CSLB Trade — Electrical (C-10) — All Questions

Per NEC Table 430.250, what is the full-load current of a 7.5 HP, 230 V, three-phase motor?

• a.11 A
• b.15.2 A
• c.22 A✓
• d.28 A

Table 430.250 lists 22 A for a 7.5 HP, 230 V three-phase motor. 15.2 A is 5 HP, 28 A is 10 HP at 230 V, and 11 A is 7.5 HP at 460 V.2023 NEC Table 430.250

For the 7.5 HP, 230 V motor (FLC 22 A), what minimum branch-circuit conductor ampacity is required by NEC 430.22?

• a.22 A
• b.25.3 A
• c.27.5 A✓
• d.24.2 A

125% of FLC: 22 x 1.25 = 27.5 A. 22 A omits the factor, 24.2 A is 110%, and 25.3 A is 115%.2023 NEC §430.22

For the 7.5 HP, 230 V motor (FLC 22 A), what is the maximum nontime-delay fuse per Table 430.52 (300%)?

• a.38.5 A
• b.55 A
• c.66 A✓
• d.176 A

Nontime-delay fuse: 300% of FLC = 22 x 3.00 = 66 A. 55 A is 250% (inverse-time breaker), 38.5 A is 175% (dual-element fuse), and 176 A is 800% (instantaneous trip).2023 NEC §430.52

When the Table 430.52 percentage produces a value that does not correspond to a standard fuse or breaker size, NEC 430.52(C)(1) Exception No. 1 permits you to:

• a.Ignore the table and use conductor ampacity
• b.Round down to the next lower standard size
• c.Double the value
• d.Use the next higher standard size of protective device✓

430.52(C)(1) Exception No. 1 allows using the next higher standard size when the calculated maximum does not match a standard rating, so the motor can start. Rounding down could cause nuisance tripping; doubling or ignoring the table is not permitted.2023 NEC §430.52

Per NEC Table 430.248, what is the full-load current of a 1 HP, single-phase, 115 V motor?

• a.16 A✓
• b.9.8 A
• c.20 A
• d.13.8 A

Table 430.248 lists 16 A for a 1 HP, 115 V single-phase motor. 9.8 A is 1/2 HP, 13.8 A is 3/4 HP, and 20 A is 1.5 HP at 115 V.2023 NEC Table 430.248

A small single-phase motor has a nameplate FLA of 14 A, service factor 1.0, no marked temperature rise. What is the maximum overload device rating under NEC 430.32(A)(1)?

• a.14 A
• b.17.5 A
• c.16.1 A✓
• d.15.4 A

Without a 1.15+ SF or <=40C rise marking, overload is limited to 115% of nameplate: 14 x 1.15 = 16.1 A. 125% (17.5 A) applies only to qualifying motors, 15.4 A is 110%, and 14 A applies no factor.2023 NEC §430.32

NEC 430.75 requires that motor control circuits be arranged so that:

• a.Control circuits need no overcurrent protection
• b.Control circuits are always 24 V
• c.The control circuit is disconnected from all sources of supply when the disconnecting means is open✓
• d.Control conductors are the same size as power conductors

NEC 430.75 requires the disconnecting means to open the motor control circuit from all sources when placed in the off position (with limited exceptions), so a technician is not exposed to energized controls. Control voltage level, conductor size parity, and 'no protection' are not the rule.2023 NEC §430.75

A 15 kVA, single-phase transformer has a 480 V primary. What is the rated primary current?

• a.36 A
• b.62.5 A
• c.72 A
• d.31.25 A✓

Single-phase: I = 15,000 / 480 = 31.25 A. Using 240 V would give 62.5 A, and the other values use incorrect voltages or the sqrt(3) factor that does not apply to single-phase.

For the 15 kVA, 480 V single-phase transformer (primary current 31.25 A), what is the maximum primary-only overcurrent device using the 125% factor of Table 450.3(B)?

• a.31.25 A
• b.39.1 A✓
• c.62.5 A
• d.46.9 A

Primary current >=9 A limits primary-only protection to 125%: 31.25 x 1.25 = 39.1 A (next standard size up permitted where needed). 31.25 A omits the factor, 46.9 A is 150%, and 62.5 A is 200%.2023 NEC §450.3

Which of the following is NOT required to be marked on a motor nameplate by NEC 430.7?

• a.Rated full-load amperes
• b.Rated frequency and number of phases
• c.The branch-circuit conductor size to be installed✓
• d.Rated voltage and horsepower (or kW)

NEC 430.7 requires the manufacturer, voltage, HP/kW, FLA, frequency, phases, speed, and similar data on the nameplate, but not the field branch-circuit conductor size - that is the installer's design calculation. All other listed items are required nameplate markings.2023 NEC §430.7

For a permanently installed swimming pool, what conductor is required for the equipotential bonding grid?

• a.No. 6 AWG solid aluminum
• b.No. 12 AWG insulated copper
• c.No. 8 AWG solid copper✓
• d.No. 10 AWG stranded copper

Section 680.26(B) requires the equipotential bonding to be established with a minimum No. 8 AWG solid copper conductor. Aluminum is not permitted in contact with pool structures, and conductors smaller than 8 AWG or stranded are not accepted for the bonding grid.2023 NEC §680.26

A non-Type IC recessed luminaire must be spaced at least how far from combustible material, except at the points of support?

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

Section 410.116(A)(1) requires a minimum 1/2 inch clearance between a non-Type IC recessed luminaire and combustible material, except at the points where the fixture is supported. Larger clearances such as 3 inches apply to thermal insulation, not to the general combustible-material spacing.2023 NEC §410.116

Thermal insulation must be kept at least how far from a non-Type IC recessed luminaire enclosure?

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

Section 410.116(B) requires thermal insulation to be kept at least 3 inches from the enclosure of a non-Type IC recessed luminaire so heat is not trapped. Only a luminaire identified as Type IC may be in direct contact with insulation; the smaller clearances apply to combustible material spacing, not insulation.2023 NEC §410.116

An emergency system must make power available to the required loads within what maximum time after normal power is lost?

• a.2 minutes
• b.60 seconds
• c.Immediately, with no delay permitted
• d.10 seconds✓

Section 700.12 requires that current supply to emergency loads be available within 10 seconds of the failure of the normal supply. Sixty seconds is the limit for legally required standby systems under Article 701, and no time limit is given for optional standby (Article 702).2023 NEC §700.12

A legally required standby system must restore power to its loads within what maximum time after normal supply is lost?

• a.60 seconds✓
• b.30 seconds
• c.10 seconds
• d.120 seconds

Section 701.12 requires that a legally required standby system supply its loads within 60 seconds of a normal-supply failure. The 10-second figure applies to true emergency systems (Article 700), which serve life-safety loads that need faster restoration.2023 NEC §701.12

How is the maximum current of a PV source circuit determined for conductor and overcurrent sizing?

• a.By the rated operating current only
• b.1.25 times the short-circuit current (Isc)✓
• c.1.0 times the short-circuit current
• d.0.8 times the short-circuit current

Section 690.8(A) sets the maximum PV source-circuit current at 1.25 times the module short-circuit current (Isc) to account for irradiance above standard test conditions. Conductors and overcurrent devices are then sized per 690.8(B); using only the operating current or a factor of 1.0 would undersize the circuit.2023 NEC §690.8

Rapid shutdown requires that controlled conductors more than 1 foot outside the array boundary be limited to what within 30 seconds?

• a.30 volts within 30 seconds✓
• b.0 volts instantly
• c.80 volts within 10 seconds
• d.50 volts within 1 minute

Section 690.12 requires that conductors leaving the array boundary be reduced to no more than 30 volts within 30 seconds of rapid-shutdown initiation. This protects firefighters and responders; the 80-volt limit applies only inside the array boundary, not to the outside conductors.2023 NEC §690.12

The ampacity of conductors from a generator terminal to the first overcurrent device must be at least what percent of the generator nameplate current rating?

• a.125%
• b.110%
• c.100%
• d.115%✓

Section 445.13(A) requires the conductors from generator terminals to the first distribution device to have an ampacity of not less than 115 percent of the nameplate current rating. This margin covers the generator's ability to deliver current above its continuous rating; 100 or 110 percent would be insufficient.2023 NEC §445.13

In a clothes closet, a surface-mounted incandescent or LED luminaire with a completely enclosed light source must maintain what minimum clearance to the nearest storage space?

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

Section 410.16(C)(1) requires a minimum 12-inch clearance between a surface-mounted incandescent or completely enclosed LED luminaire and the nearest point of a storage space. Recessed fixtures are allowed a smaller 6-inch clearance because their heat is contained within the ceiling.2023 NEC §410.16

In a clothes closet, a recessed incandescent or LED luminaire with a completely enclosed light source must maintain what minimum clearance to the nearest storage space?

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

Section 410.16(C)(3) permits a 6-inch minimum clearance for recessed incandescent or completely enclosed LED luminaires because the recessed housing limits exposed heat. Surface-mounted units require the larger 12-inch clearance.2023 NEC §410.16

Under the 2023 NEC, what unit load is used to calculate the general lighting load for a dwelling unit?

• a.10 VA per square foot
• b.5 VA per square foot
• c.3 VA per square foot✓
• d.1 VA per square foot

Table 220.12 in the 2023 NEC assigns 3 VA per square foot for the general lighting and general-use receptacle load of a dwelling unit. This value is multiplied by the floor area (using outside dimensions) to determine the calculated general lighting load.2023 NEC §220.41

A luminaire installed in a wet location must be marked with what designation?

• a.Weather resistant
• b.Suitable for Wet Locations✓
• c.Damp locations only
• d.Outdoor use

Section 410.10(A) requires luminaires installed in wet locations to be marked 'Suitable for Wet Locations' and installed so water cannot enter or accumulate in wiring compartments or lampholders. A 'damp locations' marking is not sufficient for a wet location such as one exposed to rain or hose-down.2023 NEC §410.10

Cord-connected luminaires, hanging luminaires, and similar equipment shall not have parts located within what zone measured from the bathtub rim or shower threshold, unless marked for damp or wet locations?

• a.3 feet horizontally and 8 feet vertically✓
• b.6 feet horizontally and 10 feet vertically
• c.5 feet horizontally and 8 feet vertically
• d.3 feet horizontally and 6 feet vertically

Section 410.10(D) prohibits such luminaire parts within a zone 3 feet horizontally and 8 feet vertically from the top of the bathtub rim or shower stall threshold, unless the luminaire is listed for damp or wet locations. This keeps ordinary fixtures out of reach of a person in the tub or shower.2023 NEC §410.10

The top of a wet-niche underwater pool luminaire lens (other than a listed low-voltage unit) must be installed at least how far below the normal water level?

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

Section 680.23(A)(5) requires the top of a wet-niche luminaire lens to be at least 18 inches below the normal water level. Listed low-voltage luminaires with no exposed metal parts may be as little as 4 inches below the surface, but the general rule is 18 inches.2023 NEC §680.23

What is the maximum voltage permitted for a wet-niche underwater pool luminaire?

• a.250 volts
• b.120 volts
• c.150 volts✓
• d.60 volts

Section 680.23(A)(4) limits underwater luminaires to a maximum of 150 volts between conductors. Higher voltages such as 250 volts are not permitted for underwater pool lighting because of the shock hazard in and around water.2023 NEC §680.23

How must the wiring of an emergency system generally be arranged relative to all other wiring?

• a.Run in the same raceway as normal branch circuits
• b.Kept entirely independent of all other wiring✓
• c.Combined with legally required standby wiring
• d.Installed only in a metal raceway shared with feeders

Section 700.10(B) requires emergency-system wiring to be kept entirely independent of all other wiring and equipment, with only limited exceptions such as in transfer equipment or common junction boxes at fixtures. Sharing raceways with normal or legally required standby wiring is not permitted.2023 NEC §700.10

Transfer equipment used for an emergency system must be what?

• a.Automatic and listed for emergency use✓
• b.A molded-case circuit breaker only
• c.Any general-use switch rated for the load
• d.A manual knife switch

Section 700.5 requires transfer equipment for emergency systems to be automatic, identified for emergency use, and approved by the authority having jurisdiction. A manual knife switch or ordinary general-use switch cannot meet the automatic-transfer and listing requirements for life-safety loads.2023 NEC §700.5

For an optional standby system, what signage does the NEC require?

• a.A sign only inside the generator enclosure
• b.A sign only if the system is over 600 volts
• c.A sign at the service-equipment location indicating the type and location of the on-site optional standby power source✓
• d.No signage is required

Section 702.7 requires a sign at the service-equipment or grounding-electrode location indicating the type and location of each on-site optional standby power source. This warns anyone working on the service that a second source of supply exists; signage is not limited to high-voltage systems or the generator enclosure.2023 NEC §702.7

On a portable generator, GFCI protection for personnel is generally required on which receptacles?

• a.Required only on 240 V outlets
• b.Required on 125 V, 15 A and 20 A receptacles✓
• c.Not required on generators
• d.Required only above 50 A

Section 445.20 requires that 125-volt, 15- and 20-ampere receptacles on portable generators be provided with listed GFCI protection for personnel (or comply with the limited exception for older equipment). Protection is targeted at the common 125-volt convenience outlets used with cord sets, not only high-amperage circuits.2023 NEC §445.20

A generator disconnecting means must be capable of doing what?

• a.Only opening the neutral conductor
• b.It is optional for standby units
• c.Disconnecting the generator and all protective devices and control apparatus, and be lockable in the open position✓
• d.Serving as a plug and receptacle only

Section 445.18 requires a disconnecting means that shuts down the generator, disconnects it and all protective devices and control apparatus from the load, and can be locked in the open position. Opening only the neutral or relying on a cord-and-plug connection does not satisfy the full disconnect and lockout requirement.2023 NEC §445.18

How must emergency illumination be arranged with respect to the failure of a single lighting element?

• a.Failure of any individual lighting element shall not leave the area in total darkness✓
• b.A single bulb per room is acceptable
• c.Battery packs are prohibited
• d.Only exit signs are required

Section 700.16 requires emergency lighting to be designed and installed so that the failure of any individual lighting element, such as a single lamp burning out, cannot leave any space that requires emergency lighting in total darkness. Relying on a single bulb per room would violate this single-failure requirement.2023 NEC §700.16

Which loads are typically served by a legally required standby system?

• a.Personal comfort loads in a residence
• b.Ventilation, smoke removal, and communication systems required by code for safety✓
• c.Life-safety egress lighting only
• d.Data-center revenue equipment chosen by the owner

Legally required standby systems (Article 701) supply loads such as heating and ventilation, smoke removal, sewage disposal, and communication systems whose failure could create hazards or hamper firefighting and rescue. Pure life-safety egress loads fall under emergency systems (700), and owner-selected convenience loads fall under optional standby (702).2023 NEC §701.2

Transfer equipment for an optional standby system must do what regarding the normal and standby sources?

• a.Always be an automatic type
• b.Prevent inadvertent interconnection of the normal and standby sources✓
• c.Allow the generator to backfeed the utility freely
• d.Require no interlock between sources

Section 702.5 requires transfer equipment to prevent the inadvertent interconnection of the normal source and any optional standby source, unless the installation is designed for parallel operation per Article 705. Allowing free backfeed to the utility would endanger line workers; optional standby transfer equipment may be manual or automatic.2023 NEC §702.5

What does the NEC require regarding testing of emergency systems?

• a.Periodic testing on a scheduled basis under simulated or maximum load✓
• b.No testing once commissioned
• c.Testing only every 10 years
• d.Testing performed only by the utility

Section 700.3 requires emergency systems to be tested periodically on a schedule acceptable to the authority having jurisdiction to ensure they are maintained in proper operating condition, including a witnessed acceptance test at installation. Leaving a system untested after commissioning would violate this requirement.2023 NEC §700.3

What capacity must an emergency system power source have?

• a.No minimum capacity is specified
• b.Adequate capacity to carry all emergency loads simultaneously✓
• c.Only the largest single load
• d.50% of the connected emergency load

Section 700.4 requires the emergency source to have adequate capacity and rating to supply all loads that will operate simultaneously. Sizing for only a fraction of the load or the largest single load would leave emergency loads unsupplied during an outage.2023 NEC §700.4

A storage-battery emergency source must be capable of maintaining the total emergency load for what minimum time and voltage?

• a.1 hour at 90% of nominal
• b.2 hours at 100% of nominal
• c.1 1/2 hours at not less than 87 1/2% of nominal voltage✓
• d.30 minutes at 80% of nominal

Section 700.12 requires a storage battery serving as an emergency source to maintain the total load for a minimum of 1 1/2 hours without the voltage falling below 87 1/2 percent of nominal. Shorter durations or lower voltage thresholds do not meet the emergency-source requirement.2023 NEC §700.12

A PV system disconnecting means must be installed how?

• a.Located only on the roof
• b.Concealed behind the inverter cover
• c.Readily accessible and plainly marked as the PV system disconnect✓
• d.Optional for systems under 100 volts

Section 690.13 requires the PV system disconnecting means to be readily accessible and to be legibly marked to identify it as the photovoltaic system disconnect. A disconnect hidden on the roof or behind the inverter cover would not be readily accessible as required.2023 NEC §690.13

For a one- or two-family dwelling, what is the maximum permitted PV system DC voltage?

• a.600 volts✓
• b.300 volts
• c.1500 volts
• d.1000 volts

Section 690.7 limits the maximum PV system DC voltage on or in one- and two-family dwellings to 600 volts. The higher 1000-volt and 1500-volt levels are used on larger commercial and utility installations, not on dwellings.2023 NEC §690.7

Under the busbar interconnection rule, the sum of the main utility overcurrent device plus the inverter (power-production) overcurrent device generally may not exceed what percent of the busbar rating?

• a.150% of the busbar ampacity
• b.120% of the busbar ampacity✓
• c.80% of the busbar ampacity
• d.100% of the busbar ampacity

Section 705.12(B)(3) allows the sum of the ampere ratings of the main supply overcurrent device and the power-production (inverter) overcurrent device to be up to 120 percent of the busbar rating when the inverter breaker is at the opposite end from the main. Exceeding 120 percent would risk overloading the busbar.2023 NEC §705.12

The DC PV disconnect label must display what information?

• a.Nothing is required
• b.AC frequency of the system
• c.Maximum PV system voltage and maximum circuit current of the DC circuit✓
• d.Only the manufacturer name

Section 690.53 requires the DC photovoltaic system disconnect to be marked with the rated maximum voltage and the maximum circuit current for the DC circuits, among other values. This information helps responders and service personnel understand the DC hazard; manufacturer name or AC frequency alone would not satisfy the labeling requirement.2023 NEC §690.53

A power-limited fire alarm (PLFA) power source is limited to what maximum output?

• a.50 VA
• b.250 VA
• c.1000 VA
• d.100 VA✓

Section 760.121 limits a PLFA power source to the output of a listed Class 3 supply not exceeding 100 volt-amperes. Sources exceeding these limits are treated as non-power-limited fire alarm (NPLFA) circuits and must follow Chapter 3 wiring methods.2023 NEC §760.121

How must fire alarm circuit cables be installed and supported?

• a.Left unsupported above ceilings
• b.Run only in EMT
• c.Bundled together with power conductors
• d.Installed in a neat and workmanlike manner and supported so the cable will not be damaged by normal building use✓

Section 760.24 requires fire alarm cables to be installed in a neat and workmanlike manner, adequately supported by the building structure, and protected from physical damage. Leaving cable unsupported above a ceiling or bundling it with power conductors is not permitted; conduit is not the only allowed method.2023 NEC §760.24

What best characterizes a Class 2 circuit?

• a.It requires no overcurrent protection because it is high power
• b.It operates above 600 volts
• c.It is identical to a Class 1 circuit
• d.Its power is limited by a listed Class 2 power source, providing protection from electric shock and fire ignition✓

A Class 2 circuit's safety comes from limiting the power available from a listed Class 2 source, which restricts both shock and fire-ignition hazards. This power limitation is why Class 2 wiring is treated differently from Class 1 and from line-voltage power circuits.2023 NEC §725.121

How must Class 2 conductors generally be separated from electric light and power conductors?

• a.12 inches always
• b.They may be freely mixed with 480 V conductors
• c.6 inches with no exceptions
• d.At least 2 inches from power conductors unless a permitted separation method is used✓

Section 725.136 generally requires Class 2 conductors to be separated at least 2 inches from conductors of electric light, power, and Class 1 circuits, unless one of the permitted separation methods (such as a barrier or listed cable) is used. Freely mixing them in a raceway or enclosure with power conductors is not allowed.2023 NEC §725.136

When is a primary protector required on a communications circuit?

• a.Required only for fiber-optic cable
• b.Where the circuit is exposed to lightning or to accidental contact with power conductors over 300 V to ground✓
• c.Never required
• d.Required only for indoor circuits

Section 805.90 requires a listed primary protector where communications circuits are exposed to accidental contact with power conductors over 300 volts to ground or are subject to lightning exposure. Fiber-optic cables carry no metallic conductors, so they do not require this electrical protector.2023 NEC §805.90

What is the minimum size of the bonding/grounding conductor for a communications system?

• a.10 AWG copper
• b.16 AWG copper
• c.14 AWG copper✓
• d.18 AWG copper

Section 800.100 requires the communications bonding conductor or grounding-electrode conductor to be not smaller than 14 AWG copper (or equivalent). Smaller 16 or 18 AWG conductors would not meet the minimum, and 10 AWG is larger than required.2023 NEC §800.100

The equipotential bonding for perimeter surfaces around a permanently installed pool must extend how far from the inside walls of the pool?

• a.3 feet horizontally around the inside and outside pool walls✓
• b.5 feet
• c.1 foot
• d.10 feet

Section 680.26(B)(2) requires perimeter-surface bonding to extend for 3 feet horizontally beyond the inside walls of the pool and include walkways and surfaces within that zone. Larger distances such as 5 or 10 feet are not required by the equipotential-bonding rule.2023 NEC §680.26

A disconnecting means for pool utilization equipment such as a pump motor must be within sight and located at least how far from the inside walls of the pool?

• a.5 feet✓
• b.10 feet
• c.20 feet
• d.3 feet

Section 680.12 requires the disconnecting means for pool equipment to be readily accessible, within sight of the equipment, and located at least 5 feet horizontally from the inside walls of the pool unless separated by a permanent barrier. The 5-foot spacing keeps a person from reaching the disconnect while in the water.2023 NEC §680.12

General-purpose receptacles serving a dwelling-unit pool must be located at least how far from the inside walls of the pool?

• a.3 feet
• b.20 feet
• c.10 feet
• d.6 feet✓

Section 680.22(A) requires general-purpose receptacles to be located at least 6 feet from the inside walls of the pool. A required receptacle for pump-motor service may be between 6 and 20 feet away with GFCI protection; placing general receptacles closer than 6 feet is not permitted.2023 NEC §680.22

What GFCI requirement applies to the outlets supplying a packaged self-contained spa or hot tub?

• a.Required only for indoor spas
• b.Not required
• c.Required only above 240 volts
• d.Required GFCI protection for the outlets supplying the spa or hot tub✓

Section 680.44 generally requires the outlets that supply a self-contained spa or hot tub to be protected by a ground-fault circuit interrupter. This protection applies to both indoor and outdoor units and is not limited to higher-voltage circuits.2023 NEC §680.44