Exam Cheat Sheet · Quick Reference
ICC R18 Residential Electrician Exam (2023 NEC)
National · Pearson Vue
Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
60
Passing score
70%
Exam time
180 min
Administered by
Pearson Vue
Format
Reference materials allowed
National State Portion 60 questions
General Knowledge
7 Q · 12%
Electrical Theory and General Electrical Load CalculationsCode Definitions and TermsNEC Purpose, Scope, and Code ArrangementSeries, Parallel, and Combination Circuit AnalysisAC Circuit Properties: Impedance, Reactance, Inductance, and CapacitancePower Factor, Apparent Power (kVA), and Power Factor CorrectionDwelling Unit Load Calculations (Lighting, Small-Appliance, Laundry, Cooking, and Dryer Loads)Feeder and Service Load Calculations with Demand FactorsElectrical Symbols and Wiring DiagramsUnits of Measurement, Metric System, and Electrical Conversions
Services and Service Equipment
13 Q · 22%
Service Load CalculationsService Equipment & Service ConductorsSystem Grounding and BondingService Disconnect Requirements and RatingsOvercurrent Protection for ServicesGrounding Electrode System and Electrode TypesSurge Protection Requirements for ServicesService Conductor Installation Methods and ClearancesDemand Factors for Dwelling and Non-Dwelling Loads
Feeders
8 Q · 13%
Load CalculationsEquipment GroundingFeeder conductor ampacity and minimum sizing (NEC 215.2)Overcurrent protection for feeders (NEC 215.3)Feeder disconnecting means for separate buildings and structures (NEC 225.31–225.39)Neutral conductor sizing for feeders (NEC 215.2(B), 220.61)Common neutral conductors and parallel feeder installations (NEC 215.4)Surge-protective device requirements for feeders supplying dwelling units (NEC 215.18, 225.42)Conductor identification for feeders — grounded, ungrounded, and EGC (NEC 215.12)Outside feeder conductor clearances and installation requirements (NEC 225.18–225.19)
Branch Circuits and Conductors
15 Q · 25%
Branch Circuit CalculationsRequired Outlets & GFCI/AFCI ProtectionOvercurrent ProtectionEquipment GroundingConductorsVoltage Drop Calculations and Conductor SizingConductor Ampacity Tables and Temperature RatingsAmpacity Correction and Adjustment FactorsConductor Insulation Types and ApplicationsGrounded Conductor Identification and UseMultiwire Branch Circuit RequirementsBranch Circuit Voltage Limitations and Ratings
+1 more
Wiring Methods and Materials
8 Q · 13%
Raceway InstallationsBoxes and EnclosuresFlexible Cords and CablesCable Wiring Methods (NM, MC, SE, USE, UF) — Uses Permitted and ProhibitedProtection of Cables and Raceways Against Physical DamageConductor Fill and Conduit Sizing CalculationsUnderground Installation Requirements and Minimum Cover DepthsConduit Bending Techniques and CalculationsSecuring and Supporting Requirements for Cables and RacewaysCorrosion Protection for Raceways and EnclosuresWiring in Ducts, Plenums, and Special Locations
Equipment and Devices
5 Q · 8%
LuminairesReceptacles, Switches and Other DevicesAppliances and Other EquipmentLuminaire location requirements (wet, damp, closets, bathtub/shower zones)Recessed luminaire installation (Type IC, clearances, thermal protection)Lighting track installation and construction requirementsLow-voltage lighting system requirements and voltage limitationsSwitch ratings, types, and connection requirementsReceptacle installation requirements (grounding, tamper-resistant, weather-resistant, GFCI)NEMA receptacle configurations and attachment plug wiring diagramsAppliance disconnecting means and GFCI protection requirements
Special Occupancies, Equipment, and Conditions
4 Q · 7%
Swimming Pools and Similar InstallationsLow Voltage Circuits, Alarm & Similar SystemsFire Alarm Circuit Types: Power-Limited (PLFA) vs. Non-Power-Limited (NPLFA)Fire Alarm Circuit Power Source Requirements and Branch Circuit ProtectionSeparation and Mixing Rules for Fire Alarm Conductors and Other Circuit TypesFire Alarm Cable Types, Listings, and Application Requirements (FPLP, FPLR, FPL, NPLFP, etc.)Class 2 and Class 3 Power-Limited Circuit Wiring Methods and Power Source RequirementsCommunications System Grounding, Bonding, and Primary Protector RequirementsCable Installation Methods by Location: Plenums, Risers, and General-Purpose Spaces
Key Distinctions
Direct-buried cable minimum cover (Table 300.5(A), all locations not specified)vsRigid metal conduit / intermediate metal conduit minimum cover (all locations not specified)
In locations not otherwise specified in Table 300.5(A), direct-buried cables or conductors require 600 mm (24 in.) of cover while RMC or IMC requires only 150 mm (6 in.).
NEC 2023 Table 300.5(A)One- and two-family dwelling driveway / outdoor parking area used only for dwelling-related purposesvsGeneral streets, highways, roads, alleys, driveways and parking lots
Under a dwelling driveway the minimum cover is 450 mm (18 in.) for both direct-burial cable and rigid metal conduit, while under general streets, highways, roads, alleys, driveways and parking lots the requirement is 600 mm (24 in.) for all wiring methods.
NEC 2023 Table 300.5(A)Series circuit currentvsParallel circuit current
In a series circuit the total current equals the current in any other part of the circuit (IT = I1 = I2 = I3), whereas in a parallel circuit the total current equals the sum of the individual branch currents.
Ugly's Electrical References, 2023 ed., Series Circuits, Page 3 (2020 ed.: Series Circuits)Straight pulls in pull boxes (conductors 4 AWG or larger)vsAngle or U pulls (and splices) in pull boxes (conductors 4 AWG or larger)
For straight pulls the box length shall not be less than eight times the trade size of the largest raceway, while for angle or U pulls the distance from each raceway entry to the opposite wall shall not be less than six times the trade size of the largest raceway in a row.
NEC 2023 Section 314.28(A)(1)14 AWG box-fill volume allowancevs12 AWG box-fill volume allowance
Each 14 AWG conductor requires 32.8 cm³ (2.00 in.³) while each 12 AWG conductor requires 36.9 cm³ (2.25 in.³) per Table 314.16(B)(1).
NEC 2023 Table 314.16(B)(1)Grounded (neutral) conductor color, 120/240-volt single-phase three-wire systemvsUngrounded conductor colors, 120/240-volt single-phase three-wire system
The grounded neutral is white or gray (per NEC 200.6(A)), while the two ungrounded conductors are black (line one) and red (line two).
Ugly's Electrical References, 2023 ed., Common Electrical Distribution Systems, Page 13 (2020 ed.: Common Electrical Distribution Systems)Standard ampere ratings for fusesvsStandard ampere ratings for inverse time circuit breakers
Table 240.6(A) ratings apply to both, but 1, 3, 6 and 601 amperes are additional standard ratings for fuses only — 601 is not a standard inverse time circuit breaker rating.
NEC 2023 Section 240.6(A) and Table 240.6(A)Copper conductor K factor (12.9)vsAluminum conductor K factor (21.2)
Aluminum has roughly 1.6 times the resistance of copper, so its K value of 21.2 is used in voltage-drop calculations instead of copper's 12.9; using 12.9 for aluminum understates the drop.
Overhead service conductor minimum size — coppervsOverhead service conductor minimum size — aluminum or copper-clad aluminum
Overhead service conductors shall not be smaller than 8 AWG copper, or 6 AWG aluminum or copper-clad aluminum.
NEC 2023 Section 230.23(B)Continuous load in feeder/service conductor sizingvsNoncontinuous load in feeder/service conductor sizing
The continuous load is multiplied by 125 percent while the noncontinuous load is taken at 100 percent, and the two are added to obtain the minimum conductor ampacity.
NEC 2023 Section 215.2(A)(1)Switch symbol S₃vsSwitch symbols S₂, S₄ and Sₑ
On electrical plans S₃ designates a three-way switch, while S₂ is a double-pole switch, S₄ is a four-way switch and Sₑ is an electrolier switch.
Ugly's Electrical References 2020, Page 125Ampacity adjustment factors for conductor countvsAmbient temperature basis of Table 310.16
Adjustment factors of Table 310.15(C)(1) reduce ampacity for conductor count (4–6 = 80%, 7–9 = 70%, 10–20 = 50%), while Table 310.16 values themselves are based on a 30°C (86°F) ambient and require separate correction factors for other ambients.
NEC 2023 Table 310.15(C)(1)Key Terms
Authority Having Jurisdiction (AHJ) NEC 2023 Section 90.4(B)
Per NEC 90.4, the authority having jurisdiction for enforcement of the Code is responsible for making interpretations of the rules, deciding on approval of equipment and materials, and granting special permission contemplated in a number of the rules.
NEC scope exclusions (90.2) NEC 2023 Section 90.2(D)
The Code does not cover installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles.
Arrangement of the Code (90.3) NEC 2023 Section 90.3
The NEC is divided into an introduction and nine chapters: Chapters 1–4 apply generally, Chapters 5–7 apply to special conditions, Chapter 8 covers communications, and Chapter 9 consists of tables.
Service disconnecting means rating, one-family dwelling (230.79(C)) NEC 2023 Section 230.79(C)
For a one-family dwelling the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
Optional calculation for a dwelling unit (220.82(A)) NEC 2023 Section 220.82(A)
The optional calculation applies to a dwelling unit whose total connected load is served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 or greater.
Free conductor length at boxes (300.14) NEC 2023 Section 300.14
At least 150 mm (6 in.) of free conductor, measured from where it emerges from its raceway or cable sheath in the box, shall be left at each outlet, junction and switch point for splices or connection of luminaires or devices.
Stranded conductors in raceways (310.3(C)) NEC 2023 Section 310.3(C)
Where installed in raceways, conductors 8 AWG and larger shall be stranded unless specifically permitted or required elsewhere in the Code to be solid.
Parallel conductors (310.10(G)(1)) NEC 2023 Section 310.10(G)(1)
Aluminum, copper-clad aluminum, or copper circuit conductors for each ungrounded, grounded or neutral conductor are permitted to be connected in parallel only in sizes 1/0 AWG and larger.
Main bonding jumper / system bonding jumper that is a screw only (250.28(B)) NEC 2023 Section 250.28(B)
If a main bonding jumper or system bonding jumper is a screw only, the screw shall be identified with a green finish that is visible with the screw installed.
Vegetation as support (230.10 and 225.26) NEC 2023 Section 230.10
Vegetation such as trees shall not be used for support of overhead service conductors or service equipment (230.10), nor for support of overhead conductor spans for outside branch circuits and feeders (225.26) — an absolute prohibition.
THHN insulation designation Conductor insulation type letters (THHN)
T = thermoplastic insulation, HH = high heat resistance (90°C dry) and N = a nylon outer jacket adding abrasion and gasoline/oil resistance; Type THHN has a maximum operating temperature of 90°C (194°F) in dry and damp locations.
Device (yoke or strap) box fill allowance (314.16(B)(4)) NEC 2023 Section 314.16(B)(4)
Each yoke or strap containing one or more devices or equipment requires a double volume allowance from Table 314.16(B)(1) based on the largest conductor connected to a device or equipment supported by that yoke or strap.
Field-installed drainage openings in damp or wet locations (314.15) NEC 2023 Section 314.15
Approved drainage openings not smaller than 3 mm (1/8 in.) and not larger than 6 mm (1/4 in.) in diameter are permitted to be installed in the field in boxes or conduit bodies listed for use in damp or wet locations.
Raceway-supported enclosure (314.23(E)) NEC 2023 Section 314.23(E)
An enclosure that contains no device other than splicing devices and supports no luminaire, lampholder or other equipment, and is supported by entering raceways, shall not exceed 1650 cm³ (100 in.³) in size.
Nonmetallic-sheathed cable sheath entry into a box (314.17(B)(2)) NEC 2023 Section 314.17(B)(2)
Where cable assemblies with nonmetallic sheaths are used, the sheath shall extend not less than 6 mm (1/4 in.) inside the box and 6 mm (1/4 in.) beyond the end of any cable clamp.
Supplemental grounding electrode spacing (250.53(A)(3)) NEC 2023 Section 250.53(A)(3)
Where multiple rod, pipe or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.
Dwelling hallway lighting outlet (210.70(A)(2)) NEC 2023 Section 210.70(A)(2)
At least one lighting outlet controlled by a listed wall-mounted control device shall be installed in hallways of dwelling units; separately, 210.52(H) requires at least one receptacle outlet in hallways 10 ft or more in length.
Protection of cables/raceways through wood members (300.4(A)(1), (A)(2), (D)) NEC 2023 Section 300.4(A)(1)
Bored holes shall have their edge not less than 32 mm (1 1/4 in.) from the edge of the wood member; cables/raceways run parallel to framing members where nails or screws are likely to penetrate shall keep the nearest outside surface at least 32 mm (1 1/4 in.) from the edge; and where that distance cannot be maintained (or where laid in notches) a steel plate at least 1.6 mm (1/16 in.) thick, of appropriate length and width, shall protect against nail or screw penetration.
kVA Metric prefixes (kilo = 1,000)
Kilo means 1,000, so 1 kVA equals 1,000 volt-amperes; transformer and service capacities are commonly rated in kVA.
DPDT Ugly's Electrical References 2020, Page 126
On electrical drawings DPDT means Double Pole Double Throw — a switching contact controlling two separate circuits, each with two positions.
Formulas to Know
Current from watts and volts (Ohm's Law)
Amperes = Watts ÷ Volts; e.g., 1500 W ÷ 120 V = 12.5 AResistance and voltage (Ohm's Law)
Ohms = Volts ÷ Amperes (e.g., 240 V ÷ 8 A = 30 Ω) and E = I × R (e.g., 10 A × 12 Ω = 120 V); for a 1200 W, 120 V appliance: I = P/E = 10 A, then R = E/I = 12 Ω (or R = E²/P = 14,400/1200 = 12 Ω)Power (Ohm's Law power formulas)
P = E × I (volts × amperes = watts); when volts and ohms are known, P = E² ÷ R, e.g., 240² ÷ 20 = 2,880 WMinimum feeder / service-entrance conductor ampacity with continuous loads
Minimum ampacity = noncontinuous load + (125% × continuous load); e.g., 100 A continuous + 30 A noncontinuous = (100 × 1.25) + 30 = 155 A; 60 A continuous + 40 A noncontinuous = 40 + 75 = 115 A (overcurrent device/assembly not listed for 100% rating)Single-phase voltage drop
VD = (2 × K × I × L) ÷ CM, where the 2 accounts for the out-and-back length of both conductors; copper K = 12.9, aluminum K = 21.2. Example (copper): (2 × 12.9 × 16 A × 60 ft) ÷ 6,530 cmil = 3.79 V (≈3.2% of 120 V). Example (aluminum): (2 × 21.2 × 30 A × 100 ft) ÷ 26,240 cmil = 4.85 VVoltage drop solved for maximum length or minimum conductor size
Allowable VD = system volts × percent limit; L = (VD × CM) ÷ (2 × K × I) — e.g., (7.2 V × 16,510) ÷ (2 × 12.9 × 40) = 115 ft one-way; CM = (2 × K × I × L) ÷ VD — e.g., (2 × 12.9 × 20 × 80) ÷ 3.6 V = 11,466 cmil, so 8 AWG (16,510 cmil) is the smallest size that qualifiesPull box dimensions for conductors 4 AWG or larger
Straight pulls: box length ≥ 8 × trade size of largest raceway (3 in. raceway → 8 × 3 = 24 in. / 610 mm). Angle or U pulls and splices: distance from each raceway entry to the opposite wall ≥ 6 × trade size of the largest raceway in a rowSeries-parallel DC circuit analysis
Equal parallel branches: Rp = R ÷ (number of branches); unequal two branches: Rp = (R1 × R2) ÷ (R1 + R2); series-connected parts add; RT = R_series + Rp; IT = E ÷ RT; branch voltage = IT × Rp; branch current = branch voltage ÷ branch R. Parallel circuit total current also equals the sum of branch currents (120 V across 10 Ω, 20 Ω, 20 Ω = 12 + 6 + 6 = 24 A)Dwelling general lighting plus small appliance and laundry load (Article 220, before demand factors)
Total VA = (sq ft × 3 VA/sq ft) + (1,500 VA × number of small appliance circuits) + (1,500 VA × number of laundry circuits). Examples: 2,000 sq ft + 2 small appliance + 1 laundry = 6,000 + 3,000 + 1,500 = 10,500 VA; 1,800 sq ft + 3 small appliance + 2 laundry = 5,400 + 4,500 + 3,000 = 12,900 VA; 2,500 sq ft + 3 small appliance + 1 laundry = 7,500 + 4,500 + 1,500 = 13,500 VA; four multifamily units of 1,200 sq ft + 2 small appliance + 1 laundry = 8,100 VA each × 4 = 32,400 VATotal ampacity of parallel conductor sets and elevator feeder demand
Parallel sets: total ampacity = per-set ampacity × number of sets, e.g., 350 kcmil THHN copper at 90°C = 350 A, two sets = 700 A. Elevator feeder (Table 620.14, based on 50% duty cycle): multiply by demand factor — 1 = 1.00, 2 = 0.95, 3 = 0.90, 4 = 0.85, 5 = 0.82, 6 = 0.79, 7 = 0.77, 8 = 0.75, 9 = 0.73, 10 or more = 0.72