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Conductors with _____ marked on the insulation are NOT approved for use in a wet location. a. THW b. THHW c. THHN d. THWN - correct answer ✅THHN As shown in Table 310.104(A), conductors with THHN insulation are approved for use in dry and damp locations only and conductors with THWN, THHW, and THW insulation are recognized for use in dry and wet locations. Given: A one-family dwelling unit with a demand load of 200 amperes is supplied with a 120/240 volt, single-phase, electrical system from the local utility company. What is the MINIMUM size aluminum THW conductors required for use as service-entrance conductors for this residence? a. 1/0 AWG b. 4/0 AWG c. 3/0 AWG d. 2/0 AWG - correct answer ✅4/0 AWG Section 310.15(B)(7)(1) permits one-family dwelling 120/240 volt, single-phase, service-entrance conductors to be sized at an ampacity of not less than 83% of the service rating. Therefore, 200 amperes x 83% = 166 amperesTable 310.15(B)(16) indicates size 4/0 AWG THW aluminum conductors with an allowable ampacity of 180 amperes should be selected for this dwelling. Where a 150 kVA, single-phase transformer having a secondary voltage of 120/240 is installed at a multi-family dwelling, the full-load current rating, in amperes, of the secondary is _____. a. 625 amperes
b. 265 amperes c. 526 amperes d. 1250 amperes - correct answer ✅625 ampreres To find the full-load current rating of the single-phase transformer apply the single-phase current formula as shown: I = (150 kVA x 1000) / 240 volts = 15,000/240 = 625 amperes Which one of the following listed circuit breakers is NOT a standard ampere rating?a. 75 amperes b. 90 amperes c. 110 amperes d. 225 amperes - correct answer ✅75 amperes Table 240.6(A) illustrates the standard ampere ratings for fuses and circuit breakers. A circuit breaker with an ampere rating of 75 amperes is not a standard ampere rating. The MINIMUM length of free conductor to be left at each junction box for the purpose of splicing conductors, or making connections to luminaires or devices shall be _____ .a. 4 inches b. 10 inches c. 8 inches d. 6 inches - correct answer ✅6 inches As per Section 300.14 at least 6 in. of free conductor is to be left at each junction box for splices or the connection of luminaires or devices. The intent of this rule is to ensure enough conductor slack for the terminal connections or splices to be made easily.
b. To limit galvanic corrosion. c. To establish an effective ground-fault path and facilitate the operation of the overcurrent protective device. d. To reduce electrolysis. - correct answer ✅To establish an effective ground- fault path and facilitate the operation of the overcurrent protective device. Electrical continuity is required for metallic conduit to establish an effective ground-fault path and facilitate the operation of the overcurrent protective device. Reference Section 250.4(A)(4) and (5). In dwelling units, receptacle outlets installed for countertop surfaces, must be located above, but NOT more than _____ above the countertop or work surface. a. 12 inches b. 18 inches c. 20 inches d. 24 inches - correct answer ✅20 inches In compliance with Section 210.52(C)(5), receptacle outlets installed for countertop or work surfaces in dwelling units may be located on or above, but not more than 20 in. above the countertop or work surface. The intent of this rule is to eliminate the use of unsightly extension cords (which reduces the amount of usable countertop space) on the countertop or work surface to supply cord-and- plug connected appliances. Also, receptacles located more than 20 inches above countertops or work surfaces may interfere with the cabinetry to be installed. When conductors are installed in a conduit or tubing nipple of _____ or less in length, the ampacity adjustment factors for more than three (3) current-carrying conductors in the raceway, are not required to be applied. a. 24 inches
b. 30 inches c. 36 inches d. 48 inches - correct answer ✅24 inches Section 310.15(B)(3)(a)(2) clarifies that adjustment factors for more than three (3) current-carrying conductors in raceways shall not apply where the raceway is not more than 24 inches in length. Where more than 3 current-carrying conductors are installed in short lengths of conduit or tubing, the heating effect caused from the additional conductors is insignificant therefore, the allowable ampacity of the conductors is not greatly reduced. In compliance with the NEC, the total marked rating of a 120-volt, cord-and-plug- connected room air conditioner shall not exceed _____ of the rating of a branch circuit when lighting units, general-use receptacles, or other appliances are supplied from the branch circuit. a. 40% b. 50% c. 70% d. 80% - correct answer ✅50 % Part VII of Article 440 outlines the special provisions for room air conditioners which are (1) rated not over 250-volts ac, single-phase and (2) which are cord-and- attachment plug connected. In order to prevent overloading the branch circuit, as per Section 40.62(C), the total rating of the A/C unit shall not exceed 50% of the rating of a branch circuit where lighting units, general-use receptacles or appliances are also supplied. Which of the following shall not be located over the steps of a stairway? a. general-use receptacles b. overcurrent devices
a. the service equipment enclosure b. the grounded conductor at the service c. the grounding electrode conductor d. any of the above - correct answer ✅any of the abovePart V of Article 250 covers the requirements for bonding of electrical installations. Section 250.104(A) (1) requires metal water piping systems to be bonded to any of (1) the service entrance enclosure, (2) the grounded conductor at the service, (3) the grounding electrode conductor.Where mechanical and electrical connections are within equipment, a failure of electrical insulation can result in the connected piping systems becoming energized. For example, an insulation failure in an electrical circuit of a water heater could energize the metal water piping.Metal water piping systems must be bonded so that when a fault occurs between an ungrounded (hot) conductor and the piping, the potential difference between the two is minimized, thereby reducing the risk of electrical shock.Also, note where installed in or attached to a building or structure, all metal piping systems, including gas piping, that is likely to become energized shall be bonded to a grounded source. [250.104(B)] When armored cable, Type AC, is installed in an accessible attic and is run parallel to the sides of rafters, studs, or floor joists, _____. a. the cable shall be protected with running boards b. the cable shall be protected by guard strips at least as high as the cable c. either A or B d. neither guard strips nor running boards shall be required - correct answer ✅neither guard strips nor running boards shall be required The installation specifications for armored cable, Type AC, are addressed in Part II of Article 320. Section 320.23(B) makes it explicit, where the armored cable is installed parallel to the sides of rafters, studs or floor joists, neither guard strips nor running boards shall be required to protect the cable in accessible attics.As per Section 320.23(A), if the cables run across the top of the floor joists in an attic
that is not accessible by permanent studs or ladders, protection of the cable is required where within six (6) feet of the nearest edge of the scuttle hole or attic entrance. Generally, in a movie theater the manual switch for controlling the emergency lighting systems is permitted to be located _____. a. in the motion picture projection booth b. in an accessible location in the lobby c. on the stage or platform d. at any of these locations - correct answer ✅in an accessible location in the lobby The requirements of Article 520 apply buildings used as a theater or for a similar purpose. Section 520.8 mandates the control of emergency systems in theaters to comply with the rules set forth in Article 700; Part V of Article 700 applies to the control of emergency lighting circuits. Section 700.21 does not permit a manual control switch for emergency lighting to be placed in a motion picture projection booth or on a stage or platform; the switch shall be located in the lobby or at a convenient accessible location.Emergency lighting systems are designed and installed to maintain a specific degree of illumination for means of egress of the building in the event of fire, or similar emergency, or if the normal power supply fails. Single-conductor cable such as _____ and single-conductor cable listed and identified as solar photovoltaic (PV) wire are permitted for use in PV source circuits within the PV array. a. UF b. THHN c. USE- d. PVC-2 - correct answer ✅USE-
no ground-fault protection is installed, (2) the meter enclosure is adjacent to the service disconnecting means, and (3) the grounded service conductor is not smaller than the size specified in Table 250.122. In a dwelling unit where a 125-volt, 15- or 20-ampere receptacle is located under the counter for an in-sink waste disposer, the receptacle must be provided with _____. a. AFCI protection only b. GFCI protection only c. both AFCI and GFCI protection d. neither AFCI nor GFCI protection - correct answer ✅both AFCI and GFCI protection Because of the presence of water and grounded surfaces that contributes to a potential shock hazard, Section 210.8(A)(7) confirms any 125-volt, 15- or 20- ampere receptacle installed within six (6) feet of a sink is required to be GFCI protected. Section 210.12(A) verifies AFCI protection is required for all 120-volt, 15- or 20-ampere branch-circuits that supply outlets in kitchens in dwellings.AFCI devices are designed to determine resistance to unwanted tripping due to the presence of arcing that occurs in utilization equipment under normal operating conditions or to a loading condition that closely mimics an arcing fault. .Where a 125-volt, 15-ampere receptacle is connected to a 120-volt branch circuit supplying two (2) or more receptacles or outlets, the maximum permitted cord- and-plug-connected load to the receptacle is _____. a. 12 amperes b. 15 amperes c. 10 amperes
d. 7.5 amperes - correct answer ✅12 amperes Article 210 provides the general rules regarding branch circuits. Branch circuit and receptacle ratings are addressed in Part II of Article 210. To prevent overheating receptacles, a receptacle shall not supply a total cord-and-plug-connected load in excess of the maximum specified in Table 21(B)(2), where connected to a branch circuit supplying multiple receptables or other outlets. This table shows a 15- ampere rated receptacle may carry a maximum cord-and-plug-connected load of 12 amperes under this condition. In industrial establishments only, when a 200-ampere rated busway is tapped from a 600-ampere rated busway, what is the maximum permitted length of the 200-ampere busway where overcurrent protection is not provided for the 200- ampere busway? a. 100 feet b. 50 feet c. 75 feet d. 125 feet - correct answer ✅50 feet Part II of Article 368 governs the permitted installation of busways. For busways in industrial establishments only, providing overcurrent protection at the point where the busway size is changed is not required if the busway having the smaller ampacity does not exceed fifty (50) feet in length and has an ampacity of at least one-third the rating of the overcurrent protection of the larger usway. 1/3 of 600 amperes = 200 amperes Reference Section 368.17(B), exception When installing nonmetallic sheathed cable enclosed in an underground buried PVC conduit, the cable _____.
In regard to a commercial building, where a service-entrance conduit having a length of six (6) feet contains four (4) size 2 AWG THWN insulated copper current- carrying conductors, each of the conductors have an allowable ampacity of _____. a. 92 amperes b. 100 amperes c. 115 amperes d. 110 amperes - correct answer ✅92 amperes To solve this problem first locate the conductor size on the left side of Table 310.15(B)(16) and look under the copper THWN column with a temperature rating of 75°C and note the ampacity of the conductors is 115 amperes. The table is based on an ambient temperature of 86°C and not more than 3 current-carrying conductors in the raceway.In this situation there are 4 current-carrying conductors in the raceway therefore, we must apply the correct adjustment factor (derating value) as shown in Table 310.15(B)(3)(a) as follows: 2 AWG THWN ampacity = 115 amperes (before derating) 115 amperes x 80% (adjustment factor) = 92 amperes
