Branch-Circuit and Appliance Calculations
Worked Examples (210.19–210.23, 422.10–422.13, 424.4, 440.32, Table 220.55)
NFPA 70 National Electrical Code, 2023 edition · Reviewed 2026-09-21
Branch Circuits and Conductors supplies calculation items on both Georgia exams (and a large share of the Residential exam). The problems: size a circuit for continuous + noncontinuous load, count required circuits, apply the 80 %/50 % permissible-load limits, size an appliance circuit (water heater, range, cooktop + oven, dryer, heater, A/C), and pick the receptacle rating. Written from the 2023 text.
1. Conductor and OCPD for a branch circuit — 210.19(A) / 210.20(A)
- Ampacity and OCPD rating ≥ noncontinuous + 125 % of continuous (100 %-rated assemblies excepted); conductors also ≥ the load after 310.15 adjustment/correction.
- 240.4(D) small conductors: 14 AWG Cu 15 A; 12 AWG Cu 20 A; 10 AWG Cu 30 A (Al/CCA: 12 AWG 15 A, 10 AWG 25 A); 18 AWG Cu 7 A and 16 AWG Cu 10 A only under the listed-device / Class CC-CF-J-T fuse conditions of 240.4(D)(1)/(2) (Table 310.16 itself starts at 14 AWG in 2023).
Example 1. 16 A of continuous lighting + 4 A noncontinuous: 4 + 16 × 1.25 = 24 A → 25 A OCPD with 10 AWG Cu (30 A; 12 AWG is capped at 20 A by 240.4(D)).
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