuit is protected with a 20-ampere overcurrent protection device. - No. 12 THHN (Table 310-15(b)(3a)): When four or more current-carrying conductors are bundled together for more than _____, the conductor allowable ampacity must be reduced according to the factors listed in Table 310-15(b)(3a). - 24 inches (Table 310-15(b)(3a)): What is the ampacity for four No. 1/0 THHN conductors? - 136 amperes
(Table 310-15(b)(3a)): A raceway contains eight current-carrying conductors. What size conductor is required to feed a 21 ampere noncontinuous lighting load? The overcurrent protection device is rated 30 ampere. - No. 10 THHN Ambient Temperature and Conductor Bundling Derating Factors: What is the ampacity of eight current-carrying No. 10 THHN conductors installed in ambient temperature of 100F? - 26 ampere Current Carrying Conductors(310-15(B)(5) : The neutral conductor of a balanced 3-wire delta circuit, or 4 wire wye circuit is considered a current-carrying conductor for the purpose of applying the derating factors in Table 310-15(b)(2a). - False Current Carrying Conductors(310-15(B)(5): The neutral conductor of a balanced 4 wire wye circuit that is at least 50 percent loaded with nonlinear loads (electric discharge lighting, electronic ballast, dimmers, controls, computers, laboratory test equipment, medical test equipment, recording studio equipment, etc.) is not considered a current-carrying conductor for the purpose of applying bundle adjustment factors.(True/False) - False Current Carrying Conductors(310-15(B)(5): The neutral conductor of a balanced 3-wire wye circuit is not considered a current-carrying conductor for the purpose of applying bundle adjustment factors. (True/False) - False (310-15(B)(3)(a)(2)The ampacity of a conductor can be different along the length of the conductor. The higher calculated ampacity can be used if the length of the lower ampacity is no more than 10 feet or no more than 10 percent of the length of the circuit conductors.(True/False) - True (110-14(C) Most terminals are rated 60C for equipment 100 ampere and less and 75C for equipment terminals rated over 100 ampere. Regardless of the conductor ampacity, conductors must be sized no smaller than the terminal temperature rating.(True/False) - True
The ampacity of the nine current-carrying No. 10 THW conductors installed in a 20 inch long raceway is_____. - 35 amperes The ampacity of 10 current-carrying No. 6 THHW conductors installed in an 18 inch long raceway with an ambient temperature of 39C is ____. - 68 amperes A raceway contains the following: One 4-wire multiwire branch circuit that supplies a balanced incandescent 120 volt lighting load; one 4-wire multiwire branch circuit that supplies a balanced 120 volt fluorescent lighting load; two conductors that supply a receptacle; and there is one equipment grounding conductor. The system is 3-phase 208Y/120 volts. Taking all these factors into consideration, how many of these conductors are considered current carrying? - 9 There is a total of nine No. 10 THW conductors in a raceway. The system voltage is 3-phase, 208Y/ Volts. One conductor is an equipment grounding conductor; four conductors supply a 4 wire multiwire branch circuit for balanced electric-discharge lighting, and the remaining conductors supply a 4-wire multiwire branch circuit for balanced incandescent lighting. Taking all of these factors into consideration, how many of these conductors are considered current-carrying? - 7 (250) A service that contains No. 12 service-entrance conductors, shall require a No. _____ grounding electrode conductor. - 8 (250-68(B)) The connections (attachment) of the grounding electrode conductor to a grounding electrode shall be made in a manner that will ensure a permanent and effective _____. - Ground (250-70) The connection of the grounding electrode conductor to a buried grounding electrode (driven ground rod) shall be made with a listed terminal device that is _____. - Suitable for direct burial
(250-86) Metal enclosures for conductors added to existing installations of nonmetallic sheathed cable, knob and tube wiring, or open wiring, which do not provide an equipment ground, are not required to be grounded if they are less than25 feet long free from probable contact with grounded conductive material.(True/False) - True (250-94, bonding of other systems) An accessible point must be available for bonding of communications systems to the building grounding electrode. This Section requires the accessible bonding point to be exposed metallic service raceways, exposed grounding electrode conductor, or 6 inches of No. 6 copper conductor connected to the service equipment or raceway(True/False) - True (250-96(a)) Metal parts that serve as the grounding conductor must be ______ together to ensure electrical continuity and have the capacity to conduct safely any fault current likely to be imposed. - bonded. (250-96(b)) Where required for the reduction of electric noise for electronic equipment, electrical continuity of metal raceway is not required, and the metal raceway can terminate to a(n) ______ nonmetallic fittings(s)or spacer on the electronic equipment. - Listed (250-102(c)(1)) The bonding jumper for service raceways must be sized according to the _____. - Service entrance conductor size (Table 250-122) What is the minimum size equipment grounding conductor required for equipment connected to a 40 ampere rated circuit? - No. 10 (250-104(A)(1)) A building or structure, which is supplied by a feeder, must have the interior metal water piping system bonded with a conductor sized from _____. - Table 250- (250-110) Exposed noncurrent-carrying metal parts likely to become energized must be grounded where within 8 feet vertically or 5 feet horizontally of ground or grounded objects, located in wet or damp locations, or in electrical contact with metal(True/False). - True
True (250-164(A)) DC systems to be grounded and supplied from an off premises source shall have the grounding connection made at _____. - One of more supply stations (250-172) Cases or frames of instrument transformers are not required to be grounded when accessible to qualified persons only or for current transformers where the primary is not over 150 volts to ground and which are used exclusively to supply current to meters.(True/False) - True (280-12)The conductor used to connect the surge arrester to _____ shall not be any longer than necessary. - Ground (300-2) Unless specified elsewhere in the Code, Chapter 3 shall be used for voltages of _____. - 600 volts nominal, or less (300-3(c)(1)) Circuit conductors that operate at 277 volts (with 600 volt insulation) may occupy the same enclosure or raceway with 48-volt dc conductors that have an insulation rating of 300 volts. (True/False) - True (300-4(b)(1)) Where nonmetallic sheathed cables pass through cut or drilled slots or holes in metal members, the cable needs to be protected by bushings or grommets securely covering all metal edges fastened in the opening prior to installation of the cable.(True/False) - True (Table 300-5) UF cable is used to supply power to a 120 volt 15 ampere GFCI protected circuit. If the cable is installed outdoors under the driveway of a one-family dwelling, the minimum cover requirement is _____ inches. - 12
(300-5(D)(1)) Where underground conductors and cables emerge from underground, they shall be protected to a point ____ feet above finished grade. In no case shall the protection be required to exceed 18 inches below grade. - 8 (300-5(F)) Backfill used for underground wiring must not damage the wiring method, contribute to the corrosion of the raceway or prevent compaction of the fill.(True/False) - True (300-5(I)) All conductors of a circuit are required to be in the same raceway and in close proximity in the same trench.(True/False) - True (300-6(D)) The provisions required for mounting conduits on indoor walls or in rooms that must be hosed down frequently is ______ between the mounting surface and the electrical equipment. - A ¼ inch air space (300-10) All metal raceways, cable armor, boxes, fittings, cabinets and other enclosures for conductors must be _____ joined together to form a continuous electrical conductor. - Metallically (300-13(A)) Conductors in raceways must be _____ between outlet devices and there shall be no splice or tap within a raceway itself. - Continuous (300-14) An 8" x 8" x 4" deep junction/splice box would only require 6 inches of free conductor measured from the point in the box where the conductors enter the enclosure. The 3 inch outside the box rule _____ apply. - Does not (300-16(B)) A bushing can be used instead of a box where conductors emerge from a raceway and enter or terminate at equipment such as switchboards, unenclosed control equipment, or similar equipment.(True/False) - True
(590-4(E)) Multiwire branch circuits for temporary wiring shall be provided with a means to disconnect simultaneously all _____ conductors at the power outlet or panelboard where the branch circuit originated. - Ungrounded (590-4(J)) Cable assemblies, as well as flexible cords and cables, shall be supported at intervals that ensure protection from physical damage. Support shall be in the form of staples, cable ties, straps or similar fittings designed as not to damage the cable or cord assembly.(True/False) - True (590-6(A)(1)) All 125 volt single phase 15, 20 and 30 ampere receptacle outlets in use by personnel for temporary power shall have ground-fault circuit-interrupter protection for personnel.(True/False)
- True (310-106(C)) Where installed in raceways, conductors No. _____ and larger shall be stranded. - 8 (310-10(H)(1)) In general, the minimum size phase, neutral or grounded conductor permitted for use in parallel is No. ___. - 1/ (Table 310-106(A)) The minimum size conductor permitted in a commercial building for branch circuits under 600 volts is No. _____. - 14 (310-15(3)) Where conductors of different insulation are associated together, the limiting temperature of any conductor shall not be exceeded.(True/False) - True (310-120(C)) Suffixes to designate the number of conductors within a cable are D "Two insulated conductors laid in parallel" or M "Two or more insulated conductors twisted spirally".(True/False) - True
(310) TFE-insulated conductors are manufactured in sizes from No. 14 through No. _____. - 4/ (310) Where six current-carrying conductors are run in the same conduit or cable, the ampacity of each conductor shall be adjusted by a factor of _____ percent. - 80 (310) On a 4 wire-3-phase wye circuit, where the major portion of the load consists of electrical discharge lighting, data processing equipment , or other harmonic current inducting loads, the neutral conductor shall be counted when applying Section 310-15(b)(2) adjustment factors.(True/False) - True (310-15(B)(2)(A)) In designing circuits, the current-carrying capacity of conductors should be corrected for heat at room temperatures above ______ degrees F. - 86 (310-60(A)) Thermal resistivety is the reciprocal of thermal conductivity; it is designated Rho and expressed in units of ______. - Degrees C-cm/watt (310-60(C)(71)) Table 310-71 provides ampacities of an insulated three-conductor copper cable isolated in air, based on conductor temperature of 90 C (194 F) and ambient air temperature of 40 C (104 F). If the conductor size is No. 4/0 AWG, MV-105, and the voltage range is 2001 to 5000, the ampacity is _____ amperes - 320 (392-12) Cable tray systems shall not be used in hoistways or _______. - Where subject to physical damage. (392-18(B)) Each run of cable tray shall be _____ before the installation of cables. - Completed
