Electrical Contractors Industry Terminology

AHJ (Authority Having Jurisdiction)

The organization or individual (e.g., building department, fire marshal, utility) that interprets and enforces codes and approves installations.

Coordinate pre-construction meetings with the AHJ to confirm inspection milestones; The AHJ requires AFCI protection per the latest code cycle; Submit the service riser diagram to the AHJ for approval.

Arc Flash

A dangerous energy release from an arcing fault that produces extreme heat, pressure, and light; managed through engineering studies, labeling, PPE, and work practices (NFPA 70E).

Update arc-flash labels after any gear or settings changes; Wear the specified PPE category before racking out the breaker; The arc-flash study informs our selective coordination and ZSI settings.

Bid Bond

A surety bond guaranteeing the bidder will enter into a contract and furnish required performance and payment bonds if awarded.

Include a 10% bid bond with the proposal per the RFP; Our surety increased our bonding capacity so we can pursue the hospital project; The GC rejected bids without a bid bond.

BIM (Building Information Modeling)

A model-based process enabling 3D/4D coordination, clash detection, prefabrication planning, and quantification across trades.

Run a BIM clash review to resolve conduit vs duct conflicts; Use the coordinated model to generate prefab spool drawings; Export quantities from BIM to speed the electrical QTO.

Change Order

A formal modification to contract scope, price, and/or schedule triggered by design changes, unforeseen conditions, or owner/GC directives.

Submit a change order for the added receptacle circuits; The owner issued a CCD that we converted into a change order; Track approved change orders in the SOV and job cost reports.

Conduit

A raceway that protects and routes conductors; common types include EMT, IMC/RMC, PVC, ENT, and FMC; sized and filled per NEC.

Upsize the EMT to meet conduit fill and future capacity; Use PVC for underground and transition to RMC above grade; Specify RMC in the mechanical room per the spec section.

Design-Build

A project delivery method where design and construction are under one contract entity, enabling faster decisions and constructability input.

Propose design-build for the tenant improvement to compress schedule; Our design-build team optimized the feeder routing; The GMP was established after the design-build schematic phase.

Duct Bank

A grouped set of underground conduits, often encased in concrete with spacers, used for feeders, primary, or telecom routes.

Maintain duct bank spacing to control mutual heating; Coordinate duct bank elevations with civil and storm utilities; Add spare conduits to the primary duct bank for future loads.

EGC (Equipment Grounding Conductor)

The conductor that bonds equipment enclosures and non-current-carrying metal parts to ground so OCPDs clear faults rapidly.

Verify the EGC size per NEC Table 250.122; Use a separate EGC with EMT where required by spec; Bond all metallic raceways back to the source with the EGC.

Estimating

The preconstruction process of quantifying labor, materials, equipment, and indirects; assessing risk; and pricing a competitive bid or GMP.

Use assemblies to speed the lighting takeoff; Apply NECA labor units and adjust for project difficulty; Include general conditions and contingency in the estimate.

Fault Current

The prospective short-circuit current at a point in the system, used to select AIC ratings, PPE, and protective device settings.

Confirm AIC ratings based on utility available fault current; Perform a short-circuit study before submittals; High fault current drives our bus bracing and breaker selection.

Feeder

Conductors that run from service equipment to distribution equipment or between panels, sized for ampacity, voltage drop, and conditions of use.

Upsize the feeder to limit voltage drop to 3%; Route the 600A feeder in a concrete-encased duct bank; Derate the feeder for ambient temperature in the boiler room.

GFCI (Ground-Fault Circuit Interrupter)

A device that trips on small ground-fault currents (typically 4–6 mA) to protect people from shock, required in specific locations by NEC 210.8.

Provide GFCI receptacles in kitchens and bathrooms; Use a GFCI breaker on the whirlpool tub circuit; Test GFCI function during commissioning.

Grounding Electrode

A conductive element (rod, concrete-encased rebar/Ufer, metal water pipe, plate) that connects the system to earth as part of the grounding electrode system.

Install two 5/8 in rods 6 ft apart per spec; Tie the rebar footing into the grounding electrode system; Bond the metal water service within 5 ft of entry.

Harmonics

Non-sinusoidal current/voltage components at multiples of the fundamental frequency caused by nonlinear loads (VFDs, LED drivers), which can overheat neutrals and transformers.

Specify K-rated transformers to handle harmonic currents; Install filters for the VFD bank; Measure THD during power quality troubleshooting.

Hot Work Permit

A documented authorization and safety plan for energized electrical work or spark-producing tasks (welding, cutting), requiring controls, PPE, and sometimes a fire watch.

Obtain a hot work permit before opening energized gear; Justify energized work per NFPA 70E and implement barriers; Coordinate with the GC for fire watch coverage.

IBEW (International Brotherhood of Electrical Workers)

A labor union representing electrical workers; its collective bargaining agreements set wages, benefits, classifications, and hiring hall procedures.

Verify wage rates per the IBEW CBA; Request travelers through the IBEW hall for peak periods; Follow the IBEW agreement for overtime and shift differentials.

IP Rating (Ingress Protection)

A two-digit code indicating an enclosure’s protection against solids and liquids (e.g., IP20, IP65), per IEC 60529.

Specify IP65 fixtures for the washdown area; The VFD needs an IP54/NEMA 12 enclosure; Compare NEMA Type to IP ratings when substituting products.

J-Box (Junction Box)

An enclosure where conductors are spliced or terminated; must be accessible, covered, and comply with box fill requirements.

Add a J-box above the ceiling for the homeruns; Label all J-boxes per the ceiling plan; Check box fill before adding another splice.

Job Costing

Tracking labor, materials, equipment, and subcontract costs by cost code to monitor WIP, productivity, and profitability.

Review job cost reports weekly against the S-curve; Code prefab hours to the correct cost code; Slippage in branch rough-in labor showed up in job costing.

Knockout

A removable stamped slug in boxes and enclosures used to create conduit entries; properly sized and bushed to protect conductors.

Use a 1/2 in KO for the EMT stub-up; Install bonding bushings on concentric KOs; Replace the KO seal per the NEMA Type rating.

kVA (Kilovolt-Amperes)

A unit of apparent power used to size transformers, generators, and UPS systems; kVA = volts × amps ÷ 1000 for single-phase (adjust for 3-phase).

Select a 150 kVA transformer for the panel group; Confirm the generator kVA based on motor starting inrush; The UPS is rated at 80 kVA with 0.9 power factor.

LED (Light-Emitting Diode)

A high-efficacy solid-state light source with long life; key metrics include CCT, CRI, efficacy, and dimming compatibility.

Specify 3500K LED troffers with 0–10V dimming; Verify LED driver compatibility with the lighting controls; LED retrofits reduced load for the service calc.

Lockout/Tagout (LOTO)

A safety procedure to isolate and control hazardous energy by applying locks and tags to disconnecting means before servicing equipment.

Implement LOTO before working on the MCC bucket; Verify zero energy state and test before touch; Maintain LOTO logs per company policy and OSHA.

MCC (Motor Control Center)

A metal-enclosed lineup containing motor starters, VFDs, feeders, and control components with vertical and horizontal bus and removable buckets.

Provide a 65 kAIC rated MCC with integral metering; Coordinate feeder breakers and VFDs in the MCC; Allow front clearances per NEC 110.26.

Megger Testing (Insulation Resistance)

Applying a DC test voltage with a megohmmeter to measure insulation resistance of cables and windings to verify integrity and dryness.

Test feeders at 1000 VDC for 1 minute per spec; Record insulation resistance values on the commissioning report; Investigate low megger readings before energization.

NEC (National Electrical Code)

NFPA 70, the widely adopted minimum standard for safe electrical installations in the U.S., updated on a 3-year cycle.

Size conductors and OCPDs per the NEC; The local AHJ adopted the 2023 NEC with amendments; Ensure GFCI and AFCI locations align with NEC 210.

NEMA Enclosure Rating

Standards defining enclosure types (e.g., 1, 3R, 4, 4X, 12) for environmental protection; not one-to-one with IP ratings.

Specify NEMA 3R for outdoor panels; Use NEMA 4X in corrosive washdown areas; Replace the panel to meet the required NEMA Type.

OCPD (Overcurrent Protective Device)

A device such as a circuit breaker or fuse that interrupts current during overloads or short circuits, protecting conductors and equipment.

Select a 20A breaker per conductor ampacity and load; Use Class J fuses for high interrupting rating; Adjust electronic trip settings to coordinate with downstream OCPDs.

OSHA (Occupational Safety and Health Administration)

The U.S. agency and set of regulations governing workplace safety, including electrical safety standards in 29 CFR 1910 and 1926.

Train crews on OSHA electrical standards and LOTO; Perform Job Hazard Analyses per OSHA requirements; Keep OSHA 300 logs current for the project.

Panelboard

A wall-mounted distribution assembly with bus and breakers for branch circuits, typically up to 600V, requiring directories and clearances.

Provide a series-rated panelboard per coordination study; Label the panel directory with circuit descriptions; Specify copper bus for the critical panelboard.

Power Factor

The ratio of real power (kW) to apparent power (kVA); low PF increases current and losses; corrected with capacitors or filters.

Add PF correction capacitors on the 480V system; Verify generator sizing at 0.8 PF; The utility imposes penalties for poor power factor.

QA/QC (Quality Assurance/Quality Control)

Processes to prevent and detect defects, including procedures, inspections, testing, and documentation for code and spec compliance.

Implement a QA plan with hold points for inspections; Use QC checklists for gear terminations; Track rework costs to improve QA/QC.

QTO (Quantity Takeoff)

Measuring and counting project quantities (conduit, wire, devices, fixtures) from drawings or models to support estimating and procurement.

Use digital QTO to count receptacles by type; Linear takeoff the feeders from the one-line and plans; Export QTO from BIM to the estimate.

Raceway

An enclosed channel designed expressly for holding wires, cables, or busbars, such as conduit, cable tray, or wireway.

Verify raceway fill and derating for the home runs; Use cable tray instead of multiple conduits for feeders; Bond metallic raceways per NEC 250.

RFI (Request for Information)

A formal question submitted to clarify plans, specs, or conflicts, used to document direction and avoid assumptions.

Issue an RFI about the feeder size discrepancy; Reference the RFI response on the as-builts; RFIs must be resolved before fabrication.

Submittals

Shop drawings, product data, and samples submitted for design team review to verify compliance before fabrication and procurement.

Submit switchgear shop drawings for approval; Track submittal status on the log to protect schedule; Provide cut sheets for all luminaires and controls.

Switchgear

Metal-enclosed assemblies of switching and protective devices (often at higher amperages/voltages) that distribute and control power; focus on AIC, bus ratings, and coordination.

Specify 65 kAIC switchgear with main-tie-main; Provide arc-resistant gear in the utility room; Program ZSI between mains and feeders.

T&M (Time and Materials)

A billing method in which the client pays for actual labor hours and material costs plus an agreed markup, often used for small, undefined, or emergency work.

Use T&M for troubleshooting and small tenant requests; Submit daily T&M tickets for GC signoff; Switch to lump sum after scope is defined.

Transformer

An electromagnetic device that transfers power between circuits and changes voltage levels; types include dry-type, oil-filled, isolation, and autotransformers.

Provide a 480V to 208/120V dry-type transformer; Confirm impedance and temperature rise on submittals; Isolate harmonics with a K-rated transformer.

Undergrounding

Installing conduits and cables below grade per trench details, burial depths, backfill requirements, and warning tape standards.

Maintain 24 in minimum cover for the 600V feeders; Use red warning tape 12 in above the duct bank; Coordinate trench routing with civil and landscape.

UPS (Uninterruptible Power Supply)

A system providing short-term backup and power conditioning using batteries and inverters; topologies include offline, line-interactive, and online double conversion.

Size the UPS for 15 minutes at full load; Bypass the UPS during maintenance using a wrap-around; Monitor battery health in the BMS.

Value Engineering

A structured approach to improving value by reducing cost without degrading required function, performance, or quality.

Propose MC cable in lieu of EMT where allowed; Offer alternate luminaires meeting photometric criteria; Relocate gear to reduce conduit lengths.

Voltage Drop

The reduction in voltage along a conductor due to resistance and current; typically limited to about 3% branch and 5% feeder/overall in design practice.

Upsize conductors to reduce VD on long runs; Increase system voltage to mitigate voltage drop; Verify VD for the parking lot lighting circuits.

Wattage

The measure of real power in watts; used for load calculations, energy code compliance, and equipment sizing.

Confirm lighting wattage allowances per energy code; Calculate service size from connected and demand loads; Select a 1500W heater for the vestibule.

Wireway

A sheet-metal or nonmetallic trough with a removable cover used for protecting and routing conductors in control and industrial installations.

Use wireway above control panels to manage conductors; Stay within wireway fill and derating limits; Provide hinged covers for frequent access areas.

XHHW (Cross-Linked Polyethylene Insulated Wire)

A thermoset insulation type rated for wet and dry locations, typically 90°C, available in copper and aluminum; XHHW-2 rated 90°C wet.

Specify aluminum XHHW-2 feeders to reduce cost; Pull XHHW conductors in EMT per spec; Use XHHW in rooftop UV-exposed runs where allowed.

Y (Wye) Connection

A three-phase system configuration with a common neutral point; common secondary voltages include 208Y/120V and 480Y/277V.

Order a 480Y/277V service for lighting and motors; Balance single-phase loads across phases on the wye system; Specify a neutral for wye-connected loads.

Zone Selective Interlocking (ZSI)

A protective scheme where downstream breakers or relays signal upstream devices to delay tripping during downstream faults, improving selectivity and reducing arc energy.

Enable ZSI between the main and feeder breakers; Verify control wiring for ZSI during startup; Use ZSI to maintain uptime on critical panels.

Zoning Ordinance

Local land-use regulations that impact electrical work such as transformer siting, generator placement, setbacks, heights, and noise limits.

Confirm the zoning allows the rooftop generator and screen wall; Meet setback requirements for the pad-mount transformer; Coordinate with planning for lighting cutoff compliance.