Exam Cheat Sheet · Quick Reference
Idaho Limited Electrical Photovoltaic 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
60
Passing score
70%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Idaho State Portion 60 questions
2017 National Electrical Code, NFPA – Introduction
5 Q · 8%
Purpose and scope of the NEC (practical safeguarding of persons and property)NEC scope: covered and excluded installations (Article 90.2)Code arrangement: chapters, their hierarchy, and how they apply (Article 90.3)Authority having jurisdiction (AHJ): enforcement powers and special permissions (Article 90.4)Mandatory vs. permissive rules vs. explanatory material (Article 90.5)Equipment examination, listing, and approval for safety (Article 90.7)Wiring planning for future expansion and circuit limitations in enclosures (Article 90.8)Units of measurement: SI and inch-pound dual system and compliance (Article 90.9)
2017 National Electrical Code, NFPA – Chapter 1
7 Q · 12%
Article 100 key definitions for PV and electrical installations (e.g., photovoltaic system, interactive system, stand-alone system, hybrid system, charge controller)Equipment approval, listing, labeling, and identification requirementsElectrical connections: terminals, splices, conductor materials, and temperature limitationsWorking space and clearance requirements around electrical equipmentGuarding of live parts and arc-flash hazard warning markingEquipment marking requirements: manufacturer identification, ratings, and field-applied hazard labelsWiring integrity, wiring methods, and conductor sizing standardsEnclosure type selection for indoor and outdoor environmentsArticle 100 - DefinitionsArticle 110 - Requirements for Electrical Installations
2017 National Electrical Code, NFPA – Chapter 2
7 Q · 12%
Grounding and bonding requirements for PV and electrical systems (Article 250)Grounding electrode system types, installation, and sizingEquipment grounding conductor types, identification, and sizingBranch circuit requirements, ratings, and GFCI/AFCI protection (Article 210)Branch-circuit, feeder, and service load calculations (Article 220)Service conductor installation, disconnecting means, and overcurrent protection (Article 230)Overcurrent protection devices, ratings, and location requirements (Article 240)Surge-protective device (SPD) types, installation, and connection requirements (Article 285)Article 250 - Grounding and Bonding
2017 National Electrical Code, NFPA – Chapter 3
6 Q · 10%
Conductor ampacity tables and temperature rating corrections (Article 310)Conductor insulation types, applications, and marking requirementsConductors in parallel — requirements and restrictionsGeneral wiring methods — protection against physical damage and underground installation requirements (Article 300)Outlet, device, pull, and junction box sizing, fill calculations, and support (Article 314)Raceway types — permitted uses, securing, supporting, and bending requirements (EMT, RMC, IMC, FMC, LFMC, PVC, LFNC)Cable wiring methods — permitted uses and installation requirements (Type MC, NM, UF, SE/USE)Cabinets, cutout boxes, and enclosures — conductor deflection, wiring space, and installation (Article 312)Article 310 - Conductors for General Wiring
2017 National Electrical Code, NFPA – Chapter 4
6 Q · 10%
Transformer overcurrent protection requirements (Articles 450.3, 450.4)Transformer installation types and location requirements (dry-type, oil-insulated, liquid-filled)Transformer vault construction, ventilation, and access requirementsSwitchboard, switchgear, and panelboard overcurrent protection and groundingSwitch installation, ratings, and connection requirementsStorage battery installation, disconnecting means, and ventilationGenerator overcurrent protection, conductor ampacity, and disconnecting meansFlexible cord and cable uses, ampacity, and prohibited applicationsArticle 450 - Transformers and Transformer Vaults (Including Secondary Ties)
2017 National Electrical Code, NFPA – Chapter 5
6 Q · 10%
Classification of hazardous locations (Class I, II, III; Divisions 1 and 2; Zones 0, 1, 2, 20, 21, 22)Wiring methods and sealing requirements in Class I, II, and III locationsProtection techniques for hazardous locations (explosionproof, intrinsically safe, flameproof, pressurization, encapsulation)Electrical requirements for specific hazardous occupancies (commercial garages, aircraft hangars, motor fuel dispensing facilities, bulk storage plants, spray application areas)Essential electrical systems and wiring requirements for health care facilitiesElectrical installations for mobile homes, manufactured homes, recreational vehicles, and park trailersWiring methods and grounding for marinas, floating buildings, and agricultural buildingsTemporary electrical installations and wiring for assembly occupancies, theaters, and similar locationsArticle 517 - Health Care Facilities
2017 National Electrical Code, NFPA – Chapter 6
10 Q · 17%
PV system definitions and terminology (Article 690 Part I)Maximum voltage calculations for PV source and output circuitsCircuit sizing and maximum current calculations for PV systemsOvercurrent protection requirements for PV system DC circuitsPV system disconnecting means requirements and ratingsWiring methods, conductor types, and labeling for PV system DC circuitsSystem grounding, equipment grounding, and bonding for PV arraysRequired markings and labels for PV system components and disconnectsArticle 690 - Solar Photovoltaic (PV) Systems
2017 National Electrical Code, NFPA – Chapter 7
5 Q · 8%
Interconnected electric power production sources: point of connection and equipment approval (Article 705)Disconnecting means requirements for interconnected systems and energy storage systemsEnergy storage system (ESS) classification, circuit sizing, and overcurrent protection (Article 706)ESS location requirements: ventilation, guarding, working space, and egressCharge control and diversion charge controller requirements for ESSStand-alone system wiring, equipment approval, and capacity requirements (Article 710)DC microgrid system grounding, ground-fault detection, and arc fault protection (Article 712)Loss of primary source disconnection and anti-islanding requirementsArticle 706 - Energy Storage Systems
2017 National Electrical Code, NFPA – Chapter 9
3 Q · 5%
Conduit and tubing fill percentages (Table 1 — 1, 2, and over 2 conductors)Conduit bend radius requirements (Table 2)Cross-sectional area and fill calculations for specific conduit types (EMT, RMC, IMC, PVC, FMC, LFMC, LFNC)Insulated conductor dimensions and cross-sectional areas by wire type and AWG size (Table 5)Compact conductor nominal dimensions and areas (Table 5A)Bare conductor properties, DC resistance, and stranding data (Table 8)AC resistance and reactance for conductors in conduit, including effective impedance at 0.85 power factor (Table 9)Conductor stranding classes by size for copper and aluminum (Table 10)
2017 National Electrical Code, NFPA Calculations – Chapters 4 and 9
5 Q · 8%
PV source and output circuit current calculations (Article 690.8)Maximum PV system voltage determination and temperature correction factors (Article 690.7)Conductor ampacity tables and temperature correction/adjustment factors (Article 310.15)Branch-circuit, feeder, and service load calculations (Article 220)Motor branch-circuit conductor sizing and full-load current tables (Article 430.22 and Tables 430.247–430.250)Motor branch-circuit short-circuit and ground-fault protective device ratings (Table 430.52)Conduit fill calculations using Chapter 9 Tables 1, 4, and 5Overcurrent protection sizing for PV system dc circuits (Article 690.9)Article 430 - Motors, Motor Circuits, and Controllers
Key Distinctions
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, 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
An insulated conductor is encased in 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)NEC Chapter 9 tablesvsInformative annexes
Chapter 9 consists of tables that are applicable (enforceable) as referenced elsewhere in the Code, while informative annexes are not part of the Code requirements.
NEC 2017 Section 90.3Chapters 1 through 4vsChapters 5, 6, 7 and Chapter 8
Chapters 1–4 apply generally to all electrical installations; Chapters 5–7 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 90.3240.4(B) next higher standard ratingvs240.4(C) devices rated over 800 amperes
240.4(B) permits the next higher standard overcurrent device rating above conductor ampacity only where that selected rating does not exceed 800 amperes; where the device is rated over 800 amperes, 240.4(C) requires conductor ampacity equal to or greater than the device rating.
NEC 2017 Section 240.4(B)Motor branch-circuit conductors (continuous duty, 430.22)vsGenerator output conductors (445.13(A))
Conductors supplying a single continuous-duty motor must have ampacity not less than 125 percent of motor full-load current, while conductors from generator output terminals to the first overcurrent device must be not less than 115 percent of the generator nameplate current rating.
NEC 2017 Section 430.22Class I locationsvsClass II and Class III locations
Class I locations involve flammable gases, flammable liquid-produced vapors, or combustible liquid-produced vapors in ignitible quantities; combustible dusts are Class II and fibers/flyings are Class III.
NEC 2017 Section 500.5(B)(1)Class II, Division 1 wiring methodsvsClass II, Division 2 wiring methods
Division 1 permits threaded rigid metal conduit, Type MI cable, and Type MC-HL cable (industrial establishments with limited public access), while EMT is permitted only in Division 2, not in Division 1.
NEC 2017 Section 502.10(A)(1) and 502.10(B)(1)(2)Class III max surface temperature — equipment not subject to overloadingvsClass III max surface temperature — equipment that may be overloaded
Per 503.5, surface temperature shall not exceed 165°C (329°F) for equipment not subject to overloading, but shall not exceed 120°C (248°F) for equipment such as motors or power transformers that may be overloaded.
NEC 2017 Section 503.5Isolating devicevsEquipment disconnecting means (690.15)
A simple isolating device is acceptable at or below 30 amperes, but an equipment disconnecting means for isolation is required where maximum circuit current is greater than 30 amperes for a dc combiner output circuit or a charge controller/inverter input circuit.
NEC 2017 Section 690.15Concrete-encased electrode bare copper conductor (250.52(A)(3))vsGround ring conductor (250.52(A)(4))
A concrete-encased electrode made of bare copper shall not be smaller than 4 AWG (at least 20 ft), whereas 2 AWG is the minimum size for a ground ring.
NEC 2017 Section 250.52(A)(3)Transformer secondary conductors protected by primary OCPDvsSecondary conductors NOT protected by primary OCPD (240.4(F))
Two-wire single-phase and delta-delta 3-wire secondaries are permitted to be protected by the primary-side device, while single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) secondary conductors are not considered protected by the primary overcurrent device.
NEC 2017 Section 240.4(F)Hybrid system power sourcesvsEnergy storage
Under the Article 100 hybrid system definition, photovoltaic, wind, microhydro, and engine-driven generators count as power sources, but energy storage such as batteries, flywheels, or superconducting magnetic storage does not constitute a power source.
NEC 2017 Article 100 — Definition of 'Hybrid System'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) (Article 100) 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.
Hybrid System (Article 100) NEC 2017 Article 100 — Definition of 'Hybrid System'
A system comprised of multiple power sources such as photovoltaic, wind, microhydro, and engine-driven generators, where energy storage (batteries, flywheels, superconducting magnetic storage) is not counted as a power source.
DC-to-DC Converter (690.2) NEC 2017 Section 690.2
A device installed in the PV source circuit or PV output circuit that can provide an output dc voltage and current at a higher or lower value than the input dc voltage and current.
Functional Grounded PV System (690.2) NEC 2017 Section 690.2
A PV system that has an electrical reference to ground that is not solidly grounded, often connected to ground through a fuse, circuit breaker, resistance device, non-isolated grounded ac circuit, or electronic means that is part of a listed ground-fault protection system.
Photovoltaic Source Circuit (690.2) NEC 2017 Section 690.2
Circuits between modules and from modules to the common connection point(s) of the dc system.
Solar Cell (690.2) NEC 2017 Section 690.2
The basic PV device that generates electricity when exposed to light, distinct from a module, panel, or array.
Intrinsically Safe Circuit (Article 504 / 504.2) NEC 2017 Section 504.1 and 504.2
A circuit in which any spark or thermal effect is incapable of causing ignition of a flammable or combustible mixture under prescribed test conditions; Article 504 covers intrinsically safe apparatus, wiring, and systems for Articles 500 through 516.
Intrinsic Safety "i" protection types (505.8(D)) NEC 2017 Section 505.8(D)
Intrinsic safety is designated type of protection "ia" for Zone 0 locations, "ib" for Zone 1, and "ic" for Zone 2.
Material Group IIIA (506.6) NEC 2017 Section 506.6
Under the Zone 20/21/22 classification, Group IIIA covers ignitible fibers and flyings (Group IIIB is non-conductive combustible dusts and Group IIIC is conductive combustible dusts).
Supplementary overcurrent protection (240.10) NEC 2017 Section 240.10
Overcurrent protection that shall not be used as a substitute for required branch-circuit overcurrent devices or in place of required branch-circuit protection.
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) restricted access, its ampere rating is the maximum setting possible.
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 when protected in accordance with 430.40.
Directory at PV system disconnecting means (690.4(D)) NEC 2017 Section 690.4(D)
Where multiple PV systems on a building are remotely located from each other, a directory in accordance with 705.10 shall be provided at each PV system disconnecting means.
Coordination system for orderly shutdown (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 shall be permitted.
Self-regulating PV source circuit for charge control (690.72) NEC 2017 Section 690.72
A PV source circuit matched to the battery voltage rating and charge current requirements whose maximum charging current multiplied by 1 hour is less than 3 percent of rated battery capacity in ampere-hours (or as recommended by the battery manufacturer) is deemed to comply with charge control requirements.
Formulas to Know
120 percent rule for load-side interactive inverter connection (705.12(B)(2)(3)(b))
125% of power source output circuit current + rating of main overcurrent device shall not exceed 120% of busbar ampacity. Worked example: 200 A busbar × 120% = 240 A; 240 A − 200 A main breaker = 40 A maximum PV backfed breaker.Generator output conductor ampacity (445.13(A))
Ampacity not less than 115% × generator nameplate current rating. Worked example: 200 A × 1.15 = 230 A minimum.Single continuous-duty motor branch-circuit conductors (430.22)
Ampacity not less than 125% × motor full-load current rating.Wye-start, delta-run motor conductors between controller and motor (430.22(C))
Not less than 72% of motor full-load current (individual conductors carry 58% of rated load current; 58% × 1.25 = 72%).PV source circuit conductor sizing multiplier (690.8(A)(1), 690.8(B)(1) Informational Note)
Sum of parallel module rated short-circuit currents × 125% (maximum current), then × 125% for continuous duty = 156% of rated short-circuit current, before adjustment and correction factors.PV common-return conductor ampacity (690.8(C))
Ampacity not less than the SUM of the ampere ratings of the overcurrent devices of the individual output circuits.Voltage drop — minimum conductor circular mils (single-phase copper, K = 12.9)
CM = (2 × K × I × L) / VD. Worked example: 120 V × 3% = 3.6 V allowed; (2 × 12.9 × 20 A × 80 ft) / 3.6 = 11,466 cmil → 8 AWG (16,510 cmil), since 10 AWG (10,380 cmil) is too small.Conductor dc resistance corrected for temperature (Chapter 9, Table 8 notes)
R2 = R1[1 + α(T2 − 75)], with α(copper) = 0.00323 at 75°C (167°F).Box fill volume required (314.16(B), Table 314.16(B))
Minimum volume = number of volume allowances × volume per conductor (2.00 cu in for 14 AWG; 2.25 cu in for 12 AWG). Allowance count example: 7 insulated conductors + 1 for all EGCs (3 grounds = 1) + 0 clamps + 0 stud + 2 for device yoke = 10 → 10 × 2.00 = 20.00 cu in; a pigtail wholly inside the box is not counted. Additional conductors permitted = (box volume − required volume) ÷ per-conductor volume, whole conductors only.Conduit fill with exactly two conductors (Chapter 9, Table 1)
Use the 31% column for exactly two conductors. Worked example: 2 × 0.0507 sq in (6 AWG THHN) = 0.101 sq in; smallest EMT whose 31% area (0.165 sq in) is at least that is ¾ in.