# Motor feeder conductors and protection (NEC 430.24, 430.62)

> A feeder for several motors needs conductors rated at least 125% of the largest motor's table full-load current plus the full-load currents of the other motors (NEC 430.24). The feeder breaker or fuse may be no larger than the largest motor branch-circuit device plus the other motors' full-load currents (430.62(A)), so you round down.

Exams: Journeyman Electrician, Master Electrician. Motors.

## Formula

    Feeder ampacity (A) = 1.25 × largest motor FLC + sum of other motor FLCs + 1.25 × continuous other loads + noncontinuous other loads
    Feeder OCPD (A) ≤ largest motor branch OCPD rating + sum of other motor FLCs, rounded down to a standard size

## Variables

- **FLC**: Table 430.250 full-load current of each motor (A)
- **Largest branch OCPD**: Rating of the biggest motor branch-circuit fuse or breaker, from 430.52 (A)

## Open your 2026 NEC to

- 430.24: Feeder conductors: 125% of the largest motor plus the other motors and other loads
- 430.62(A): Feeder protection: largest branch device plus the other motors' full-load currents, not exceeded
- Table 430.52(C)(1): Branch-circuit device percentages used to find the largest branch device
- Table 430.250: Three-phase motor full-load currents
- 240.6(A): Standard fuse and breaker ratings

Several motors on one feeder will not all start at once and rarely all run at full load. The NEC sizes the feeder from the largest motor plus the running current of the rest. Under 430.24 the conductors must carry 125% of the largest motor's table full-load current, plus 100% of the other motors, plus any other loads: 125% of continuous non-motor loads and 100% of noncontinuous ones.

The feeder protective device follows 430.62(A). Start with the branch-circuit short-circuit device of the motor that has the largest one, as sized under 430.52. Add the full-load currents of all the other motors. The feeder device may not be larger than that total, so if the total is not a standard size you go down to the next standard rating. This is the opposite of the branch-circuit rule.

If two motors are the same size, count one of them as the largest and the other at 100%. The 2026 NEC adds an exception to 430.24 for feeders with Design BE or CE motors, which can need larger conductors; the problems here use ordinary squirrel-cage motors.

## Worked example

A feeder supplies three 230 V three-phase squirrel-cage motors, all continuous duty: 7-1/2 hp, 30 hp and 2 hp. There is no other load. Using NEC 430.24, what is the minimum ampacity of the feeder conductors?

1. Look up Table 430.250, 230 V column, 7-1/2 hp: 22.0 A.
2. Look up Table 430.250, 230 V column, 30 hp: 80.0 A.
3. Look up Table 430.250, 230 V column, 2 hp: 6.8 A.
4. NEC 430.24: 125% of the largest motor (30 hp) plus 100% of the others: 1.25 × 80.0 = 100.00 A.
5. Minimum ampacity: 100.00 + 22.0 + 6.8 = 128.80 A.

**Answer: 128.80 A**

## How to solve it on the exam

1. Look up every motor's full-load current in Table 430.250 (or 430.248), not the nameplates.
2. Feeder conductors: 1.25 × the largest FLC, plus the other FLCs, plus other loads (125% if continuous).
3. Pick the conductor from Table 310.16 using the terminal temperature column.
4. Feeder protection: size the largest motor's branch device under 430.52, add the other motors' FLCs, then round down to a standard size.

## Common mistakes

- Taking 125% of every motor instead of only the largest.
- Rounding the feeder breaker up. Under 430.62(A) you round down.
- Adding all the branch breaker ratings together for the feeder breaker.
- Using nameplate currents instead of table full-load currents.
- Counting a continuous non-motor load at 100%.

## Exam tips

- Write the motors in order from largest to smallest current before you start. The question will often list them in a different order.
- Feeder conductors round up to a conductor that is big enough. The feeder breaker rounds down. Mark that on your 430.62 tab.

## Questions people ask

### How do you size a feeder for multiple motors?

Take 125% of the largest motor's table full-load current and add 100% of every other motor's full-load current, plus other loads. That total is the minimum conductor ampacity under NEC 430.24.

### How do you size the breaker for a motor feeder?

Add the rating of the largest motor branch-circuit breaker or fuse to the full-load currents of the other motors. Under 430.62(A) the feeder device may not exceed that, so round down to a standard size.

### Why does the motor feeder breaker round down?

Because 430.62(A) sets a maximum: the feeder device may not be greater than the calculated value. There is no next-size-up permission for motor feeders like the one in 430.52 for branch circuits.

### What if two motors are the largest?

Use one of them as the largest motor at 125% (or its branch device for 430.62) and count the other at 100% of its full-load current.

## Sources

- [TDLR: Electrician examination information](https://www.tdlr.texas.gov/electricians/elecexam.htm)
- [PSI: Texas electrician candidate information bulletin](https://test-takers.psiexams.com/api/content/bulletin/1682)
- [IEC: 2026 NEC changes to Chapter 4](https://ieci.org/national-electrical-code-2026-changes-to-chapter-four/)

Interactive practice: https://texaselectricianexam.com/calculations/motor-feeder/