Feeder Sizing for Multiple Motors
Feeder conductor (NEC 430.24) and feeder overcurrent device (NEC 430.62) for several motors on one feeder.
Example
You enter
- Motors, one per line as FLC,branch-device (A) flc (A) 28, branch device (A) 40; flc (A) 16, branch device (A) 25; flc (A) 10, branch device (A) 15
You get
- Min feeder conductor ampacity (A) 61
- Max feeder device (A) 60
Checked against published worked examples from: NEC Articles 430.24 / 430.62 (by name).
Details, formula, and sources
ScopeWith the largest-motor term shown.
Formula or tableFeeder conductor (NEC 430.24) >= 1.25 * FLC_largest + sum(FLC_other) + non-motor load. Feeder OCPD (NEC 430.62) <= largest_branch_device + sum(FLC_other), not rounded up (next standard size down where the sum is not a standard rating).
Source and editionFeeder conductor and feeder overcurrent sizing for several motors on one feeder per NEC 430.24 and 430.62, by name; table FLC (not nameplate FLA) per 430.6(A). The AHJ-adopted NEC edition governs.
Free accessNEC is free to read at nfpa.org/freeaccess. Table FLC and branch-device ratings are user-supplied.
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namesmotors, conductor_min_A, feeder_ocpd_max_A
- FLC source NEC Table 430.250 (etc.) table full-load current, not nameplate FLANEC 430.6(A)