Motor branch-circuit short-circuit and ground-fault protective devices are not sized like standard receptacle or lighting circuits. If you apply the standard 125% continuous load rule to a motor, the breaker will trip instantly every time the motor starts. To account for the massive inrush current (Locked Rotor Current) required to spin a motor from a dead stop, the National Electrical Code (NEC) requires using NEC Table 430.52. For the standard thermal-magnetic breakers found in residential and commercial panels, the maximum breaker size is typically 250% of the motor's Full Load Current (FLC).

Safety & Code Caveat: Working inside electrical panels exposes you to lethal mains voltage. Always de-energize the panel, lock out the main breaker, and verify dead with a tested non-contact voltage meter and multimeter before touching any bus bars or terminals. NEC-style guidance is provided here for educational purposes; your local Authority Having Jurisdiction (AHJ) has final say on all installations.

The NEC Table 430.52 Motor Breaker Sizing Chart

This chart provides the maximum rating for branch-circuit short-circuit and ground-fault protection based on the motor's Full Load Current (FLC). The FLC values below are drawn directly from NEC Table 430.248 (for single-phase AC motors), and the breaker maximums are calculated using the 250% multiplier from NEC Table 430.52 for inverse-time breakers. If the exact calculation does not correspond to a standard breaker size (per NEC 240.6), you are permitted to round up to the next standard size.

Motor Rating (HP) 115V FLC (Amps) 115V Max Breaker 230V FLC (Amps) 230V Max Breaker
1/4 HP 5.8 A 15 A 2.9 A 15 A (Min Standard)
1/3 HP 7.2 A 20 A 3.6 A 15 A
1/2 HP 9.8 A 25 A 4.9 A 15 A
3/4 HP 13.8 A 35 A 6.9 A 20 A
1 HP 16.0 A 40 A 8.0 A 20 A
1.5 HP 20.0 A 50 A 10.0 A 25 A
2 HP 24.0 A 60 A 12.0 A 30 A
3 HP 34.0 A 90 A 17.0 A 45 A
5 HP 56.0 A 150 A 28.0 A 70 A

Source: NFPA 70 (National Electrical Code), Article 430.52 and Table 430.248. For a complete overview of NEC motor circuit requirements, refer to the NFPA 70 standard documentation.

Bookmark Quick-Jump: The most frequently queried rows for DIYers and residential electricians are the 1 HP and 1.5 HP motors (common for well pumps, pool pumps, and air compressors). Remember: a 1 HP motor on 230V draws 8A FLC and requires a maximum 20A breaker. A 1.5 HP motor on 230V draws 10A FLC and requires a maximum 25A breaker.

Applying the Chart: Columns, Derating, and Edge Cases

If you look at the actual NEC Table 430.52 in the codebook, you will see four distinct columns: Nontime Delay Fuse, Time-Delay Fuse, Instantaneous Trip Breaker, and Inverse-Time Breaker. The Inverse-Time Breaker column is the one that applies to 99% of standard installations. This is the standard thermal-magnetic breaker (like a Square D QO, Eaton BR, or Siemens QP) that uses a bimetallic strip for thermal overload and an electromagnet for instantaneous short-circuit tripping.

How Derating and Exceptions Modify the Base Value

The 250% multiplier is a maximum baseline, but real-world motors don't always read the codebook. If your motor has a high starting torque requirement, or if it's driving a high-inertia load (like a large centrifugal fan or a loaded conveyor), the inrush current might last long enough to trip a breaker sized exactly at 250%.

  • Exception 1 (Next Standard Size): If the motor starts and trips the 250% breaker, NEC 430.52(C)(1)(Ex. 1) allows you to increase the breaker to the next standard size, even if it exceeds the 250% calculation.
  • Exception 2 (Up to 400%): If the next standard size still trips, and the motor is rated 100 amps or less, you are permitted to increase the inverse-time breaker up to a maximum of 400% of the FLC, provided the motor starts successfully and the manufacturer's instructions do not forbid it.

However, you cannot use these exceptions to bypass wire sizing rules. The breaker protects against short circuits; the wire must still be sized to handle the continuous running current without melting.

What This Chart Cannot Tell You

A common point of failure on jobsite inspections is confusing branch-circuit short-circuit protection (the breaker in the panel) with motor overload protection (the heater or dial at the motor starter). Table 430.52 only sizes the breaker. It does not tell you three critical things:

  1. Overload Protection Sizing: Overloads protect the motor from burning itself out if it runs too hot or gets jammed. Per NEC 430.32, overloads are sized based on the nameplate Full Load Amps (FLA) of the specific motor, typically at 115% to 125% of the nameplate FLA. This is handled by the thermal overload relay on your contactor, not the panel breaker.
  2. Wire Sizing: You do not use Table 430.52 to size your wire. Per NEC 430.22, motor branch circuit conductors must be sized at 125% of the motor FLC (from Table 430.248). This creates a scenario where the breaker is physically larger than the wire's ampacity—a deliberate design choice allowed by the NEC because the motor's internal overloads will protect the wire from continuous overcurrent, while the breaker only catches dead shorts.
  3. Continuous Duty vs. Short-Time Duty: Table 430.52 assumes standard continuous duty motors. If you are wiring a short-time duty motor (like a valve actuator or a hoist that only runs for 5 minutes), different thermal mass rules apply to both the wire and the breaker.

For a deeper dive into the physical differences between the breaker's job and the overload's job, Schneider Electric's engineering FAQs provide an excellent breakdown of short-circuit versus thermal overload protection mechanisms.

Motor Breaker Sizing Chart FAQ

Can I use a standard breaker for a motor or do I need a motor circuit protector (MCP)?

For most residential, agricultural, and light commercial applications under 600V, a standard inverse-time thermal-magnetic breaker (like a standard 2-pole 240V breaker) is perfectly legal and code-compliant when sized via Table 430.52. A Motor Circuit Protector (MCP) is a specialized device that only provides short-circuit protection (it has no thermal strip) and must be paired with a specific, tested motor starter assembly to be UL listed. Unless you are building a factory-approved Motor Control Center (MCC) or using a specific manufacturer's listed combination starter, stick to standard inverse-time breakers.

Why is my motor breaker larger than the wire ampacity?

This is the most common reason DIYers fail electrical inspections. If you have a 1.5 HP, 230V pool pump, the FLC is 10A. The wire is sized at 125% of 10A (12.5A), so you use 12 AWG copper wire (rated for 20A). However, the breaker is sized at 250% of 10A (25A). You end up with a 25A breaker protecting 12 AWG wire. This is explicitly permitted by NEC Article 430 because the motor's internal thermal overloads (or the external overload relay on the contactor) will trip and open the circuit if the motor draws a continuous 18A, long before the 12 AWG wire overheats. The 25A breaker is only there to clear a catastrophic dead-short.

How do I size a breaker for a motor with a high starting torque or hard-start condition?

If you are wiring a motor that starts under a heavy load (like a rock crusher, a loaded conveyor belt, or a positive displacement compressor), the Locked Rotor Current (LRC) will be higher and last longer than a standard motor. First, calculate the baseline using the 250% multiplier in Table 430.52. If the breaker trips during the start-up phase, utilize NEC 430.52(C)(1) Exception 1 to step up to the next standard breaker size. If it still trips, you may invoke Exception 2 to go up to 400% of the FLC, provided the motor nameplate does not specify a lower maximum protective device rating. Always verify that your wire is still sized for 125% of the FLC, regardless of how large the breaker gets.