WA Electrician flashcards

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

Ohm's Law

Voltage equals current multiplied by resistance (E = I × R); rearranged, I = E ÷ R and R = E ÷ I. In a resistive circuit, power equals E × I.

Single-phase voltage drop formula

VD = (2 × K × I × L) ÷ circular mils, where K is 12.9 for copper and 21.2 for aluminum, I is amperes, and L is the one-way length in feet.

Series circuit current

In a series circuit the same current flows through every component, total resistance is the sum of the resistances, and source voltage equals the sum of the voltage drops.

Parallel circuit voltage

In a parallel circuit the voltage is identical across every branch, total current is the sum of branch currents, and total resistance is less than the smallest branch resistance.

Dwelling general lighting load

NEC 220.12 assigns a general lighting load of 3 volt-amperes per square foot for dwelling occupancies, which is then reduced by the demand factors of Table 220.42.

Small appliance branch circuit load

A dwelling unit requires at least two 20-ampere small appliance branch circuits, each computed at 1,500 volt-amperes when calculating the service or feeder load.

Washington electrical code adoption

Washington adopts the National Electrical Code with amendments published in WAC 296-46B, administered by the Department of Labor & Industries, which licenses electricians and inspects installations.

Continuous load 125 percent factor

A continuous load operates for three hours or more; branch-circuit conductors, overcurrent devices, and feeders serving it must be sized at 125 percent of the load current.

Securing Type NM cable

Type NM cable must be fastened within 12 inches of every box and at intervals not exceeding 4.5 feet, and its ampacity is limited to the 60°C column.

EMT fastening intervals

Electrical metallic tubing must be secured within 3 feet of each box or fitting and at intervals not exceeding 10 feet along the remainder of the run.

Raceway fill for three conductors

Three or more conductors in a raceway may occupy no more than 40 percent of the interior cross-sectional area; a single conductor is limited to 53 percent.

Box fill per 12 AWG conductor

Each 12 AWG conductor requires 2.25 cubic inches of box volume, 14 AWG requires 2.00 cubic inches, and 10 AWG requires 2.50 cubic inches under Table 314.16(B).

Equipment working space dimensions

For equipment operating at 150 volts to ground or less, working space must be at least 3 feet deep, 30 inches wide, and 6 feet 6 inches high.

Derating for bundled conductors

Where four to six current-carrying conductors share a raceway, ampacity drops to 80 percent; seven to nine drop to 70 percent; ten to twenty drop to 50 percent.

Protecting cable in bored holes

Cable run through a bored hole less than 1¼ inches from the nearest edge of a framing member must be protected by a steel plate at least 1/16 inch thick.

Identifying the grounded conductor

The grounded conductor is identified by a white or gray finish; equipment grounding conductors use green, green with yellow stripes, or bare copper conductors.

Dwelling wall receptacle spacing

In dwelling units no point along the floor line of a wall space may be more than 6 feet from a receptacle, and spaces 2 feet or wider require one.

Countertop receptacle spacing

Kitchen countertop receptacles must be placed so that no point along the counter wall is more than 24 inches from a receptacle, with one on each island.

GFCI protection in bathrooms

All 125-volt, single-phase, 15- and 20-ampere receptacles installed in dwelling unit bathrooms require ground-fault circuit-interrupter protection for personnel.

Inverse-time breaker for motors

A motor branch circuit may use an inverse-time circuit breaker sized up to 250 percent of the motor full-load current for short-circuit and ground-fault protection.

Dual-element fuse motor limit

Time-delay, dual-element fuses providing short-circuit protection for a motor branch circuit may be sized up to 175 percent of the motor full-load current.

Motor overload trip setting

Overload protection for a continuous-duty motor with a marked service factor of 1.15 or more is set at no more than 125 percent of nameplate full-load amperes.

Motor branch conductor size

Conductors supplying a single motor must have an ampacity of at least 125 percent of the motor full-load current taken from Tables 430.248 through 430.250.

Motor disconnect location

The motor disconnecting means must be within sight of the motor and driven machinery and within 50 feet of it, unless the device can be locked open.

Pool receptacle distance

Receptacles serving a permanently installed swimming pool must be at least 6 feet from the inside wall of the pool and no more than 20 feet from it.

Overhead conductors near pools

Insulated overhead conductors rated up to 750 volts must be at least 10 feet horizontally from the pool edge, with greater clearances where diving structures are installed.

PV rapid shutdown

Photovoltaic conductors more than 1 foot from the array must be reduced to 80 volts or less within 30 seconds after rapid shutdown is initiated.

Class I Division 2 location

An area where ignitable concentrations of flammable gases or vapors are expected only under abnormal operating conditions, such as equipment failure or a fault.

Emergency lighting duration

Exit signs and emergency illumination supplied by an emergency system must be capable of providing the required level of light for at least 90 minutes.

GFCI on construction sites

All 125-volt, 15- and 20-ampere receptacles used for temporary wiring on construction sites must be protected by ground-fault circuit interrupters.

Arc flash boundary

The distance from energized equipment at which a person could receive a second-degree burn, defined as an incident energy of 1.2 calories per square centimeter.

Limited approach boundary

A shock-protection boundary that unqualified persons may not cross unless continuously escorted by a qualified person; the distance depends on voltage and appears in NFPA 70E tables.