Exam Cheat Sheet · Quick Reference
Idaho Limited Electrical Sign Installer
Idaho · PSI Services Contractor
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
40
Passing score
70%
Exam time
120 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Idaho State Portion 40 questions
2017 National Electrical Code, NFPA – Introduction
3 Q · 8%
Purpose and scope of the NEC (practical safeguarding of persons and property)Installations covered and not covered under NEC scope (90.2)Code arrangement and chapter organization (90.3)Mandatory vs. permissive rules and explanatory material (90.5)Authority having jurisdiction (AHJ) enforcement and special permission (90.4)Equipment examination, listing, and approval for safety (90.7)Wiring planning for future expansion and circuit limitations (90.8)Units of measurement and dual SI/inch-pound system (90.9)
2017 National Electrical Code, NFPA – Chapter 1
5 Q · 12%
Key NEC definitions applicable to electrical sign installations (Article 100)Equipment approval, listing, and labeling requirementsElectrical connections, splices, and terminal temperature limitationsWorking space and clearance requirements around electrical equipmentGuarding of live parts and enclosure type selectionEquipment marking requirements including arc-flash hazard warningsMechanical execution of work and equipment mounting standardsConductor materials, sizes, and wiring integrity requirementsArticle 100 - DefinitionsArticle 110 - Requirements for Electrical Installations
2017 National Electrical Code, NFPA – Chapter 2
11 Q · 28%
Grounding and bonding requirements (Article 250) — system grounding, grounding electrode systems, and equipment grounding conductorsBranch circuit requirements — ratings, conductor sizing, GFCI and AFCI protection, and required outlets (Article 210)Overcurrent protection — fuses, circuit breakers, standard ratings, and location requirements (Article 240)Branch-circuit, feeder, and service load calculations — lighting loads, demand factors, and dwelling unit optional calculations (Article 220)Outside branch circuits and feeders — conductor clearances, disconnecting means, and wiring methods for exterior installations (Article 225)Identification and use of grounded conductors — color coding, terminal identification, and polarity requirements (Article 200)Bonding methods for services, piping systems, and structural metal (Article 250, Part V)Grounding electrode types, installation, and conductor sizing (Article 250, Parts III and IV)Article 250 - Grounding and Bonding
2017 National Electrical Code, NFPA – Chapter 3
5 Q · 12%
General wiring installation requirements (Article 300)Conductor ampacity tables and temperature correction/adjustment factors (Article 310)Conductor types, insulation designations, and permitted uses by locationConductors in parallel — requirements and restrictionsOutlet, device, pull, and junction box sizing and fill calculations (Article 314)Cabinets, cutout boxes, and wire-bending space requirements (Article 312)Conduit types — uses permitted, securing, supporting, and bending requirements (EMT, RMC, IMC, FMC, LFMC, PVC, LFNC)Cable assembly types — uses permitted and installation requirements (NM, MC, SE, USE, UF)Article 310 - Conductors for General Wiring
2017 National Electrical Code, NFPA – Chapter 6
16 Q · 40%
Branch circuit requirements for electric signs and outline lighting systemsDisconnecting means location and lockout requirements for signsGrounding and bonding of sign equipment and metal partsListing, marking, and labeling requirements for signs and retrofit kitsEnclosure construction requirements for signs and outline lightingNeon secondary-circuit wiring over 1000 volts (GTO cable, conduit, spacing, and length limits)Ballasts, transformers, electronic power supplies, and Class 2 power source installation requirementsElectrode connections and neon tubing support requirements
Key Distinctions
Festoon lightingvsOutline lighting
Festoon lighting is a string of outdoor lights suspended between two points, while outline lighting is an arrangement of light sources used to outline or call attention to features such as the shape of a building.
NEC 2017 Article 100 (Definitions: Festoon Lighting; Outline Lighting)Main bonding jumpervsSystem bonding jumper
The main bonding jumper is the connection between the grounded circuit conductor and the equipment grounding conductor at the service; the system bonding jumper serves a similar function at a separately derived system.
NEC 2017 Article 100 (Definition: Bonding Jumper, Main)Insulated conductorvsCovered conductor
An insulated conductor is encased within material of composition and thickness recognized by the Code as electrical insulation, while a covered conductor is encased in material not recognized as electrical insulation.
NEC 2017 Article 100 (Conductor, Insulated)Type MI cable, switchboard wires, metal-covered single-conductor cables, Type AC cable (marking)vsNonmetallic-sheathed, service-entrance and tray cables (marking)
The first group is marked by a printed tag attached to the coil, reel, or carton per 310.120(B)(3), while the second group is durably surface marked under 310.120(B)(1).
NEC 2017 Section 310.120(B)(3)240.4(B) next higher standard OCPD ratingvs240.4(C) devices rated over 800 amperes
240.4(B) permits the next higher standard rating above conductor ampacity only where that selected rating does not exceed 800 amperes; where the overcurrent device is rated over 800 amperes, 240.4(C) requires the conductor ampacity to be equal to or greater than the device rating.
NEC 2017 Section 240.4(B)Supplementary overcurrent protectionvsBranch-circuit overcurrent device
Per 240.10, supplementary overcurrent protection shall not be used as a substitute for required branch-circuit overcurrent devices or in place of required branch-circuit protection.
NEC 2017 Section 240.10Transformer secondaries protected by the primary OCPDvsTransformer secondaries not protected by the primary OCPD
Per 240.4(F), 2-wire single-phase and delta-delta 3-wire secondary conductors are permitted to be protected by the primary-side device, but single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) secondary conductors shall not be considered protected by the primary device.
NEC 2017 Section 240.4(F)Lay-in ceiling access opening (110.26(A)(4)(a))vsCrawl space access opening
Equipment 1000 volts or less installed above a lay-in ceiling requires an opening not smaller than 22 in. × 22 in., whereas the 22 in. × 30 in. dimension applies to a crawl space access opening.
NEC 2017 Section 110.26(A)(4)(a)NEC Chapters 1, 2, 3 and 4vsNEC Chapters 5, 6, 7 and Chapter 8
Chapters 1 through 4 apply generally to all electrical installations; Chapters 5, 6 and 7 cover special occupancies, special equipment or other special conditions and may supplement or modify Chapters 1 through 7, and Chapter 8 (communications systems) is independent except where specifically referenced.
NEC 2017 Section 90.3Informational notes / explanatory materialvsEnforceable Code requirements
Per 90.5(C), explanatory material such as informational notes is included for informational purposes only and is not enforceable as a requirement of the Code.
NEC 2017 Section 90.5(C)Standard ampere ratings of fuses and inverse time circuit breakers (Table 240.6(A))vsRecognized branch-circuit ratings for other than individual branch circuits (210.18)
Table 240.6(A) lists standard device ratings such as 45, 70 and 110 amperes (85 amperes is not listed), while 210.18 recognizes only 15, 20, 30, 40 and 50 amperes as ratings for other than individual branch circuits — so 25- and 60-ampere standard devices are not recognized branch-circuit ratings.
NEC 2017 Table 240.6(A)Retail/store general lighting unit loadvsDwelling unit general lighting unit load
The unit load for a retail occupancy is 1.9 VA per square foot in NEC 2020 Table 220.12 / 2023 Table 220.42(A) / 2026 Table 120.42(A) (3 VA per square foot was the NEC 2017 unit load for stores), while Table 220.12 specifies 3 volt-amperes per square foot for dwelling units.
NEC 2020 Table 220.12 (2020), Table 220.42(A) (2023), Table 120.42(A) (2026); 220.14(I) (120.14(I) in 2026); NEC 2026 Table 120.42(A); NEC 2023 Table 220.42(A) and 220.14(I)Outline lighting assembled from listed luminairesvsOutline lighting listed as a system
Per 600.3(B), outline lighting is not required to be listed as a system where it consists of listed luminaires wired in accordance with Chapter 3 wiring methods.
NEC 2017 Section 600.3(B)Key Terms
Ampacity (Article 100) NEC 2017
The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
Continuous Load (Article 100) NEC 2017 Article 100
A load where the maximum current is expected to continue for 3 hours or more.
Authority Having Jurisdiction (AHJ) NEC 2017 Article 100 (Definitions)
An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure; per 90.4 the AHJ makes interpretations of the rules, decides on approval of equipment and materials, and grants special permission.
Effective ground-fault current path NEC 2017 Section 250.4(A)(5)
A low-impedance circuit capable of safely carrying maximum ground-fault current to the supply source to facilitate operation of the overcurrent device; per 250.4(A)(5) the earth shall not be considered an effective ground-fault current path, and per 250.4(A)(3) bonding normally non-current-carrying conductive materials together and to the supply source establishes this path.
Trade size designators (90.9(C)(1)) NEC 2017 Section 90.9(C)(1)
Designators used in place of dimensions where the actual measured size of a product is not the same as the nominal size — one of the four cases permitted to use soft conversion — with trade practices followed in all cases.
Equipment bonding jumper installed outside a raceway (250.102(E)(2)) NEC 2017 Section 250.102(E)(2)
A bonding jumper routed with and on the outside of the raceway or enclosure, limited to 1.8 m (6 ft) in length, with an exception permitting longer jumpers at outside pole locations.
Working space at a sign ballast/transformer enclosure (600.21(D)) NEC 2017 Section 600.21(D)
A space at least 900 mm (3 ft) high × 900 mm (3 ft) wide × 900 mm (3 ft) deep required at each ballast, transformer, electronic power supply and Class 2 power source, or at its enclosure where not installed in a sign.
Sign bonding conductors (600.7(B)(7)(1)) NEC 2017 Section 600.7(B)(7)(1)
Bonding conductors for electric signs shall be copper and not smaller than 14 AWG.
Attic/soffit installation of sign power supplies (600.21(E)) NEC 2017 Section 600.21(E)
Ballasts, transformers, electronic power supplies and Class 2 power sources are permitted in attics and soffits where there is an access door at least 36 in. × 22 1/2 in., a passageway at least 3 ft high by 2 ft wide, and a permanent walkway at least 300 mm (12 in.) wide extending from the point of entry to each component.
Adjustable-trip circuit breaker rating (240.6(B)) NEC 2017
Where the breaker has external means for adjusting the long-time pickup current setting and does not meet 240.6(C) for restricted access, its rating is the maximum setting possible.
Ground-fault protection of equipment (240.13) NEC 2017 Section 240.13
Required for solidly grounded wye systems of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase, for each individual device used as a building or structure main disconnecting means rated 1000 amperes or more.
Coordination system under 240.12 NEC 2017 Section 240.12
Where an orderly shutdown is required to minimize hazards, a system of coordination based on (1) coordinated short-circuit protection and (2) overload indication based on monitoring systems or devices is permitted.
Thermal relays and similar devices (240.9) NEC 2017 Section 240.9
Devices not designed to open short circuits or ground faults shall not protect conductors against short-circuit or ground-fault overcurrent, but are permitted to protect motor branch-circuit conductors from overload where protected in accordance with 430.40.
Grounded conductor identification, 6 AWG or smaller (200.6(A)) NEC 2017 Section 200.6(A)
Identified by a continuous white outer finish, a continuous gray outer finish, or three continuous white or gray stripes along the conductor's entire length on other than green insulation.
Voltage considered (110.4) NEC 2017 Section 110.4
Throughout the Code the voltage considered shall be that at which the circuit operates, and the voltage rating of equipment shall not be less than the nominal voltage of the circuit to which it is connected.
Mechanical execution of work — unused openings (110.12(A)) NEC 2017 Section 110.12(A)
Unused openings, other than those intended for equipment operation, for mounting purposes, or permitted as part of the design of listed equipment, shall be effectively closed to afford protection substantially equivalent to the wall of the equipment.
Conductor sizes (110.6) NEC 2017 Section 110.6
Conductor sizes are expressed in American Wire Gage (AWG) or in circular mils — AWG up to 4/0, circular mils (kcmil) for larger conductors.
Formulas to Know
Minimum feeder conductor ampacity with continuous and non-continuous load
(continuous load × 125%) + non-continuous load; worked example: (100 A × 125%) + 30 A = 155 ARetail store combined general lighting and receptacle load (before demand factors)
(area sq ft × 1.9 VA/sq ft) + (number of receptacle outlets × 180 VA); worked example: 3,500 × 1.9 = 6,650 VA, 20 × 180 = 3,600 VA, total 10,250 VA (1.9 VA/sq ft per NEC 2020 Table 220.12 / 2023 Table 220.42(A) / 2026 Table 120.42(A))Dwelling general lighting + small-appliance + laundry load
(area sq ft × 3 VA/sq ft) + (1,500 VA × number of small-appliance circuits) + (1,500 VA × number of laundry circuits); worked 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 VAReceptacle outlet load (220.14(I))
Not less than 180 VA for each single or each multiple receptacle on one yoke; a single piece of equipment consisting of a multiple receptacle of four or more receptacles is calculated at not less than 90 VA per receptacleShow window receptacle outlets (210.62)
At least one 125-volt, single-phase, 15- or 20-ampere receptacle within 450 mm (18 in.) of the top of the show window for each 3.7 m (12 linear ft) or major fraction thereof; worked example: 44 ft = three full 12-ft sections (36 ft) + 8 ft (a major fraction) = 4 receptacle outletsConduit fill — exactly two conductors
Use the 31% column of Chapter 9, Table 1; sum conductor areas and pick the smallest trade size whose 31% area is at least that sum. Examples: 2 × 0.0211 (10 AWG THHN) = 0.042 sq in → ½ in. EMT (0.094 sq in); 2 × 0.0507 (6 AWG THHN) = 0.101 sq in → ¾ in. EMT (0.165 sq in)Total conductor cross-sectional area in a raceway (Chapter 9, Table 5)
Sum of (quantity × Table 5 area per conductor), including the equipment grounding conductor at its actual area (Chapter 9 Note 3); worked example: 7 × 0.0211 + 3 × 0.0133 + 1 × 0.0133 = 0.201 sq inBox fill volume allowances (314.16(B), NEC 2020/2023)
Insulated conductors (1 each) + all EGCs counted as 1 + clamps + stud + device yoke (2); conductors wholly inside the box (pigtails) are not counted. Worked example: 4 + 1 + 0 + 0 + 2 = 7 allowancesGrounded conductor size for parallel service conductors
Add the parallel conductor areas, then size from Table 250.102(C)(1); worked example: 2 × 350 kcmil = 700 kcmil (over 600 through 1,100 kcmil) → 2/0 AWG copperBends between pull points in RMC (344.26)
Not more than the equivalent of four quarter bends (360 degrees total) between pull points such as conduit bodies and boxes