Exam Cheat Sheet · Quick Reference
Idaho Limited Electrical Manufacturing Equipment 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
6 Q · 15%
Purpose and scope of the NEC (practical safeguarding of persons and property)Installations covered and not covered under NEC scope (Article 90.2)Code arrangement and chapter hierarchy (Chapters 1–9 and informative annexes)Mandatory vs. permissive rules and explanatory material (shall/shall not vs. shall be permitted)Authority having jurisdiction (AHJ) enforcement powers and special permissionExamination and listing of equipment for safety (Article 90.7)Units of measurement and dual SI/inch-pound system (Article 90.9)Wiring planning for future expansion and circuit limitation in enclosures (Article 90.8)
2017 National Electrical Code, NFPA – Chapter 1
6 Q · 15%
Key NEC Article 100 definitions (approved, listed, labeled, identified, AHJ)Equipment examination, installation, and use requirements (Article 110.3)Working space and clearance requirements around electrical equipment (110.26)Electrical connections, splices, and termination temperature ratings (110.14)Equipment marking requirements including arc-flash hazard warnings and disconnecting means identificationGuarding of live parts and enclosure type selection (110.27, 110.28)Conductor materials, sizes, and wiring integrity requirements (110.5–110.8)Grounding and bonding definitions (grounded conductor, EGC, grounding electrode, bonding jumper)Article 100 - DefinitionsArticle 110 - Requirements for Electrical Installations
2017 National Electrical Code, NFPA – Chapter 2
9 Q · 22%
Grounding and bonding requirements (Article 250) — general principles and definitionsGrounding electrode system — types, installation, and sizing of grounding electrodesEquipment grounding conductors — types, identification, sizing, and installationBonding methods for services, piping systems, and structural metalBranch circuit requirements — ratings, conductor sizing, GFCI/AFCI protection, and required outletsOvercurrent protection — fuses, circuit breakers, standard ratings, and location requirementsBranch-circuit, feeder, and service load calculations — demand factors and calculation methodsFeeder requirements — minimum conductor sizing, overcurrent protection, and grounded conductor identificationArticle 250 - Grounding and Bonding
2017 National Electrical Code, NFPA – Chapter 3
10 Q · 25%
Conductor ampacity tables and temperature correction/adjustment factors (Article 310)Wiring methods — uses permitted and not permitted for conduit types (RMC, EMT, FMC, LFMC, LFNC, PVC)Securing and supporting requirements for raceways and cablesBox and conduit body fill calculations and sizing requirements (Article 314)Underground installation requirements and minimum cover depths (Articles 300, 310)Cable tray systems — installation, fill, ampacity, and grounding (Article 392)Conductors in parallel — requirements and restrictions (Article 310)Cabinets, cutout boxes, and enclosures — wiring space and conductor deflection (Article 312)Article 310 - Conductors for General Wiring
2017 National Electrical Code, NFPA – Chapter 4
6 Q · 15%
Motor branch-circuit conductor sizing and ampacity (Article 430, Part II)Motor overload protection requirements and device ratings (Article 430, Part III)Motor branch-circuit short-circuit and ground-fault protective device ratings (Article 430, Part IV)Motor disconnecting means types, ratings, and location requirements (Article 430, Part IX)Motor controller ratings, marking, and design requirements (Article 430, Parts VII–VIII)Transformer overcurrent protection, installation, and transformer vault requirements (Article 450)Industrial control panel and industrial machinery supply conductor sizing and overcurrent protection (Articles 409 and 670)Flexible cord and flexible cable types, permitted uses, and ampacity (Article 400)Article 430 - Motors, Motor Circuits, and Controllers
2017 National Electrical Code, NFPA – Chapter 7
3 Q · 8%
Class 1 circuit classifications and power source requirements (power-limited vs. remote-control/signaling)Class 2 and Class 3 power source requirements and interconnection restrictionsWiring methods and installation of Class 1 circuitsSeparation requirements for Class 2 and Class 3 circuits from power and Class 1 conductorsCable types, listing requirements, and substitution hierarchy for Class 2, Class 3, and PLTC cablesInstallation locations and permitted uses for Class 2, Class 3, and PLTC cables by building area (plenum, riser, general-purpose)Type ITC cable uses permitted, construction specifications, and overcurrent protection requirementsArticle 725 - Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits
Key Distinctions
NEC Chapter 9 tablesvsInformative annexes
Per NEC 90.3, Chapter 9 consists of tables that are applicable as referenced elsewhere in the Code and are enforceable when referenced, whereas informative annexes are not part of the requirements.
NEC 2017 Section 90.3Chapters 1-4vsChapters 5-7 and Chapter 8
Per NEC 90.3, Chapters 1, 2, 3, and 4 apply generally to all electrical installations, Chapters 5, 6, and 7 apply to 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 90.3Soft conversion (trade size designators)vsHard conversion
NEC 90.9(C)(1) permits soft conversion for trade sizes — where a product's actual measured size differs from the nominal size, trade size designators are used rather than dimensions — and extracted material is also permitted to use soft conversion rather than hard conversion.
NEC 2017 Section 90.9(C)(1)Tag marking on coil, reel, or carton (310.120(B)(3))vsDurable surface marking (310.120(B)(1))
Type MI cable, switchboard wires, metal-covered single-conductor cables, and Type AC cable are marked by printed tag attached to the coil, reel, or carton, while nonmetallic-sheathed, service-entrance, and instrumentation tray cables are durably surface marked.
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 overcurrent device rating above conductor ampacity provided the selected rating does not exceed 800 amperes, while 240.4(C) requires that where the device is rated over 800 amperes the conductor ampacity 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 240.10Main bonding jumpervsSystem bonding jumper
Per Article 100, the main bonding jumper is the connection between the grounded circuit conductor and the equipment grounding conductor at the service, while the system bonding jumper makes that connection (to the supply-side bonding jumper, the equipment grounding conductor, or both) at a separately derived system.
NEC 2017 Article 100 (Definition: Bonding Jumper, Main)Insulated conductorvsCovered conductor
Per Article 100, an insulated conductor is encased within material of composition and thickness recognized by the Code as electrical insulation, whereas a covered conductor is encased in material not recognized as electrical insulation.
NEC 2017 Article 100 (Conductor, Insulated)Wye-start, delta-run motor conductors (430.22(C))vsPart-winding connected motor conductors (430.22(D))
Conductors between the controller and the motor shall be not less than 72 percent of motor full-load current for wye-start/delta-run motors, but not less than 62.5 percent for part-winding connected motors.
NEC 2017 Section 430.22(C)Utilization equipment fastened in place (210.23(A)(2))vsCord-and-plug-connected equipment not fastened in place (210.23(A)(1))
On a multiple-outlet branch circuit also supplying lighting units or cord-and-plug equipment, equipment fastened in place (other than luminaires) is limited to 50 percent of the branch-circuit rating, while any one cord-and-plug-connected utilization equipment not fastened in place is limited to 80 percent of the branch-circuit rating.
NEC 2017 Section 210.23(A)(2)Transformer primary-only protection (Table 450.3(B))vsTransformer primary and secondary protection (Table 450.3(B))
For transformers rated 1000 volts or less with currents of 9 amperes or more, primary-only protection is limited to a maximum of 125 percent of rated primary current, while with primary and secondary protection the primary shall not exceed 250 percent and the secondary shall not exceed 125 percent of rated current.
NEC 2017 Table 450.3(B)Design B energy-efficient squirrel cage motor — instantaneous trip breakervsOther AC polyphase motors — instantaneous trip breaker
Per Table 430.52, Design B energy-efficient squirrel cage motors are permitted instantaneous trip breaker protection at a maximum of 1100 percent of full-load current, versus the 800 percent allowed for other AC polyphase motor types.
NEC 2017 Table 430.52THHNvsTHHN/THWN dual-rated
Per 310.10(C), Type THHN alone is a dry- and damp-location insulation and is not among the types listed for wet locations, while conductors marked dual-rated THHN/THWN qualify because of the THWN marking.
NEC 2017 Section 310.10(C)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.
Dwelling, Multifamily (Article 100) NEC 2017 Article 100 — Dwelling, Multifamily
A building that contains three or more dwelling units (a building with exactly two units is a two-family dwelling).
Scope of the Code (90.2(A)) NEC 2017
The Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings.
Extracted text (90.9(C)(2)) NEC 2017 Section 90.9(C)(2)
Material extracted from another standard whose original context shall not be compromised or violated, with any editing confined to making the style consistent with that of the NEC.
Standard ampere ratings (Table 240.6(A)) NEC 2017 Table 240.6(A)
The listed standard ratings for fuses and inverse time circuit breakers, which include 45, 70, and 110 amperes; 85 amperes is not a standard rating.
Adjustable-trip circuit breaker rating (240.6(B)) NEC 2017
For breakers having external means for adjusting the long-time pickup current setting and not meeting 240.6(C) for restricted access, the 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.
System of coordination (240.12) NEC 2017 Section 240.12
Where an orderly shutdown is required to minimize hazards, a system based on (1) coordinated short-circuit protection and (2) overload indication based on monitoring systems or devices shall be permitted.
Thermal relays and similar devices (240.9) NEC 2017 Section 240.9
Devices not designed to open short circuits or ground faults; they shall not protect conductors against overcurrent due to short circuits or ground faults, but are permitted to protect motor branch-circuit conductors from overload where protected in accordance with 430.40.
Unprotected transformer secondary conductors (240.4(F)) NEC 2017 Section 240.4(F)
Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors, which shall not be considered protected by the primary overcurrent protective device.
Working space width (110.26(A)(2)) NEC 2017 Section 110.26(A)(2)
For equipment operating at 1000 volts or less, the working space width shall be the width of the equipment or a minimum of 30 in., whichever is greater, and in all cases must permit at least a 90-degree opening of equipment doors or hinged panels.
Mechanical execution of work — unused openings (110.12(A)) NEC 2017 Section 110.12(A)
Unused openings in boxes, raceways, and enclosures, other than those intended for equipment operation or mounting or permitted as part of listed-equipment design, shall be effectively closed to afford protection substantially equivalent to the wall of the equipment.
Temperature limitations at terminations (110.14(C)) NEC 2017 Section 110.14(C)
When making connections at equipment terminals, the temperature ratings of both the conductors and the equipment terminals must be considered.
Expansion fittings for PVC conduit (352.44) NEC 2017 Section 352.44
Fittings provided to compensate for thermal expansion and contraction where the expected length change is 1/4 in. (6 mm) or greater in a straight run between securely mounted items.
Class 1 remote-control and signaling circuits (Article 725) NEC 2017 Section 725.41(B)
Circuits that are not permitted to exceed 600 volts.
Parallel conductors (310.10(H)(1)) NEC 2017 Section 310.10(H)(1)
Aluminum, copper-clad aluminum, or copper conductors of each phase, polarity, neutral, or grounded circuit that are permitted to be electrically joined at both ends only in sizes 1/0 AWG and larger.
Formulas to Know
Minimum feeder conductor ampacity with continuous and noncontinuous loads (215.2(A)(1)(a))
Ampacity ≥ noncontinuous load + (125% × continuous load); example: 120 A + (80 A × 1.25) = 220 AMinimum feeder overcurrent device rating, assembly not listed for 100% operation (215.3)
OCPD ≥ noncontinuous load + (125% × continuous load), then go up to the next standard rating in Table 240.6(A) if the result is not a standard size; example: (120 A × 1.25) + 45 A = 195 A → 200 AMinimum branch-circuit conductor ampacity for a single continuous-duty motor (430.22 / 430.22(A))
Ampacity ≥ 125% × motor full-load current from the applicable NEC tables (Tables 430.247 through 430.250 used for general motor applications rather than nameplate current)Conductors between controller and wye-start, delta-run motor (430.22(C))
Ampacity ≥ 72% × motor FLC, derived from 58% of load current × 1.25Conductors between controller and part-winding connected motor (430.22(D))
Ampacity ≥ 62.5% × motor FLC (50% × 1.25); line-side branch-circuit conductors sized at 125% of motor FLCMotor inverse time circuit breaker sizing and failure-to-start exception (Table 430.52(C)(1); 430.52(C)(1) Ex. No. 2)
Maximum = 250% × motor FLC; if the motor fails to start, the rating may be increased but shall in no case exceed 400% of FLC for motors of 100 A or less (300% for motors above 100 A); example: 50 A × 2.5 = 125 A, increased maximum 50 A × 4 = 200 AMinimum bending radius, Type MC cable with interlocked armor or corrugated sheath (330.24(B))
Radius = 7 × external diameter of the metallic sheath; example: 7 × 1.5 in. = 10.5 in.Raceway conductor fill, over 2 conductors (Chapter 9 Tables 4 and 5, Note 7)
Number of conductors = (40% fill area of raceway) ÷ (area per conductor), dropping the fraction when it is below 0.8; examples: 1½" EMT 0.814 ÷ 0.0507 = 16.06 → 16 of 6 AWG THHN; 2½" EMT 2.343 ÷ 0.0507 = 46.21 → 46 of 6 AWG THHNBox fill volume allowances and minimum box volume (314.16(B), Table 314.16(B))
Count allowances per 314.16(B)(1)-(5): each insulated conductor entering the box = 1, all EGCs together = 1, device yoke = 2, conductors wholly inside the box (pigtails) = 0; example total 4 + 1 + 0 + 0 + 2 = 7 allowances. Minimum volume = allowances × volume per conductor size (14 AWG = 2.00 cu in.); example 12 × 2.00 = 24.00 cu in. Spare capacity: (box volume − required volume) ÷ 2.00 cu in. = additional 14 AWG conductors; example (14.0 − 14.00) ÷ 2.00 = 0Dwelling general lighting, small-appliance, and laundry load (Article 220; Table 220.12 dwelling unit load 3 VA/sq ft)
Total VA = (sq ft × 3 VA/sq ft) + (number of small-appliance circuits × 1,500 VA) + (laundry circuit 1,500 VA); examples: 2,000 sq ft → 6,000 + 3,000 + 1,500 = 10,500 VA; 1,200 sq ft per unit → 3,600 + 3,000 + 1,500 = 8,100 VA per unit × 4 units = 32,400 VA before demand factorsRetail store general lighting plus receptacle load before demand factors (Table 220.12 (2020)/220.42(A) (2023)/120.42(A) (2026); 220.14(I))
Total VA = (sq ft × 1.9 VA/sq ft for retail occupancy) + (number of receptacle outlets × 180 VA per single or multiple receptacle on one yoke); example: 3,500 × 1.9 = 6,650 VA + 20 × 180 = 3,600 VA → 10,250 VA. Note: 3 VA/sq ft was the NEC 2017 unit load for stores, and a multiple receptacle of four or more receptacles on one piece of equipment is calculated at not less than 90 VA per receptacle.