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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
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Figure 01
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Figure 01
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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
Note: The answers to these questions are based on the 2020 NEC.
Q1. What are the rules related to minimum conductor sizing and material?
310.3 Conductors, Minimum Size and Material
(A) Minimum Size Conductors. The minimum sizes of conductors are 14 AWG copper or 12 AWG aluminum or copper-clad aluminum, except as permitted elsewhere in this Code.
Author’s Comment:
►There is a misconception that 12 AWG copper is the smallest conductor permitted for commercial or industrial facilities. Although it is not true based on NEC rules, it might be a job specification or local code requirement.
►Conductors smaller than 14 AWG are permitted to be installed for Class 1 power-limited circuits [724.43], fixture wire [402.6], and motor control circuits [Table 430.72(B)].
(B) Conductor Material. Conductors must be copper, aluminum, or copper-clad aluminum.
Aluminum and copper-clad aluminum conductors must comply with the following:
(1) Solid aluminum conductors 8 AWG, 10 AWG, and 12 AWG must be made of an AA-8000 series electrical grade aluminum alloy conductor material.
(2) Stranded aluminum conductors must be made of an AA-8000 series electrical grade aluminum alloy conductor material.
(3) The copper of a copper-clad aluminum conductor only makes up 10 percent of the cross-sectional area. The aluminum core of a copper-clad aluminum conductor must be made of an AA-8000 series electrical grade aluminum alloy conductor material. Figure 01
According to Article 100, “Copper-Clad Aluminum Conductor” is drawn from a copper-clad aluminum rod, with the copper metallurgically bonded to an aluminum core.
(C) Stranded Conductors. Conductors 8 AWG and larger installed in a raceway must be stranded to be solid, unless specifically permitted or required elsewhere in this Code.
Author’s Comment:
►A grounding electrode conductor is an example of where an 8 AWG and larger solid conductor can be installed in a raceway when it is required to be protected from physical damage [250.64(B)].
(D) Insulated. Conductors must be insulated, unless specifically permitted to be bare.
2. What Code rules address conductor construction, types, and it’s use?
310.4 Conductor Construction and Application
Table 310.4(1) provides information on conductor insulation properties such as letter type, maximum operating temperature, application, insulation, and outer cover properties.
Author’s Comment:
►When a “–2” is at the end of an insulation type (such as THWN-2), the conductor has a maximum operating temperature of 90°C and is suitable to be installed in a dry or wet location.
3. What are the NEC rules addressing conductor identification?
310.6 Conductor Identification
(A) Neutral Conductor. Insulated neutral conductors must be identified white or gray in accordance with 200.6.
(B) Equipment Grounding Conductor. Insulated equipment grounding conductors must be identified green or green with yellow stripe in accordance with 250.119.
(C) Identification of Phase Conductors. Phase conductor insulation can be any color but white [200.7] or green [250.119].
Author’s Comment:
►Although the NEC does not require a specific color code for phase conductors, electricians often use the following color system:
►120/240V, single-phase—black, red, and white
►120/208V, three-phase—black, red, blue, and white
►120/240V, three-phase—(high-leg) black, orange, blue, and white
►277/480V, three-phase—brown, orange, yellow, and gray; or, brown, purple, yellow, and gray
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