Exam Cheat Sheet · Quick Reference
Idaho Limited Electrical Water Pump 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 of the NEC: practical safeguarding of persons and propertyScope of NEC coverage: premises, structures, and installation types includedInstallations not covered by the NEC (exclusions and exemptions)Code arrangement: role and hierarchy of Chapters 1–9 and informative annexesMandatory vs. permissive rules and explanatory material (shall/shall not vs. shall be permitted)Authority having jurisdiction: enforcement, interpretations, and special permissionEquipment examination, listing, and approval for safetyUnits of measurement: SI and inch-pound dual system
2017 National Electrical Code, NFPA – Chapter 1
4 Q · 10%
Key NEC definitions and terminology (Article 100 Part I)Equipment approval, listing, and labeling requirementsElectrical connections, splices, and temperature limitationsWorking space and clearance requirements around electrical equipmentGuarding of live parts and enclosure type selectionEquipment marking and arc-flash hazard warning labelsWiring integrity, conductor materials, and conductor sizingDeteriorating agents and environmental protection of equipmentArticle 100 - Definitions
2017 National Electrical Code, NFPA – Chapter 2
14 Q · 35%
Grounding and bonding requirements for motor-operated water pumps and submersible pumpsEquipment grounding conductor types, sizing, and identificationGrounding electrode system and permitted grounding electrodesBonding of piping systems, structural metal, and service equipmentOvercurrent protection for branch circuits and feedersBranch circuit ratings, conductor sizing, and GFCI protection requirementsLoad calculations for branch circuits, feeders, and servicesOutside branch circuits and feeders — clearances, disconnecting means, and conductor requirementsArticle 250 - Grounding and BondingArticle 210 - Branch Circuits
2017 National Electrical Code, NFPA – Chapter 3
8 Q · 20%
Conductor ampacity tables and temperature ratings (Article 310)Ampacity correction and adjustment factors for ambient temperature and bundled conductorsUnderground installation minimum cover requirements (Table 300.5 and Table 300.50)Wiring method selection, uses permitted, and uses not permitted for conduit types (RMC, IMC, EMT, FMC, LFMC, LFNC, PVC)Securing and supporting requirements for raceways and cablesBox and conduit body fill calculations and sizing (Article 314)Protection of conductors against physical damage (Article 300)Cable type applications: Type MC, NM, UF, SE/USE, and conductor identification and markingArticle 310 - Conductors for General Wiring
2017 National Electrical Code, NFPA – Chapter 4
10 Q · 25%
Motor branch-circuit conductor sizing and ampacity requirements (Article 430 Part II)Motor overload protection selection and settings for continuous-duty motors (Article 430 Part III)Motor branch-circuit short-circuit and ground-fault protective device ratings (Table 430.52)Motor disconnecting means types, ratings, and location requirements (Article 430 Part IX)Motor controller ratings, marking, and design requirements (Article 430 Part VII)Motor control circuit overcurrent protection and disconnection (Article 430 Part VI)Flexible cord and cable permitted uses, ampacity, and prohibited applications (Article 400)Switch installation, ratings, grounding, and accessibility requirements (Article 404)Article 430 - Motors, Motor Circuits, and Controllers
2017 National Electrical Code, NFPA Calculations
1 Q · 2%
Motor branch-circuit conductor sizing (125% rule for single motors, Article 430.22)Branch-circuit short-circuit and ground-fault protective device ratings for motors (Table 430.52 percentages by motor type and protective device)Full-load current determination from NEC tables (Tables 430.247–430.250) vs. nameplate valuesFeeder conductor ampacity for multiple motors (430.24 summation method)Motor overload protection sizing (430.32 trip current percentages by service factor and temperature rise)Feeder overcurrent protection rating for motor loads (430.62 largest branch-circuit device plus sum of other motor FLCs)Branch-circuit load calculations for motor outlets under Article 220 (220.14(C), 220.18(A), 220.50)Locked-rotor current and code letter kVA/hp values (Table 430.7(B) and Tables 430.251(A)/(B)) for disconnecting means sizingArticle 430 - Motors, Motor Circuits, and Controllers
Key Distinctions
Wye-start, delta-run motor conductors (430.22(C))vsPart-winding connected motor conductors (430.22(D))
Conductors between the controller and the motor must be not less than 72 percent of motor full-load current for wye-start, delta-run (58% × 1.25), but not less than 62.5 percent for part-winding connected motors (50% × 1.25).
NEC 2017 Section 430.22(C)Branch-circuit conductors for a single continuous-duty motor (430.22)vsFeeder conductors supplying several motors (430.24)
A single motor's conductors must be not less than 125 percent of that motor's full-load current, while a feeder must be not less than 125 percent of the HIGHEST rated motor plus 100 percent of the full-load currents of all other motors plus non-motor loads.
NEC 2017 Section 430.22NEC 240.4(B) next higher standard OCPD ratingvsNEC 240.4(C) overcurrent device rated over 800 amperes
240.4(B) permits the next higher standard 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 to be equal to or greater than the device rating.
NEC 2017 Section 240.4(B)Supplementary overcurrent protection (240.10)vsRequired branch-circuit overcurrent device
Supplementary overcurrent protection shall not be used as a substitute for, or in place of, required branch-circuit overcurrent devices.
NEC 2017 Section 240.10Thermal relays used against short circuits/ground faultsvsThermal relays used for motor branch-circuit overload (240.9)
Devices not designed to open short circuits or ground faults shall not protect conductors against those faults, but their use is permitted to protect motor branch-circuit conductors from overload where protected in accordance with 430.40.
NEC 2017 Section 240.9Table 310.15(B)(16) ampacitiesvsTables 310.15(B)(18), (19), (20) ampacities
Table 310.15(B)(16) ampacities (not more than three current-carrying conductors in raceway, cable, or directly buried) are based on a 30°C (86°F) ambient, while the high-temperature and free-air/messenger tables are based on 40°C.
NEC 2017 Table 310.15(B)(16)Transformer secondaries protected by the primary OCPDvsTransformer secondaries NOT protected by the primary OCPD (240.4(F))
Two-wire single-phase and delta-delta 3-wire secondary conductors are permitted to be protected by primary-side devices, while 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)Instantaneous trip breaker for Design B energy-efficient squirrel cage motorvsInstantaneous trip breaker for other AC polyphase motors
Per Table 430.52 the maximum is 1100% of full-load current for Design B energy-efficient squirrel cage motors versus 800% for the other AC polyphase motor types.
NEC 2017 Table 430.52Table 430.52(C)(1) inverse time breaker maximumvs430.52(C)(1) Exception No. 2 increased rating
The table maximum for an inverse time circuit breaker is 250% of motor full-load current; where the motor will not start, the rating may be increased but shall in no case exceed 400% of FLC for motors of 100 A or less (300% above 100 A), rather than simply going to the next standard size.
NEC Section 430.52(C)(1), Exception No. 2; Table 430.52(C)(1)System grounding purpose (250.4(A)(1))vsBonding of equipment purpose (250.4(A)(3))
Bonding connects normally non-current-carrying conductive materials together and to the electrical supply source to establish an effective ground-fault current path, which is a different purpose than system grounding; the earth shall not be considered an effective ground-fault current path.
NEC 2017 Section 250.4(A)(3)Receptacle outlet on one yoke (220.14(I))vsSingle piece of equipment with four or more receptacles (220.14(I))
Each single or multiple receptacle on one yoke is calculated at not less than 180 volt-amperes, while a single piece of equipment consisting of a multiple receptacle of four or more receptacles is calculated at not less than 90 volt-amperes per receptacle.
NEC 2017 Section 220.14(I)NEC Chapters 1, 2, 3, and 4vsNEC Chapters 5, 6, 7 and Chapter 8
Per 90.3, Chapters 1 through 4 apply generally to all electrical installations, Chapters 5, 6, and 7 apply to special occupancies/equipment/conditions and may supplement or modify Chapters 1 through 7, and Chapter 8 (communications systems) is independent except where specifically referenced.
NEC 2017 Section 90.3Key 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 — definitions of "Dwelling, One-Family," "Dwelling, Two-Family," and "Dwelling, Multifamily"
A building containing three or more dwelling units; exactly two units is a two-family dwelling and one unit is a one-family dwelling.
Volatile Flammable Liquid (Article 100) NEC 2017 Article 100 — definition of "Volatile Flammable Liquid"
A flammable liquid with a flash point below 38°C (100°F), a flammable liquid whose temperature is above its flash point, or a Class II combustible liquid with a vapor pressure not exceeding 276 kPa (40 psia) at 38°C (100°F) whose temperature is above its flash point.
Effective ground-fault current path (250.4(A)(5)) NEC 2017 Section 250.4(A)(5)
A low-impedance circuit capable of safely carrying the maximum ground-fault current to facilitate operation of the overcurrent device; the earth shall not be considered such a path.
Objectionable current (250.6(D)) NEC 2017 Section 250.6(D)
Currents that introduce noise or data errors in electronic equipment shall NOT be considered the objectionable currents addressed in 250.6, so they do not justify the alterations permitted by 250.6(B).
Equipment bonding jumper installed outside a raceway (250.102(E)(2)) NEC 2017 Section 250.102(E)(2)
A bonding jumper routed on the outside of a raceway or enclosure whose length shall not exceed 1.8 m (6 ft) and that shall be routed with the raceway or enclosure, with longer lengths permitted at outside pole locations.
Grounded conductor identification, 6 AWG or smaller (200.6(A)) NEC 2017 Section 200.6(A)
An insulated grounded conductor 6 AWG or smaller is identified by a continuous white outer finish, a continuous gray outer finish, or three continuous white or gray stripes along its entire length on other than green insulation.
Grounding electrode conductor (Table 250.66) NEC 2017 Table 250.66
The conductor sized from Table 250.66; where the largest ungrounded copper service-entrance conductor is over 3/0 AWG through 350 kcmil, the minimum copper grounding electrode conductor is 2 AWG.
Equipment grounding conductor (Table 250.122) NEC 2017 Table 250.122
The conductor sized by overcurrent device rating; where the automatic overcurrent device rating does not exceed 100 amperes, the minimum copper equipment grounding conductor is 8 AWG.
Adjustable-trip circuit breaker rating (240.6(B)) NEC 2017
For a breaker with external means for adjusting the long-time pickup setting that does not meet 240.6(C) restricted access, the ampere rating is the maximum setting possible.
Standard ampere ratings (Table 240.6(A)) NEC 2017 Table 240.6(A)
The listed standard ratings for fuses and inverse time circuit breakers include values such as 45, 70, and 110 amperes; 85 amperes is not a standard rating.
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.
Part-winding start induction motor protection (430.4) NEC 2017 Section 430.4
Each motor-winding connection of a standard part-winding start induction motor shall have branch-circuit short-circuit and ground-fault protection rated at not more than one-half that specified by 430.52.
Formulas to Know
Minimum feeder conductor ampacity with continuous and non-continuous load
(continuous load × 125%) + non-continuous load; example: (100 A × 125%) + 30 A = 155 ABranch-circuit conductor ampacity for a single continuous-duty motor
Not less than 125% of the motor full-load current rating from the applicable NEC tables (430.22/430.22(A))Controller-to-motor conductors, wye-start delta-run
Not less than 72% of motor full-load current (58% per-winding current × 1.25) per 430.22(C)Controller-to-motor conductors, part-winding connected motor
Not less than 62.5% of motor full-load current (50% × 1.25) per 430.22(D)Feeder conductors for several motors (430.24)
125% of the full-load current of the highest rated motor + sum of the full-load currents of all other motors (100%) + any non-motor loadsMinimum bending radius, Type MC cable with interlocked armor or corrugated sheath
7 × external diameter of the metallic sheath; example: 7 × 1.5 in. = 10.5 in. (330.24(B))Inverse time circuit breaker for a motor, table maximum and increased rating
Table 430.52(C)(1) maximum = 250% × FLC (example: 50 A × 2.5 = 125 A); if the motor fails to start, Exception No. 2 permits an increase in no case exceeding 400% × FLC for motors of 100 A or less (300% above 100 A) — examples: 50 A × 4 = 200 A; 60 A × 400% = 240 APart-winding start induction motor branch-circuit short-circuit/ground-fault protection
Each motor-winding connection: not more than one-half of the value specified by 430.52Conduit fill count (Chapter 9 Table 4, Table 5, Note 7)
Over 2 wires → 40% conduit area ÷ conductor area; drop the fraction if below 0.8. Example: 1½ in. EMT 40% area 0.814 sq in ÷ 0.0507 sq in (6 AWG THHN) = 16.06 → 16 conductorsGrounded conductor size for parallel service conductors
Add the kcmil of the parallel sets, then use Table 250.102(C)(1); example: 2 × 350 kcmil = 700 kcmil, which falls in 'over 600 through 1100 kcmil' → 2/0 AWG copper