KY Electrician cheat sheet

NEC structure (90.3): Chapters 1-4 apply generally, Chapters 5-7 supplement or modify them, Chapter 8 is independent, and Chapter 9 contains reference tables and examples.

Working space depth at 600 V or less (Table 110.26(A)(1)): Condition 1 = 3 ft, Condition 2 = 3.5 ft, Condition 3 = 4 ft, measured from the enclosure front.

Working space width and height (110.26(A)(2) and (A)(3)): 30 in minimum or the width of the equipment, whichever is greater, and 6.5 ft of headroom.

Dedicated equipment space (110.26(E)): the space directly above and below switchboards and panelboards is reserved for electrical equipment only.

Termination rule (110.14(C)): conductor ampacity is limited by the lowest temperature rating among the conductor insulation and the terminations unless listed and identified otherwise.

Field markings: 110.22 disconnect identification, 110.16 arc-flash hazard labels, and 110.24 available fault current marking at service equipment in other than dwelling units.

AHJ authority (90.4): the authority having jurisdiction enforces the Code, may interpret its provisions, approve listed materials, and grant special permission for equivalent safety.

Kentucky adopts the National Electrical Code by statewide regulation; permits, inspections, and amendments are administered by the state electrical inspection authority.

Chapter 3 governs wiring methods; 300.4 requires protection where conductors are within 1.25 in of the framing surface or otherwise subject to physical damage.

Minimum cover (Table 300.5): 24 in for direct burial in general, 12 in for residential 120/240 V branch circuits 20 A or less with GFCI, 6 in for rigid metal conduit, 18 in for PVC.

NM cable (334.30): secured within 12 in of every box and at intervals not exceeding 4.5 ft along the run.

EMT (358.30): supported within 3 ft of a box or termination and at intervals not exceeding 10 ft; running threads are not permitted on conduit couplings.

Free conductor (300.14): at least 6 in of free conductor at each box, with at least 3 in extending outside the box opening.

Box required (300.15) at every splice, termination, pull point, and outlet; conduit bodies used as pull points must be sized and supported accordingly.

Conductor identification (200.6, 250.119): grounded conductors white or gray; equipment grounding conductors green or green with a yellow stripe.

Ampacity from Table 310.16 is corrected for ambient temperature and adjusted for more than three current-carrying conductors in a raceway or cable.

250.50: every grounding electrode present at the building or structure must be bonded together to form a single grounding electrode system.

Electrode types (250.52(A)): metal water pipe with 10 ft or more of earth contact, rod or pipe 8 ft long, concrete-encased electrode, ground ring of 20 ft of 2 AWG, and plate electrodes.

Rod and pipe rule (250.53(A)(2)): a single 8 ft rod must measure 25 ohms or less to earth; otherwise a second rod at least 6 ft away must be added.

GEC sizing (Table 250.66) is based on the largest ungrounded service conductor; the required copper conductor need not exceed 3/0 for service conductors of 1100 kcmil or larger.

EGC sizing (Table 250.122) is based on the rating of the overcurrent device protecting the circuit, not on the circuit conductor size.

Permitted equipment grounding conductors (250.118) include copper conductors, rigid metal conduit, IMC, EMT, and listed armored cable, subject to the stated restrictions.

Service bonding (250.24): the grounded service conductor connects to the grounding electrode conductor, the service enclosures, and the supply-side bonding jumper.

Where a grounding electrode conductor passes through ferrous metal enclosures it must be bonded to the enclosure at both ends (250.64(E)); grounding continuity must be maintained at boxes (250.148).

240.4(D): 14 AWG copper limited to 15 A, 12 AWG to 20 A, and 10 AWG to 30 A, except as permitted by the listed exceptions.

240.6(A) standard ratings include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600 A.

240.4(B) next-size-up rule applies when the device does not exceed 800 A, the conductor ampacity does not exceed 800 A, and the 240.4(D) small-conductor limits are not involved.

Tap rule (240.21(B)(1)): a tap up to 10 ft requires ampacity at least one-tenth the upstream device rating, enclosure in a raceway, and termination in a single breaker.

Ambient correction (Table 310.15(B)(2)(a)) uses a 30 degrees C base; multipliers include 0.96 (31-35 C), 0.91 (36-40 C), 0.87 (41-45 C), and 0.82 (46-50 C).

Adjustment (310.15(C)(1)): 4 to 6 current-carrying conductors = 80 percent, 7 to 9 = 70 percent, 10 to 20 = 50 percent of table ampacity.

Table 310.16 copper example: 12 AWG THHN is 20 A at 60 C, 25 A at 75 C, and 30 A at 90 C before correction or adjustment.

Arc energy reduction (240.87): overcurrent devices rated 1200 A or more require an approved means such as zone-selective interlocking or energy-reducing maintenance switching.

210.52(A): receptacles spaced so no point along the wall line is more than 6 ft from a receptacle, which produces the 12 ft wall-space rule.

210.52(C): kitchen countertop receptacles arranged so no point along the counter wall space is more than 24 in from a receptacle.

Branch-circuit ampacity (210.19(A)(1)) is not less than 125 percent of the continuous load plus 100 percent of the noncontinuous load, with the device sized per 210.20.

GFCI (210.8) is required for 125 V, 15 and 20 A receptacles in dwelling bathrooms, garages, outdoors, basements, and within 6 ft of sinks.

AFCI (210.12): dwelling-unit branch circuits supplying outlets in living areas require arc-fault circuit-interrupter protection.

Box fill (Table 314.16(B)): 14 AWG = 2.00 cu in, 12 AWG = 2.25 cu in, 10 AWG = 2.50 cu in per conductor; a device yoke counts as two conductors and all EGCs count as one.

Raceway fill (Chapter 9, Table 1): 53 percent for one conductor, 31 percent for two, and 40 percent for three or more conductors.

Pull and junction boxes (314.28): 8 times the largest raceway for straight pulls and 6 times for angle or U pulls, measured from the raceway entry to the opposite wall.

430.6(A)(1): use the full-load current tables (430.247 through 430.250) for conductor and short-circuit protection sizing, not the motor nameplate current.

Branch-circuit conductors (430.22) are at least 125 percent of the motor full-load current for a single continuous-duty motor.

Short-circuit protection (Table 430.52): inverse-time breaker 250 percent, dual-element fuse 175 percent, non-time-delay fuse 300 percent, instantaneous-trip breaker 800 percent of FLC.

Overload protection (430.32) is set at 125 percent of nameplate current where the service factor is 1.15 or greater, otherwise 115 percent.

Feeder sizing (430.24): 125 percent of the largest motor full-load current plus 100 percent of the other motor loads plus other connected loads.

Disconnecting means (430.102(B)) must be within sight of and readily accessible from the motor and driven machinery, and capable of being locked open.

Air conditioning (440.32): branch-circuit conductors are sized at 125 percent of the rated-load current or branch-circuit selection current, whichever is greater.

Control circuits (430.72) require overcurrent protection based on the control conductor size and source rating; appliance branch circuits follow 422.11.

500.5 classifies locations by Class I (flammable gases or vapors), Class II (combustible dust), Class III (ignitable fibers and flyings), and by Division 1 or 2 for likelihood of the hazard.

Class I Division 1 (500.5(B)(1)): ignitable concentrations exist under normal conditions or frequently because of repair, maintenance, or leakage.

Articles 511 (commercial garages), 513 (aircraft hangars), 514 (motor fuel dispensing), and 515 (bulk storage plants) impose specific area classifications and wiring methods.

517.30 divides the health care essential electrical system into the life safety branch, the critical branch, and the equipment branch.

Articles 518 and 520 add requirements for assembly occupancies and theaters, including emergency lighting and specialized wiring methods.

547.10: agricultural buildings with livestock confinement require an equipotential plane bonded to reduce voltage gradients that could shock animals.

Article 550 covers mobile homes, Article 551 recreational vehicles, and Article 555 marinas and boatyards including shore power ground-fault protection.

690.8: photovoltaic circuit conductors and overcurrent devices are sized at 125 percent of the calculated maximum current.

690.12: PV systems on buildings require rapid shutdown that limits conductors outside the array boundary upon activation.

700.10(A): emergency system wiring must be entirely independent of all other wiring and installed in separate raceways, boxes, and cabinets.

680.26: pool, spa, and fountain metal parts, the water, and specified perimeter surfaces must be bonded to a common equipotential bonding grid.

620.51 and 620.62: elevators require a disconnecting means, and where multiple driving machines are supplied the disconnects must be selectively coordinated.

625 covers electric vehicle supply equipment; 625.40 requires an individual branch circuit for each outlet and 625.54 requires GFCI protection for the receptacle.

695: fire pump supply conductors and overcurrent protection must be arranged to avoid accidental interruption of power to the fire pump.

Article 725 covers Class 1, Class 2, and Class 3 remote-control and signaling circuits; Class 2 and 3 power limits appear in Chapter 9 Tables 11(A) and 11(B).

725.136: Class 2 and Class 3 conductors must be separated from light and power conductors by spacing or a barrier unless a specific exception permits otherwise.

Article 760 covers fire alarm systems: Part II governs non-power-limited fire alarm circuits (NPLFA) and Part III governs power-limited fire alarm circuits (PLFA).

Article 800 covers communications circuits; 800.100 requires a grounding conductor of at least 14 AWG copper, no longer than 20 ft, run to the grounding electrode system.

Article 770 covers optical fiber cable, Article 820 community antenna television and radio distribution, and Article 830 network-powered broadband.

Cable substitution follows the hierarchy CMP over CMR over CM, with comparable ordering among CL3P, CL3R, and CL3 cables.

725.121: Class 2 and Class 3 power supplies must be listed for the purpose or supplied from a listed source with inherently limited output.

110.24: service equipment in other than dwelling units must be field-marked with the available fault current and the date the calculation was performed.

110.16: arc-flash hazard warning labels are required on equipment likely to be examined, adjusted, serviced, or maintained while energized.

110.26(D): working space illumination must be provided and must not be controlled only by automatic means.

300.21: openings around electrical penetrations through fire-rated walls, floors, and ceilings must be firestopped with approved materials.

590.6(A): temporary wiring on construction sites requires GFCI protection for all 125 V, 15 and 20 A receptacle outlets.

NFPA 70E requires establishing an electrically safe work condition: de-energize, lock and tag, and verify the absence of voltage before work begins.

Article 700 emergency systems and Article 701 legally required standby systems must be inspected and tested periodically, with records retained.

Items verified before energizing a new service typically include box fill, grounding and bonding continuity, overcurrent device ratings, and 110.26 working-space clearances.