Idaho Limited Electrical Manufacturing Equipment Installer

2017 National Electrical Code, NFPA — Article 90, Introduction

Key Concepts

Purpose — 90.1(A). The purpose of the Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. The Code is not intended as a design specification or an instruction manual for untrained persons.

Adequacy — 90.1(B). Compliance with the Code 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 attributes overloading hazards to the fact that initial wiring did not provide for increases in the use of electricity.

International standards — 90.1(C). The Code's requirements address the fundamental principles of protection for safety contained in Section 131 of IEC Standard 60364-1, Electrical Installations of Buildings.

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 — such as office buildings, warehouses, garages, machine shops, and recreational buildings — **that are not an…

Key Concepts

Article 100 definitions (Part I applies throughout the Code; Part II applies 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." (Article 100, Page 9)
• Continuous Load — a load where the maximum current is expected to continue for 3 hours or more. (Article 100, Page 8)
• Approved — "Acceptable to the authority having jurisdiction." Authority Having Jurisdiction (AHJ) — an organization, office, or individual responsible for enforcing code requirements or for approving equipment, materials, an installation, or a procedure. (Article 100)
• Conductor, Insulated — a conductor encased within material of composition and thickness recognized by the Code as electrical insulation (a covered conductor is encased in material not recognized as insulation). (Article 100)
• Bonding Jumper, Main — the connection between the grounded circuit conductor and the equipment grounding conductor at the service. Bonding Jumper, System — that same type of connection (to the supply-side bonding jumper, the EGC, or both) at a separately derived system. (Article 100)
• In Sight From (Within Sight) — visible and not more than 15 m (50 ft) distant. Both conditions must be met. (Article 100)
• Copper-Clad Aluminum Conductors — copper forms a minimum of 10 percent of the cross-sectional area of a solid conductor or each strand. (Article 100)…

Key Concepts

Grounding electrodes (250.52, 250.53) - Metal underground water pipe qualifies only if in direct contact with earth for 3.0 m (10 ft) or more and electrically continuous to the points of connection — 250.52(A)(1). - A concrete-encased electrode must consist of at least 6.0 m (20 ft) of either (1) bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods not less than 13 mm (1/2 in.) in diameter, or (2) bare copper conductor not smaller than 4 AWG — 250.52(A)(3). - Rod electrodes of stainless steel or copper- or zinc-coated steel must be at least 15.87 mm (5/8 in.) in diameter unless listed; the 3/4 trade size applies to pipe/conduit electrodes — 250.52(A)(5)(b) and (a). - A ground ring must be installed not less than 750 mm (30 in.) below the earth's surface — 250.53(F); plate electrodes, same depth — 250.53(H). - A single rod, pipe, or plate electrode must be supplemented, except where its resistance to earth is 25 ohms or less — 250.53(A)(2) Exception. Multiple rods must be not less than 1.8 m (6 ft) apart — 250.53(A)(3). - Aluminum or copper-clad aluminum GECs used outside shall not be terminated within 450 mm (18 in.) of the earth — 250.64(A).

Key Concepts

Bends in one run. RMC, PVC, FMC, LFMC and EMT each permit "not more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes" (344.26, 352.26, 348.26, 350.26, 358.26).

Trade size limits. Minimum is trade size ½ for RMC (344.20(A)), PVC (352.20(A)), EMT (358.20(A)), FMC and LFMC (348.20(A), 350.20(A), with ⅜ permitted for the listed special uses). Maximums: RMC trade size 6 (344.20(B)); PVC trade size 6 (352.20(B)); FMC trade size 4 (348.20(B)); LFMC trade size 4 (350.20(B)); EMT trade size 4 (358.20(B)).

Securing and supporting. - EMT: fastened at intervals not to exceed 10 ft, and within 3 ft of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination (358.30(A)). - RMC: secured within 3 ft of each termination (increase to 5 ft where structural members do not readily permit); supported at intervals not exceeding 10 ft, or per Table 344.30(B)(2) (344.30). - PVC: securely fastened within 3 ft (900 mm) of each termination (352.30(A)); supports per Table 352.30. - FMC and LFMC: fastened within 12 in. (300 mm) of each box, cabinet, conduit body, or other termination, and supported at intervals not to exceed 4½ ft (348.30(A), 350.30(A)). - Type MC: secured at intervals not exceeding 6 ft; cables with four or fewer conductors no larger than 10 AWG secured within 12 in. of…

Key Concepts

Determining current values (430.6(A)(1)). For general motor applications, use the values in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 to determine conductor ampacity and the ampere ratings of switches and branch-circuit short-circuit and ground-fault protection — instead of the nameplate current. Separate motor overload protection, by contrast, is based on the motor nameplate current rating (430.6(A)(2)).

Single-motor conductors (430.22). Conductors supplying a single motor in a continuous duty application shall have an ampacity not less than 125 percent of the motor full-load current rating as determined by 430.6(A)(1). Special cases: - Wye-start, delta-run: line-side conductors not less than 125%; conductors between controller and motor not less than 72 percent (58% × 1.25) — 430.22(C). - Part-winding: line-side not less than 125%; controller-to-motor not less than 62.5 percent (50% × 1.25) — 430.22(D). - DC motor, rectified single-phase supply: 190 percent for a single-phase half-wave bridge, 150 percent for a single-phase full-wave bridge; input side of rectifier is 125% of rated input current — 430.22(A).

Feeders (430.24). Not less than 125 percent of the full-load current of the highest rated motor plus the sum of the full-load current ratings of all the other motors in the group.

Idaho Limited Electrical Manufacturing Equipment Installer Exam — 3 questions (8%)

Key Concepts

Circuit requirements by class (725.35). Class 1 circuits comply with Parts I and II of Article 725; Class 2 and Class 3 circuits comply with Parts I and III.

Class 1 classification (725.41). A Class 1 circuit is either power-limited or remote-control and signaling: - Class 1 power-limited (725.41(A)): supplied from a source with a rated output of not more than 30 volts and 1000 volt-amperes. Transformers must comply with the applicable sections of Parts I and II of Article 450 (725.41(A)(1)). - Class 1 remote-control and signaling (725.41(B)): shall not exceed 600 volts; the power output of the source is not required to be limited.

Non-transformer Class 1 power sources (725.41(A)(2)). Protected by overcurrent devices rated at not more than 167 percent of the source's volt-ampere rating divided by rated voltage; the device shall not be interchangeable with higher-rated devices and may be integral to the supply. To comply with the 1000 VA limitation, VA max is limited to 2500 volt-amperes, and the product of I max and V max shall not exceed 10,000 volt-amperes, determined with any overcurrent device bypassed.