NEC Electrical Engineering flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Working space depth

Minimum clear distance in front of electrical equipment per NEC 110.26(A): 3 ft for 0-150 V to ground, 3.5 ft for 151-300 V, 4 ft for 301-600 V, and 5 ft above 600 V.

Dedicated equipment space

Space reserved per NEC 110.26(E) from floor to 6 ft above equipment or structural ceiling, whichever is higher, kept clear of foreign piping and ducts not related to the equipment.

Informational Note status

NEC Informational Notes are explanatory only and are not enforceable code requirements; only mandatory text and referenced standards govern the installation.

NM cable support interval

Nonmetallic-sheathed cable must be secured within 12 in of boxes and supported at intervals not exceeding 4.5 ft per NEC 334.30.

EMT fastening rule

Electrical metallic tubing must be securely fastened within 3 ft of boxes and supported at intervals not exceeding 10 ft per NEC 358.30.

Direct burial cover depth

NEC 300.5 requires 24 in minimum cover for general direct-buried conductors, 18 in for residential GFCI branch circuits, and 12 in for 120 V landscape lighting.

Dwelling receptacle spacing

NEC 210.52(A) requires that no point along a dwelling wall floor line is more than 6 ft from a receptacle, and wall spaces 2 ft or wider need a receptacle.

Small-appliance branch circuits

NEC 210.11(C)(1) requires at least two 20 A small-appliance branch circuits to serve dwelling kitchen countertop receptacles.

Dwelling optional calculation

NEC 220.82 method: 100 percent of the first 10 kVA of general load plus 40 percent of the remainder, plus nameplate ratings of appliances and motors.

Grounding electrode conductor sizing

NEC 250.66 sizes the grounding electrode conductor using Table 250.66 based on the largest service-entrance conductor; no conductor smaller than 8 AWG copper is permitted.

Equipment grounding conductor sizing

NEC 250.122 sizes the equipment grounding conductor using Table 250.122 based on the rating of the overcurrent device protecting the circuit.

Single rod 25 ohm rule

NEC 250.53(A)(2) requires a supplemental electrode where a single rod, pipe, or plate electrode has a resistance to ground exceeding 25 ohms.

Standard ampere ratings

NEC 240.6(A) lists standard overcurrent device ratings including 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 125, 150, 200, 400, and 600 A.

Next higher rating rule

NEC 240.4(B) permits the next higher standard overcurrent device where conductor ampacity does not match a standard rating, subject to limits for 800 A and below.

Series-rated systems

NEC 240.86 requires listed and marked combinations of overcurrent devices for series ratings; the sum of ratings must not exceed the load-side device rating.

Motor conductor sizing

NEC 430.22 requires motor branch-circuit conductors to have ampacity of at least 125 percent of the motor full-load current from NEC tables.

Motor overload protection

NEC 430.32 sets overload protection at 115-125 percent of nameplate current for motors over 1 hp with service factor 1.15 or higher.

Motor disconnect requirement

NEC 430.102 requires a disconnecting means within sight of the motor and driven machinery, and 430.103 requires it to open all ungrounded conductors.

Class I Division 1

NEC Article 500 location where flammable gases or vapors are present under normal operating conditions or frequently during repair and maintenance.

Zone classification system

NEC Article 505 uses Zones 0, 1, and 2 for gases and Zones 20, 21, and 22 for dusts, with Zone 0 indicating continuous presence of flammable gas.

Pool equipotential bonding

NEC 680.26 requires bonding of pool shells, decks, metal parts, and associated equipment to an equipotential bonding grid to limit voltage gradients.

Emergency system scope

NEC Article 700 covers emergency systems for illumination and power required for safety during interruption of normal power, with a 90-minute minimum illumination requirement.

Legally required standby

NEC Article 701 covers legally required standby systems that supply power for systems required by law, distinct from emergency systems under Article 700.

Class 2 circuit limits

NEC Article 725 covers Class 2 remote-control and signaling circuits, which are limited in power and voltage and may use smaller conductors than Class 1 circuits.

Limited approach boundary

NFPA 70E distance from exposed energized conductors within which a shock hazard exists; for 120-750 V it is 10 ft for movable conductors and 3 ft 6 in for fixed parts.

Restricted approach boundary

NFPA 70E boundary within which only qualified persons with shock protection may enter; for 120-750 V it is 1 ft from exposed energized parts.

AHJ authority

NEC 90.4 gives the authority having jurisdiction responsibility for interpreting the code, granting approvals, and enforcing compliance with electrical installations.

Continuous load factor

NEC 210.19(A) requires branch-circuit conductors to have ampacity of at least the noncontinuous load plus 125 percent of the continuous load.

GFCI dwelling locations

NEC 210.8 requires GFCI protection in dwelling bathrooms, garages, outdoors, kitchens, laundry areas, and within 6 ft of sinks.

AFCI protection

NEC 210.12 requires arc-fault circuit-interrupter protection for dwelling branch circuits supplying most habitable rooms, including bedrooms and living areas.

Supply-side bonding jumper

NEC 250.102(C) sizes the supply-side bonding jumper using Table 250.102(C)(1) based on the largest ungrounded supply conductor.

Fire pump feeder

NEC 695.6 covers the dedicated fire pump feeder, which has specific overcurrent protection limits to ensure reliable operation during a fire.