Motor Feeder Sizing Calculator

Inputs

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Full-load current of the HIGHEST-rated motor, from your adopted code's Table 430.250/248 (not the nameplate). 34 A ≈ 25 hp at 460 V three-phase.
A
Table FLCs of every other motor on the feeder, added together. 14 + 7.6 = 21.6 A ≈ 10 hp + 5 hp at 460 V.
A
Non-motor load expected to run 3 hours or more — counted at 125%.
A
Other non-motor load — counted at 100%.
A
Rating of the largest motor's branch-circuit short-circuit device from your 430.52 sizing. 0 skips the feeder-OCPD output.
A

Results

Default result
Edit inputs
Minimum feeder ampacity(I_min)
64.1A
Pass

The 430.24 floor — take it to your adopted ampacity table with its correction factors.

Also computed

Motor portion64.1A

1.25 × largest + the rest, before non-motor loads.

Max feeder OCPD (430.62(A))Pass111.6A

Round DOWN to a standard rating.

Largest branch device + other motors' FLC — round DOWN to a standard 240.6(A) rating.

Method notes 4 notes
  • 430.24 structure: 125% of the largest motor FLC + the sum of the other motors' FLCs + 125% of continuous and 100% of noncontinuous non-motor load. FLC values are the adopted code's table values (430.250/248), not nameplates — you enter them; nothing is embedded here.
  • The 430.62(A) ceiling rounds DOWN to a standard 240.6(A) rating — the next-size-up allowance belongs to 430.52 branch protection, not feeders.
  • Duty-cycle motors (430.22(E)), interlocked motors that cannot run together, and adjustable-speed-drive rules modify the sum — those exceptions are engineering calls outside this screen.
  • The minimum ampacity goes to your adopted ampacity table with its ambient and conductor-count correction factors (the ampacity derating calculator runs that step).

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