2023 NEC

Lesson 14: Inspections and Course Review

NEC 110, 230.95, 300.21, 408.4, 700.3 and course review · 20 practice questions

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Reading

Thirteen lessons have taught what the 2023 NEC requires in commercial buildings. This last lesson turns those rules into the checks an inspector, plan reviewer or construction manager makes in the field, and then reviews the whole course module by module. One point comes first. The NEC is an installation code. It says what a compliant installation looks like and it gives the authority having jurisdiction (AHJ) the power to approve or reject, but it does not list inspections or set their order. The local building department does that, so the sequence below is the usual field practice, not a code requirement. Local adoption governs: Lesson 1 dated the state and Houston adoption of the 2023 edition, so confirm the edition and any local administrative rules before you write a correction.

A checklist tied to NEC sections. The NEC does not set the order of inspections; the local building department does. Items on the left are checked while they can still be seen, items on the right when the equipment is set.

What the NEC sets and what the jurisdiction sets

Section 90.4 makes the AHJ the interpreter of the Code and the judge of whether equipment is approved (Lesson 1). Which inspections a permit requires, what must be notified, and the sequence are set by the local building department under its adopted administrative rules. Many departments call for an underground or slab check, a rough-in inspection before walls and ceilings close, a release for the utility to energize, and a final, but the names, the order and the notice rules differ from place to place. Ask the department, in writing, before a schedule is built around any of them. Local rules generally expect work to stay visible until it is approved, and the cost of opening a closed wall lands on the project.

Approval, listing and instructions (110.2, 110.3, 110.12)

Conductors and equipment the Code requires or permits are acceptable only if they are approved (110.2). The inspector weighs suitability, strength, heating and the other factors in 110.3(A), and checks that testing and listing came from a recognized qualified laboratory (110.3(C)). The everyday check is 110.3(B): listed or labeled equipment is installed and used the way its instructions say, and those instructions may be paper, a QR code or an internet address. At the panel, look for the listing mark, the manufacturer's name (110.21(A)), a nameplate that matches the plans, and the instructions on hand. Workmanship is part of the same list. Equipment is installed in a professional and skillful manner, and unused openings are closed so the enclosure keeps protection equal to its wall (110.12, 110.12(A)). An open knockout in a panel is one of the most common final-inspection corrections.

Terminations and torque (110.14)

Two checks apply to every lug. The first is temperature. For circuits of 100 A or less, or terminals marked for 14 through 1 AWG, the conductor is used at its 60 degree C ampacity unless the equipment is listed and marked for more. Above 100 A, or for conductors larger than 1 AWG, the value is 75 degrees C (110.14(C)). A 6 AWG THHN conductor rated 75 A at 90 degrees C is therefore worth 55 A at an ordinary 60 degree C terminal. The second check is torque. Terminal connections are tightened to the value on the equipment or in the manufacturer's instructions, and an approved means is used to reach it, such as a torque tool or a shear-bolt or breakaway device with a visual indicator (110.14(D)). Ask the installer how the values were reached, and ask for the instruction sheet when the value is not marked.

Markings and labels (110.16, 110.22, 110.24, 230.70, 408.4)

Labels are cheap to add before the final and awkward afterward. Other than in dwelling units, switchboards, switchgear, enclosed panelboards, industrial control panels, meter socket enclosures and motor control centers likely to be serviced energized carry an arc-flash warning (110.16(A)). Service equipment and feeder-supplied equipment rated 1000 A or more also carry a permanent arc-flash label with the date it was applied (110.16(B)). Each disconnect is marked for its purpose and, other than in one- and two-family dwellings, with the identification and location of the circuit source that supplies it, unless these are evident (110.22(A)). Each service disconnect is permanently marked as a service disconnect (230.70(B)). Panelboards get two markings under 408.4. Every circuit and circuit change has a legible, permanent directory description that is specific, includes spare positions and does not depend on who occupies the room (408.4(A)). A panelboard fed by a feeder, other than in a one- or two-family dwelling, also carries a permanent, non-handwritten label with the source and its location (408.4(B)).

Available fault current and interrupting rating (110.24, 110.9)

Service equipment other than in dwelling units is marked in the field with the available fault current and the date the calculation was performed. The marking must last in its environment, and the calculation is documented and available to those who design, install and inspect (110.24(A)). If work changes the available fault current at the service, such as a larger utility transformer, the value is verified or recalculated and the marking is updated (110.24(B)). The reason is 110.9: equipment that interrupts fault current must have an interrupting rating at least equal to the available fault current at its line terminals. In a small clinic, a calculation of 22,000 A at the service means a main breaker marked 10,000 A fails, and one marked 22,000 A or more passes. Combination ratings for existing installations are a separate topic that Lesson 6 pointed to.

Working space and dedicated space (110.26)

The final walk of an electrical room repeats Lesson 2 with a tape measure. Depth comes from Table 110.26(A)(1): a 208Y/120 V panel is 120 V to ground and needs 3 ft, and a 480Y/277 V panel needs 3 ft 6 in. with a concrete wall across from it or 4 ft with live parts across from it. The space is as wide as the equipment or 30 in., whichever is greater, with doors opening at least 90 degrees, and clear from the floor to 6 1/2 ft or the height of the equipment, whichever is greater. The working space is never used for storage (110.26(B)). Above the equipment sits the dedicated space, as wide and deep as the equipment and up to 6 ft above it or to the structural ceiling, whichever is lower. No piping, ducts or other systems foreign to the electrical installation may run in it, though sprinkler piping is allowed (110.26(E)(1)). Confirm at the same visit that the entrance, egress and lighting of 110.26(C) and (D) are in place.

Grounding and bonding checks (Article 250)

Lesson 7 gives a short list for the walk. The neutral is bonded to the enclosure at the service main bonding jumper and nowhere downstream, so open each downstream panel and look for a bonding screw or strap on the neutral bar (250.24(B), (C)). The grounding electrode conductor runs unbroken except for the splices 250.64(C) allows. Service raceways with oversized or concentric knockouts get a bonding jumper, because locknuts and bushings alone are not enough (250.92(B)). Water piping and structural steel are bonded as Lesson 7 described. The one item that cannot wait for the final is the concrete-encased electrode. It must be seen in the footing before the concrete is placed (250.52(A)(3)).

Rough-in checks before anything is covered (300.21 and others)

Rough-in is the last chance to see what will be hidden. Openings around electrical penetrations of fire-resistance-rated walls, floors and ceilings are firestopped by approved methods that keep the rating (300.21). Cable and conduit in bored framing stay 1-1/4 in. from the edge or get a steel plate at least 1/16 in. thick (300.4(A)(1)). Wiring is supported independently of ceiling grids (300.11). Boxes are checked for volume and conduit for fill (Lesson 9). Trenches are checked for cover depth (Table 300.5(A)) before backfill, and the wiring method is checked against the construction type, since NM cable is limited to Types III, IV and V, and Types I and II allow it only inside raceways (334.10, Lesson 9). These are the items that make a reinspection expensive.

Tests and records the code requires

The NEC asks for few tests, and each one produces a record. A ground-fault protection system on a service is performance tested when first installed on site, by a qualified person, by primary current injection, and a written record is made and kept available to the AHJ (230.95(C)). An emergency system is commissioned under AHJ conduct or witness on installation and periodically afterward, tested on a schedule the AHJ approves, maintained to manufacturer instructions, and recorded in writing, and the installation must offer a way to test under maximum anticipated load (700.3). Legally required standby has the same commissioning and periodic test provisions (701.3), and the source sign at the service is checked with them (700.7(A)). Optional standby has no such section. Construction GFCI protection under 590.6 is checked by looking at the site, not by a test record. Acceptance testing of a fire alarm system belongs to NFPA 72 and the adopted fire code, not to the NEC, so ask for that record from the fire code side (Lesson 13).

Key numbers: inspection checkpoints

The NEC does not set an inspection schedule; the local building department sets the rough-in and final sequence
Terminals: 60 degrees C for 100 A or less (14 to 1 AWG), 75 degrees C above; torque by an approved means (110.14(C), (D))
Service equipment field marking: available fault current plus the date; interrupting rating at least equal to it (110.24, 110.9)
Arc-flash warning on listed equipment types; dated permanent label at 1000 A and up (110.16)
Working space never used for storage; dedicated space kept free of foreign piping (110.26(B), (E))
Panel directory for every circuit including spares; source label not handwritten (408.4)
Ground-fault protection: primary injection test with written record (230.95(C)). Emergency system: AHJ commissioning, periodic tests, records (700.3)

In the field

A GCHS reviewer walks the finished electrical room of a converted church annex that is now a clinic. The 480Y/277 V service has a 1,200 A main, so the reviewer asks for the ground-fault test record first. Then the tape comes out: 3 ft 6 in. from the panel front to the block wall, with a mop bucket and a shelf in the space. At the panel, an open knockout, a handwritten source label, a directory that says "Room 4" for two circuits, and a neutral bond in the downstream panel. The available fault current marking shows a date from before the utility replaced the transformer. Every item was cheap to fix before the final, and the reviewer writes each one with its section number.

Course review

The six modules below follow the course order. Each keeps the numbers most often needed in the field and the hedges the lessons carried. Where a number has a section beside it, open that section in the adopted edition before you cite it in a comment. Local adoption governs, and a number that a lesson described without a value stays described without one.

Module 1: Administration and General Requirements (Lessons 1 and 2)

Lesson 1 covered how the book is built and who enforces it. Article 90 sets the purpose as safeguarding people and property, and following the Code does not make an installation efficient or adequate for growth (90.2(A) and (B)). Chapters 1 to 4 apply generally, Chapters 5 to 7 modify them for special conditions, Chapter 8 is communications and Chapter 9 holds the tables (90.3). The AHJ interprets the Code and approves equipment, and special permission is written consent. Texas adopted the 2023 NEC as its statewide minimum effective September 1, 2023, and Houston's local administrative provisions took effect January 1, 2024 (its ordinance text names the 2020 edition), all to be confirmed with TDLR and the Permitting Center before you rely on them. Lesson 2 was Article 110: approval, listing, terminations, working space, dedicated space and labels.

Key numbers: Lessons 1 and 2

In sight from: visible and not more than 50 ft away. Continuous load: expected to run 3 hours or more (Article 100)
Terminals: 60 degrees C for 100 A or less or 14 to 1 AWG; 75 degrees C above (110.14(C))
Working space depth 3 ft to 5 ft by voltage to ground and Condition 1, 2 or 3; width 30 in. or equipment width; height 6 1/2 ft (Table 110.26(A)(1))
Two entrances of 24 in. by 6 1/2 ft for large equipment (1200 A and over, more than 6 ft wide) (110.26(C)(2))
Arc-flash label with date at 1000 A or more; fault current marked with the date on service equipment (110.16(B), 110.24)

Module 2: Branch Circuits, Feeders, and Services (Lessons 3 to 5)

Lesson 3 covered GFCI in other than dwelling units (within 6 ft of a sink measured along the cord path, and the listed locations), AFCI in the few commercial sleeping spaces, and the 125 percent rule for continuous loads. Lesson 4 turned the Article 220 method into a small-office calculation: unit loads that already include the continuous multiplier, 180 VA per receptacle yoke, demand on receptacles, and the 1 VA per square foot floor for offices. Lesson 5 followed the service from the pole: one service per building with exceptions, overhead clearances by what is underneath, disconnect location and marking, up to six disconnects, and ground-fault protection for large wye services.

Key numbers: Lessons 3 to 5

Continuous load: noncontinuous plus 125 percent of continuous. A 20 A breaker not listed for 100 percent carries 16 A continuous (210.20(A))
Cord-and-plug limits: 12 A on a 15 A receptacle, 16 A on 20 A, 24 A on 30 A (Table 210.21(B)(2))
Servicing receptacle within 25 ft of HVAC equipment on the same level (210.63)
Unit loads, VA per sq ft: office 1.3, retail 1.9, restaurant 1.5, school 1.5, religious 2.2, warehouse 1.2 (Table 220.42(A))
Receptacle demand: first 10 kVA at 100 percent, the rest at 50 percent (Table 220.47)
Service clearances: 10 ft entrance and pedestrian areas, 12 ft commercial without trucks, 15 ft over 300 V to ground, 18 ft truck lanes and streets; 8 ft 6 in. over a roof (230.24)
Ground-fault protection: wye over 150 V to ground, disconnect 1000 A or more (230.95)

Module 3: Overcurrent Protection and Grounding (Lessons 6 and 7)

Lesson 6 started with the rule that a conductor is protected at its ampacity, then the exceptions inspectors watch: the next-size-up rule for devices of 800 A or less (not for a circuit with more than one receptacle for portable loads), no round-up above 800 A, the small-conductor limits, and taps. Taps do not use the next-size-up rule. Lesson 7 separated grounding from bonding: one intentional neutral-to-ground bond at the service, one grounding electrode system, and conductor sizes from Tables 250.66 and 250.122.

Key numbers: Lessons 6 and 7

Standard ratings include 60, 70, 80, 90, 100, 110, 125, 150, 175 and 200 A; there is no 65 A or 75 A (Table 240.6(A))
Copper small conductors: 14 AWG 15 A, 12 AWG 20 A, 10 AWG 30 A (240.4(D))
Taps: 10 ft or less needs one-tenth of the feeder device when it leaves the enclosure; 25 ft or less needs one-third (240.21(B))
Breaker handle no higher than 6 ft 7 in. (240.24(A))
Copper GEC and main bonding jumper: 1/0 for 350 to 600 kcmil, 2/0 for over 600 through 1,100 (Table 250.66)
GEC to a rod alone 6 AWG, to footing rebar alone 4 AWG; concrete-encased electrode 20 ft, 2 in. of concrete (250.66, 250.52(A)(3))
Copper EGC by device: 20 A 12, 60 A 10, 100 A 8, 200 A 6, 400 A 3 (Table 250.122)

Module 4: Wiring Methods and Materials (Lessons 8 and 9)

Lesson 8 covered protection in framing, support in fire-rated assemblies, burial depths and Table 310.16 with correction and adjustment, and its worked example showed that the answer is the smaller of the derated ampacity and the termination value. Lesson 9 covered conduit fill, the support and use rules for EMT, RMC, PVC, MC and NM, box fill and pull box size. NM cable in commercial work is limited by construction type, which links to the building code's construction-type lessons.

Key numbers: Lessons 8 and 9

Cover: cable 24 in., RMC or IMC 6 in., EMT or listed PVC 18 in.; 24 in. under streets, driveways and parking lots (Table 300.5(A))
Bored wood framing: 1-1/4 in. from the edge or a 1/16 in. steel plate (300.4(A)(1))
Table 310.16 assumes 30 degrees C and no more than three current-carrying conductors. Adjustment: 4 to 6 conductors 80 percent, 7 to 9 70, 10 to 20 50 (Table 310.15(C)(1))
Ambient 41 to 45 degrees C: 0.87 at 90 C, 0.82 at 75 C, 0.71 at 60 C; rooftop adder 33 degrees C if under 3/4 in. above the roof
Conduit fill: 53 percent for one conductor, 31 for two, 40 for more than two (Chapter 9, Table 1)
Support: EMT within 3 ft of boxes and every 10 ft; MC every 6 ft; NM every 4-1/2 ft and within 12 in. of boxes, as open cable only in Types III, IV and V
Box allowances: 14 AWG 2.00, 12 AWG 2.25, 10 AWG 2.50, 8 AWG 3.00, 6 AWG 5.00 cu in.; straight pull 8 times the largest trade size (314.16, 314.28)

Module 5: Equipment, Motors, and HVAC (Lessons 10 and 11)

Lesson 10 collected the general-use equipment rules: switch height, tamper-resistant receptacles in the listed commercial locations, panelboard rating and marking, luminaire clearances, appliance GFCI and transformer protection. Lesson 11 built a motor branch circuit from parts. The table current sizes conductors, the switch and the short-circuit device, and the nameplate current sets the separate overload. Air-conditioning equipment adds the MCA and MOCP marking, and the field check is conductor at or above MCA and device at or below MOCP.

Key numbers: Lessons 10 and 11

Switch or breaker handle center: 6 ft 7 in. maximum (404.8(A)); a 2-pole breaker counts as two devices, a 3-pole as three (408.54)
Recessed non-IC luminaire: 1/2 in. from combustibles, no insulation within 3 in. (410.116)
Transformer, primary protection only: 125 percent of primary current with the next standard size allowed (Table 450.3(B)); dry-type indoors 12 in. from combustibles up to 112 1/2 kVA (450.21)
Motor conductors 125 percent of the table current; inverse-time breaker up to 250 percent, dual-element fuse 175, nontime-delay fuse 300 (430.22, Table 430.52(C)(1))
Overload 125 percent of nameplate with service factor 1.15 or more, otherwise 115; disconnect at least 115 percent and in sight, within 50 ft (430.32, 430.102, 430.110)
Single compressor: conductors 125 percent, device up to 175 percent, disconnect 115 percent (440.32, 440.22(A), 440.12(A)(1))

Module 6: Special Occupancies, Equipment, Systems, and Review (Lessons 12 to 14)

Lesson 12 recognized hazardous locations and health care spaces at a pointer level, taught assembly occupancies and temporary wiring in more detail, and laid out the construction-site GFCI rules. Lesson 13 covered signs, EV charging, PV at a summary level, the three levels of emergency and standby power and a pointer to fire alarm wiring. The adopted building and fire code decides which loads must be on an emergency or standby system, and the NEC tells you how to wire, transfer, mark and test it. This lesson gathered the inspection checkpoints and required tests.

Key numbers: Lessons 12 to 14

Assembly occupancy: designed for 100 or more persons; metal wiring methods, NM and nonmetallic raceways only in nonrated construction (518.1, 518.4)
Fuel dispenser emergency shutoff: at least 20 ft and not more than 100 ft away (514.11(A)); Category 2 hospital patient bed: two circuits, eight receptacles (517.18; the circuit rule is not for clinics)
Holiday lighting: temporary for not more than 90 days; construction GFCI on 125 V, 15, 20 and 30 A receptacles, and on portable generators of 15 kW or less (590.3(B), 590.6)
Signs: 20 A branch circuit at each tenant entrance, sign circuits continuous, 14 ft above vehicle areas (600.5, 600.9)
EV charging: device at 125 percent, disconnect above 60 A or 150 V to ground, connector 18 in. indoors and 24 in. outdoors (625.41, 625.43, 625.50)
PV rapid shutdown: 30 V within 30 seconds outside the array boundary (690.12)
Emergency power in 10 seconds, 2 hours of fuel, batteries for illumination 1-1/2 hours; legally required standby in 60 seconds; optional standby no time limit (700.12, 701.12, Article 702)

The practice exam

The practice exam is the next step. It draws 60 questions, weighted by each topic area's share of the question bank, with a 120-minute time limit. It is a practice tool GCHS built for its own staff development. On an actual project, the locally adopted code, not this course, governs.

Practice questions

1. A clinic's new 480Y/277 V, 800 A service equipment is being finished in Houston. What must the field marking on this service equipment (other than in a dwelling unit) show under 110.24(A)?

The arc-flash incident energy and the required protective equipment category, with the date of the label
The interrupting rating of the main breaker and the date the breaker was manufactured
The available fault current and the date the fault-current calculation was performed
The utility transformer size and the date the utility energized the service

2. A new 100 A panelboard lug in a small retail store's electrical room is marked with a manufacturer torque value. What does 110.14(D) require for tightening the terminal connections?

Tighten to the marked or instructed torque value, using an approved means such as a torque tool or a shear-bolt lug
Tighten by hand plus one quarter turn, which the NEC accepts for any terminal on a circuit of 100 A or less
Tighten to the value the installer prefers, since the NEC sets no method or value for terminal connections
Tighten to the value in Chapter 9, Table 1, which applies when the manufacturer's value is not visible

3. A new office building has a solidly grounded 480Y/277 V service with a 1,200 A main breaker that carries ground-fault protection of equipment. At the inspection, what does 230.95(C) call for?

A factory test of the relay by the manufacturer, with a certificate mailed to the owner instead of a field test
An annual test by the building owner using a clamp meter, with no written record required of the result
A visual check that the sensor is installed on the neutral, since the NEC does not require a performance test
An on-site performance test by primary current injection, with a written record available to the authority having jurisdiction

4. A community assembly hall has just had a generator and transfer switch installed for its emergency lighting system. Under 700.3(A), who conducts or witnesses the commissioning?

The manufacturer's start-up technician alone, with no role for the authority having jurisdiction
The authority having jurisdiction, on installation and periodically afterward
The electrical contractor alone, who certifies the system in writing to the owner after installation
No commissioning is required when the transfer switch carries a listing mark from a testing laboratory

5. At the final inspection of a church electrical room, a 208Y/120 V panelboard has three mop buckets and a shelf of paper supplies standing in front of it. Which code section is violated?

110.26(A)(1), because a 120 V to ground panel needs 4 ft of working depth, which the room cannot provide
110.26(C)(1), because a panelboard may not be placed in a room that has a lockable door
110.26(E), because the dedicated space may hold only paper products stored above the equipment
110.26(B), because the working space may not be used for storage

6. At the final for a new 42-space panelboard fed from a switchboard in a school building, which finding is a violation of 408.4?

Spare positions with unused breakers are listed on the directory as spare
The circuit directory is fastened inside the panelboard door instead of outside
The label naming the feeder source and its location is handwritten in marker
Abbreviations on the directory are explained in a key on the same card

7. In a church rehab, a 480 V motor disconnect is visible from the motor across an open hall, but it sits 60 ft away. Under the Article 100 definition, is it in sight from the motor?

No, because in sight from means visible and not more than 50 ft away
Yes, because visibility from the motor is the only test the definition applies to a disconnect
Yes, because the distance limit rises to 75 ft for equipment operating at more than 300 V
No, because the definition requires the disconnect to be within 25 ft of the motor it serves

8. A 480Y/277 V panelboard in a clinic electrical room has an unfinished concrete block wall directly across from it and nothing live opposite. What is the minimum working space depth under Table 110.26(A)(1)?

3 ft, because live parts on one side and nothing live opposite is always Condition 1 for 277 V to ground
3 ft 6 in., because the concrete wall is treated as a grounded part (Condition 2)
4 ft, because any masonry wall across from 277 V equipment is treated as live parts (Condition 3)
5 ft, because the 601 to 1000 V row applies to any panelboard rated 480 V

9. A retail store lighting circuit (120 V, breaker and assembly not listed for 100 percent operation) carries 12 A of continuous load and 3 A of noncontinuous load. What is the minimum load the overcurrent device and conductors must be sized to carry under 210.20(A) and 210.19(A)(1)?

15 A, the plain sum of the continuous and noncontinuous loads
18 A, which is 3 A plus 125 percent of the 12 A continuous load
18.75 A, which is 125 percent applied to the whole 15 A of load
12 A, because only the continuous load counts toward the sizing

10. A 2,000 sq ft retail store, measured on the outside, is being calculated under Table 220.42(A). What is the minimum general lighting load?

3,800 VA, at 1.9 VA per sq ft, with the 125 percent continuous multiplier already inside the unit load
4,750 VA, at 1.9 VA per sq ft, with a further 125 percent multiplier added for continuous lighting
2,600 VA, at the office unit load of 1.3 VA per sq ft, since retail counts as office space
3,000 VA, at the restaurant unit load of 1.5 VA per sq ft, since a store serves food and drink

11. A 208Y/120 V overhead service drop crosses the rear delivery lane of a clinic, a lane trucks use. What is the minimum clearance to the lowest point of the drop under 230.24(B)?

12 ft, because 208Y/120 V is 300 V or less to ground and the same value applies over any commercial lot
15 ft, because a lane behind a commercial building is treated as over 300 V to ground
10 ft, because a drop over a service area is treated the same as an entrance or a pedestrian-only path
18 ft, because the lane is a driveway on other than residential property carrying trucks

12. A 400 A feeder in a clinic electrical room supplies a new panelboard 22 ft away by a 25 ft tap under 240.21(B)(2). What is the minimum tap conductor ampacity?

40 A, which is one-tenth of the feeder rating, the figure used for a 10 ft tap that leaves its enclosure
200 A, which is one-half of the feeder rating for any tap longer than 10 ft
133 A, which is one-third of the 400 A feeder overcurrent device rating
400 A, because a tap conductor gets no reduction from the rating of the feeder device

13. A 208Y/120 V service in a small clinic has one 500 kcmil copper conductor per phase and a grounding electrode system of a footing electrode, a rod and metal water pipe. What copper grounding electrode conductor does Table 250.66 require for the system?

2 AWG, from the row for over 3/0 AWG through 350 kcmil
1/0 AWG, from the row for over 350 through 600 kcmil
2/0 AWG, from the row for over 600 through 1,100 kcmil
4 AWG, the most that any single concrete-encased electrode is ever required to have

14. A 10 AWG copper THHN circuit (40 A in the 90 degree C column of Table 310.16) runs in EMT with six current-carrying conductors in a 30 degree C ambient. Before the termination check, what is its adjusted ampacity?

28 A, which is 40 A times 70 percent for 7 to 9 conductors
20 A, which is 40 A times 50 percent for 10 to 20 conductors
40 A, because adjustment does not apply to THHN conductors installed in EMT
32 A, which is 40 A times 80 percent for 4 to 6 conductors

15. A contractor proposes concealing Type NM cable behind gypsum board in the walls of a new three-story office building of Type IIB construction. Under 334.10, is that permitted?

No, because in Type II construction NM is allowed only inside a raceway, not as concealed cable
Yes, in any building, provided the cable is behind a thermal barrier with a 15-minute finish rating
Yes, provided the ampacity is limited to the 60 degree C column of Table 310.16
Yes, because concealment in walls is the only condition the article puts on commercial use

16. A 45 kVA, 480 V three-phase dry-type transformer in a clinic has primary protection only, and its primary current is 54.1 A. What is the largest primary device permitted by Table 450.3(B)?

60 A, because the device may not exceed the rating just below 125 percent of primary current
90 A, because the primary-only limit is 167 percent of primary current
70 A, because 125 percent is 67.6 A and the next higher standard rating is permitted
125 A, because the primary may go to 250 percent when only the primary is protected

17. A 20 hp, 460 V, three-phase, continuous-duty motor in a community center has a Table 430.250 value of 27 A and a nameplate current of 25.5 A. What is the minimum conductor ampacity under 430.22?

33.75 A, which is 125 percent of the 27 A table value
31.9 A, which is 125 percent of the 25.5 A nameplate current
27 A, which is the table value with no added percentage
67.5 A, which is 250 percent of the table value

18. A 12 kW portable generator at a clinic construction site supplies 125 V, 20 A tool receptacles. Under 590.6(A)(3), what protection do those receptacles need?

An assured equipment grounding conductor program alone, because generator power is exempt from GFCI rules
Listed GFCI protection for personnel, because the generator is 15 kW or less
GFCI protection only when the generator is rated over 15 kW, since smaller units are considered isolated
No added protection when the generator frame is bonded to a driven ground rod at the site

19. A church parking lot gets a wall-mounted EV charger with a 40 A nameplate maximum on a 240 V single-phase supply. Under 625.41, what is the minimum rating of its overcurrent device?

40 A, because the device may match the nameplate current of the charger
60 A, because the device must be sized at 150 percent of the maximum load
80 A, because the device must be twice the maximum load of the charger
50 A, which is 125 percent of 40 A because EV charging is a continuous load

20. A church fellowship hall is designed for the gathering of 120 persons for worship and meals. Under 518.1, is it an assembly occupancy covered by Article 518?

No, because Article 518 applies only to spaces designed for 300 or more persons
No, because places of religious worship are excluded from Article 518 and follow Article 517
Yes, because Article 518 covers spaces designed for 100 or more persons for worship, eating and similar purposes
Yes, but only when the hall has a stage or fixed seating, since those define an assembly space

Glossary

Approved: Acceptable to the authority having jurisdiction. Conductors and equipment the Code requires or permits are acceptable only if approved (110.2).
Available fault current: The largest current the supply can deliver into a fault at a point. Service equipment other than in dwelling units is field marked with it and the date of the calculation (110.24(A)).
Interrupting rating: The highest fault current a device can open at its rated voltage. It must be at least equal to the available fault current at the device's line terminals (110.9).
Terminal torque: The tightening value for a connection, taken from the equipment or its instructions and reached by an approved means such as a torque tool or shear bolt (110.14(D)).
Dedicated space: The zone as wide and deep as the equipment, from the floor to 6 ft above it or the structural ceiling, reserved for the electrical installation and free of foreign piping and ducts (110.26(E)(1)).
Firestopping: Approved sealing of openings around electrical penetrations of fire-resistance-rated assemblies so the rating is kept (300.21).
Performance test: The on-site primary current injection test of a ground-fault protection system, with a written record for the AHJ (230.95(C)).
Commissioning witness test: The AHJ's conduct or witnessing of the commissioning of a complete emergency system on installation and periodically afterward (700.3(A)).

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