Idaho Limited Electrical Refrigeration, Heating & Air Conditioning Installer

Key Concepts

90.1(A) Purpose — Practical Safeguarding. 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.

90.1(B) Adequacy. 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."

90.1(C) Relation to Other International Standards. The Code's requirements address the fundamental principles of protection for safety contained in Section 131 of IEC Standard 60364-1.

90.2(A) Covered. 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 integral…

Topic: 2017 NEC, Chapter 1

Key Concepts

Article 100 definitions (Part I applies wherever the terms are used throughout the Code):

• 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. This definition drives the 125 percent sizing rules applied elsewhere in the Code. (NEC 2017, Page 8, Article 100)
• In Sight From (Within Sight From, Within Sight) — the specified equipment must be visible AND not more than 15 m (50 ft) distant from the other equipment. Both conditions must be met. (Article 100 — Definitions)
• Ground-Fault Circuit Interrupter (GFCI) — the Informational Note states a Class A GFCI trips when current to ground is 6 mA or higher and does not trip when current to ground is less than 4 mA. (Article 100 — Definitions)
• Dwelling, Multifamily — a building containing three or more dwelling units. A building with exactly two units is a two-family dwelling. (Article 100 — Definitions)
• Overcurrent Protective Device, Branch-Circuit…

2017 National Electrical Code, NFPA — Chapter 2

Key Concepts

Grounding fundamentals (Article 250, Part I) - The earth shall not be considered an effective ground-fault current path — 250.4(A)(5). - Bonding non–current-carrying conductive materials connects them together and to the electrical supply source to establish an effective ground-fault current path — 250.4(A)(3). - Currents introducing noise or data errors in electronic equipment shall NOT be considered the objectionable currents addressed in 250.6 — 250.6(D).

Grounding electrodes (Part III) - Rod and pipe electrodes: not less than 8 ft (2.44 m) in length — 250.52(A)(5); at least 8 ft of length in contact with the soil — 250.53(G). - Supplemental electrode not required if a single rod, pipe, or plate has resistance to earth of 25 ohms or less — 250.53(A)(2) Exception. - Multiple rod, pipe, or plate electrodes: not less than 6 ft (1.8 m) apart — 250.53(A)(3). - Concrete-encased electrode: at least 20 ft of bare copper not smaller than 4 AWG — 250.52(A)(3)(2). - Ground ring: at least 20 ft of bare copper not smaller than 2 AWG — 250.52(A)(4).

Idaho Limited Electrical Refrigeration, Heating & A/C Installer Exam — 6 questions (13%)

Key Concepts

Raceway bends, supports, and sizes - 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). - RMC maximum size: larger than metric designator 155 (trade size 6) shall not be used (344.20(B)). Minimum: smaller than metric designator 16 (trade size ½) shall not be used (344.20(A)). - EMT securing: securely fastened in place at intervals not to exceed 3 m (10 ft), and each run between termination points 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)). - FMC and LFMC securing: securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination, and supported and secured at intervals not to exceed 1.4 m (4½ ft) (348.30(A); 350.30(A)). - PVC expansion fittings: provided to compensate for thermal expansion and contraction where the length change, in accordance with Table 352.44,…

Key Concepts

Which current to use (Art. 430, Part I) - For general motor applications, use the values in Table 430.247 through Table 430.250 — not the nameplate current — to determine conductor ampacity and ampere ratings of switches and branch-circuit short-circuit and ground-fault (BCSC/GF) protection [430.6(A)(1)]. - Separate motor overload protection is based on the motor nameplate current rating [430.6(A)(2)]. - The highest rated or smallest rated motor of a group (for 430.24, 430.53(B), 430.53(C)) is based on table full-load current [430.17]. - Rectifier-derived system voltage = nominal value of the ac voltage being rectified [430.18].

Markings — time rating shall be 5, 15, 30, or 60 minutes, or continuous [430.7(A)(6)]; code letter or locked-rotor amperes if an ac motor rated ½ hp or more [430.7(A)(8)]; dc winding type, except fractional-hp dc motors 175 mm (7 in.) or less in diameter [430.7(A)(12)]; wye-start/delta-run single-speed motors marked for the wye connection [430.7(B)(2)]; part-winding start motors marked for the full winding [430.7(B)(5)]. Control-circuit devices with screw-type pressure terminals used with 14 AWG or smaller copper: torque to a minimum of 0.8 N·m (7 lb-in.) unless identified otherwise [430.9(C)].

Key Concepts

Article 720 — Circuits and Equipment Operating at Less Than 50 Volts

• Scope (720.1): Covers installations operating at less than 50 volts, dc or ac.
• Exemptions (720.2): Installations covered by 411.1 through 411.8; Part VI of Article 517; Part II of Article 551; Parts II and III and 552.60(B) of Article 552; 650.1 through 650.8; 669.1 through 669.9; Parts I and VIII of Article 690; Parts I and III of Article 725 (Class 2 and Class 3 power-limited circuits); or Parts I and III of Article 760 are not required to comply with Article 720.
• Conductors (720.4): Not smaller than 12 AWG copper or equivalent. Conductors for appliance branch circuits supplying more than one appliance or appliance receptacle shall not be smaller than 10 AWG copper or equivalent.
• Lampholders (720.5): Standard lampholders rated not less than 660 watts shall be used.
• Receptacle rating (720.6): Not less than 15 amperes.
• Receptacles required (720.7): Not less than 20-ampere rating in kitchens, laundries, and other locations where portable appliances are likely to be used.

Article 725 — Class 1 Circuits (Part II)

Idaho Limited Electrical Refrigeration, Heating & Air Conditioning Installer Exam

Key Concepts

Motor full-load current source. For general motor applications, the values in Table 430.247 through Table 430.250 are used to determine conductor ampacity and ratings of switches and branch-circuit short-circuit and ground-fault (SCGF) protection instead of the nameplate current — except for motors built for low speeds (less than 1200 RPM), high torques, or multispeed motors, where nameplate current is used (430.6(A)(1)).

Branch-circuit conductors — wye-start, delta-run. Conductors between the controller and a wye-start, delta-run motor shall have an ampacity of at least 72 percent of the motor full-load current (430.22(C)). The 58 percent figure is the actual winding current (informational note); 62.5 percent applies to part-winding motors under 430.22(D); 125 percent applies to the line-side branch-circuit conductors.

Overload protection — continuous-duty motors over 1 hp (430.32(A)(1)). A separate overload device responsive to motor current is selected to trip or be rated at no more than: - Marked service factor 1.15 or greater — 125% - Marked temperature rise 40°C or less — 125% - All other motors — 115%