Motor Calculations — Worked Examples (430.6, 430.22, 430.24, 430.32, 430.52, 430.62, 430.110, 430.122)
Six of the Master's 30 scored calculation items are motor calculations; the Journeyman has two. They all run the same six-step chain, and the exam traps are (1) using the nameplate where the Code says table (or vice versa), (2) forgetting that 430.52 rounds *up* while 430.32 does not, and (3) the 25 % adder applies to the largest motor once. Written from the 2026 text.
NFPA 70 National Electrical Code, 2026 edition · Reviewed 2026-09-19
Six of the Master's 30 scored calculation items are motor calculations; the Journeyman has two. They all run the same six-step chain, and the exam traps are (1) using the nameplate where the Code says table (or vice versa), (2) forgetting that 430.52 rounds up while 430.32 does not, and (3) the 25 % adder applies to the largest motor once. Written from the 2026 text.
The six-step chain
| Step | What | Current used | Factor |
|---|---|---|---|
| 1 | Branch-circuit conductors — 430.22(A) | table FLC (430.6(A)) | 125 % |
| 2 | Overload — 430.32 | nameplate FLA | 125 % (SF ≥ 1.15 or rise ≤ 40°C) / 115 % others; may go to 140 % / 130 % if needed (430.32(C)) |
| 3 | Branch-circuit short-circuit/ground-fault device — 430.52 / Table 430.52(C)(1) | table FLC | nontime-delay fuse 300 %; dual-element fuse 175 %; instantaneous-trip breaker 800 % (1100 % Design B/BE/CE energy-efficient); inverse-time breaker 250 %; wound-rotor 150 %; next size up permitted (430.52(C)(1)(a)); if still insufficient — ≤ 400 % / 225 % / 400 % (≤ 100 A FLC) or 300 % (> 100 A) |
| 4 | Feeder conductors — 430.24 | table FLC | 125 % of the largest motor + 100 % of the others + non-motor loads (125 % continuous) |
| 5 | Feeder OCPD — 430.62(A) | — | largest branch-circuit device + the other motors' FLC; round down to a standard size |
| 6 | Disconnect — 430.110 | table FLC / Table 430.251 LRC | ≥ 115 % of FLC; hp-rated by combined FLC and LRC (430.110(C)) |
2026 note: Table 430.52(C)(1) adds "Design BE and Design CE" to the energy-efficient row (instantaneous trip 1100 %); 430.22(G) was rewritten for 18/16 AWG small-motor conductors; 430.22(H) adds a conductor-temperature check for Design BE/CE motors.
This is where the public part ends.
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