Equipment for General Use

Equipment for General Use (Minnesota Journeyman)

Learning Objectives

1.1 Flexible Cords and Cables (Articles 400 and 402)

Article 400 governs flexible cords and cables, listing permitted uses in 400.10; cord used as permanent wiring is a violation. Article 402 covers fixture wire, with ampacities in Table 402.5. Cord ampacity comes from Table 400.5(A)(1) or Table 400.5(A)(2); above three current-carrying conductors, those values are reduced by Table 400.5(A)(3).

Five conductors therefore gives 80 percent, not 70 percent. Section 400.13 requires cord in continuous lengths without splice or tap; repair of hard-service and junior hard-service cord (Table 400.4) 14 AWG and larger is permitted where conductors are spliced per 110.14(B) and the splice retains the insulation, outer sheath properties, and usage characteristics of the cord. Branch-circuit protection of cord follows 240.5.

1.2 Switches, Receptacles, and Panelboards (Articles 404, 406, and 408)

Section 404.5(A) requires switch enclosures to provide the wire-bending and gutter space of 312.9; 404.5(B) prohibits using them as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping to other switches or overcurrent devices unless the enclosure complies with 312.11. Section 404.9 requires switches, circuit breakers, and molded case switches to indicate open (off) or closed (on) in a visible location, and with vertical operation the up position is closed (on).

Section 406.12 requires grounding-type receptacles on 15- and 20-ampere branch circuits, with grounding terminals connected per 406.24 and 250.146. Where a grounding means exists or an equipment grounding conductor is installed per 250.130(C), grounding-type receptacles must be connected per 406.12(C) or 250.130(C). Where no grounding means exists, 406.12(D)(2) permits a GFCI-type receptacle only if the receptacle or cover plate is marked "No Equipment Ground" and its grounding terminal is not connected to outlets supplied from it; the "GFCI Protected" marking of 406.12(D)(2)(c) applies instead where a grounding-type receptacle is fed through a GFCI.

Section 408.4(A) requires every circuit to carry a legible, permanent description specific to its purpose, including spare positions. Section 408.10(E)(1) sets the A, B, C bus arrangement and makes the B phase the high leg on 3-phase, 4-wire delta systems, and 408.10(F)(1) requires the caution marking where one phase is grounded at its midpoint. Section 408.36 requires the main device rated not greater than the panelboard; its Exception No. 1 allows two mains in other than service equipment, capped at 42 overcurrent protective devices counted as two for a 2-pole breaker and three for a 3-pole breaker; 408.36(C) prohibits delta breakers without 3-phase buses; and 408.36(D) requires a backfed plug-in device to be held by an additional fastener that requires other than a pull. Section 408.40 governs panelboard grounding, 408.41 requires an individual terminal for each grounded conductor (parallel conductors may share one where the terminal is identified), 408.54 requires means against extra devices, and 408.55 sets wire-bending space.

1.3 Luminaires and Lighting Systems (Articles 410 and 411)

Section 410.11 limits adjacent combustible material to 90°C (194°F); 410.12 requires lampholders over highly combustible material to be unswitched and, unless individually switched, at least 2.5 m (8 ft) above the floor or guarded. Section 410.16 governs clothes closets: the storage space description in 410.16(A) uses 600 mm (24 in.), while 410.16(D) requires 300 mm (12 in.) for surface-mounted incandescent or LED luminaires with a completely enclosed light source and 150 mm (6 in.) for surface-mounted fluorescent and recessed luminaires.

Section 410.62(A) requires a metal lampholder on a flexible cord to have an insulating bushing at the inlet, not smaller than metric designator 12 (trade size 3/8) if threaded, and 410.62(B) keeps the cord of an adjustable luminaire free of strain. Section 410.64 requires luminaires used as raceways to be listed and marked and permits a 2-wire branch circuit, or one multiwire branch circuit, plus one additional 2-wire branch circuit, but never a feeder. Section 410.96 addresses damp and wet locations.

Section 410.115(A) limits combustible material to 90°C (194°F). Section 410.116(A)(1) requires the recessed parts of a Non-Type IC luminaire to be 13 mm (1/2 in.) from combustible materials, though a Type IC luminaire may contact them under 410.116(A)(2); 410.116(B) prohibits thermal insulation above a luminaire or within 75 mm (3 in.) of its enclosure, wiring compartment, ballast, transformer, LED driver, or power supply unless it is marked Type IC. Section 410.140(A) prohibits open-circuit voltages over 1000 volts in dwelling occupancies; 410.143(B) limits a discharge-lighting secondary to 15,000 volts with 7500 volts to ground at any output terminal; 410.143(C) limits its short-circuit current to 150 mA over 7500 volts or 300 mA at or below 7500 volts. Section 410.150 requires lighting track to be permanently installed, with a connected load not exceeding the track rating and a branch circuit rated not more than the track, and 120.46(B) confirms the load calculation does not limit track length or luminaire count.

1.4 Low-Voltage Lighting (Article 411)

Section 411.6(B) requires 3.0 m (10 ft) from the edge of a pool, spa, or fountain. Section 411.7(A) prohibits grounding the secondary circuit except where a Class 2 source is listed for secondary grounding; 411.7(B) requires an isolating transformer; 411.7(C) permits exposed bare conductors indoors only, not less than 2.1 m (7 ft) above the finished floor unless listed lower. Non-Class 2 power sources are limited to branch circuits of not more than 20 amperes.

1.5 Appliances (Article 422)

Section 422.10 requires an appliance branch circuit rated not less than the appliance rating, and 422.10(A)(3) applies 125 percent to continuous loads. Section 422.11 covers overcurrent protection, including subdivision: 422.11(F)(1) requires resistance-type heating elements rated more than 48 amperes to be subdivided to not more than 48 amperes each and protected at not more than 60 amperes, 422.11(F)(2) uses 120 amperes for commercial cooking appliances, and 422.11(F)(3) uses the same 120 amperes, protected at not more than 150 amperes, for water heaters and steam boilers. Section 422.12 requires central heating equipment other than fixed electric space heating to be supplied by an individual branch circuit, and 422.16(A)(3) requires a heater cord from Table 400.4 where the appliance produces more than 121°C (250°F) on surfaces the cord is likely to contact. Section 422.18(B) keeps any part of a ceiling-suspended paddle fan out of a zone 900 mm (3 ft) horizontally and 2.5 m (8 ft) vertically from the top of a bathtub rim or shower threshold, including directly over it.

1.6 Fixed Electric Space-Heating Equipment (Article 424)

Section 424.19 requires a disconnecting means lockable open per 110.25, rated not less than 125 percent of the total load of the motors and heaters, that simultaneously disconnects the heater, motor controllers, and supplementary overcurrent devices; more than one source, feeder, or branch circuit requires grouped disconnecting means identified as multiple. Section 424.36 requires wiring above heated ceilings to be at least 50 mm (2 in.) above the ceiling with ampacity based on an assumed 50°C (122°F), and 424.94 repeats 50 mm (2 in.) and 50°C (122°F) for heating panels. Section 424.41(I) requires a 65 mm (2 1/2 in.) clear space under a joist for dry board ceiling cable, and 424.43 requires 150 mm (6 in.) of free nonheating lead in a junction box. Section 424.44(E) requires GFCI protection, in addition to 210.8, for cables in heated floors of bathrooms and kitchens and in hydromassage bathtub locations, and 424.48 requires GFCI under 424.48(2) and AFCI under 424.48(4) for cables in, on, or behind walls, with identification and a grounding means. Section 424.95(B) bases the ampacity of wiring behind heating panels in interior walls or partitions on an assumed 40°C (104°F) with the correction factors of 310.15(B)(1), while 424.95(A) covers exterior walls.

1.7 Deicing, Snow-Melting, and Pipeline Heating (Articles 426 and 427)

Section 426.12 requires guarding, isolation, or thermal insulation where surfaces exceed 60°C (140°F). Section 426.20(B) spaces embedded deicing cable runs at least 25 mm (1 in.) apart, and 426.20(C)(1) requires at least 50 mm (2 in.) of cover in a base at least 50 mm (2 in.) thick. Section 426.21(C) permits bridging an expansion joint only with provision for expansion and contraction, 426.28 requires ground-fault protection with the trip level as specified by the manufacturer, and 426.32 limits impedance heating secondary voltage to 30 volts. Section 427.10 requires listed, identified equipment; 427.22 requires ground-fault protection and excuses it only in industrial establishments with alarm indication where qualified persons service the systems and continued circuit operation is necessary; 427.27 limits isolation transformer secondary voltage to 30 volts; and 427.30 requires the secondary conductors to be at least 100 percent of the total load of the heater. The 450 mm (18 in.) seal distance of 501.15(A)(1) and the 93°C (200°F) sealing compound of 501.15(C)(2) and 505.16(C)(2) belong to Articles 501 and 505, not here.

1.8 Motors, Motor Circuits, and Controllers (Article 430)

Section 430.6(A)(1) requires Table 430.247 through Table 430.250 values instead of nameplate current for conductor ampacity, switch current ratings, and branch-circuit short-circuit and ground-fault protection. A 10-horsepower, three-phase motor is 28 amperes at 230 volts, 14 amperes at 460 volts, 30.8 amperes at 208 volts, and 32.2 amperes at 200 volts in Table 430.250.

Section 430.22 requires 125 percent of the Table full-load current for a single continuous-duty motor, while 430.22(H) relaxes the rule for small motors, using 5.5 amperes with 3.5 amperes and 8 amperes as related thresholds. Section 430.24 requires 125 percent of the full-load current of the highest rated motor, plus the sum of the full-load currents of all other motors, plus 100 percent of the noncontinuous non-motor load and 125 percent of the continuous non-motor load. Section 430.32(A)(1) sets overload at not more than 125 percent of nameplate full-load current for motors marked 1.15 service factor or a 40°C rise and 115 percent for others, while 430.32(C) permits 140 percent and 130 percent where the device will not carry the motor.

Section 430.52 limits branch-circuit short-circuit and ground-fault protection to the percentages of Table 430.52(C)(1). For single-phase motors:

The notes to Table 430.52(C)(1), including the small-motor rule of 430.52(C)(1)(a), permit increases such as 150 percent where the device will not carry the starting current. Section 430.53(A) permits several motors, each not over 1 horsepower and each with a full-load rating not over 6 amperes, on a 120-volt branch circuit protected at not over 20 amperes or a circuit of 1000 volts or less protected at not over 15 amperes, with overload protection per 430.32. Section 430.62(A) sets the feeder device for fixed motor loads at the largest branch-circuit device rating permitted by 430.52, or 440.22(A) for a hermetic refrigerant motor-compressor, plus the full-load currents of the other motors; 430.63 adds the other load(s) to the rating permitted by 430.52 for one motor, 440.22 for one hermetic compressor, or 430.62 for two or more motors.

Sections 430.75(A) and 430.75(B) require the control circuit to be disconnected from all sources, with any transformer in the controller enclosure connected to the load side of that disconnecting means, and 430.72(C)(4) permits 500 percent of the rated primary current for a control transformer under 2 amperes. Section 430.102(A) requires an individual disconnecting means for each motor controller in sight from the controller, with an out-of-sight exception over 1000 volts ac or 1500 volts dc where it is lockable open and the controller is marked; 430.102(B) covers the motor's own disconnecting means. Section 430.110(A) requires a motor-circuit disconnecting means rated not less than 115 percent of the full-load current, except a listed unfused motor-circuit switch with a horsepower rating not less than the motor.

1.9 Air Conditioning and Refrigerating Equipment (Article 440)

Section 440.10 requires an adequate short-circuit current rating, 440.12(A) bases the disconnecting means rating on rated-load, branch-circuit selection, and locked-rotor current, and 440.14 requires that means within sight from and readily accessible from the equipment. Section 440.22(A) permits a branch-circuit short-circuit and ground-fault protective device at not more than 175 percent of the motor-compressor rated-load current or branch-circuit selection current, whichever is greater, capable of carrying the starting current; Exception No. 2 allows up to 225 percent where needed for starting, and Exception No. 3 provides that the device need not be less than 15 amperes. Section 440.32 requires conductors at not less than 125 percent of that same greater value, with 72 percent permitted between the controller and a wye-start, delta-run motor-compressor. Section 440.62(B) limits a cord- and attachment-plug-connected room air conditioner to 80 percent of the branch-circuit rating where no other loads are supplied, and 440.62(C) reduces that to 50 percent where lighting outlets, other appliances, or general-use receptacles share the circuit. Sections 440.63 and 440.64 allow a plug and receptacle to serve as the disconnecting means where the controls are within 1.8 m (6 ft) of the floor, and limit the supply cord to 3.0 m (10 ft) at 120 volts or 1.8 m (6 ft) at 208 or 240 volts. Section 440.65 requires one of three factory-installed devices — a leakage-current detector-interrupter, an arc-fault circuit interrupter, or a heat detecting circuit interrupter — at the plug or within 300 mm (12 in.) of it in the cord; GFCI is not one of the three (see 440.62 and 210.8).

1.10 Generators, Transformers, and Capacitors (Articles 445, 450, and 460)

Section 445.13(A) requires conductors from the generator terminals to the first distribution device containing overcurrent protection to be at least 115 percent of the nameplate current, or 100 percent where the design prevents overloading. Section 445.13(B) permits taps from the load side of the protected terminals per 240.21(B) where the set has a listed overcurrent device or a current transformer and relay, but not for portable generators of 15 kW or less, and 445.13(C) covers the neutral conductor.

Table 450.5(A), for transformers over 1000 volts:

Secondary protection is not required in the supervised row. Table 450.5(B), for transformers 1000 volts or less, gives primary-only protection of 125 percent where the primary current is 9 amperes or more, 167 percent where it is less than 9 amperes, and 300 percent where it is less than 2 amperes; with primary and secondary protection, the primary device is 250 percent and the secondary device is 125 percent at 9 amperes or more or 167 percent below that. Section 450.6(A)(2) requires an autotransformer rated 1000 volts or less to have an individual overcurrent device in each ungrounded input conductor at not more than 125 percent of the rated full-load input current, with the next higher standard rating from 240.6 permitted by 450.6(A)(3) at 9 amperes or more. Section 450.11 requires ventilation, 450.15(B) permits dry-type transformers not over 50 kVA in hollow spaces not permanently closed in by structure, and 450.21(A) requires 300 mm (12 in.) from combustible material for indoor dry-type transformers rated 112 1/2 kVA or less, except enclosed units rated 1000 volts or less. Section 460.8 sets capacitor circuit conductors at not less than 135 percent of the capacitor rated current, and conductors from a capacitor to a motor or its circuit conductors at not less than one-third the ampacity of the motor circuit conductors.

1.11 Equipment Over 1000 Volts (Article 495)

Article 495 covers equipment over 1000 volts ac, 1500 volts dc, nominal. Section 495.22 requires non-load-break isolating switches to be interlocked with a series circuit interrupting device, or arranged so that the circuit is de-energized before the switch is operated. Section 495.42 requires interrupter switches with stored energy mechanisms to have mechanical interlocks that prevent access to the switch compartment unless the mechanism is discharged or blocked; an alarm or warning sign does not satisfy this rule. Section 495.44(C) requires the switching mechanism to be operable from outside the enclosure where the operator is not exposed to energized parts, to open all ungrounded conductors of the circuit simultaneously with one operation, and to be lockable open in accordance with 110.25, and 495.44(B) requires a backfeed warning sign. Section 495.46 requires circuit breakers used as the disconnecting means to be capable of being locked open.

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Common Exam Traps

Practical Field Points

Summary

This chapter covers the equipment articles from 400 through 495, and its questions are almost always numeric: the stem describes an installation and asks for a percentage, a clearance, or a device rating. Article 400 supplies the cord ampacity tables and adjustment factors; Articles 404, 406, and 408 cover switches, receptacles, and panelboards, where the tested points are the raceway rule of 404.5(B), the vertical handle rule of 404.9, the receptacle replacement cases in 406.12, the 42-device cap in Exception No. 1 to 408.36, and the individual terminal requirement of 408.41.

For heat-producing equipment the exam pairs a distance with a temperature: 13 mm (1/2 in.) from combustible material and 75 mm (3 in.) from insulation at recessed luminaires, 300 mm (12 in.) in closets, 50 mm (2 in.) above heated ceilings at 50°C (122°F), 40°C (104°F) behind interior-wall heating panels, 121°C (250°F) for appliance heater cords, and 60°C (140°F) for deicing surfaces. Motors and refrigeration follow a fixed sequence: full-load current from the Code tables, 125 percent for conductors, 115 percent for the disconnecting means, and protection from Table 430.52(C)(1) or the 175 percent limit of 440.22(A). Transformers, generators, and capacitors close the chapter with the two Tables 450.5, 125 percent for autotransformers, 115 percent for generator terminal conductors, and 135 percent for capacitor circuit conductors, while Article 495 makes interlocking, simultaneous opening, and lockable-open capability the answers above 1000 volts.