Equipment for General Use practice questions (Articles 402–470)

Correct: D — 402.5

402.5 hosts Table 402.5, the ampacity table for fixture wires by size and insulation type. 402.3 only lists the recognized insulation Types and their temperature ratings, not ampacity; 402.6 sets minimum conductor size, not current-carrying capacity.

Correct: D — 402.8

402.8 requires the grounded fixture wire to be identified by a continuous white stripe on other-than-green insulation (or the 400.22(A)-(E) methods). 402.9 covers marking of the wire's insulation type/rating, not conductor identification, and 402.6 (minimum size) and 402.3 (types) don't address identification at all.

Correct: A — A printed tag attached to the coil, reel, or carton

Per 402.9(A), only thermoplastic-insulated fixture wire uses the 610 mm (24 in.) surface-marking interval. All other fixture wire types are identified with a printed tag on the coil, reel, or carton, regardless of packaging.

Correct: A — 402.3

Table 402.3, located at 402.3, lists every recognized fixture wire type with its insulation, size, and voltage rating. 402.5 covers only ampacity values and 402.6 covers only minimum conductor size, so neither lists the full set of recognized wire types.

Correct: A — Ahead of the panel, or as a single main OCPD within the panel

409.21(B) permits either an OCPD located ahead of the panel or a single main OCPD located within the panel — not one exclusively, and not a scheme with no main device at all. This is directly stated in 409.21(B).

Correct: D — A, B, C

Per 409.102(B), 3-phase horizontal and vertical buses must be arranged A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the panel. The other orderings listed are not permitted arrangements.

Correct: B — Supply voltage, phases, frequency, and full-load current for each incoming supply circuit

409.110(2), the supply voltage/phase/frequency/full-load current marking, must be on the outside of the enclosure. The manufacturer's name (409.110(1)), enclosure type number (409.110(7)), and short-circuit current rating (409.110(4)) are all permitted on either the inside or the outside.

Correct: C — 409.100

409.100 points to Table 110.28 as the basis for choosing an industrial control panel enclosure for a given location. 409.106 covers internal spacings between uninsulated parts, not enclosure environmental ratings, and 409.108 addresses service equipment provisions, not enclosure selection.

Correct: D — 409.60(B)

409.60(B) requires multisection industrial control panels to be bonded together using an equipment bonding jumper sized per 250.102(D). 409.60(A) instead covers grounding of a single-section panel, and 409.102(A) only addresses busbar support and arrangement, not bonding between sections.

Correct: A — The panel must not be installed at that location

Per 409.22(A), a panel shall not be installed where available fault current exceeds its marked SCCR — here 50,000 A exceeds 42,000 A, so installation is prohibited outright. Documentation under 409.22(B) is a separate, additional requirement that applies once a panel is properly rated for its location; it doesn't cure an SCCR shortfall, and adding disconnecting means isn't how 409.22(A) resolves an SCCR mismatch.

Correct: A — 15 volts ac or 30 volts dc

Per 411.3, where wet contact is likely, the operating voltage is limited to 15 volts ac or 30 volts dc. The 30 volts ac or 60 volts dc figure is the general limit that applies only when wet contact is not likely, not the reduced wet-contact limit.

Correct: C — When supplied by a Class 2 power source listed and identified as suitable for secondary grounding

411.7(A) permits grounding only when the secondary circuit is supplied by a Class 2 power source that is listed and identified as suitable for secondary grounding. The indoor/bare-conductor condition relates to 411.7(C), not grounding, and the isolating transformer requirement in 411.7(B) is a separate, unrelated requirement.

Correct: D — 411.6(A)

411.6(A) governs conductors concealed or extended through a wall, floor, or ceiling, requiring either a Chapter 3 wiring method or listed Class 2 wiring per 725.130. 411.6(B) instead sets the horizontal clearance from pools and similar water features, which doesn't apply to a wall penetration.

Correct: C — It provides an effective ground-fault current path for operation of ground-fault protection equipment

427.23 states the conductive covering shall provide an effective ground-fault current path for operation of ground-fault protection equipment. Thermal performance, mechanical protection, and moisture resistance may be side benefits of construction, but they are not the stated code purpose of this specific covering requirement.

Correct: D — It must be the indicating type and capable of being locked in the open (off) position

Per 427.55(A), a readily accessible branch-circuit switch or breaker may serve as the disconnect only if it is of the indicating type and capable of being locked in the open position. GFCI protection and within-sight placement aren't the requirement here — readily accessible plus indicating/lockable is.

Correct: B — It must be capable of being locked in the open position

427.56(A) permits a temperature control with an "off" position that opens all ungrounded conductors to serve as the disconnecting means only if it can also be locked in the open position. Ampacity margin, sight-visibility, and owner-only access are not conditions this section imposes.

Correct: D — 30 volts ac

427.27 sets a default cap of 30 volts ac for the secondary output. The 80-volt and 132-volt allowances apply only 'in industrial establishments' with additional safeguards, so a commercial building without that industrial designation is limited to 30 volts.

Correct: C — 150 mm (6 in.)

427.18(A) requires not less than 150 mm (6 in.) of nonheating leads within the junction box. The 300 mm and 75 mm figures are plausible-sounding but not the code value, and a minimum does in fact exist.

Correct: C — At both ends, with intermediate grounding points permitted as the design requires

427.48 requires the envelope to be grounded at both ends, with intermediate grounding points permitted where the design calls for them. Bonding at joints is a separate, additional requirement under the same section — it doesn't substitute for the required end grounding.

Correct: D — An insulated connector identified as suitable for that use

427.19(A) specifically requires insulated connectors identified as suitable for use under thermal insulation. A box or fitting per 110.14/300.15 is the requirement for splices made outside the insulation under 427.19(B), not under it. Ordinary tape-and-twist methods aren't identified for this buried application.

Correct: B — An industrial plant with ground-fault alarm indication, qualified-persons-only service, and a process that must keep running for safety

427.22 allows skipping automatic GFPE only in industrial establishments that have ground-fault alarm indication AND both listed conditions: qualified-persons-only servicing and a safety need for continued operation. An industrial site alone isn't enough without those conditions, and the exception doesn't extend to commercial or dwelling occupancies.

Correct: C — No, securing must be accomplished by means other than the thermal insulation

427.14 explicitly requires the heating element assembly to be secured by means other than the thermal insulation — insulation is not an acceptable securing method regardless of its rating or pipe orientation.

Correct: A — 427.28

427.28 requires all current-carrying components of fixed electric heating equipment to be installed per 300.20, which governs avoiding induced currents in ferrous metal enclosures. 427.29 covers grounding, not induction, and 427.22 covers ground-fault protection of equipment, so neither addresses induced heating in enclosures.

Correct: D — 115 percent of the generator's nameplate current rating

445.13(A) sets the default minimum at 115 percent of nameplate current rating. The 100 percent figure only applies when the generator's design and operation prevent overloading — it's not the default. 125 percent and 80 percent are not thresholds used in this section.

Correct: D — It must disable all prime mover start control circuits and require a mechanical reset before restart

445.19(A) requires the shutdown provisions to disable all prime mover start control circuits (rendering it incapable of starting) and to initiate a shutdown requiring a mechanical reset. Leaving start circuits energized, as in the breaker-only option, would defeat the purpose of an emergency shutdown, and nothing in 445.19 involves automatic restart or utility notification.

Correct: B — When the 125-volt receptacle is interlocked so it can't be used while a 125/250-volt receptacle is in use

Per 445.20(A), unbonded generators only skip GFCI on 125-volt receptacles if those receptacles are interlocked so they aren't available while a 125/250-volt receptacle is in use. Outdoor use, total generator wattage, and receptacle amperage aren't factors in this exception.

Correct: C — A bushing with smooth, well-rounded surfaces at the point of conductor contact

445.16 requires a bushing with smooth, well-rounded surfaces to protect conductors from sharp edges at any field-wiring opening. A grounding-type bushing and current ratings from the motor tables belong to other rules (like 445.17's terminal housing sizing), not the basic bushing requirement.

Correct: D — 445.18(B)

445.18(B) specifically covers paralleled generators, requiring the ability to isolate each unit's output terminals from the paralleling bus without mandating the disconnect be at the generator. 445.18(A) is the general single-generator disconnect rule, and 445.12(D) covers balancer sets, an unrelated overcurrent topic.

Correct: B — Its equivalent locked-rotor current must be at least 200% of nonmotor loads plus the largest motor's locked-rotor current plus other motors' full-load current

455.8(C)(2) requires the equivalent locked-rotor current of the horsepower-rated switch to be not less than 200% of the sum of nonmotor loads, the largest motor's 3-phase locked-rotor current from Table 430.251(B), and the full-load current of other motors operating simultaneously. The 250% figure belongs to the current-rated disconnect option in 455.8(C)(1), not this one, and the 115% figure is the general default in 455.8(C), not the horsepower-rated method.

Correct: B — Not less than 125% of the phase converter nameplate single-phase input full-load amperes

455.6(A)(1) requires variable-load conductors sized at not less than 125% of the phase converter nameplate single-phase input full-load amperes. The 250%-of-3-phase-FLA approach only applies to fixed loads under 455.6(A)(2), and the other two options aren't the code's method.

Correct: B — 455.8(A)

455.8(A) requires the disconnecting means to be readily accessible and located in sight from the phase converter. 455.8(B) covers the type of switch, not its location, and 455.20 is the disconnecting means rule for a different context (utilization equipment supplied from the converter's derived system), not the converter's own supply disconnect.

Correct: D — 430.12

Section 455.10 requires a terminal housing on a phase converter in accordance with 430.12, the motor terminal housing provisions. There is no separate Article 455 terminal housing standard, and 250.8 and 455.5 govern the equipment grounding connection, not the terminal housing itself.

Correct: A — 3-phase amperes at full load

455.4(7) requires 3-phase amperes at full load specifically for rotary-phase converters, in addition to the six markings required of all phase converters. Manufacturer's name, voltages, and single-phase input full-load amperes are general requirements under 455.4(1) through (4).

Correct: C — To detect and interrupt fault current likely to cause dangerous pressure within an individual capacitor

460.25(A) requires a means to detect and interrupt fault current likely to cause dangerous pressure within an individual capacitor. Inrush limiting, duty-cycle disconnection, and overvoltage protection during light load are different concerns not addressed by this section.

Correct: C — No, because 460.6(B) prohibits manual means of switching or connecting the discharge circuit

460.6(B) requires the discharge circuit to be either permanently connected or automatic on removal of voltage — manual switching or connecting is explicitly not permitted, regardless of timing or technician oversight. There's no voltage-class carve-out in this section.

Correct: A — 135 percent

460.8(C)(3) requires the disconnecting means rating to be not less than 135 percent of the capacitor's rated current. 100 percent and 115 percent undersize it, and 150 percent is a threshold from other NEC contexts (like some motor calculations), not this rule.

Correct: B — 460.27

460.27 covers grounding of capacitor cases, including the exception for cases supported on structures designed to operate at other than ground potential. 460.10 addresses grounding of capacitors used with Class 1E systems in nuclear facilities, not general case grounding, and 460.26/460.28 cover identification and discharge means, not grounding.

Correct: D — 50 volts or less within 5 minutes

460.28(A) requires residual voltage to drop to 50 volts or less within 5 minutes after the capacitor is disconnected from the source. The 1-minute option confuses the time limit, and the zero-volts and 100-volt options both misstate the specified threshold.

Correct: A — A switching procedure prominently displayed at the switching location

460.24(C) lists three acceptable methods: mechanically sequenced isolating and bypass switches, interlocks, or a switching procedure prominently displayed at the switching location. A voltage warning label, equipment grounding conductor sizing, and disconnect location are separate NEC concerns and don't address switching sequence.

Correct: D — A visible gap in the circuit adequate for the operating voltage

460.24(B)(1) requires the isolating means to provide a visible gap adequate for the operating voltage — a physical, visually confirmable break, not an audible signal, enclosure feature, or remote indicator.

Correct: D — 305 mm (12 in.)

470.20(C) sets the minimum clearance from combustible materials at 305 mm (12 in.). The 152 mm option is too small to meet the rule, and the 610 mm and 914 mm options are larger clearances sometimes confused with other equipment-clearance rules, but not what 470.20(C) requires.

Correct: D — They must be connected to the equipment grounding conductor

470.21 states resistor and reactor cases or enclosures shall be connected to the equipment grounding conductor. Isolating them, requiring a direct electrode connection, or treating grounding as optional are not what the section specifies.

Correct: A — Install a thermal barrier between the reactor and the partition

Per 470.11, any space less than 305 mm (12 in.) between a resistor or reactor and combustible material requires a thermal barrier. 8 in. is under that threshold, so a barrier is mandatory — reducing load current or relying on working-space clearance rules doesn't satisfy this requirement.