Texas Residential Appliance Installer

In dwelling units GFCI is required for 125-volt through 250-volt receptacles in listed areas (bathrooms, garages, outdoors, crawl spaces, basements, kitchens, areas with sinks, laundry areas, etc.) on single-phase circuits rated 150 volts or less to ground, while in other than dwelling units it is required for receptacles within 1.8 m (6 ft) of the top inside edge of a sink bowl, on single-phase circuits 150 volts or less to ground and 50 A or less or three-phase circuits 150 volts or less to ground and 100 A or less.

Per Article 90.3, Chapters 1–4 apply generally to all electrical installations; Chapters 5, 6, and 7 cover special occupancies, equipment, or conditions and may supplement or modify Chapters 1–4, while Chapter 8 (communications systems) is not subject to Chapters 1–7 except where specifically referenced.

Per 90.9(A) and (B), SI (metric) is the Code's measurement system of preference and SI units appear first, with inch-pound units immediately following in parentheses.

Chapter 9, Table 1 permits 31% fill for 2 conductors and 40% for 3 or more (53% for 1 conductor), while Note (4) permits nipples not exceeding 600 mm (24 in.) between boxes to be filled to 60%.

Grounded conductors 6 AWG or smaller use a continuous white or gray outer finish (white or silver terminals, or 'white'/'W'), while an equipment grounding conductor in a flexible cord must be continuous green or green with one or more yellow stripes and must not be used for other purposes.

Nonmetallic-sheathed cable run parallel to framing members less than 32 mm (1¼ in.) from the edge (or in notches) must be protected by a steel plate at least 1.6 mm (1/16 in.) thick, while rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, and electrical metallic tubing are not required to have steel plate protection.

NEC 300.14 requires at least 150 mm (6 in.) of free conductor measured from where it emerges from the raceway or cable sheath at each outlet, junction, and switch point; additionally, where the opening is less than 200 mm (8 in.) in any dimension, each conductor must extend at least 75 mm (3 in.) outside the opening.

A single-motor branch circuit is sized at 125% of the motor full-load current (430.22), while a feeder to several motors is sized at 125% of the largest motor's FLC plus the sum of the full-load currents of the remaining motors (430.24).

Branch-circuit conductors must have ampacity of at least 125% of the rated-load current, while the branch-circuit protective device must not exceed 175% of RLA (next higher standard size permitted by Exception No. 1, and up to 225% of RLA under Exception No. 2 if needed to carry starting current).

Table 430.52 permits a maximum of 250% of full-load current for a single-phase motor's inverse time breaker, but where the motor fails to start, the rating may be increased to the next higher standard size and in no case over 400% of FLC for currents of 100 A or less.

Ordinary motor branch-circuit conductors are 125% of FLC, but per 430.22(C) conductors between the controller and a wye-start, delta-run motor need be only 72% of the motor full-load current (58% of load current × 1.25).

Per 220.14(I), each single or multiple receptacle on one yoke is calculated at not less than 180 volt-amperes, but a single piece of equipment consisting of a multiple receptacle of four or more receptacles is calculated at not less than 90 volt-amperes per receptacle.

In a three-phase system with voltage and current held constant, raising the power factor increases real power (P = √3 × V × I × cos θ) while apparent power, the vector sum of real and reactive power, remains unchanged.