Questions and Answers
Match the title with the associated part:
General = Part I Installation = Part III Construction Specs = Part II
The scope of Article 310 covers fixture wires, flexible cords, and cables.
False
Match the title with the NEC reference for conductors used in different locations:
Dry and Damp Locations = 310.10B Dry Locations = 310.10A Locations Exposed to Direct Sunlight = 310.10D Wet Locations = 310.10C
Match the title with the NEC reference for uses permitted for conductors:
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Which of the following tables provides the allowable ampacities of insulated conductors rated up to and including 2,000 volts?
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Insulated conductors or cables used where exposed to direct rays of the sun must be listed as being sunlight resistant.
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Insulated conductors and cables used in wet locations must comply with what NEC reference?
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Conductors used for direct burial applications are required to be what type?
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Match the title with the NEC reference for provisions allowing conductors of size 1/0 AWG and larger connected in parallel:
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Where more than one ampacity applies for a circuit length for conductors rated 0 to 2,000 volts, what is generally required?
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The minimum size of conductors for voltage ratings up to and including 2,000 volts shall be _____ copper or _____ aluminum.
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Ampacities for conductors rated 0 to 2,000 volts can be determined by which NEC provisions?
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Ampacities for conductors rated 0 to 2,000 volts in ambient temperatures other than those shown in the ampacity tables shall be corrected under what provision?
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Which NEC reference relates to conductors in parallel where aspects like phase, polarity, and neutral are concerned?
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Where run in parallel, cables or raceways with conductors must have the same _____.
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Where the number of current-carrying conductors in a raceway or cable exceeds three, what must happen?
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Where raceways or cables are exposed to direct sunlight, they should be installed a minimum of _____ above the roof.
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When bare or covered conductors rated 0 to 2,000 volts are installed with insulated conductors, what is required of their temperature ratings?
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A neutral conductor rated 0 to 2,000 volts that only carries unbalanced current must be counted when applying which NEC provisions?
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In a 3-wire circuit of two phase conductors and a neutral conductor, the common conductor must be counted in what NEC provisions?
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On a 4-wire, 3-phase wye circuit with nonlinear loads, what is considered a current-carrying conductor?
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Ampacities for conductors rated 2,001 to 35,000 volts must follow which tables?
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What is the insulation thickness of 2/0 AWG Type USE cable?
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What is the trade name for type letter THHN?
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What is the maximum operating temperature of type letter UF with moisture-resistant insulation?
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Type THHW has a maximum operating temperature of 75°C in a wet location, and _____ in a dry location.
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Note 5 of Table 310.4(A) indicates to see Section 340.80 for ampacity limitation.
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Type letter MTW has an application provision as machine tool wiring and has a maximum operating temperature of what degree?
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Match the title to the NEC reference for conductor identification provisions:
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Ampacities for conductors rated 0 to 2,000 volts must be specified in allowable ampacity tables 310.16 through 310.21 as modified by which section?
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Conductors 4 AWG and larger installed in raceways must be?
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Study Notes
Conductors for General Wiring
-
General Structure:
- Part I: General
- Part II: Construction Specifications
- Part III: Installation
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Provisions per NEC:
- Article 310 does not cover fixture wires and flexible cords—this is false (NEC 310.1).
- Uses permitted for conductors:
- Dry Locations: NEC 310.10A
- Damp Locations: NEC 310.10B
- Wet Locations: NEC 310.10C
- Direct Sunlight Exposure: NEC 310.10D
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Conductors in Parallel:
- Provisions exist for conductors running in parallel and must adhere to:
- Equipment grounding: NEC 310.10G2
- General connection requirements: NEC 310.10G3
- Conductors must have the same electrical characteristics.
- Provisions exist for conductors running in parallel and must adhere to:
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Ampacity Regulations:
- Allowable ampacities of insulated conductors rated up to 2,000 volts are determined from Table 310.16.
- Ampacity must be adjusted where more than three current-carrying conductors are present in a raceway (NEC Table 310.15(C)(1)).
- Highest ampacity value applies for given circuit lengths rated 0 to 2,000 volts.
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Installation Requirements:
- Insulated conductors exposed to direct sunlight must be sunlight resistant according to NEC 310.10D.
- Conductors used in wet locations must meet specific criteria per NEC 310.10C.
- Direct burial conductors must be type approved for such installations (NEC 310.10E).
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Temperature Ratings:
- Minimum size of conductors (up to 2,000 volts) is specified in NEC 310.3A for copper and aluminum.
- Ampacities for conductors rated 0 to 2,000 volts can be adjusted for ambient temperature variations in accordance with NEC 310.15.
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Special Conditions:
- For circuits where the neutral carries unbalanced loads, it is counted as a current-carrying conductor (NEC 310.15E1).
- Common conductor in wye-connected systems shares load and must be considered in ampacity calculations (NEC 310.15E2).
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Cable Types and Insulation:
- 2/0 AWG Type USE cable has an insulation thickness of 80 mils.
- Type THHN’s trade name and its maximum operating temperatures differ in wet and dry locations.
- Type MTW is designated for machine tool wiring with a max operating temperature of 60°C in dry conditions.
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Reference Tables:
- NEC tables, such as Table 311.60, detail conductor ampacity limits for higher voltage ratings (2,001 to 35,000 volts).
- Refer to Section 340.80 for ampacity limitations indicated in Note 5 of Table 310.4(A).
These summaries encapsulate critical information regarding NEC standards for electrical conductors, their installation, and ampacity considerations essential for safe and efficient electrical wiring practices.
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Description
Test your knowledge on the specifications and installation procedures of conductors as outlined by the NEC. This quiz covers ampacity regulations, uses permitted for conductors in various locations, and the requirements for conductors in parallel. Prepare to dive into the key aspects of general wiring!
