South Carolina - NASCLA-Accredited Trade Examination for Residential Electrical Contractor

Key Concepts

Ohm's Law. Current is directly proportional to voltage and inversely proportional to resistance (Theory 12.6(A)). The formula and its transpositions (Theory 12.6(B), 12.7): I = E/R (amperes), E = I × R (volts), R = E/I (ohms). Place your finger on the unknown in the Ohm's Law Formula Circle and the two remaining variables show the formula (Theory 12.7). Ugly's states the same three basic formulas plus the 12-formula power wheel (Ugly's, Ohm's Law, Page 1).

Meters. Voltmeters connect in parallel with the load and measure the difference of potential between the two test leads (Theory 12.3(B)). Ohmmeters measure resistance in ohms (Theory 12.4(B)). Series-connected ammeters connect in series; handheld series-connected ammeters are typically limited to a maximum current of 10 amperes (Theory 12.5(B)(1)). Clamp-on ammeters measure current without opening the circuit and can measure current in…

Key Concepts

Electrically safe work condition & lockout/tagout - Conductors/circuit parts at 50 volts or more must be put into an electrically safe work condition before work when the employee is within the limited approach boundary, or interacts with equipment where conductors are not exposed but an increased likelihood of arc flash injury exists [NFPA 70E 110.2(B)]. - Energy isolation devices for machinery/equipment installed after January 2, 1990 shall be capable of accepting a lockout device [120.4(A)]. - A tagout device attachment means shall withstand at least 222.4 N (50 lb) of force at a right angle to the disconnecting means surface, and be nonreusable, attachable by hand, self-locking, nonreleasable, and equal to an all-environmental tolerant nylon cable tie [120.4(D)(3)]. - Tagout without a lock is permitted only where equipment design precludes installing a lock, and at least one…

Key Concepts

Dwelling unit minimum unit load. In one-family, two-family, and multifamily dwellings the minimum unit load shall be not less than 33 volt-amperes/m² (3 volt-amperes/ft²) — NEC 2023, 220.41 (verified questions also cite 220.12/Table 220.12). That unit load already covers all general-use receptacle outlets of 20-ampere rating or less, the receptacle outlets of 210.52(E) and (G), and the lighting outlets of 210.70; no additional calculation is required for them.

Floor area. Calculated from the outside dimensions; for dwelling units it shall not include open porches or unfinished areas not adaptable for future use as a habitable room — 220.5(C). Under the optional method, garages are also excluded — 220.82(B)(1).

Key Concepts

• Purpose of system grounding: Grounded systems shall be connected to earth in a manner that limits the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that stabilizes the voltage to earth during normal operation — 250.4(A)(1).
• Connection methods: Listed pressure connectors, terminal bars, exothermic welding, machine screw-type fasteners engaging not less than two threads (or secured with a nut), and other listed means are permitted — 250.8(A). Devices or fittings that depend solely on solder shall not be used — 250.8(B). Connections to electrodes also may not depend on solder — 250.70(A).
• Clean surfaces: Paint, lacquer, enamel must be removed from threads and contact surfaces, or fittings designed to make removal unnecessary must be used — 250.12.
• Grounded conductor at the service: It shall not be reconnected to…

Key Concepts

Swimming pools, spas, hot tubs (Art. 680 / IRC Ch. 42) - Permanently wired pool pump motors: not less than 1.5 m (5 ft) from the inside wall of the pool, unless listed for a lesser distance or part of a listed assembly — NEC 680.22(B). - Receptacles: not less than 1.83 m (6 ft) from the inside walls — NEC 680.22(A)(1), (A)(3). The required 125-volt, 15- or 20-ampere general-purpose receptacle must be not less than 6 ft and not more than 20 ft from the inside wall, and not more than 6 ft 6 in. above the floor, platform or grade level — IRC 2024 E4203.1.3 [NEC 680.22(A)(1)]. - Deck junction box on conduit running directly to a wet-niche forming shell: not less than 4 ft from the inside wall unless separated by a solid fence,…

South Carolina NASCLA Residential Electrical Contractor — 7 questions (7%)

Key Concepts

Conduit bending (Ugly's Electrical References 2023) - 90° stub-up (p. 169): mark the EMT at stub height − take-up from the end, align the bender arrow with that mark, bend to the 90° mark. - Offset bends (Offset Bends, p. 168): distance between bends = offset depth × multiplier for the chosen angle; align the arrow with the first mark, bend, slide down, bend the second mark to the same degree line. An offset shrinks the overall run, so marks move toward the far end by the shrink. - Back-to-back bends (p. 170): after the first 90°, align the back-to-back mark with the star mark on the bender and bend 90°. - Three-point saddle (p. 171): mark center first; multiply obstruction height × 2.5 and mark that…

Key Concepts

Continuous-load sizing. Branch-circuit conductors and OCPDs: not less than the noncontinuous load plus 125 percent of the continuous load [210.19(A), 210.20(A)]. Feeders use the same rule for conductors [215.2(A)(1)] and for the overcurrent device [215.3].

Conductor protection — small conductors. 14 AWG Cu = 15 A; 12 AWG Cu = 20 A; 10 AWG Cu = 30 A; 12 AWG Al/CCA = 15 A; 10 AWG Al/CCA = 25 A [240.4(D)(4)–(8)]. 18 AWG Cu = 7 A with listed devices, and continuous loads shall not exceed 5.6 A [240.4(D)(1)]; 16 AWG Cu = 10 A with continuous loads not over 8 A [240.4(D)(2)].

South Carolina NASCLA Residential Electrical Contractor | 17 questions (17%)

Key Concepts

Protection against physical damage (300.4) - Bored holes in wood members: the edge of the hole shall be not less than 32 mm (1¼ in.) from the edges of the wood member. Where that distance cannot be maintained, the cable/raceway shall be protected from screw or nail penetration by a steel plate — NEC 2023, 300.4(A)(1). - Cables/raceways in notches in wood members: protect with a steel plate at least 1.6 mm (1/16 in.) thick, of appropriate length and width — 300.4(A)(2). - Parallel to framing members/furring strips: nearest outside surface not less than 32 mm (1¼ in.) from the nearest edge where nails or screws are likely to penetrate; otherwise protect with steel plate, sleeve, or equivalent at least 1.6 mm (1/16 in.) thick — 300.4(D).…

Key Concepts

Motor branch-circuit conductors - Conductors supplying a single continuous-duty motor: ampacity not less than 125 percent of the motor full-load current (FLC) determined by 430.6(A)(1) — 430.22. - DC motor from a rectified single-phase supply, conductors between rectifier output terminals and motor: not less than 190 percent (half-wave bridge) or 150 percent (full-wave bridge) of FLC — 430.22(A). - Wye-start, delta-run: conductors between controller and motor not less than 72 percent of FLC (58% × 1.25) — 430.22(C). - Other-than-continuous duty: use Table 430.22(E) percentages of nameplate current; intermittent duty, 30- and 60-minute rated = 90 percent — 430.22(E). - Several motors: 125 percent of the highest rated motor only, plus the sum of all other motor FLCs at 100 percent — 430.24. - 18 AWG copper is permitted for a motor over 3.5 A up to…

Key Concepts

Scope (NEC 2023, 750.1). Article 750 applies to the installation and operation of energy management systems (EMS). An informational note states that performance provisions in other codes establish prescriptive requirements that may further restrict Article 750's requirements.

Listing (NEC 2023, 750.6). An energy management system shall be one of the following: 1. Listed as a complete energy management system 2. Listed as a kit for field installation in switch or overcurrent device enclosures 3. Listed individual components assembled as a system

Alternate power sources (NEC 2023, 750.20). An EMS shall not override any control necessary to ensure continuity of an alternate power source for: fire pumps, health care facilities, emergency systems, legally required standby systems, and critical operations power systems.