Arizona R-11 Electrical Residential

Key Concepts

Ohm's Law and circuit behavior - Current is found with I = E ÷ R. Per NEC 110.4, the voltage considered throughout the Code is that at which the circuit operates (nominal voltage). - In a parallel circuit, total resistance is always less than the resistance of any individual branch, because added parallel paths give current more routes and reduce overall opposition (Ugly's Electrical References, Ohm's Law principles; parallel circuit theory).

Distribution systems and voltage definitions - In a 120/240-volt, single-phase, 3-wire system, voltage between the two ungrounded conductors is 240 volts, and each ungrounded conductor to the grounded neutral is 120 volts (Section 200.2 context; Exhibit 250.5). - Article 100, "Voltage (of a circuit)" is "the…

Key Concepts

Branch-circuit conductor minimum size. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load (210.19(A)(1)(a)); it must also be not less than the maximum load after applying any adjustment or correction factors (210.19(A)(1)(b)).

Feeder conductor and feeder OCPD sizing. Same 125 percent rule applies to feeders (215.2(A)(1)(a)). The feeder overcurrent device rating shall not be less than the noncontinuous load plus 125 percent of the continuous load (215.3). Feeder conductor ampacity shall not be less than that of the service conductors where the feeder carries the total load supplied by…

Key Concepts

Definitions (NEC Article 100). The main bonding jumper is the connection between the grounded circuit conductor and the equipment grounding conductor at the service. The system bonding jumper is that same connection at a separately derived system. A bonding conductor or jumper is a reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected. A grounded conductor is a system or circuit conductor that is intentionally grounded — often, but not always, the neutral conductor (Section 200.1 commentary).

Key Concepts

• Two ways to get ampacity. Ampacities for conductors rated 0–2000 V may be determined from tables per 310.15(B) or under engineering supervision per 310.15(C) [310.15(A)(1)]. Where more than one ampacity applies to a circuit length, the lowest value shall be used, unless the lower-ampacity portion does not exceed the lesser of 10 ft or 10 percent of the circuit [310.15(A)(2) and its exception].
• Temperature limitation. "No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved" [310.15(A)(3)/310.15(B)].
• Termination rule. Correction and adjustment factors may be applied to the conductor's own temperature rating only if the corrected and adjusted ampacity does not exceed…

Arizona R-11 Electrical Residential — 15 questions (14% of exam)

Key Concepts

Bends between pull points. All of these raceways allow no 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), EMT (358.26), LFMC (350.26), LFNC (356.26), PVC (352.26).

Sizes — minimum and maximum. - RMC: minimum trade size ½ (344.20(A), exception for enclosing motor leads per 430.245(B)); maximum trade size 6 (344.20(B)). - IMC: minimum trade size ½ (342.20(A)); maximum trade size 4 (342.20(B)). - EMT: minimum trade size ½ (358.20(A)); maximum trade size 4 (358.20(B)). - PVC: minimum trade size ½ (352.20(A)); maximum trade size 6 (352.20(B)). - FMC: minimum trade size…

Key Concepts

Hazardous (classified) location documentation — All areas designated as hazardous (classified) locations shall be properly documented, and that documentation shall be available to those authorized to design, install, inspect, maintain, or operate electrical equipment at the location (NEC 500.4(A)).

Class definitions - Class I, Division 2: flammable gases or flammable/combustible liquid–produced vapors are handled, processed, or used but are normally confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown, or in case of abnormal operation of equipment (NEC 500.5(B)(2)). - Class II: locations hazardous because of the presence of combustible dust (NEC 500.5(C)). Class II, Division 1 includes locations where combustible dust is in the air…

Topic: Electrical Devices

Key Concepts

NEMA enclosure types (NEC 2017, Section 110.28 / NEMA 250-2018 definitions) - Type 4 — constructed for either indoor or outdoor use; protects against falling dirt, windblown dust, rain, sleet, snow, splashing water, and hose-directed water; undamaged by external formation of ice. - Type 3 — does not include hose-directed water protection; Type 3R provides even less solid foreign object protection. - Type 12 — constructed without knockouts, indoor use; protects against falling dirt, circulating dust, lint, fibers, and flyings; dripping and light splashing of water; and light splashing and seepage of oil and non-corrosive coolants. Type 12K is the version with knockouts. Type 13 adds protection against spraying of oil. Type 5…

Key Concepts

• Size motor circuits from input current, not output. Motors are rated in horsepower output, but circuits are sized on input amperes, which include motor losses and power factor (Article 430, Part I commentary; one horsepower ≈ 746 watts).
• Table values vs. nameplate — 430.6(A)(1) and (A)(2). For general motor applications, the values in Table 430.247 (DC), 430.248 (single-phase AC), 430.249 (two-phase AC), and 430.250 (three-phase AC) determine conductor ampacity and the ampere ratings of switches, the disconnecting means, and branch-circuit short-circuit and ground-fault protection — instead of the nameplate current. Separate overload protection is based on the motor nameplate current rating [430.6(A)(2)]; Ugly's adds that overload heaters must be based on the nameplate and sized…

Key Concepts

Low-voltage lighting (NEC Article 411) - Article 411 covers lighting systems and their associated components operating at no more than 30 volts ac or 60 volts dc. Where wet contact is likely to occur, the limits are 15 volts ac or 30 volts dc (NEC 411.1). - A low-voltage lighting system consists of an isolating power supply, low-voltage luminaires, and associated equipment identified for the use; output circuits of the power supply are rated 25 amperes maximum under all load conditions (NEC 411.3). - Secondary circuits shall not be grounded and shall be insulated from the branch circuit by an isolating transformer (NEC 411.6(A), (B)). Exposed bare conductors are permitted indoors only, and not less than **2.1…

Key Concepts

Low-voltage lighting (Article 411) - Article 411 covers lighting systems and components operating at no more than 30 volts ac or 60 volts dc; where wet contact is likely, the limits drop to 15 volts ac or 30 volts dc (411.1). - A low-voltage lighting system consists of an isolating power supply, low-voltage luminaires, and associated equipment identified for the use; output circuits of the power supply shall be rated 25 amperes maximum under all load conditions (411.3). - Systems under Article 411 shall be supplied from a maximum 20-ampere branch circuit (411.7). - Lighting systems shall be installed not less than 3 m (10 ft) horizontally from the nearest edge of the water of pools, spas,…

Arizona R-11 Electrical Residential | 5 questions (5% of exam)

Key Concepts

Equipment listing and general requirements - Equipment constructed and installed in conformity with NFPA 72 shall be listed for the purpose for which it is used (NFPA 72, Section 10.3.1). - All notification appliances installed in conformity with Chapter 18 shall be listed for the purpose for which they are used (Section 18.3.1).

Pathway class designations (Chapter 12) - Class A (Section 12.3.1): includes a redundant path; operational capability continues past a single open, and the single open fault shall result in the annunciation of a trouble signal; conditions affecting intended operation are annunciated as trouble; operational capability is maintained during a single ground fault, and a…

Key Concepts

Accident prevention responsibilities (29 CFR 1926.20(b)) - It is the employer's responsibility to initiate and maintain such programs as may be necessary to comply with Part 1926 — §1926.20(b)(1). - Programs shall provide for frequent and regular inspections of the job sites, materials, and equipment, made by competent persons designated by the employers — §1926.20(b)(2). - Machinery, tools, materials, or equipment not in compliance are prohibited; they must be tagged or have controls locked to render them inoperable, or be physically removed — §1926.20(b)(3). - Only employees qualified by training or experience may operate equipment and machinery — §1926.20(b)(4). - Competent person = one capable of identifying existing and predictable hazards and who has **authorization to take…

Key Concepts

Continuous-load 125% rule (three places to know it) - Branch circuit: where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the OCPD rating shall not be less than the noncontinuous load plus 125 percent of the continuous load — 210.20(A). - Feeder: same requirement — 215.3. - Service-entrance conductors: minimum size shall have allowable ampacity not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads — 230.42(A)(1).

Conductor protection - Where the OCPD is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than the rating of the OCPD; the next-higher-standard-size permission of 240.4(B) does not apply…

Key Concepts

Maximum voltage (NEC 690.7). PV system dc circuits on or in one- and two-family dwellings are permitted a maximum voltage of 600 volts or less; dc circuits on or in other types of buildings are permitted up to 1000 volts.

Scope (NEC 690.1). Article 690 applies to solar PV systems other than those covered by Article 691, including the array circuit(s), inverter(s), and controller(s). Systems may be interactive, stand-alone, or both, may or may not connect to energy storage, and may have ac or dc output.