Electrical System Repair Glossary of Terms
Electrical system repair involves a precise technical vocabulary that spans diagnostic procedures, code compliance, component classification, and safety standards. This glossary defines the core terms encountered across residential, commercial, and industrial electrical repair contexts in the United States. Mastery of this terminology supports accurate communication between property owners, licensed contractors, inspectors, and code enforcement authorities. The definitions below align with established standards from the National Electrical Code (NEC), OSHA, and NFPA.
Definition and scope
A glossary in the electrical repair trade serves as a standardized reference for component names, fault classifications, regulatory designations, and procedural vocabulary. Scope extends from service entrance equipment through branch circuits, overcurrent protection, grounding systems, and low-voltage subsystems.
Electrical terminology is not uniform across all contexts. The NEC (NFPA 70) governs most definitions used in the US building trades and is adopted — with local amendments — by all 50 states and the District of Columbia. OSHA 29 CFR Part 1910, Subpart S governs electrical standards in general industry workplaces (OSHA Electrical Standards). NFPA 70E addresses electrical safety in the workplace with its own defined vocabulary, including terms such as "arc flash boundary" and "incident energy."
Understanding whether a term applies in a residential, commercial, or industrial context is essential. A "feeder" in NEC Article 100 means a conductor set between the service equipment and the final branch circuit overcurrent device — but its sizing requirements differ sharply across residential, commercial, and industrial installations.
How it works
Electrical repair terminology is structured around three classification layers: component identity, fault type, and code designation. Each layer carries specific vocabulary.
Component Identity Terms
- Service entrance: The conductors and equipment that deliver power from the utility to the first means of overcurrent protection in a building.
- Panelboard: An assembly of overcurrent protective devices, buses, and associated equipment housed in a cabinet; defined in NEC Article 408.
- Branch circuit: The circuit conductors between the final overcurrent device and the outlets served; classified as general-purpose, individual, or multi-wire per NEC Article 210.
- Feeder: Conductors between service equipment and the branch circuit overcurrent device.
- Overcurrent protective device (OCPD): A circuit breaker or fuse that interrupts current above a rated threshold; covered under NEC Article 240.
- Ground fault: An unintentional electrical path between an energized conductor and ground, addressed by GFCI protection under NEC 210.8.
- Arc fault: A high-power discharge of electricity between conductors; mitigated by AFCI devices required under NEC 210.12. See arc fault and ground fault protection repair.
- Bonding: The intentional connection of conductive parts to create electrical continuity; distinct from grounding, which establishes a reference to earth potential. See grounding and bonding repair.
Fault Classification Terms
- Open circuit: A break in the conducting path preventing current flow.
- Short circuit: An unintended low-resistance connection between two conductors, producing excessive current.
- Ground fault: Current returning via an unintended ground path rather than the neutral conductor.
- Overload: A condition where current exceeds the circuit's rated capacity without constituting a short circuit.
- High-resistance connection: A loose or corroded joint that generates heat under load; a leading cause of electrical fires per the U.S. Fire Administration (USFA Electrical Fire Data).
Code Designation Terms
- NEC Article number: The NEC is organized by articles (e.g., Article 250 for grounding and bonding, Article 300 for wiring methods).
- AHJ (Authority Having Jurisdiction): The organization, office, or individual responsible for enforcing the code and approving equipment or installations; defined in NEC Article 100.
- Listing: A product's certification by a recognized testing laboratory (e.g., UL, CSA) that it meets specific safety standards.
- Approved: Acceptable to the AHJ; a term of art under NEC Article 100 that is narrower than "listed."
Common scenarios
Glossary terms appear in distinct patterns depending on the repair context:
Permit and inspection language: When permits and inspections are required, AHJs use NEC-defined terms in their documentation. A failed inspection citing "improper bonding of service equipment" refers specifically to NEC 250.92 requirements.
Contractor communication: When hiring a licensed electrical repair contractor, property owners encounter terms such as "load calculation," "service upgrade," and "OCPD coordination." Load calculation refers to the process defined in NEC Article 220 for determining minimum service and feeder sizes.
Older system repairs: Properties with knob-and-tube or aluminum wiring carry their own terminology. "Remediation" differs from "replacement" in scope and cost. The aluminum wiring repair and remediation context specifically uses terms like "pigtailing" (connecting aluminum conductors to copper via listed connectors) and "CO/ALR" (a device rating indicating compatibility with aluminum conductors under UL 486B).
Diagnostic vocabulary: Electrical system troubleshooting relies on terms like "continuity," "impedance," "megohmmeter testing," and "thermal imaging," each describing a specific measurement or diagnostic method.
Decision boundaries
Repair vs. replacement terminology: The term "repair" implies restoring a component to its original operating condition. "Replacement" involves installing a new component in kind. "Upgrade" involves substituting a component with one of higher capacity or newer code compliance. These distinctions affect permit requirements, contractor scope, and insurance reimbursement. The electrical system repair vs. replacement reference covers these boundaries in detail.
Grounding vs. bonding: Grounding connects the system to earth to limit voltage imposed by lightning or utility faults. Bonding connects conductive parts to eliminate voltage differences between them. The NEC treats these as distinct requirements under Article 250. Conflating them produces both code violations and genuine shock hazards.
Listed vs. approved: A listed product has undergone third-party testing. An approved product has received AHJ acceptance, which may or may not require listing. Some jurisdictions accept unlisted equipment only under specific documented conditions.
GFCI vs. AFCI protection: Ground fault circuit interrupters (GFCIs) trip at 4–6 milliamps of ground fault current to prevent electrocution. Arc fault circuit interrupters (AFCIs) detect arcing patterns that GFCIs do not address. NEC 210.8 governs GFCI placement; NEC 210.12 governs AFCI requirements. Both protections are mandatory in specific locations that have expanded with each NEC edition cycle.
Voltage class distinctions: Low voltage is generally defined as 50 volts or less under NEC Article 100. Equipment operating in the low-voltage system repair context follows different installation rules than standard branch circuits. Three-phase systems — covered under three-phase electrical system repair — carry additional vocabulary around "wye" and "delta" configurations, phase-to-phase versus phase-to-neutral voltages, and balanced load requirements.
References
- NFPA 70: National Electrical Code (NEC) — Primary source for US electrical installation and repair definitions
- OSHA 29 CFR 1910 Subpart S — Electrical — Federal workplace electrical safety standards
- NFPA 70E: Standard for Electrical Safety in the Workplace — Arc flash, incident energy, and workplace safety terminology
- U.S. Fire Administration — Residential Electrical Fire Statistics — Data on electrical fire causes including high-resistance connections
- UL 486B — Standard for Wire Connectors for Use with Aluminum Conductors — Connector rating standards relevant to aluminum wiring remediation terminology