Side-by-Side Comparison
Electrical & Wiring
Circuit Breaker Sizes & Amperage vs. Electrical Boxes
Comparing 2 standards across 18 specifications. 18 key differences identified.
Comparing:
Circuit Breaker Sizes & Amperage
Electrical Boxes
Residential and commercial circuit breakers are standardized under National Electrical Code (NEC Article 240) and UL 489 into standard continuous trip ratings (15A, 20A, 30A, 40A, 50A, 60A, 100A, 200A), single-pole (120V) vs double-pole (240V) formats, and mandatory AFCI/GFCI protection types.
Standard electrical outlet and junction boxes are specified by trade dimensions and minimum internal cubic inch volume, including 4-inch square boxes (1900/1920 boxes, 21.0–30.3 cu in), 4-inch octagon ceiling boxes (15.5–21.5 cu in), and single-gang device boxes (18.0 cu in).
Specification Comparison Table
18 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standards
|
NFPA 70 (NEC) / UL 489 / NEMA AB 1 (Circuit Breakers) | NEMA OS 1 / NEC Article 314.16 |
|
15-Amp Single Pole (120V)
|
Wire Gauge: 14 AWG Copper | Standard residential lighting and general bedroom/living outlets | — |
|
20-Amp Single Pole (120V)
|
Wire Gauge: 12 AWG Copper | Kitchen countertop, bathroom receptacles, laundry, garage, workshop | — |
|
30-Amp Double Pole (240V)
|
Wire Gauge: 10 AWG Copper | Electric clothes dryers, 30-gallon water heaters, small RV hookups | — |
|
40-Amp Double Pole (240V)
|
Wire Gauge: 8 AWG Copper | Electric cooking ranges, cooktops, heat pump auxiliary heat | — |
|
50-Amp Double Pole (240V)
|
Wire Gauge: 6 AWG Copper | Level 2 EV charging (NEMA 14-50), commercial cooking ovens | — |
|
60-Amp Double Pole (240V)
|
Wire Gauge: 4 AWG Copper (or 6 AWG THHN) | Central air conditioning compressors, sub-panel feeds | — |
|
100A–200A Main Service
|
2/0 AWG Copper / 4/0 AWG Aluminum | Main residential service disconnect panel | — |
|
80% Continuous Load Rule
|
NEC 210.20: Continuous loads (operating 3+ hours) must not exceed 80% of breaker rating (e.g. 16A max on 20A breaker) | — |
|
4" Square Box (1-1/2" Deep–1900 Box)
|
— | 4.0 × 4.0 × 1.5 in (102 × 102 × 38 mm) | 21.0 cu in (344 cm³) |
|
4" Square Box (2-1/8" Deep–1920 Box)
|
— | 4.0 × 4.0 × 2.125 in (102 × 102 × 54 mm) | 30.3 cu in (496 cm³) |
|
4" Octagon / Round Ceiling Box
|
— | 4.0 × 4.0 × 1.5 in (102 × 102 × 38 mm) | 15.5 to 21.5 cu in |
|
Handy / Utility Box (Surface 2×4")
|
— | 4.0 × 2.125 × 1.875 in | 13.0 to 14.5 cu in |
|
Single-Gang Plastic Device Box
|
— | Standard 18.0 to 22.5 cu in (supports up to 9 × 14 AWG conductors) |
|
Double-Gang Plastic Device Box
|
— | Standard 32.0 to 35.0 cu in |
|
Volume Allowance per 14 AWG Conductor
|
— | 2.00 cu in (32.8 cm³) per wire |
|
Volume Allowance per 12 AWG Conductor
|
— | 2.25 cu in (36.9 cm³) per wire |
|
Volume Allowance per 10 AWG Conductor
|
— | 2.50 cu in (41.0 cm³) per wire |
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