Journeyman Electrician Exam (NEC) flashcards

The NEC limits how far service entrance conductors can run inside a building before terminating at the service disconnecting means, to minimize fire risk from unprotected conductors.

• NEC 230.6 defines conditions under which service conductors are considered 'outside' a building.
• One condition allows for up to 10 feet of raceway-enclosed service conductors within a wall or ceiling.
• This rule ensures that overcurrent protection is installed as close as practicable to the point of entry.

Memory trick: Ten feet in the wall, or concrete for all!

The maximum number of conductors permitted in a conduit is determined by the conduit's trade size, the conductor's size (AWG), and the insulation type.

• NEC Chapter 9, Tables C.1 through C.12, provide specific fill capacities for various conduit types and insulation.
• THHN insulation generally allows for more conductors due to its smaller overall diameter compared to other types.
• Conduit fill limits prevent overheating and allow for easier pulling of conductors.

Memory trick: Fill the pipe right, or circuits take flight!

Conductor ampacity must be adjusted (derated) for ambient temperatures exceeding 30°C (86°F) and for more than three current-carrying conductors in a raceway or cable.

• NEC Table 310.16 provides base ampacities at 30°C.
• NEC Table 310.15(B)(2)(a) (now integrated into 310.16 tables as correction factors) provides ambient temperature correction factors.
• NEC Table 310.15(B)(3)(a) provides adjustment factors for the number of current-carrying conductors.
• Always use the lowest appropriate temperature column (e.g., 90°C for THHN) for the conductor's insulation rating before applying correction factors.

Memory trick: Base, then adjust, for heat and conductor trust!

The equipment grounding conductor in flexible cords and cables must be uniquely identified by a green or green with yellow stripes insulation to prevent misidentification and ensure safety.

• NEC 400.22(B) mandates the color coding for flexible cord conductors.
• Green is reserved exclusively for grounding conductors.
• Proper color identification is critical to prevent shock hazards.

Memory trick: Green means ground, safe and sound!

The minimum length of conductor that must be left extending from an outlet, junction, or switch box to facilitate making splices or connections to devices.

• Minimum of 6 inches required.
• Measured from where the conductor emerges from raceway/cable sheath.
• Applies to all conductors at these points.

Memory trick: Give the wires 'six inches of freedom' for connections, don't be stingy.

The reduction in the allowable current-carrying capacity of conductors when more than three current-carrying conductors are installed in a raceway, cable, or bundle, due to reduced heat dissipation.

• Applies when more than three current-carrying conductors are present.
• Adjustment factors are found in NEC Table 310.15(C)(1).
• Neutral conductors are generally not considered current-carrying unless unbalanced or on a 3-phase, 4-wire wye system with nonlinear loads.

Memory trick: Three's a crowd, four's a derate: count the 'current carriers' for heat's sake.

The NEC specifies maximum distances between points of support for Type MC cable to prevent sagging, damage, and maintain proper installation integrity.

• Maximum support interval is 6 feet.
• Must be secured within 12 inches of boxes or fittings.
• Specific rules apply for unsupported lengths in suspended ceilings (330.30(D)).

Memory trick: MC cable needs a hug every 'six-foot stretch', don't let it sag.

NEC requirement for the minimum distance from the edge of a wood member when boring holes for cables or raceways, designed to protect the wiring from physical damage.

• Minimum 1 1/4 inches from the nearest edge.
• Applies to cables and raceways in bored holes.
• Protects against nails and screws.

Memory trick: Wood holes need a 'one-and-a-quarter buffer' for cable safety.

The process of connecting the end of an electrical conductor to a device, terminal, or equipment without joining it to another conductor (i.e., not a splice).

• Connects a conductor directly to a terminal point.
• Examples: connecting to a circuit breaker, receptacle, switch, or terminal block.
• Different from a splice, which joins conductors together.

Memory trick: Connections are either 'splices for joining' or 'terminations for ends'.

The NEC specifies various wiring methods and materials suitable for different applications in residential buildings, considering location (dry/wet, exposed/concealed) and protection.

• Type NM-B is the most common for dry, concealed residential wiring.
• Type UF is primarily for direct burial and wet locations.
• Type SE and Type MC cables have broader applications, including residential interiors.
• Choosing the correct cable type is crucial for safety and code compliance.

Memory trick: Every home has a 'N-U-M' of cables, but only some fit in the wall!

The NEC mandates specific raceway types or protection methods for installations in corrosive environments to prevent degradation and ensure the longevity and safety of the electrical system.

• NEC Article 300.6 details protection against corrosion.
• Rigid Nonmetallic Conduit (RNC), such as PVC, is inherently corrosion-resistant.
• Metallic raceways may require supplementary protection (e.g., special coatings, wraps) in corrosive areas.
• The suitability of a raceway depends on the specific corrosive agents present.

Memory trick: Corrosive fumes? PVC assumes!

Outlet boxes used to support ceiling-suspended fans must be specifically listed for the purpose and have a weight rating appropriate for the fan it will support.

• Standard boxes can support up to 35 lbs without specific marking.
• Fans over 35 lbs require boxes listed for the specific weight.
• Maximum fan weight for any box is generally 70 lbs (314.27(C)).

Memory trick: Fan boxes have limits, check the 'weight tag' to prevent a drop.

Flexible Metal Conduit (FMC) can serve as an equipment grounding conductor only under specific conditions, including limitations on circuit amperage and the maximum length of the conduit run.

• NEC 250.118 lists acceptable equipment grounding conductors.
• FMC can be an EGC if listed for grounding, and the circuit's OCPD is 20A or less, AND the FMC length is 6 feet or less.
• Exceptions exist for larger FMC (1-1/4 inch or larger) with OCPD up to 60A.
• A separate EGC is generally required if these conditions are not met.

Memory trick: Six feet for flex, or a separate ground annex!

The minimum allowed radius for a conduit bend, specified in the NEC to prevent damage to conductors during installation and to facilitate wire pulling.

• Minimum bend radii vary by conduit type and size.
• Ensures conductors are not damaged during installation.
• Found in NEC Chapter 9, Table 2.

Memory trick: Bends prevent kinks, check the chart, don't be a sharp-corner smarty.

Specific wiring methods required in Class I, Division 2 hazardous locations to prevent the ignition of flammable gases or vapors, characterized by the need for sealed or explosionproof integrity.

• Hazardous locations are defined by NEC Article 500.
• Class I, Division 2 means ignitable concentrations are present only under abnormal conditions.
• Wiring methods must prevent gas/vapor entry to prevent ignition.

Memory trick: In Div 2, seal it tight, don't let the gas ignite, EMT is not the 'safe tube'.

The smallest gauge of conductor permitted by the NEC for a given overcurrent protective device rating, ensuring safe current carrying capacity.

• Minimum size for 15A circuit is 14 AWG copper.
• Minimum size for 20A circuit is 12 AWG copper.
• Minimum size for 30A circuit is 10 AWG copper.

Memory trick: Small wires for small amps, big wires for big amps, remember the 'AWG current rule'.

Any penetration of a fire-resistant-rated assembly by electrical wiring or equipment must be sealed with an approved firestop system to prevent the spread of fire and smoke.

• NEC 300.21 directly addresses the protection of openings in fire-rated barriers.
• The firestop material must be 'approved' for the specific application and rating.
• Failure to properly firestop can compromise building safety and violate code.

Memory trick: Seal the hole, save a soul!

The maximum number of specific conductor types and sizes permitted within a given conduit trade size, ensuring that the conduit is not overfilled, which could lead to overheating and difficulty in pulling wires.

• Based on conductor insulation type and size.
• Found in NEC Chapter 9, Tables C.1 through C.12(A).
• Prevents overheating and facilitates installation.

Memory trick: Fill the pipe right, don't cram, use the 'C' tables for the count.

The NEC provides exceptions to standard box volume calculations, such as for integral junction boxes in luminaires where no additional splices or connections are made.

• NEC 314.16(A) outlines general box fill calculations.
• Exception No. 2 specifically addresses luminaires with integral junction boxes.
• This exception simplifies calculations when the integral box serves only as a connection point for the fixture's supply conductors.

Memory trick: No extra wires, no extra count, for the light fixture's mount!

Wiring methods in Class I, Division 1 hazardous locations must be explosionproof and designed to prevent the ignition of flammable gases or vapors.

• NEC 501.10(A) lists permitted wiring methods.
• Rigid metal conduit (RMC) and Intermediate metal conduit (IMC) with threaded connections are primary methods.
• Specific types of Type MC cable are also permitted.
• Flexible connections generally require explosionproof flexible fittings or listed flexible conduit.

Memory trick: RMC, IMC, MC are tough, LFMC is not enough!

A motor control scheme using momentary pushbuttons and a holding contact to prevent automatic restart of the motor after a power failure or significant voltage drop, thus providing undervoltage protection.

• Uses momentary Start/Stop buttons.
• Relies on a holding contact (auxiliary contact) for maintained operation.
• Provides 'low-voltage release' (undervoltage protection).
• Safer for many industrial applications.

Memory trick: Three wires are for safety's sake, preventing the motor's unexpected wake.

NEC Table 430.72(A) specifies minimum conductor sizes for motor control circuits based on the OCPD rating and circuit voltage. For 120V circuits with 15A protection, 16 AWG is typically the minimum when conductors do not extend beyond the control enclosure.

• Minimum conductor size depends on OCPD rating and voltage.
• Table 430.72(A) provides specific requirements.
• Smaller gauges (e.g., 18 AWG, 16 AWG) are allowed for control circuits.
• Scope of conductor routing (within/beyond enclosure) impacts sizing.

Memory trick: Fifteen amps, inside the box, sixteen gauge unlocks.

NEC requirement for protecting cables from nails or screws when routed through bored holes in wood framing members.

• Prevents damage to conductors from fasteners.
• Requires specific spacing or steel plate protection.
• Applies to studs, joists, rafters, and similar wood members.

Memory trick: Wood Wires Need Wide Clearance.

NEC requirement for sizing junction boxes used for straight pulls based on the largest raceway trade size.

• Ensures adequate space for pulling conductors without damage.
• Applies to raceways 1/2 inch trade size and larger.
• Rule is 8 times the trade size of the largest raceway.

Memory trick: Eight Times the Raceway, Straight and True.

The NEC requirement for the maximum spacing between supports for Type MC cable in general wiring applications.

• Prevents sagging and mechanical stress.
• Ensures cable integrity over its length.
• Specific distances are outlined in NEC Article 330.

Memory trick: MC Runs Six Feet Smoothly.

A Variable Frequency Drive (VFD) is an electronic device that controls the speed and torque of an AC motor by varying the motor's input frequency and voltage, offering precise control over acceleration, deceleration, and running speed.

• Provides continuous speed variation.
• Offers controlled acceleration and deceleration ramps.
• Improves energy efficiency in variable-torque loads.
• Reduces mechanical stress on the motor and driven equipment.

Memory trick: For 'Fine-Tune' and 'Flexibility', the VFD is the key.

A condition where a three-phase motor loses power to one of its phases, causing it to hum, fail to start or run weakly, and draw excessive current in the remaining phases, leading to rapid overload tripping.

• Motor operates on only two phases.
• Causes unbalanced currents.
• Leads to overheating of windings.
• Overloads trip quickly to prevent damage.

Memory trick: A hum and no start, means a phase is apart.

Specific wiring methods permitted by the NEC for locations where combustible dust is normally present or present in ignitable quantities.

• Focus on preventing dust ingress and containing internal explosions.
• Requires robust, sealed wiring methods.
• NEC Article 502 governs these requirements.

Memory trick: Dusty Zones Demand Durable Ducts.

Motor controllers, if rated in amperes, must have a continuous current rating not less than 115% of the motor's full-load current rating.

• Applies to controllers rated in amperes, not horsepower.
• Minimum rating is 115% of motor FLA.
• Ensures controller can safely handle continuous motor operation.

Memory trick: Controller's current needs a little extra 'oomph' beyond the motor's pull.

The process of determining the minimum size of the grounding electrode conductor (GEC) based on the size of the ungrounded service conductors as per NEC Table 250.66.

• GEC connects the electrical system to the grounding electrode.
• Sizing depends on the largest ungrounded service conductor or equivalent area for parallel conductors.
• NEC Table 250.66 is the primary reference for GEC sizing.

Memory trick: Grounding Every Circuit Safely.

According to NEC 430.72(C)(1), if a control transformer's secondary is not separately protected, its primary overcurrent protective device must be rated or set at not more than 250% of the transformer's rated primary current.

• Applies when no secondary OCPD is present.
• Maximum primary OCPD is 250% of primary current.
• Primary current is typically very low for control transformers.
• Ensures protection of the transformer itself.

Memory trick: No secondary watch, primary gets a 'two-and-a-half' stretch.

The minimum radius allowed for a bend in Rigid Metal Conduit (RMC) when made in the field, as specified by NEC Table 2.

• Prevents damage to conductors during pulling.
• Sized as a multiple of the conduit's trade size.
• Differs based on conductor type and bending method (e.g., one-shot bender).

Memory trick: Bending Rules Reduce Wire Woes.

The fire resistance rating required for materials or assemblies used to seal penetrations through fire-rated walls, floors, or ceilings.

• Must match or exceed the fire rating of the penetrated assembly.
• Prevents spread of fire and smoke.
• NEC 300.21 addresses this general requirement.

Memory trick: Match the Wall's Hour, or More Power.

The determination of the minimum size for an equipment grounding conductor for a feeder circuit, based on the rating of the overcurrent protective device.

• Sized by the feeder's overcurrent protection.
• Ensures adequate fault current path.
• Found in NEC Table 250.122.

Memory trick: Overcurrent protection dictates the EGC's strong connection.

The specific minimum size for a grounding electrode conductor when connected to a ground rod, irrespective of the service entrance conductor size.

• Overrides standard GEC sizing tables.
• Applies specifically to ground rod, pipe, or plate electrodes.
• Ensures adequate fault current path to the electrode.

Memory trick: Six gauge copper, for the ground rod's cover.

NEC 430.52(C)(1) Exception No. 1 allows the maximum setting for an inverse-time circuit breaker protecting a motor branch circuit to be increased up to 400% of the motor's FLC if the standard setting (250%) is insufficient for motor starting.

• Standard maximum for inverse-time CB is 250% FLC.
• Can be increased if motor starting current trips the standard setting.
• Absolute maximum increase for inverse-time CB is 400% FLC.
• Higher multipliers exist for other protection types (e.g., fuses).

Memory trick: When the motor 'shocks' the breaker, you can give it a 'fourth' chance.

The NEC-mandated maximum distance from a box or fitting where Type MC cable must be secured.

• Prevents strain on connections.
• Ensures cable stability.
• Applies to all terminations of MC cable.

Memory trick: Twelve inches close, to keep MC cable composed.

An electronic switching device that uses semiconductor components (e.g., SCRs, MOSFETs) to switch power to a motor, offering advantages over mechanical contactors in terms of lifespan, noise, and maintenance.

• No moving parts, eliminating mechanical wear.
• Faster switching speeds.
• Longer operational life, especially with frequent switching.
• Generates less electrical noise (arcing).

Memory trick: For a 'silent switch' and 'long life', solid-state is right.

For continuous-duty motors, thermal overload devices are sized based on the motor's nameplate full-load current (FLA) and its service factor (SF) or temperature rise. Motors with SF ≥ 1.15 or 40°C rise use 125% FLA, others use 115% FLA.

• SF ≥ 1.15 or 40°C rise: Max 125% of FLA.
• SF < 1.15 or > 40°C rise: Max 115% of FLA.
• Protects against sustained overcurrents.
• Based on motor nameplate FLA, not NEC table FLC.

Memory trick: Service Factor 1.15 or more, add a quarter; less than that, add fifteen.

Specific wiring methods required in locations where combustible dust is present under normal operating conditions.

• Focus on preventing dust ingress.
• Requires robust, dusttight enclosures and raceways.
• Examples include RMC, IMC, dusttight wireways.

Memory trick: Dusty DIV 1 demands rigid, sealed conduits.

The reduction in a conductor's allowable ampacity when the number of current-carrying conductors in a raceway, cable, or bundle exceeds a specified limit.

• Caused by heat buildup from adjacent conductors.
• Governed by NEC Table 310.15(C)(1) (formerly Table 310.15(B)(3)(a)).
• Applies when more than three current-carrying conductors are present.

Memory trick: Three is Free, More is Less.

The NEC requirement for determining the minimum size of the equipment grounding conductor for a branch circuit, based on the rating of its overcurrent protective device.

• Prevents dangerous voltage on non-current-carrying metal parts.
• Sized according to NEC Table 250.122.
• Must be capable of safely carrying fault current during a ground fault.

Memory trick: Overcurrent Protects, Grounding Connects.

The maximum continuous temperature that an electrical conductor's insulation can withstand without degradation, as specified by the NEC and manufacturer.

• Affects conductor ampacity (higher rating = higher ampacity).
• Termination temperature ratings often limit the effective ampacity of conductors (NEC 110.14(C)).
• Common ratings are 60°C, 75°C, and 90°C.

Memory trick: Cool Wires Prevent Overheat.

The motor disconnecting means must be located within sight of the controller. Additionally, a separate disconnecting means must be within sight of the motor and its driven machinery, or the controller's disconnect must be capable of being locked in the open position.

• Disconnect must be in sight of the controller (430.102(A)).
• Disconnect must be in sight of the motor and driven machinery (430.102(B)).
• Exception: Out of sight of motor is permitted if disconnect is lockable open (430.102(B) Ex.).
• Ensures personnel safety during maintenance.

Memory trick: See the control, or see the motor with a lock.

NEC 430.32(A)(1) specifies the maximum allowable setting for a separate thermal overload relay based on the motor's full-load current (FLA) and its service factor or temperature rise rating.

• For motors with a service factor of 1.15 or greater, or a temperature rise not over 40°C, the overload device must be sized at not more than 125% of the motor's FLA.
• For all other motors, the overload device must be sized at not more than 115% of the motor's FLA.
• These percentages can be increased if the motor trips, up to a maximum of 140% (for 125% initial setting) or 130% (for 115% initial setting).

Memory trick: Overload Safety: Service Factor Sets the Limit!

Conductors connecting the output of a variable frequency drive (VFD) to a motor must have an ampacity not less than 125% of the motor's full-load current rating.

• Applies to conductors between VFD and motor.
• Minimum ampacity is 125% of motor FLA.
• Different from VFD input conductor sizing.
• Accounts for potential harmonic distortion and motor heating.

Memory trick: VFD's output needs a 'quarter-extra' current capacity.

The maximum continuous current a branch circuit can safely carry, which is limited to 80% of the overcurrent protective device rating, unless the OCPD and its assembly are specifically listed for 100% continuous operation.

• A load is considered continuous if it operates for 3 hours or more.
• Protects conductors and overcurrent devices from excessive heat buildup.
• NEC 210.20(A) and 215.2(A)(1) are the governing sections.

Memory trick: 80 percent rule: For loads that stay, 16 amps lead the way!

Percentages applied to the total connected load of fixed electric cooking appliances to determine the demand load for service and feeder calculations, as per NEC Table 220.55.

• Used to avoid oversizing electrical systems due to diversity of use.
• Factors vary based on the number of appliances and their individual ratings.
• NEC Table 220.55 provides the specific demand factors.

Memory trick: Table 220.55: Cook up your demand, don't over-plan!

Determining the minimum allowable conductor size and corresponding overcurrent protection for Class 1 control circuits, which are typically used for motor control or other similar applications, as per NEC Article 725.

• Class 1 circuits have power limitations and voltage limitations.
• Ampacity and overcurrent protection are specified in NEC 725.43(A).
• Smaller conductors (No. 18, 16 AWG) have specific OCPD limits.

Memory trick: Control circuits, Class One, 18 gauge, 7 amp run!

Determining the maximum inverse-time circuit breaker rating for motor branch-circuit short-circuit and ground-fault protection based on the motor's full-load current (FLA) and NEC rules.

• NEC Table 430.52 provides multiplier percentages.
• Inverse-time circuit breakers have a maximum of 250% of FLA.
• NEC 240.6(A) lists standard overcurrent device ratings.
• Exception allows using the next higher standard size if calculated value isn't standard.

Memory trick: Motor protection is a two-step dance: calculate, then find the standard size.

Sizing the overcurrent protective device for the primary side of a transformer rated 600 volts or less, based on its full-load primary current and NEC 450.3(B).

• Primary protection only: generally 125% of primary FLA.
• Next higher standard size permitted if calculated value isn't standard.
• NEC Table 450.3(B) details rules for primary and secondary protection combinations.

Memory trick: Primary protection: calculate 125%, then find the next standard size, it's a primary prize!

For motor control circuits protected by an overcurrent device, the minimum conductor size is determined by the OCPD rating, with specific allowances for smaller conductors when confined within a motor starter enclosure.

• NEC 430.72(B) and Table 430.72(B) govern sizing.
• Smaller conductors (18, 16 AWG) are allowed for lower OCPD ratings.
• 14 AWG is the minimum for a 15A OCPD within an enclosure.
• Conductors extending beyond the enclosure often require larger sizes.

Memory trick: Control Wires: Smallest gauge depends on fuse and where it goes.

The minimum number of general-purpose branch circuits for a dwelling unit is determined by dividing the total general lighting and receptacle load (in VA) by the VA rating of each individual circuit, then rounding up to the next whole number.

• General lighting/receptacles are calculated at 3 VA per square foot or given total VA.
• Circuit VA = Amperes * Volts.
• Always round up to the next whole number of circuits.

Memory trick: Divide total VA by circuit VA, then always round up for safety.

The NEC specifies minimum cover depths for underground wiring methods to protect conductors from physical damage, with rigid metal conduit (RMC) often having reduced requirements due to its inherent strength.

• NEC Table 300.5 dictates cover depths.
• Depth varies by wiring method (RMC, PVC, direct burial).
• Depth varies by location (under buildings, under roads, general).
• RMC and IMC often have shallower depth requirements.

Memory trick: Conduit type, voltage, and traffic tell the burial depth story.

For continuous-duty motors with a service factor of 1.15 or greater, separate overload protection devices must be set at no more than 125% of the motor's full-load current (FLA) as marked on the nameplate.

• Applies to continuous-duty motors.
• Service factor must be 1.15 or greater.
• Maximum setting is 125% of FLA.
• Ensures motor protection without nuisance tripping.

Memory trick: Overload's Factor: If SF is high, multiply by 1.25 to stay safe.

NEC 110.26(A) mandates minimum clear working space around electrical equipment to ensure safe operation and maintenance, based on voltage to ground and the condition of the opposing wall.

• Working space depth depends on voltage to ground.
• Three conditions (1, 2, 3) define the opposing wall.
• NEC Table 110.26(A)(1) provides specific dimensions.

Memory trick: Voltage to ground and the opposite wall's condition tell you the clear space.

For household electric ranges, the demand load is determined by NEC Table 220.55, which provides a demand factor based on the nameplate rating and number of ranges, then converted to amperes.

• NEC Table 220.55 is specifically for household electric cooking appliances.
• For ranges 12 kW or less, Column C is typically used for a single range.
• Demand load is converted to amperes using I = P/V.

Memory trick: Ranges need a table to shrink their power, then convert to amps.

Overcurrent protective devices for feeders supplying continuous loads must be sized at 125% of the continuous load plus 100% of the noncontinuous load, then rounded up to the next standard OCPD size if necessary.

• Continuous loads are multiplied by 125%.
• Noncontinuous loads are multiplied by 100%.
• Feeder OCPD must be sized to protect the conductors.
• NEC 215.3 and 240.6(A) apply.

Memory trick: Continuous loads need an extra boost, then pick the next standard fuse.

The minimum size of a grounding electrode conductor (GEC) for a concrete-encased electrode is determined by the size of the service entrance conductors or the overcurrent protection of the service, as per NEC Table 250.66.

• NEC Table 250.66 is used for sizing GECs.
• Concrete-encased electrodes typically require a larger GEC than ground rods.
• Aluminum conductors require a larger gauge than copper for the same ampacity.

Memory trick: Grounding Electrode Conductors need careful sizing for safety.

NEC 430.32(A)(1) specifies that for continuous-duty motors with a Service Factor (SF) of 1.15 or greater, the thermal overload protection device must be sized at not more than 125% of the motor's full-load current (FLA).

• Applies to continuous-duty motors.
• Applies when the motor's Service Factor (SF) is 1.15 or greater.
• Maximum setting is 125% of the motor's nameplate Full-Load Amps (FLA).

Memory trick: Service Factor 1.15 or more, add a quarter more!