Journeyman Electrician (NEC) — All Questions

What is the maximum number of service disconnecting means permitted for a single set of service-entrance conductors?

• a.Eight
• b.Two
• c.Four
• d.Six✓

Up to six service disconnects are permitted, but current code requires them to be in separate enclosures or in a listed assembly with individual disconnects, each marked as a service disconnect. Two and four are below the ceiling but are not the code maximum, and eight exceeds the limit.2023 NEC §230.71

What is the minimum service disconnecting means rating for a one-family dwelling?

• a.60 amperes
• b.100 amperes✓
• c.125 amperes
• d.200 amperes

A one-family dwelling service disconnect must be rated at least 100 amperes, 3-wire. The 60-ampere minimum applies to certain limited installations and older code cycles, while 125 and 200 amperes are common design choices but exceed the code minimum.2023 NEC §230.79(C)

What is the minimum clearance above a residential driveway for overhead service conductors limited to 150 volts to ground?

• a.18 feet
• b.10 feet
• c.12 feet✓
• d.15 feet

Residential driveways and commercial areas not subject to truck traffic require 12 feet of clearance. The 10-foot clearance applies only above finished grade, sidewalks and platforms accessible to pedestrians, and 18 feet is required over public streets, alleys and roads.2023 NEC §230.24(B)

Overhead service conductors must maintain what minimum clearance from a window that is designed to be opened?

• a.6 feet
• b.5 feet
• c.10 feet
• d.3 feet✓

Service conductors must keep 3 feet of clearance from windows designed to open, doors, porches, balconies, stairs and similar locations. Conductors run above the top level of a window are considered out of reach and are exempt, and the other distances do not appear in this rule.2023 NEC §230.9(A)

Ground-fault protection of equipment is required for a solidly grounded wye service with more than 150 volts to ground when the disconnect is rated at least what value?

• a.800 amperes
• b.1,000 amperes✓
• c.600 amperes
• d.1,200 amperes

The threshold is a service disconnect rated 1,000 amperes or more on a solidly grounded wye system of more than 150 volts to ground but not exceeding 1,000 volts phase-to-phase, which describes a typical 480Y/277-volt service. The 1,200-ampere figure is the maximum permitted setting of the ground-fault protection, not the threshold at which it is required.2023 NEC §230.95

How must a panelboard be protected against overcurrent?

• a.By an overcurrent device rated at 125 percent of the panelboard rating
• b.By the sum of the branch-circuit devices installed in it
• c.By an overcurrent device having a rating not greater than the panelboard rating✓
• d.No separate protection is required if the feeder conductors are properly sized

Each panelboard must be protected by an overcurrent device rated no higher than the panelboard rating, located either in the panelboard itself as a main or ahead of it in the feeder. Summing the branch devices routinely exceeds the panelboard rating because of diversity, and no code rule allows protecting a panelboard at 125 percent of its rating.2023 NEC §408.36

On the load side of the service disconnecting means, what is the general rule for using the grounded neutral conductor to ground equipment enclosures?

• a.It is permitted only in dwelling units
• b.It is permitted where the grounded neutral conductor is at least 6 AWG copper and runs directly to the equipment
• c.It is permitted in any panelboard or subpanel that is supplied directly from the service equipment enclosure
• d.It is not permitted; a separate equipment grounding conductor must be used✓

Downstream of the service disconnect the neutral and the equipment grounding conductor must be kept separate so that normal load current does not travel on enclosures and raceways. Bonding them together at a subpanel creates parallel neutral paths and objectionable current, and neither conductor size nor occupancy type changes this general prohibition.2023 NEC §250.142(B)

A dry-type transformer rated 112.5 kVA or less is installed indoors. What is the minimum separation from combustible material unless it is separated by a fire-resistant heat-insulating barrier?

• a.3 inches
• b.6 inches
• c.12 inches✓
• d.18 inches

Dry-type transformers of 112.5 kVA or less must be at least 12 inches from combustible material unless separated by a fire-resistant, heat-insulating barrier or unless the unit is completely enclosed except for ventilating openings. The smaller clearances listed belong to other rules such as recessed luminaire and insulation spacing, not to transformer installation.2023 NEC §450.21(A)

A box contains six 12 AWG conductors, one internal cable clamp and one duplex receptacle, all 12 AWG. What minimum box volume is required?

• a.20.25 cubic inches✓
• b.13.5 cubic inches
• c.18.0 cubic inches
• d.22.5 cubic inches

Count six conductors, one allowance for all internal clamps and two allowances for the device yoke, giving 9 volume allowances. Each 12 AWG allowance is 2.25 cubic inches, so 9 x 2.25 = 20.25 cubic inches. Counting only the conductors gives 13.5 cubic inches, and forgetting that a yoke counts as two conductors gives 18.0 cubic inches.2023 NEC §314.16(B)

A device box has three 14-2 NM cables with equipment grounding conductors entering through internal clamps, and one single-pole switch is installed. What minimum box volume is required?

• a.20.0 cubic inches✓
• b.18.0 cubic inches
• c.16.0 cubic inches
• d.22.5 cubic inches

Six insulated conductors count individually, all equipment grounding conductors together count as one, all internal clamps together count as one, and the switch yoke counts as two, for 10 allowances. At 2.00 cubic inches for 14 AWG, 10 x 2.00 = 20.0 cubic inches. The 18.0 answer misses one allowance, 16.0 omits both the clamp and grounding allowances, and 22.5 uses the 12 AWG allowance by mistake.2023 NEC §314.16(B)

What is the minimum trade size of EMT required for nine 12 AWG THHN conductors?

• a.One-half inch✓
• b.Three-quarter inch
• c.One inch
• d.One and one-quarter inch

Annex C, Table C1 shows that one-half inch EMT accepts nine 12 AWG THHN conductors, exactly meeting the requirement. Three-quarter inch EMT holds sixteen and one inch holds twenty-six, so both are larger than the minimum. Annex C may be used directly whenever all conductors are the same size and insulation type.2023 NEC Annex C, Table C1

When more than two conductors are installed in a raceway, what is the maximum permitted percentage of the raceway cross-sectional area they may occupy?

• a.53 percent
• b.31 percent
• c.40 percent✓
• d.60 percent

Chapter 9, Table 1 allows 53 percent fill for one conductor, 31 percent for exactly two conductors and 40 percent for three or more. The 60 percent value applies only to a nipple not exceeding 24 inches in length between boxes or enclosures.2023 NEC Chapter 9, Table 1

A short raceway nipple no longer than 24 inches connects two enclosures. What fill percentage is permitted?

• a.31 percent
• b.40 percent
• c.53 percent
• d.60 percent✓

Notes to Chapter 9, Table 1 permit a nipple not exceeding 24 inches in length to be filled to 60 percent of its total cross-sectional area, because heat buildup and pulling friction are both minimal over such a short run. The 40, 53 and 31 percent values are the normal fills for three or more, one, and two conductors respectively.2023 NEC Chapter 9, Table 1, Note 4

Four 3/0 AWG THWN conductors, each 0.2679 square inch in area, are pulled into rigid metal conduit. What is the minimum trade size?

• a.2 inch✓
• b.1 and 1/2 inch
• c.2 and 1/2 inch
• d.1 and 1/4 inch

Total conductor area is 4 x 0.2679 = 1.0716 square inches, and with more than two conductors only 40 percent of the raceway may be filled. One and one-half inch RMC allows only about 0.81 square inch at 40 percent, which is too little, while 2 inch RMC allows about 1.34 square inches and is adequate. Two and one-half inch is larger than the calculated minimum.2023 NEC Chapter 9, Table 4

What is the minimum cover for a direct-buried UF cable installed in a residential yard on a 120-volt, 20-ampere circuit that is NOT GFCI protected?

• a.18 inches
• b.24 inches✓
• c.12 inches
• d.6 inches

Direct-buried cables and conductors under all locations not otherwise covered require 24 inches of cover. The 12-inch reduction applies only to residential branch circuits rated 120 volts or less, 20 amperes or less, and provided with GFCI protection, so removing the GFCI removes the reduction. The 6-inch and 18-inch values belong to metal and nonmetallic raceways respectively.2023 NEC Table 300.5

What is the minimum burial cover for rigid metal conduit installed underground in a location not otherwise specified?

• a.18 inches
• b.12 inches
• c.6 inches✓
• d.24 inches

Rigid metal conduit and intermediate metal conduit are permitted at 6 inches of cover because the metal wall provides its own physical protection. Nonmetallic raceways listed for direct burial require 18 inches, direct-buried cable requires 24 inches, and 12 inches applies to GFCI-protected residential branch circuits.2023 NEC Table 300.5

What is the minimum burial cover for a nonmetallic raceway listed for direct burial without concrete encasement, installed under a lawn?

• a.18 inches✓
• b.6 inches
• c.24 inches
• d.12 inches

Listed nonmetallic raceways buried without concrete encasement require 18 inches of cover in locations not otherwise specified. Metal conduit needs only 6 inches, direct-buried cable needs 24 inches, and 12 inches applies to GFCI-protected 120-volt residential branch circuits.2023 NEC Table 300.5

A GFCI-protected 120-volt, 20-ampere residential branch circuit is direct buried in a yard. What is the minimum cover?

• a.18 inches
• b.6 inches
• c.12 inches✓
• d.24 inches

Residential branch circuits rated 120 volts or less and 20 amperes or less that have GFCI protection may be buried with only 12 inches of cover, because a ground fault from a dig-in will clear immediately. Without GFCI protection the general 24-inch requirement applies, and the 6- and 18-inch values belong to metal and nonmetallic raceways.2023 NEC Table 300.5

How must electrical metallic tubing be secured and supported on a normal horizontal run?

• a.Secured within 3 feet of each box and supported at least every 10 feet✓
• b.Secured within 12 inches of each box and supported every 4 and 1/2 feet
• c.Secured within 3 feet of each box and supported every 6 feet
• d.Support is required only every 10 feet with no requirement near boxes

EMT must be securely fastened within 3 feet of every box, cabinet or termination and supported at intervals not exceeding 10 feet. The 12-inch and 4 and 1/2-foot figures belong to Type NM and Type AC cable, and the 6-foot interval is the MC cable support spacing.2023 NEC §358.30(A)

How must Type NM cable be supported where it enters a box equipped with cable clamps?

• a.Secured within 8 inches of each outlet box or fitting and supported at intervals not exceeding 6 feet along the run
• b.Secured within 12 inches of the box and supported at least every 4 and 1/2 feet✓
• c.Secured within 3 feet of the box and supported every 10 feet
• d.Secured within 12 inches of each box and supported at intervals not exceeding 6 feet, matching the rule for Type MC cable

Type NM cable is secured within 12 inches of each box, cabinet or fitting and supported at intervals not exceeding 4 and 1/2 feet. The 8-inch figure applies to a single-gang nonmetallic box without clamps, the 3-foot and 10-foot values are EMT, and the 6-foot interval belongs to MC cable.2023 NEC §334.30

At what maximum interval must Type MC cable be supported and secured?

• a.Every 3 feet, and within 12 inches of every termination
• b.Every 4 and 1/2 feet, and within 12 inches of every termination
• c.Every 10 feet, and within 3 feet of every termination
• d.Every 6 feet, and within 12 inches of every termination✓

Type MC cable is secured at intervals not exceeding 6 feet and within 12 inches of every box, cabinet or fitting where the cable terminates. The 4 and 1/2-foot interval belongs to Types NM and AC, and the 10-foot interval belongs to EMT and other rigid raceways.2023 NEC §330.30

At what maximum interval must Type AC cable be supported?

• a.Every 6 feet
• b.Every 4 and 1/2 feet✓
• c.Every 10 feet
• d.Every 3 feet

Type AC armored cable is supported at intervals not exceeding 4 and 1/2 feet and secured within 12 inches of each termination. The 6-foot figure is for Type MC cable and 10 feet is for EMT, so mixing the cable types is the usual source of error here.2023 NEC §320.30

What is the maximum support spacing for a 1-inch trade size rigid PVC conduit?

• a.6 feet
• b.5 feet
• c.3 feet✓
• d.10 feet

PVC expands and sags with temperature, so support spacing depends on trade size: one-half through 1 inch is supported every 3 feet, 1 and 1/4 through 2 inch every 5 feet, and larger sizes at progressively longer intervals. The 10-foot spacing belongs to EMT and rigid metal conduit, which are far stiffer.2023 NEC §352.30(B)

What is the maximum total amount of bend permitted in one run of EMT between pull points?

• a.270 degrees
• b.180 degrees
• c.360 degrees✓
• d.540 degrees

No more than the equivalent of four quarter bends, or 360 degrees total, is permitted between pull points such as conduit bodies and boxes, because friction rises sharply with each bend. The same 360-degree limit appears in the articles for rigid metal conduit and PVC, so it is worth memorizing once.2023 NEC §358.26

A cable passes through a bored hole in a wood stud. If the edge of the hole is less than 1 and 1/4 inches from the nearest edge of the stud, what is required?

• a.The cable must be removed and rerouted through a notch cut into the edge of the wood stud rather than the bored hole
• b.A steel plate or bushing at least 1/16 inch thick installed to protect the cable✓
• c.A listed nonmetallic sleeve of any thickness
• d.Nothing additional is required, provided that the cable installed in the bored hole is Type MC or Type AC armored cable

When the required 1 and 1/4-inch setback cannot be maintained, a steel plate, sleeve or bushing at least 1/16 inch thick must cover the area of the wire so a drywall screw or nail cannot reach it. Notching is more damaging to the stud and creates the same exposure, and nonmetallic sleeves do not satisfy this rule.2023 NEC §300.4(A)(1)

A pull box is used for a straight pull, and the largest raceway entering it is 3 inch trade size. What is the minimum required length of the box in the direction of the pull?

• a.18 inches
• b.24 inches✓
• c.12 inches
• d.36 inches

For straight pulls, the box length must be at least eight times the trade size of the largest raceway: 8 x 3 = 24 inches. The 18-inch answer uses a factor of six, which applies to angle and U pulls, and 12 inches uses a factor of four that appears nowhere in the rule.2023 NEC §314.28(A)(1)

An angle pull box has one 2-inch raceway and one 1-inch raceway entering the same wall, with conductors turning 90 degrees. What is the minimum distance from that wall to the opposite wall?

• a.24 inches
• b.12 inches
• c.16 inches
• d.13 inches✓

For angle pulls the distance is six times the trade size of the largest raceway plus the sum of the diameters of the other raceways on the same wall: (6 x 2) + 1 = 13 inches. The 12-inch answer forgets to add the additional raceway, and 24 inches applies the straight-pull factor of eight.2023 NEC §314.28(A)(2)

How must liquidtight flexible metal conduit be secured on a normal run?

• a.Within 12 inches of each box and at intervals not exceeding 6 feet
• b.Within 3 feet of each box and at intervals not exceeding 10 feet
• c.Within 12 inches of each box or fitting and at intervals not exceeding 4 and 1/2 feet✓
• d.Support is not required for lengths of 6 feet or less in any application

LFMC is secured within 12 inches of each box, cabinet or fitting and supported at intervals not exceeding 4 and 1/2 feet. Certain short lengths used for flexibility or for connections to luminaires are exempt, but that exemption is narrow and does not apply to ordinary runs, and the 10-foot spacing belongs to rigid raceways.2023 NEC §350.30(A)

How many 12 AWG conductors may be installed in a 4-11/16 inch by 2-1/8 inch square box with a volume of 42.0 cubic inches, assuming no clamps, devices or fittings?

• a.21
• b.20
• c.16
• d.18✓

Each 12 AWG conductor requires 2.25 cubic inches, so 42.0 / 2.25 = 18.67, and the count must be rounded down to 18 whole conductors. The 21-conductor answer uses the 14 AWG allowance of 2.00 cubic inches, and 20 comes from rounding up rather than down.2023 NEC §314.16(A)

Direct-buried conductors emerging from grade must be protected by an approved enclosure or raceway from below grade to what height?

• a.8 feet above finished grade✓
• b.6 feet above finished grade
• c.10 feet above finished grade
• d.4 feet above finished grade

Protection must extend from below grade to at least 8 feet above finished grade, and the underground portion must reach at least 18 inches below grade. Six feet leaves the conductors within easy reach of damage, and neither 4 nor 10 feet is the code value.2023 NEC §300.5(D)(1)

What is the maximum fill percentage when exactly two conductors are installed in a raceway?

• a.40 percent
• b.31 percent✓
• c.53 percent
• d.60 percent

Two conductors are limited to 31 percent fill, a lower figure than the 40 percent allowed for three or more, because two round conductors of similar size can jam in a bend and damage insulation during the pull. One conductor may fill 53 percent, and 60 percent applies only to a nipple 24 inches or shorter.2023 NEC Chapter 9, Table 1

What is the minimum trade size of EMT required for twenty-four 12 AWG THHN conductors?

• a.One inch✓
• b.Three-quarter inch
• c.One and one-quarter inch
• d.One and one-half inch

Annex C, Table C1 shows one inch EMT accepts twenty-six 12 AWG THHN conductors, so twenty-four fit. Three-quarter inch holds only sixteen and is too small, while one and one-quarter inch holds far more than needed. Remember that twenty-four current-carrying conductors would also trigger a 45 percent ampacity adjustment.2023 NEC Annex C, Table C1

Conductors installed in an underground raceway in a wet location must have which characteristic?

• a.A nylon jacket, which by itself qualifies the conductor for wet locations
• b.Any thermoplastic insulation, since the raceway keeps water out
• c.Insulation rated 90 degrees C, regardless of wet-location listing
• d.Insulation listed for use in wet locations, such as THWN or THWN-2✓

Raceways in underground and other wet locations are considered wet inside, so the conductors must carry a wet-location listing such as THWN, THWN-2 or XHHW. The W in the type designation is what matters; plain THHN without the dual THWN-2 marking is a dry- and damp-location conductor, and a temperature rating or nylon jacket alone does not confer a wet-location listing.2023 NEC §310.10(C)

A 25-horsepower, 460-volt, three-phase squirrel-cage motor has a table full-load current of 34 amperes. Using 75 degrees C terminations and copper, what is the minimum branch-circuit conductor size?

• a.6 AWG
• b.10 AWG
• c.8 AWG✓
• d.4 AWG

Single-motor branch-circuit conductors must carry at least 125 percent of the table full-load current: 34 x 1.25 = 42.5 A. In the 75 degrees C column, 10 AWG copper is 35 A and fails, while 8 AWG at 50 A is adequate. Sizes 6 and 4 AWG exceed the calculated minimum.2023 NEC §430.22

That same motor has a nameplate full-load current of 32 amperes and a marked service factor of 1.15. What is the maximum separate overload device rating?

• a.36.8 amperes
• b.40 amperes✓
• c.42.5 amperes
• d.32 amperes

Overload protection is based on the nameplate current, not the table value, and a service factor of 1.15 or greater permits 125 percent: 32 x 1.25 = 40 A. The 36.8-ampere answer applies the 115 percent factor used for motors with no marked service factor or temperature rise, and 42.5 amperes wrongly applies 125 percent to the table value of 34 A.2023 NEC §430.32(A)(1)

For that 34-ampere three-phase squirrel-cage motor, what is the maximum inverse-time circuit breaker permitted for branch-circuit short-circuit and ground-fault protection, using the next standard size allowance?

• a.90 amperes✓
• b.85 amperes
• c.100 amperes
• d.70 amperes

An inverse-time breaker is permitted at 250 percent of full-load current: 34 x 2.50 = 85 A, which is not a standard rating, so the next higher standard size of 90 amperes may be used. The 100-ampere answer skips a standard size, and 70 amperes corresponds to the 175 percent dual-element fuse calculation instead.2023 NEC Table 430.52(C)(1)

For the same 34-ampere motor, what is the maximum dual-element time-delay fuse permitted at the standard percentage?

• a.60 amperes✓
• b.70 amperes
• c.50 amperes
• d.90 amperes

Dual-element time-delay fuses are permitted at 175 percent of full-load current: 34 x 1.75 = 59.5 A, and because that is not a standard rating the next standard size of 60 amperes is used. The 90-ampere answer belongs to the inverse-time breaker at 250 percent, and 50 amperes falls below the calculated value.2023 NEC Table 430.52(C)(1)

A 5-horsepower, 230-volt single-phase motor has a table full-load current of 28 amperes. What is the minimum copper branch-circuit conductor at 75 degrees C terminations?

• a.10 AWG✓
• b.12 AWG
• c.8 AWG
• d.6 AWG

The conductor must carry 28 x 1.25 = 35 A. In the 75 degrees C column, 10 AWG copper is exactly 35 A and qualifies, while 12 AWG at 25 A does not. Note that 240.4(D) limits ordinary 10 AWG circuits to a 30-ampere device, but motor branch-circuit protection is sized under Article 430 instead.2023 NEC §430.22

A 30-horsepower, 460-volt three-phase motor has a table full-load current of 40 amperes. What is the minimum ampere rating of the disconnecting means?

• a.50 amperes
• b.40 amperes
• c.46 amperes✓
• d.60 amperes

The disconnecting means must have an ampere rating of at least 115 percent of the full-load current: 40 x 1.15 = 46 A, so a 60-ampere switch would be the practical selection. The 40-ampere answer omits the 115 percent factor entirely, and 50 or 60 amperes are available equipment ratings rather than the calculated minimum the question asks for.2023 NEC §430.110(A)

A feeder supplies a 25-horsepower motor (34 amperes) and a 10-horsepower motor (14 amperes), both 460 volts three phase. What minimum conductor ampacity is required?

• a.67.5 amperes
• b.60 amperes
• c.48 amperes
• d.56.5 amperes✓

Feeder conductors for several motors must carry 125 percent of the largest motor full-load current plus the sum of the other full-load currents: (34 x 1.25) + 14 = 42.5 + 14 = 56.5 A. The 48-ampere answer simply adds the two currents, and 67.5 amperes wrongly applies 125 percent to the total of both motors.2023 NEC §430.24

For that same two-motor feeder, if the largest branch-circuit protective device is 90 amperes, what is the maximum feeder overcurrent device rating?

• a.90 amperes
• b.104 amperes
• c.110 amperes
• d.100 amperes✓

The feeder device may not exceed the largest branch-circuit short-circuit and ground-fault protective device plus the sum of the full-load currents of the other motors: 90 + 14 = 104 A. Since 104 is not a standard rating and this is a maximum rather than a minimum, the next lower standard size of 100 amperes must be selected. Choosing 110 amperes would exceed the calculated ceiling.2023 NEC §430.62(A)

When sizing motor branch-circuit conductors and short-circuit protection, which current value must be used?

• a.The locked-rotor current from the nameplate code letter
• b.The motor nameplate full-load amperes
• c.The full-load current from Table 430.248 or 430.250✓
• d.The larger of nameplate current or table current

Conductor sizing, branch-circuit protection and disconnect rating are all based on the table values, which are conservative and independent of a particular manufacturer's nameplate. Nameplate current is used only for overload protection under 430.32, and locked-rotor current is used for withstand and disconnect horsepower comparisons, not for conductor sizing.2023 NEC §430.6(A)(1)

A continuous-duty motor over 1 horsepower is marked with a temperature rise of 40 degrees C but no service factor. What percentage of nameplate full-load current sets the maximum overload device?

• a.140 percent
• b.115 percent
• c.125 percent✓
• d.250 percent

Motors with a marked temperature rise not over 40 degrees C, like those with a service factor of 1.15 or greater, are permitted overload protection at 125 percent of nameplate current. The 115 percent figure applies to all other motors, 140 percent is the allowance when the initial setting will not carry the load, and 250 percent is a short-circuit protection value.2023 NEC §430.32(A)(1)

A continuous-duty motor over 1 horsepower has no marked service factor and no marked temperature rise. What is the maximum overload device rating as a percentage of nameplate full-load current?

• a.140 percent
• b.125 percent
• c.115 percent✓
• d.175 percent

Motors that carry neither a service factor of 1.15 or greater nor a marked temperature rise of 40 degrees C or less are limited to 115 percent of nameplate current, because there is less thermal margin available. The 125 percent value applies to the better-rated motors, 140 percent is the permitted increase when the motor will not start, and 175 percent is a fuse sizing percentage.2023 NEC §430.32(A)(1)

Where must a motor disconnecting means be located relative to the motor?

• a.Within 25 feet of the motor in all cases
• b.In sight from the motor location and the driven machinery, unless it is capable of being locked in the open position✓
• c.Anywhere on the same floor level as the motor
• d.In sight from the motor controller only, on the theory that the controller disconnect is always sufficient and that no separate in-sight rule applies to the motor itself

A disconnect must be in sight from the motor and driven machinery so a technician working on the equipment can see that it is open; the alternative is a disconnect elsewhere that is capable of being individually locked in the open position with the locking means remaining in place. In sight means visible and not more than 50 feet away, and a separate rule requires a disconnect in sight from the controller.2023 NEC §430.102(B)

An air conditioning condensing unit nameplate reads minimum circuit ampacity 24.6 and maximum overcurrent protective device 40. What overcurrent device must be installed?

• a.A 30-ampere device, the next standard size above the minimum circuit ampacity
• b.A 25-ampere device to match the minimum circuit ampacity
• c.A 50-ampere device sized at 125 percent of the marked maximum
• d.A device not exceeding 40 amperes✓

The marked maximum overcurrent protective device value is a ceiling set by the equipment manufacturer and tested with the unit, so the installed device must not exceed 40 amperes; a smaller device is acceptable only if it will carry the starting current. The minimum circuit ampacity of 24.6 sizes the conductors, not the protective device, and nothing permits multiplying the marked maximum by another factor.2023 NEC §440.4(B)

A hermetic refrigerant motor-compressor has a rated-load current of 20 amperes. What is the maximum branch-circuit short-circuit and ground-fault protective device at the standard 175 percent figure?

• a.60 amperes
• b.25 amperes
• c.45 amperes
• d.35 amperes✓

Protection for a motor-compressor is sized at not more than 175 percent of the rated-load current: 20 x 1.75 = 35 A, which is a standard rating. Where that device still will not carry the starting current it may be increased, but never above 225 percent, which here would be 45 amperes. A 25-ampere device is below the calculated value and would nuisance trip on start.2023 NEC §440.22(A)

For that same 20-ampere rated-load compressor supplied alone, what minimum conductor ampacity is required?

• a.35 amperes
• b.20 amperes
• c.25 amperes✓
• d.30 amperes

Branch-circuit conductors for a single motor-compressor must have an ampacity of at least 125 percent of the rated-load current or branch-circuit selection current, whichever is greater: 20 x 1.25 = 25 A, which calls for 10 AWG copper. The 35-ampere figure is the 175 percent protective device calculation, and 20 amperes omits the required multiplier entirely.2023 NEC §440.32

A surface-mounted luminaire with a completely enclosed light source is installed in a clothes closet. What is the minimum clearance to the nearest point of the defined storage space?

• a.12 inches✓
• b.6 inches
• c.3 inches
• d.18 inches

Surface-mounted luminaires with a completely enclosed light source require 12 inches of clearance from the storage space, while recessed luminaires with an enclosed light source are permitted at 6 inches because the housing is set back into the ceiling or wall. Open incandescent lamps are not permitted in clothes closets at all.2023 NEC §410.16(C)

A recessed luminaire that is NOT identified for insulation contact must maintain what minimum clearance from thermal insulation?

• a.1 inch
• b.1/2 inch
• c.6 inches
• d.3 inches✓

A non-IC recessed luminaire must be spaced at least 3 inches from thermal insulation so heat can dissipate, and insulation must not be installed above it in a way that traps heat. The 1/2-inch dimension is the required clearance from combustible materials other than the mounting surface, which is a different measurement.2023 NEC §410.116