Texas Maintenance Electrician

Type SHD is rated 2001–25,000 volts with three power conductors individually covered with insulation, tape and shielding plus grounding conductors, while Type G is rated 2001–5000 volts without individual conductor shielding (Type SH uses an overall shield instead of individual shields).

Class I, Division 1 is hazardous because ignitible concentrations of flammable gases or flammable/combustible liquid-produced vapors can exist under normal operating conditions, while Class II, Division 1 is hazardous because combustible dust is in the air under normal operating conditions in quantities sufficient to produce explosive or ignitible mixtures.

Continuous load is taken at 125 percent when sizing branch-circuit conductors, feeder conductors/overcurrent devices, and service-entrance conductors, while noncontinuous load is taken at 100 percent.

Per Table 300.5(A), Column 4 — residential branch circuits rated 120 volts or less with GFCI protection and a maximum overcurrent protection of 20 amperes — needs only 300 mm (12 in.) of cover in general locations, whereas direct-buried cables/conductors (Column 1) in locations not otherwise specified require 600 mm (24 in.).

Type SPT-1 (all-thermoplastic parallel cord for pendant or portable use in damp locations, not hard usage) has a maximum rating of 300 volts, while Type C lamp cord is 300 volts in 18–16 AWG and up to 600 volts in 15–10 AWG.

Cables must contain nominal 600-volt, 8 AWG to 12 AWG conductors (12 AWG minimum), but a luminaire tap no longer than 1.8 m (6 ft) intended for a single luminaire is permitted to be smaller than 12 AWG down to 18 AWG.

Chapters 1–4 apply generally and Chapters 5–7 apply to special conditions, but Chapter 8 is not subject to the requirements of Chapters 1 through 7 except where specifically referenced in Chapter 8.

The Code does not cover ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles, but it does cover mobile homes and recreational vehicles.

All conductors of the same circuit, the grounded conductor, and all equipment grounding/bonding conductors must be in the same raceway, conduit body, auxiliary gutter, cable tray, cablebus, trench, cable, or cord, except that conductors run in parallel may be distributed among multiple raceways with the rule applied separately to each portion of the paralleled installation.

Where the required 32 mm (1-1/4 in.) distance cannot be maintained, cables and raceways must be protected by a steel plate at least 1.6 mm (1/16 in.) thick, but rigid metal conduit, intermediate metal conduit, PVC, and EMT installed in notches in wood members are exempt from that plate requirement.

Branch-circuit conductors must be at least 125 percent of the rated-load current (440.32), while the branch-circuit protective device must not exceed 175 percent of the RLA (440.22(A)), with the next higher standard size permitted (Exception No. 1) and a maximum of 225 percent if starting current still cannot be carried (Exception No. 2).

Real power is P = √3 × V × I × cos θ in a three-phase system, while apparent power S = P ÷ PF; raising power factor at constant voltage and current increases real power but leaves apparent power unchanged.