Conductors: Materials and Minimum Sizes
(310.5), Insulation Types and Wet Locations (Table 310.4(1), 310.10), Identification (Article 200, 310.6), Parallel Conductors (310.10(G)) and Conductor Properties (Chapter 9 Table 8)
NFPA 70 National Electrical Code, 2023 edition · Reviewed 2026-09-21
Lesson 04-05 covered ampacity. This lesson is the rest of the Conductors sub-bullet — the questions that ask what a conductor may be made of, how small it may be, which insulation goes where, what color each conductor must be, when conductors may be paralleled, and the Chapter 9 Table 8 properties behind voltage-drop problems. Written from the 2023 text.
1. Materials and minimum sizes — 310.3, 110.5
- Conductors are copper, aluminum or copper-clad aluminum (CCA) unless otherwise specified (110.5, 310.3(B)); CCA conductor material is listed (310.3(B)(4)). Where a Code rule does not say, the size given applies to copper (110.5).
- Minimum size (310.3(A)): 14 AWG copper, or 12 AWG aluminum or copper-clad aluminum — except as permitted elsewhere in the Code (fixture wires, Class 1/2/3 and motor-control circuits, flexible cords, and the 18/16 AWG cases of 240.4(D)).
- Aluminum: solid 8, 10 and 12 AWG is an AA-8000 series alloy; stranded 8 AWG–1000 kcmil of the RHH/RHW/XHHW/XHHN/XHWN/THW/THHW/THWN/THHN/SE types is AA-8000; CCA has a copper layer of at least 10 percent of the area over an AA-8000 core.
- 8 AWG and larger conductors in raceways shall be stranded (310.3(C)) unless specifically permitted solid.
- Terminations (110.14): terminals identified for the material; no copper–aluminum intermixing unless the device is identified; 60°C column for circuits ≤ 100 A / 14–1 AWG, 75°C over 100 A / larger than 1 AWG, unless the equipment is listed for more.
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