Side-by-Side Comparison
Electrical & Wiring
Electrical Conduit vs. Wire Ampacity Ratings
Comparing 2 standards across 19 specifications. 19 key differences identified.
Comparing:
Electrical Conduit
Wire Ampacity Ratings
Electrical conduit sizing is governed by the National Electrical Code Chapter 9 Table 1 40% fill rule for three or more conductors, matching raceway types including Electrical Metallic Tubing (EMT), Schedule 40/80 PVC, and Rigid Metal Conduit (RMC).
National Electrical Code (NEC) Table 310.16 establishes allowable conductor ampacities based on conductor material (Copper vs Aluminum), ambient temperature, and insulation thermal ratings (60°C TW/NM-B Romex, 75°C THWN, 90°C THHN).
Specification Comparison Table
19 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standard
|
NFPA 70 (NEC) Chapter 9, Tables 1, 4, and 5 | — |
|
1 Conductor Maximum Fill
|
53% of total internal cross-sectional area | — |
|
2 Conductors Maximum Fill
|
31% of total internal cross-sectional area | — |
|
3 or More Conductors Max Fill
|
40% of total internal cross-sectional area (Universal Standard) | — |
|
1/2" EMT Conduit
|
ID: 0.622 in (15.8 mm) | Total Area: 0.304 sq in | 40% Usable: 0.122 sq in (9 × 12 AWG THHN max) | — |
|
3/4" EMT Conduit
|
ID: 0.824 in (20.9 mm) | Total Area: 0.533 sq in | 40% Usable: 0.213 sq in (16 × 12 AWG THHN max) | — |
|
1" EMT Conduit
|
ID: 1.049 in (26.6 mm) | Total Area: 0.864 sq in | 40% Usable: 0.346 sq in (26 × 12 AWG THHN max) | — |
|
2" EMT Conduit (Service Entrance)
|
ID: 2.067 in (52.5 mm) | Total Area: 3.356 sq in | 40% Usable: 1.342 sq in (3 × 4/0 Cu THHN) | — |
|
Schedule 80 PVC vs EMT
|
Schedule 80 has heavy thick walls; has ~15–20% smaller internal area than EMT | — |
|
Governing Code
|
— | NFPA 70: National Electrical Code (NEC) Table 310.16 |
|
Small Conductor Overcurrent Rule (NEC 240.4D)
|
— | 14 AWG Cu: Max 15A | 12 AWG Cu: Max 20A | 10 AWG Cu: Max 30A |
|
14 AWG Copper (NM-B / Romex)
|
— | 15 Amps (60°C column applied per NEC 334.80) |
|
12 AWG Copper (NM-B / Romex)
|
— | 20 Amps (Standard residential branch circuit) |
|
10 AWG Copper (NM-B / Romex)
|
— | 30 Amps (Clothes dryers, 30A water heaters) |
|
8 AWG Copper (75°C THWN / NM-B)
|
— | 40A (NM-B 60°C) / 50A (THWN 75°C conduit) |
|
6 AWG Copper (75°C THWN / NM-B)
|
— | 55A (NM-B 60°C) / 65A (THWN 75°C conduit) |
|
4 AWG Copper (75°C THWN)
|
— | 85 Amps (Residential subpanel feeder) |
|
2 AWG Copper (75°C THWN)
|
— | 115 Amps (100A subpanel / main feeder) |
|
4/0 Aluminum (75°C XHHW / SE)
|
— | 180 Amps under standard NEC Table 310.16 ampacity; commonly used as the minimum conductor for a 200A dwelling service under NEC's separate service-conductor allowance (Table 310.12, formerly 310.15(B)(7)) |