Residential electrical glossary
Plain-English definitions of the terms that come up across the Spark Shark Electric handbook. If a chapter uses one of these terms, it links here.
A
- AFCI (Arc-Fault Circuit Interrupter)
- A breaker (or outlet) that detects the characteristic electrical signature of an arc, like a loose connection sparking inside a wall, and trips before the arc starts a fire. Required by NEC on most living-area branch circuits. See safety non-negotiables.
- AHJ (Authority Having Jurisdiction)
- The local government office that enforces electrical code in your area, typically your city or county building department. The AHJ decides which NEC edition is adopted, what permits are required, and who inspects the work. See how to pull a permit.
- Ampacity
- The maximum continuous current (in amps) a wire can carry without overheating. Set by wire gauge, insulation type, temperature, and bundling. The reason a 20A breaker on 14 AWG wire is a fire hazard.
- AWG (American Wire Gauge)
- The sizing scale for residential wire. Lower number = thicker wire = more ampacity. Common residential gauges: 14 AWG (15A), 12 AWG (20A), 10 AWG (30A), 8 AWG (40–50A), 6 AWG (60A+).
B
- Bonded (bonding)
- Electrically tied together. In a main panel, the neutral and ground bars are bonded, that's the only place in the system where they should connect. In a sub-panel, neutrals and grounds stay separated; bonding them there is a common code violation.
- Branch circuit
- The wiring that runs from a single breaker to one or more outlets, lights, or hardwired devices. Most homes have 20–40 branch circuits.
- Breaker (circuit breaker)
- A resettable switch that interrupts current when it exceeds a set amount. The breaker protects the wire downstream from overheating. See breaker keeps tripping.
- Bus bar
- The metal bars inside a panel that distribute power from the main breaker to the branch breakers. Hot bus bars are energized whenever the main is on.
C
- CIB (Construction Industries Board)
- The Oklahoma agency that licenses electrical contractors and electricians. License lookup at ok.gov/cib.
- Conductor
- A wire (or other path) that carries current. The hot, neutral, and ground wires inside an NM-B cable are each conductors.
- Conduit
- A rigid or flexible tube that protects wiring run outside walls, common for garages, basements, exterior runs, and sub-panel feeders.
D
- Dedicated circuit
- A branch circuit that feeds exactly one outlet or appliance. Required by code for ranges, dryers, microwaves, dishwashers, EV chargers, and a few others.
- Disconnect
- A switch or breaker that lets you completely de-energize a piece of equipment, the main breaker is the whole-house disconnect; a sub-panel feeder breaker is a sub-panel disconnect.
E
- EGC (Equipment Grounding Conductor)
- The bare copper or green-insulated wire that ties every metal box, device chassis, and appliance frame back to the panel's ground bar. The path stray current uses instead of you.
- EVSE (Electric Vehicle Supply Equipment)
- The technical name for an "EV charger", the wall-mounted unit and its cable. See EV charger installation.
F
- Feeder
- The wiring between a main panel and a sub-panel (or between the meter and a main disconnect). Sized for the sub-panel's breaker, not a branch load.
G
- GFCI (Ground-Fault Circuit Interrupter)
- An outlet (or breaker) that compares current flowing out the hot to current returning on the neutral. If they differ by ~5 mA, it trips, because the missing current is leaking somewhere, possibly through a person. Required in bathrooms, kitchens, garages, basements, outdoors, and within 6 feet of a sink. See GFCI line vs load.
- Ground
- The reference-zero voltage point of the system, tied to actual earth through ground rods and bonding to incoming metal water pipe. Not the same as neutral, even though they're bonded at the main panel.
- Ground rod
- An 8-foot copper-coated rod driven into the earth outside the home, with a clamp and wire back to the panel's ground bar. Most homes have two, spaced at least 6 feet apart.
H
- Hot
- The energized conductor, black, red, or any color other than white/gray/green/bare. Carries the 120V or 240V supply.
- Homeowner exemption
- Oklahoma's provision that lets a property owner do electrical work on their own owner-occupied home without an electrical license, within limits, with permits where required, and subject to inspection. Does not extend to rentals, family homes you don't own, or service-entrance work. See homeowner exemption.
I
- Inspection
- The visit by your AHJ's inspector to verify permitted work is code-compliant and safe before it's closed up or energized. Rough-in inspection happens with the walls open; final inspection after trim. See passing inspection.
L
- Line (terminals)
- On a GFCI or smart outlet, the terminals that receive power from the panel. Wires from the breaker land on LINE.
- Load (terminals)
- On a GFCI or smart outlet, the terminals that send power downstream to other outlets on the same circuit. Wires going to the next outlet land on LOAD.
- Load calculation
- A code-required arithmetic check of a panel's total demand, used when adding major loads (EV chargers, hot tubs, electric ranges). Determines whether a service upgrade is needed.
- LOTO (Lock-Out / Tag-Out)
- The discipline of physically locking a breaker off and tagging it so nobody can turn it back on while you're working on the circuit. Non-negotiable for any panel-adjacent work.
M
- Main breaker
- The single breaker (usually at the top of the panel) that disconnects the whole house from utility power. The lugs feeding it stay energized even with it off, only OG&E pulling the meter de-energizes them.
- MC cable
- Metal-clad cable, insulated conductors inside a flexible metal jacket that doubles as ground path. Used where NM-B isn't allowed (commercial, some basements, exposed runs).
N
- NEC (National Electrical Code)
- NFPA 70, the model electrical code used across the United States. Updated every three years; jurisdictions adopt specific editions on their own schedule. See NEC 2023 overview.
- Neutral
- The current-return conductor, white or gray. Bonded to ground at the main panel only. Carries normal load current back to the source; should not carry current under fault conditions.
- NM-B (Romex)
- Non-metallic-sheathed cable, type B. The standard residential branch-circuit cable: 2 or 3 insulated conductors plus a bare ground inside a plastic jacket. Sized as "14/2," "12/3," etc.
O
- Overcurrent
- Any current above the rated capacity of a wire or device. Breakers and fuses are overcurrent protection devices.
P
- Panel (load center)
- The metal box housing the main breaker, bus bars, branch breakers, neutral bar, and ground bar. The heart of a residential electrical system.
- Permit
- The local government's authorization to do permitted electrical work, paired with an inspection requirement. What counts as permitted work varies by AHJ.
R
- Receptacle
- The code term for what most homeowners call an "outlet", the device a plug goes into.
- Romex
- A brand name for NM-B cable, used generically across the industry.
S
- Service drop
- The utility's wiring from the pole (or transformer) to your house. Owned and maintained by the utility, not the homeowner.
- Service entrance
- The wiring and equipment from the meter to the main disconnect (the main breaker). Conductors here are always energized when the meter is in place.
- Sub-panel
- A secondary panel fed from the main panel, used for garages, additions, workshops, or major load expansions. Neutrals and grounds must remain separated in a sub-panel, the single most-confused sub-panel code rule. See sub-panel installation.
T
- Transfer switch
- The device that safely connects a generator to a home's electrical system by transferring loads off the utility and onto the generator (and back). Required for permanent standby generators; "backfeeding" through a dryer outlet is illegal and dangerous. See generator installation.
- Three-test method
- The verification sequence before touching a wire you think is dead: (1) test the tester on a known-live source, (2) test the target wire, (3) test the known-live source again. Live, dead, live.
V
- Voltage
- Electrical pressure. Residential US: 120V leg-to-neutral, 240V leg-to-leg. Higher voltage doesn't always mean more dangerous, current and duration matter more.
W
- Wire nut
- The twist-on plastic-and-spring connector that joins two or more conductors inside an electrical box. Use the right size for the conductor count and gauge.
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