Idaho Limited Electrical Sign Installer

Key Concepts

• Purpose (90.1(A)). The Code's purpose is the practical safeguarding of persons and property from hazards arising from the use of electricity. It is not a design specification or an instruction manual for untrained persons.
• Adequacy (90.1(B)). Compliance plus proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use. The informational note explains that hazards often occur because initial wiring did not provide for increases in the use of electricity.
• Scope — covered (90.2(A), NEC 2017 Page 2). The Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for: (1) public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings; (2) yards, lots, parking lots, carnivals, and industrial substations; (3) installations of conductors and equipment that connect to the supply of electricity; (4) installations used by the electric utility (office buildings, warehouses, garages, machine shops, recreational buildings) that are not an integral part of a generating plant, substation, or control center.
• Scope — not covered (90.2(B)). Ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles; underground mine installations and self-propelled mobile surface mining machinery with its trailing cable; certain railway power/signaling installations; communications equipment under exclusive control of communications utilities outdoors or in spaces used exclusively for such installations; and specified installations under the exclusive control of an electric utility.
• Special permission (90.2(C)). The AHJ may grant exception for conductors and equipment not under…

Idaho Limited Electrical Sign Installer Examination

Key Concepts

Article 100 Definitions (scope: definitions essential to the application of the Code; Part I applies throughout, Part II applies to installations over 1000 volts, nominal)

• Ampacity — "The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating." (NEC 2017, Page 9, Article 100)
• Continuous Load — a load where the maximum current is expected to continue for 3 hours or more (NEC 2017, Page 8, Article 100). This drives the 125 percent sizing rules for conductors and overcurrent devices.
• Authority Having Jurisdiction (AHJ) — "An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure." (Article 100). Note Approved = "Acceptable to the authority having jurisdiction."
• Conductor, Insulated — a conductor encased within material of composition and thickness that is recognized by this Code as electrical insulation. A covered conductor is encased in material not recognized as electrical insulation. (Article 100)
• Bonding Jumper, Main — the connection between the grounded circuit conductor and the equipment grounding conductor at the service. (A system bonding jumper performs the similar function at a separately derived system.) (Article 100)
• In Sight From (Within Sight From, Within Sight) — visible and not more than 15 m (50 ft) distant from the other equipment. Both conditions must be met. (Article 100)
• Festoon Lighting — "a string of outdoor lights that is suspended between two points." Outline lighting is an arrangement of light sources outlining or calling attention to features such as the shape of a…

Key Concepts

Grounding and bonding fundamentals (Article 250) - The earth shall not be considered an effective ground-fault current path [250.4(A)(5)]. - Bonding of equipment on a grounded system connects non–current-carrying conductive materials together and to the electrical supply source to establish an effective ground-fault current path [250.4(A)(3)]. - High-impedance grounded neutral systems are permitted for 3-phase ac systems of 480 volts to 1000 volts, where only qualified persons service the installation, ground detectors are installed, and no line-to-neutral loads are served [250.36].

Grounding electrodes (250.52) - Metal underground water pipe: in direct contact with earth for 10 ft (3.0 m) or more [250.52(A)(1)]. - Concrete-encased electrode: rebar not less than 1/2 in. (13 mm) diameter in a continuous 20 ft length, or bare copper conductor not smaller than 4 AWG [250.52(A)(3)]. - Ground ring: at least 20 ft (6.0 m) of bare copper not smaller than 2 AWG [250.52(A)(4)]. - Rod electrodes of stainless steel or copper/zinc-coated steel: at least 5/8 in. (15.87 mm) diameter unless listed [250.52(A)(5)]. - Plate electrodes: expose not less than 2 ft² (0.186 m²) to exterior soil; iron/steel plates at least 1/4 in. (6.4 mm) thick, solid uncoated nonferrous plates at least 0.06 in. (1.5 mm) thick [250.52(A)(7)]. - Aluminum shall not be used as a grounding electrode [250.52(B)(2)].

Key Concepts

Conduit bends and fill (Chapter 3 raceway articles) - There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example conduit bodies and boxes — RMC 344.26, IMC 342.26, PVC 352.26, LFMC 350.26, EMT 358.26. - Number of conductors shall not exceed the percentage fill in Table 1, Chapter 9 (344.22, 342.22, 352.22, 358.22, 350.22(A)).

Sizes - RMC: smaller than trade size ½ shall not be used; larger than metric designator 155 (trade size 6) shall not be used — 344.20(A), (B). - IMC maximum is metric designator 103 (trade size 4) — 342.20(B). EMT maximum is trade size 4 — 358.20(B). LFMC maximum is trade size 4 — 350.20(B).

Securing and supporting - EMT: securely fastened at intervals not to exceed 3 m (10 ft), and each run securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination — 358.30(A). - RMC/IMC: fastened within 900 mm (3 ft) of terminations (5 ft where structural members do not readily permit); supported at intervals not exceeding 3 m (10 ft), or per Table 344.30(B)(2) for straight runs made up with threaded couplings — 344.30, 342.30(B)(2). - LFMC: securely fastened within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination, and supported at intervals not to exceed 1.4 m (4½ ft) — 350.30(A). - PVC: securely fastened within 900 mm (3 ft) of each termination; supported per Table 352.30 — 352.30. - PVC expansion fittings shall be provided where the length change, per Table 352.44, is expected to be 6 mm (¼ in.)…

Key Concepts

Branch circuits (600.5) - Each commercial building and each commercial occupancy accessible to pedestrians must have at least one outlet in an accessible location at each entrance to each tenant space for sign/outline lighting use; the outlet(s) must be supplied by a branch circuit rated at least 20 amperes that supplies no other load. Service hallways or corridors are not considered accessible to pedestrians — 600.5(A). - Sign branch circuits are considered continuous loads for calculations — 600.5(B). Neon tubing installations: not rated in excess of 30 amperes — 600.5(B)(1). All other signs and outline lighting: not to exceed 20 amperes — 600.5(B)(2). - Supply wiring must terminate within a sign, an outline lighting system enclosure, a suitable box, or a conduit body — 600.5(C)(1). Sign and transformer enclosures may serve as pull/junction boxes for adjacent signs, outline lighting, or floodlights that are part of a sign, and may contain both branch and secondary circuit conductors — 600.5(C)(2).

Disconnects (600.6) - Externally operable switch or circuit breaker that opens all ungrounded conductors and controls no other load, opening all ungrounded conductors simultaneously on multiwire branch circuits per 210.4(B) — 600.6. - Point of entry: at the point the feeder/branch circuit enters a sign enclosure, sign body, or pole — 600.6(A)(1). - Within sight of sign; if out of line of sight from any section able to be energized, it must be lockable per 110.25 AND a permanent field-applied marking identifying the disconnect location applied to the sign, visible during servicing — 600.6(A)(2). - External controllers: disconnect within sight of the controller or in the same enclosure; disconnects both sign and controller from all ungrounded supply conductors; designed…