North Carolina Unlimited Electrical Contractor (U)

Key Concepts

Systems required / permitted / prohibited from grounding - AC systems 50–1000 V must be grounded where the system is 3-phase, 4-wire wye with the neutral used as a circuit conductor — 250.20(B)(2); also where max voltage to ground does not exceed 150 V (250.20(B)(1)) and 3-phase, 4-wire delta with a phase midpoint used as a circuit conductor (250.20(B)(3)). - Systems under 50 V must be grounded where the transformer supply system exceeds 150 V to ground, is ungrounded, or is installed outside as overhead conductors — 250.20(A). - Systems in 250.21(A) (industrial furnaces, rectifiers for adjustable-speed drives, control-circuit systems) are permitted but not required to be grounded; ungrounded systems operating at not less than 120 V and 1000 V or less require ground…

NC Unlimited Electrical Contractor (U) · 9 questions (9%)

Key Concepts

Definitions (Article 100). Overcurrent — any current in excess of the rated current of equipment or the ampacity of a conductor; it may result from overload, short circuit, or ground fault. Interrupting Rating — the highest current at rated voltage that a device is identified to interrupt under standard test conditions. Per 110.9, equipment intended to interrupt current at fault levels must have an interrupting rating at nominal circuit voltage at least equal to the current available at the line terminals.

Key Concepts

Protection from physical damage (300.4) - Bored holes (300.4(A)(1)): The edge of the hole must be not less than 32 mm (1¼ in.) from the nearest edge of the wood member. Where that distance cannot be maintained, protect the cable or raceway with a steel plate or bushing at least 1.6 mm (1/16 in.) thick. Exception No. 1: steel plates are not required for RMC, IMC, rigid nonmetallic conduit, or EMT. - Parallel to framing members (300.4(D)): The nearest outside surface of the cable or raceway must be not less than 32 mm (1¼ in.) from the nearest edge of the framing member where nails or screws are likely to penetrate. - Under metal-corrugated sheet roof decking (300.4(E)): Not less than **38 mm (1½…

North Carolina Unlimited Electrical Contractor (U)

Key Concepts

Scope and general (Article 314, Part I) - Article 314 covers installation and use of all boxes and conduit bodies used as outlet, device, junction, or pull boxes, and handhole enclosures. Cast metal, sheet metal, nonmetallic, and other boxes such as FS, FD, and larger boxes are not classified as conduit bodies (314.1). - Round boxes shall not be used where conduits or connectors requiring locknuts or bushings connect to the side of the box (314.2). - Nonmetallic boxes are permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways — unless internal bonding means are provided between all entries (314.3, Exc. No. 1). - Metal…

North Carolina Unlimited Electrical Contractor (U) — 9 questions (9%)

Key Concepts

Installation requirements

• Conductors considered outside a building (230.6): under not less than 50 mm (2 in.) of concrete; in a raceway encased in not less than 2 in. of concrete or brick; in a vault meeting Article 450, Part III; in conduit under not less than 450 mm (18 in.) of earth beneath a building; or in RMC/IMC routed directly through an eave (not a wall) to meet 230.24 clearances. Service conductors shall not pass through the interior of another building (230.3).
• Overhead clearances (230.24): 2.5 m (8 ft) above a roof, maintained 900 mm (3 ft) in all directions from the roof edge. Exception No. 2: reduction to **900 mm (3…

North Carolina Unlimited Electrical Contractor (U) · 9 questions (9%)

Key Concepts

General information / which current to use - For general motor applications, use the values in Table 430.247, 430.248, 430.249, and 430.250 to determine conductor ampacity, switch ratings, and branch-circuit short-circuit and ground-fault (SC/GF) protection instead of the nameplate current — 430.6(A)(1). Nameplate current is used only for separate motor overload protection — 430.6(A)(2). - Multispeed motors and motors built for low speeds (less than 1200 RPM) or high torques use nameplate current — 430.6(A)(1). - For a hermetic refrigerant motor-compressor, use the rated-load current marked on the equipment nameplate (or branch-circuit selection current where so marked) — 440.6(A).

North Carolina Unlimited Electrical Contractor (U)

Key Concepts

Classification of locations (NEC 500.5) - Class I, Division 1: ignitible concentrations of flammable gases/vapors can exist under normal operating conditions (500.5(B)(1)). - Class I, Division 2 includes an area adjacent to a Division 1 location to which ignitible concentrations might occasionally be communicated — unless prevented by adequate positive-pressure ventilation from a source of clean air with effective safeguards against ventilation failure (500.5(B)(2)(3)). - Class III: locations hazardous because of easily ignitible fibers or materials producing combustible flyings that are handled, manufactured, or used, but not likely to be in suspension in quantities sufficient to produce ignitible mixtures (500.5(D)). - Refrigerant machinery rooms with ammonia refrigeration systems may be "unclassified" where adequate mechanical ventilation operates continuously or…

Key Concepts

Branch-circuit loads (Article 220, Part II) - Floor area is computed from outside dimensions; for dwelling units, exclude open porches, garages, and unused/unfinished spaces not adaptable for future use (220.11). - Dwelling minimum unit load: 3 VA/ft² for general lighting and general-use receptacles; this includes general-use receptacle outlets of 20 A or less, the outlets of 210.52(E) and (G), and lighting outlets of 210.70 — no additional calculation for those outlets (220.14(J)). - Non-dwelling lighting: use the unit load from Table 220.12 (Retail/Stores = 1.9 VA/ft², Office/Banks = 1.3 VA/ft², Warehouse = 1.2 VA/ft²). The 125 percent continuous-load multiplier is already included in these unit values (Table 220.12 Note). - Receptacle outlets, other than as covered in 220.14(J)/(K): 180 VA per single or multiple…

Key Concepts

Air conditioning and hermetic motor-compressors (Article 440) - Conductor sizing uses the MCA (minimum circuit ampacity) marked on the equipment nameplate; MOCP is for the overcurrent device, not the conductors (NEC 440.6). An AC unit marked MCA 42A / MOCP 50A needs conductors with at least 42A ampacity. - Branch-circuit conductors for a single hermetic motor-compressor must have an ampacity of at least 125% of the rated-load current (RLA) — NEC 440.32. - Maximum branch-circuit short-circuit and ground-fault protection is 175% of the RLA — NEC 440.22(A). The 2020 NEC has no next-higher-size allowance here: if 175% is not a standard rating, use the next standard size down; only if that device cannot carry the starting current may the rating be increased, to a…

Key Concepts

Definitions (NEC 2020, Article 100, Part I) — these are lifted verbatim in exam questions:

• Ampacity — "the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating." (Article 100, CMP-6)
• Continuous Load — a load where the maximum current is expected to continue for 3 hours or more. Conductors and overcurrent devices serving continuous loads are generally sized at 125 percent of the load. (Article 100 — Definitions)
• Externally Operable — "Capable of being operated without exposing the operator to contact with live parts." (Article 100, CMP-1)
• Dead Front — "Without live parts exposed to a person on the operating side of the equipment." (Article 100, CMP-9)
• Enclosed…

Key Concepts

Board and licensing law (G.S. Ch. 87, Art. 4) - The State Board of Examiners of Electrical Contractors is composed of seven members serving staggered seven-year terms, each serving until a successor is designated and qualified (G.S. 87-39(a),(b); Ch. 3). Composition: one from the NC Department of Insurance, one representing the NC Association of Electrical Contractors, and five appointed by the Governor (engineering faculty member, chief electrical inspector, an unlimited-license contractor representing the Carolinas Electrical Contractors Association, and two public members). Members may not serve consecutive complete terms (87-39(c)). - Electrical contracting = "engaging or offering to engage in the business of installing, maintaining, altering or repairing any electric work, wiring, devices, appliances or equipment" (G.S. 87-43). At least one listed qualified individual must…