Philadelphia Master Electrician Exam (ICC 211, 2020 NEC)

Per NEC 2020 Article 100, a surge arrester limits surge voltages by discharging or bypassing surge current and prevents continued flow of follow current while remaining capable of repeating these functions, whereas an SPD limits transient voltages by diverting or limiting surge current.

Per NEC 2020 Article 100, switchgear is completely enclosed on all sides and top with sheet metal (except ventilating openings and inspection windows) and contains primary power circuit switching/interrupting devices with buses and connections, while a switchboard is generally accessible from the rear and not intended for installation in cabinets and a panelboard is designed for assembly in a cabinet (a motor control center principally contains motor control units).

Per NEC 2020 Article 100, for ungrounded circuits voltage to ground is the greatest voltage between the given conductor and any other conductor of the circuit, while for grounded circuits it is the voltage between the given conductor and the grounded point or conductor.

220.82(B) takes 100 percent of the first 10 kVA plus 40 percent of the remainder of the listed loads, while 220.83(A) (used when no additional air-conditioning or electric space-heating equipment is being installed) takes 100 percent of the first 8 kVA plus 40 percent of the remainder.

A one-family dwelling's feeder disconnecting means must be rated not less than 100 amperes, 3-wire, while all installations other than one-circuit, two-circuit, or one-family dwelling disconnects require not less than 60 amperes; installations of not more than two 2-wire branch circuits require not less than 30 amperes under 225.39(B).

The inner-edge radius shall not be less than five times the cable diameter for Type AC (320.24) and Types NM/NMC (334.24), but not less than seven times the external diameter of the metallic sheath for interlocked-type armor or corrugated sheath Type MC (330.24(B)).

For AC polyphase motors other than wound-rotor, the nontime-delay fuse maximum is 300 percent of full-load current while the dual-element time-delay fuse maximum is 175 percent, with the next higher standard size permitted under 430.52(C)(1) Exception No. 1 when the calculation does not match a standard size.

The table maximum for an inverse time circuit breaker is 250 percent of motor full-load current, but if the motor will not start at that rating the breaker may be increased only up to 400 percent of full-load current for motors of 100 A or less (300 percent above 100 A), which is a cap rather than simply the next standard size.

In the delta high-leg system the B phase (higher phase voltage to ground) must be colored orange or tagged — and per NEC 110.15 the conductor or busbar with the higher phase voltage to ground on a 4-wire delta system with a grounded phase-winding midpoint must be durably and permanently marked orange or by other effective means — whereas in the 277/480-volt wye system the C phase ungrounded conductor is colored yellow.

Dwelling kitchen countertop receptacles require GFCI protection per 210.8(A)(6) and AFCI protection per 210.12(A) for 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets, while in other than dwelling units 210.8(B)(2) requires GFCI protection for 125-volt through 250-volt receptacles on single-phase branch circuits rated 150 volts or less to ground and 50 amperes or less in kitchens or areas with a sink and permanent provisions for food preparation or cooking.

For overhead spans of open conductors not over 1000 volts, clearance shall be not less than 3.0 m (10 ft) above finished grade where the voltage does not exceed 150 volts to ground and the area is accessible to pedestrians only, but not less than 5.5 m (18 ft) over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land traversed by vehicles.

Per NEC 300.14, where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension each conductor must extend at least 75 mm (3 in.) outside the opening, which is a distinct requirement from the general 150 mm (6 in.) free conductor rule.