Motor Running Overload Protection (NEC 430.32)

The running overload for a motor, sized on the NAMEPLATE FLA (not the table FLC the branch-circuit device uses) - the second of the two motor protection devices. NEC 430.32(A)(1) gives 125% of FLA for a continuous-duty motor over 1 hp with a marked service factor of 1.15+ or a marked rise of 40 C or less, 115% otherwise, and 430.32(C) permits raising to 140%/130% only if the motor will not start at the base setting. A 26 A SF-1.15 motor sets at 32.5 A with a 36.4 A ceiling - the number dialed into the overload relay or the heater table. A design aid; the AHJ governs.

hi_class = (sf >= 1.15) or (marked rise <= 40 degC); mult = hi_class ? 1.25 : 1.15; mult_max = hi_class ? 1.40 : 1.30; ol_A = fla_A x mult; ol_max_A = fla_A x mult_max.

Motor running-overload sizing on the nameplate full-load current under NEC 2023 430.32(A)(1) (125% for a marked service factor of 1.15 or more or a marked temperature rise of 40 degC or less, 115% otherwise) with the 430.32(C) will-not-start ceiling (140%/130%), by name. A computational aid; the AHJ-adopted NEC edition governs.

NEC is free to read at nfpa.org/freeaccess. The 430.32(B) small-motor rules, 430.36 fuse-as-overload, and thermally protected cases are stated as out of scope, not modeled.

Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.

Field names used by the API: fla_A, sf, rise_C, mult, ol_A, ol_max_A

• Basis current the motor NAMEPLATE FLA, not the 430.6 table FLC the 430.52 branch device usesNEC 430.32 / 430.6(A)
• Class selection 125%/140% for marked SF >= 1.15 or marked rise <= 40 degC; 115%/130% otherwise; an unmarked (blank) value does not qualifyNEC 430.32(A)(1) and (C)
• Scope a continuous-duty motor over 1 hp with a separate overload deviceNEC 430.32(A)