NASCLA Journeyman Electrician flashcards

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

Ohm's law

For a resistive circuit, voltage equals current times resistance; power equals voltage times current and also equals current squared times resistance.

Balanced three-phase power

For a balanced three-phase load, real power equals the square root of three times line voltage times line current times power factor.

Continuous load definition

A continuous load is one expected to operate at maximum current for three hours or more; its branch-circuit conductors and overcurrent device are sized at 125 percent.

RMS sine voltage

For a sine wave, root-mean-square voltage equals 0.707 times peak voltage; peak voltage equals 1.414 times RMS voltage.

Service disconnect six throws

Service disconnecting means must be grouped and marked, and no more than six switches or breakers may be used to disconnect all service conductors.

Dwelling receptacle spacing

In dwelling units, wall space must be arranged so no point is more than six feet from a receptacle; receptacles are generally spaced no more than twelve feet apart.

GFCI dwelling locations

GFCI protection is required for dwelling bathroom, garage, outdoor, kitchen, laundry, crawl-space, and unfinished-basement receptacles under NEC 210.8.

Raceway fill percentages

A raceway may be filled to 53 percent for one conductor, 31 percent for two, and 40 percent for three or more conductors; a nipple may be filled to 60 percent.

Paralleled conductor requirements

Paralleled conductors must be at least 1/0 AWG and have the same material, size, insulation, length, and termination arrangement to share current equally.

EMT support intervals

Electrical metallic tubing must be secured within three feet of boxes and supported at intervals not exceeding ten feet.

Box fill conductor volumes

For box fill, each 14 AWG conductor counts 2.00 cubic inches, each 12 AWG counts 2.25, and each 10 AWG counts 2.50; fittings and devices add volume.

Equipment grounding box count

All equipment grounding conductors entering a box are counted as one conductor when calculating box fill volume.

Device yoke box fill

Each yoke or device with a strap counts as two conductors of the largest conductor connected to it for box fill calculations.

Grounding electrode 25 ohms

A single grounding electrode such as a rod must have resistance of 25 ohms or less; if not, a second electrode must be added.

GEC versus EGC

The grounding electrode conductor connects the system to earth; the equipment grounding conductor provides a fault-current path between equipment and the grounding system.

Separately derived system bonding

At a separately derived transformer, bond the secondary neutral X0 to the enclosure and grounding electrode and install the system bonding jumper.

GFCI versus AFCI

GFCI devices protect people from ground-fault current; AFCI devices detect dangerous arcing faults in branch-circuit wiring.

Motor conductor 125 percent

Motor branch-circuit conductors for continuous-duty motors must have ampacity at least 125 percent of the motor full-load current from NEC tables.

Motor overload protection range

Motor overload protection is typically set at 115 to 125 percent of nameplate full-load amps, depending on service factor and temperature rise.

Motor disconnect location

A motor disconnecting means must be within sight of the motor and controller, readily accessible, and lockable where required by the installation.

Transformer kVA formula

Single-phase transformer capacity in kVA equals voltage times current divided by 1000; three-phase capacity uses the square root of three times line voltage times line current divided by 1000.

Transformer secondary tap rule

NEC 240.21(C) permits limited lengths of transformer secondary conductors without overcurrent protection at the transformer, subject to length and ampacity rules.

Delta-wye secondary neutral

A delta-wye transformer provides a grounded neutral on its secondary, allowing line-to-neutral loads and a separately derived grounding connection.

Hazardous location classes

Class I locations contain flammable gases or vapors; Class II contains combustible dust; Class III contains ignitable fibers or flyings.

Division 1 versus 2

Division 1 means the hazardous condition is present under normal operation; Division 2 means it is present only under abnormal conditions.

Bathroom receptacle GFCI

Dwelling bathroom receptacles require GFCI protection, and at least one receptacle must be located within three feet of the basin.

Lockout tagout steps

Lockout/tagout requires isolating all energy sources, applying locks and tags, releasing stored energy, and verifying zero energy before work begins.

OSHA construction GFCI

OSHA construction standards require GFCI protection for 15- and 20-ampere, 120-volt receptacle outlets on construction sites.

Test before touch

Before contacting conductors, verify the circuit is de-energized using a meter rated for the voltage and installation category.

Dwelling lighting load

Dwelling general lighting load is calculated at three volt-amperes per square foot; small-appliance and laundry circuits each add 1500 volt-amperes.

Dwelling demand factor

For dwelling general lighting and appliance loads, the first 3000 volt-amperes is at 100 percent and the remainder at 35 percent.

Plan scale reading

A plan scale of one-quarter inch equals one foot means one-quarter inch on the drawing represents twelve inches in the actual building.