Master Electrician (NEC) — All Questions

For equipment operating at 0-150 V to ground under Condition 1, what is the minimum depth of working space in front of the equipment?

• a.4 ft
• b.2.5 ft
• c.2 ft
• d.3 ft✓

Condition 1 (exposed live parts on one side, no grounded parts opposite) requires a minimum working clearance of 3 ft for 0-150 V.2023 NEC 110.26(A)(1)

What is the minimum required width of working space in front of electrical equipment?

• a.36 in always
• b.24 in
• c.18 in
• d.30 in or the width of the equipment, whichever is greater✓

The working space width must be at least 30 in or the width of the equipment, whichever is greater, and must permit a 90-degree door opening.2023 NEC 110.26(A)(2)

What is the minimum headroom (height) of working space about electrical equipment such as panelboards?

• a.8 ft
• b.6 ft
• c.6.5 ft✓
• d.7 ft

The minimum headroom of working space is 6.5 ft (or the height of the equipment, whichever is greater).2023 NEC 110.26(A)(3)

The dedicated equipment space above a panelboard extends how far above the equipment (or to a structural ceiling if lower)?

• a.4.5 ft
• b.7 ft
• c.6 ft✓
• d.3 ft

The dedicated electrical space extends from the equipment to 6 ft above it, or to a structural ceiling if lower, and must be kept clear of foreign systems.2023 NEC 110.26(E)(1)

Equipment rated at what current or more requires two entrances to and egress from the working space when the space is large or contains overcurrent devices?

• a.1000 A
• b.600 A
• c.1200 A✓
• d.800 A

For equipment rated 1,200 A or more and over 6 ft wide, two entrances/egress paths to the working space are required.2023 NEC 110.26(C)(2)

For a circuit rated 100 A or less, conductor ampacity is generally based on which temperature column unless the equipment is listed otherwise?

• a.90 C
• b.75 C
• c.105 C
• d.60 C✓

Terminations on equipment rated 100 A or less are based on the 60 C column unless the equipment and conductors are listed for a higher temperature.2023 NEC 110.14(C)(1)

For circuits rated over 100 A, conductor ampacity for terminations is generally based on which temperature column?

• a.Nameplate only
• b.90 C
• c.75 C✓
• d.60 C

Terminations on equipment over 100 A are based on the 75 C column unless listed and marked for a higher rating.2023 NEC 110.14(C)(1)

Which standard governs electrical safety-related work practices, including arc-flash and shock protection?

• a.OSHA 1910 only
• b.NFPA 70E✓
• c.NFPA 72
• d.NEC (NFPA 70)

NFPA 70E, Standard for Electrical Safety in the Workplace, covers safe work practices, arc-flash boundaries, and PPE selection.

Under safe electrical work practices, what is the preferred condition before working on or near exposed conductors?

• a.Energized with a permit
• b.An electrically safe (de-energized and verified) work condition✓
• c.Wearing rubber gloves
• d.Under observation

The safest and preferred approach is to place equipment in an electrically safe work condition: de-energize, lock out, and verify absence of voltage before work.

What is the primary purpose of a lockout/tagout (LOTO) procedure under Cal/OSHA?

• a.To install ground rods
• b.To label panel directories
• c.To test GFCI devices
• d.To isolate and control hazardous energy during servicing✓

LOTO isolates and controls hazardous energy sources so equipment cannot be re-energized while workers are servicing it.

During electrical construction, a rough-in (rough) inspection is generally performed:

• a.After the final inspection
• b.After energizing the system
• c.Before wiring is concealed or covered✓
• d.Only at final occupancy

The rough inspection occurs after wiring is installed but before walls or wiring are covered, so the inspector can verify concealed work.

Who is responsible for interpreting and enforcing the requirements of the NEC?

• a.The authority having jurisdiction (AHJ)✓
• b.The serving utility
• c.The NFPA
• d.The equipment manufacturer

The authority having jurisdiction enforces the Code, makes interpretations, and grants any special permission where allowed.2023 NEC 90.4

The NEC generally does not cover which of the following installations?

• a.Dwelling branch circuits
• b.Utility-owned generation and distribution under exclusive utility control✓
• c.Commercial feeders
• d.Industrial services

The Code does not apply to installations under the exclusive control of an electric utility for generation, transmission, or distribution of power.2023 NEC 90.2(B)

Service equipment (other than dwellings) must be field marked with what value related to fault protection?

• a.Maximum available fault current✓
• b.Phase rotation
• c.Installation date only
• d.The panel interrupting rating only

Service equipment must be legibly field marked with the maximum available fault current and the date of the calculation.2023 NEC 110.24(A)

Equipment likely to be examined or serviced while energized must carry what type of field-applied marking?

• a.Voltage rating only
• b.Phase-sequence label
• c.An arc-flash hazard warning label✓
• d.Equipment grounding conductor size

An arc-flash warning label must be applied to warn qualified persons of the potential arc-flash hazard before energized examination or servicing.2023 NEC 110.16

Equipment operating at 151-600 V to ground under Condition 3 requires what minimum depth of working space?

• a.3 ft
• b.3.5 ft
• c.4 ft✓
• d.5 ft

2023 NEC Table 110.26(A)(1): for 151-600 V, Condition 3 (exposed live parts on both sides of the working space) requires 4 ft. Trap: 3 ft is the Condition 1 value at this voltage.2023 NEC Table 110.26(A)(1)

Equipment that is listed or labeled must be installed and used:

• a.entirely at the discretion of the installing electrician on the job site
• b.per any instructions included in its listing or labeling✓
• c.only by the original manufacturer
• d.without regard to the product label

2023 NEC 110.3(B) requires listed or labeled equipment to be installed and used in accordance with any instructions included in the listing or labeling. Trap: field practice cannot override the listing instructions.2023 NEC 110.3(B)

For equipment operating at 151-600 V to ground under Condition 2, what is the minimum depth of working space in front of the equipment?

• a.5 ft
• b.3.5 ft✓
• c.4 ft
• d.3 ft

2023 NEC Table 110.26(A)(1): for over 150 to 600 V, Condition 2 (grounded parts on the opposite side) requires 3.5 ft of clear working depth.

For equipment operating at 0-150 V to ground, what is the minimum depth of working space regardless of condition?

• a.3 ft✓
• b.3.5 ft
• c.2.5 ft
• d.4 ft

2023 NEC Table 110.26(A)(1): at 0-150 V to ground the working depth is 3 ft for Conditions 1, 2, and 3.

Personnel doors for electrical equipment rated at what current or more must open in the direction of egress and be equipped with panic hardware?

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

2023 NEC 110.26(C)(3): where equipment rated 800 A or more has a personnel door within 7.6 m (25 ft) of the working space, the door must open in the direction of egress and have listed panic hardware.

Under 2023 NEC 110.22, each disconnecting means must be:

• a.legibly marked to indicate its purpose unless located and arranged so the purpose is evident✓
• b.installed only by the utility
• c.rated at least 100 A
• d.painted red

2023 NEC 110.22(A): each disconnecting means must be legibly marked to indicate its purpose unless located and arranged so the purpose is evident.

Under 2023 NEC 110.14(D), terminations that are marked with a tightening torque must be:

• a.tightened until the conductor deforms
• b.tightened to the specified value using a calibrated torque tool✓
• c.left finger-tight for expansion
• d.hand-tightened only

2023 NEC 110.14(D): where a tightening torque is indicated on equipment or in instructions, a calibrated torque tool must be used to achieve the specified value.

One of the primary purposes of system grounding under 2023 NEC 250.4(A)(1) is to:

• a.limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines✓
• b.carry normal load current
• c.eliminate the need for overcurrent protection
• d.reduce conductor resistance

2023 NEC 250.4(A)(1): system grounding limits the voltage imposed by lightning, line surges, and unintentional contact with higher-voltage lines and stabilizes voltage to earth during normal operation.

Under 2023 NEC 408.4(A), every circuit and circuit modification in a panelboard must be:

• a.numbered only, with no description
• b.marked only if over 100 A
• c.legibly identified as to its clear, evident, and specific purpose in a circuit directory✓
• d.identified only for motor circuits

2023 NEC 408.4(A): each circuit must be legibly identified as to its clear, evident, and specific purpose on a directory located at the panelboard.

In the 2023 NEC, the word 'shall' indicates a requirement that is:

• a.mandatory✓
• b.permissive
• c.advisory only
• d.a recommendation

2023 NEC 90.5(A): mandatory rules use the word 'shall'; permissive rules use 'shall be permitted'; explanatory material is informational.

Under 2023 NEC 110.12, electrical equipment must be installed in a manner that is:

• a.energized before inspection
• b.at the installer's sole discretion
• c.concealed from view
• d.neat and workmanlike✓

2023 NEC 110.12: electrical equipment must be installed in a neat and workmanlike manner, with unused openings closed and internal parts kept free of foreign material.

Under 2023 NEC 110.2, conductors and equipment covered by the Code are acceptable only if:

• a.approved by the authority having jurisdiction✓
• b.rated over 600 V
• c.installed by a master electrician
• d.manufactured domestically

2023 NEC 110.2: conductors and equipment required or permitted by the Code are acceptable only if approved (accepted as suitable) by the authority having jurisdiction.

Under 2023 NEC 110.11, equipment must be selected considering:

• a.the utility's meter type
• b.only the ambient temperature
• c.the installer's warranty period
• d.any deteriorating agents or environmental conditions present at the installation✓

2023 NEC 110.11: equipment must be identified for the environment; presence of moisture, corrosive vapors, dust, or other deteriorating agents must be considered in selection and installation.

Service equipment (other than one- and two-family dwellings) rated 1,200 A or more must be legibly field marked with:

• a.the installer's license number
• b.the maximum available fault current and the date of the calculation✓
• c.the panel's short-circuit color code
• d.the phase rotation only

2023 NEC 110.24(A): service equipment must be field marked with the maximum available fault current, including the date of the calculation, so the interrupting/short-circuit ratings can be verified.

In the NEC definitions, a 'continuous load' is one where the maximum current is expected to continue for:

• a.30 minutes or more
• b.8 hours or more
• c.1 hour or more
• d.3 hours or more✓

2023 NEC Article 100: a continuous load is one where the maximum current continues for 3 hours or more, which triggers the 125% conductor and device sizing rules.

Under 2023 NEC 110.26, the working space in front of energized electrical equipment must:

• a.be reduced to 24 in for panelboards
• b.be kept clear and not be used for storage✓
• c.double as an egress corridor only
• d.be usable for storage when de-energized

2023 NEC 110.26(B): the required working space must be kept clear and must not be used for storage; when normally enclosed live parts are exposed for service, the space must be guarded.

For equipment operating at 151-600 V to ground under Condition 1, what is the minimum depth of working space?

• a.3 ft✓
• b.4 ft
• c.2.5 ft
• d.3.5 ft

2023 NEC Table 110.26(A)(1): at over 150 to 600 V, Condition 1 (no grounded or live parts on the opposite side) requires 3 ft of working depth.

Because jurisdictions adopt different Code editions and amendments, a master electrician sizing a service should always:

• a.assume the newest published NEC applies everywhere
• b.use whichever edition is most economical
• c.verify the NEC edition and any local amendments the jurisdiction has adopted✓
• d.follow the manufacturer's catalog instead of the Code

The NEC is adopted (often with amendments) on a state/local basis, and Article 220 was renumbered in the 2023 edition; always verify the edition and local amendments your jurisdiction has adopted before finalizing a calculation.

Under 2023 NEC 110.14(C), the temperature rating of a conductor used for ampacity at a termination is governed by:

• a.the ambient temperature only
• b.the lowest temperature rating of any connected termination, conductor, or device✓
• c.the 90 C column in all cases
• d.the highest-rated component in the circuit

2023 NEC 110.14(C): the conductor ampacity at a termination is based on the lowest temperature rating of any connected termination, conductor, or device, so the 90 C column is generally usable only for derating, not for final termination sizing.