Motor Overload Sizing Guide: 430.32 at 115%, 125% and 140% (2026)

Motor overload sizing under NEC 430.32 comes down to 115%, 125% and 140% of the nameplate full-load current, never the table current. Under 2017 NEC 430.32(A)(1), the overload may trip at no more than 125% of nameplate current when the motor is marked with a service factor of 1.15 or more or a temperature rise of 40°C or less, and 115% for every other motor. If that setting won't start the motor, 430.32(C) lets you go up to 140% or 130%. The percentages are the same in the 2017 and 2020 editions. If you only need the service-factor question exams miss most, JCR's shorter motor overload and service factor explainer covers it; this page is the full sizing guide.

Test your speed on the free 25-question 2017 NEC mock exam. It has a 430.32(C) question, gives instant feedback and shows the NEC reference for every answer.

Motor overload sizing chart: 430.32 at 115%, 125%, 130% and 140%

430.32(A)(1) covers a separate overload device on a continuous-duty motor rated more than 1 hp. Find the nameplate marking in the left column, then read across.

Only one of the two 125% conditions has to be true. A motor marked SF 1.0 with a 40°C rise still gets 125%. The branch-circuit breaker is a separate calculation from Table 430.52; JCR's motor breaker sizing guide walks through it.

The trap: nameplate current, not table current

Article 430 uses two different currents, and the exam tests whether you know which one goes where:

• Overloads use the nameplate. 430.6(A)(2) says separate motor overload protection is based on the motor nameplate current rating.
• Conductors and breakers use the table. 430.6(A)(1) sends you to Table 430.248 (single-phase) or Table 430.250 (three-phase) for conductor ampacity and branch-circuit short-circuit and ground-fault protection.

Notice that 125% shows up twice. Conductors are 125% of the table FLC. A 1.15 SF overload is 125% of the nameplate FLA. Same percentage, different starting number, different answer.

Motor overload calculation: three worked examples

Example 1: 10 hp, 230 V, three-phase, SF 1.15

Nameplate FLA is 26 A. Table 430.250 lists 28 A for this motor.

• Overload: 26 A × 125% = 32.5 A maximum. If it won't start: 26 A × 140% = 36.4 A.
• Conductors: 28 A × 125% = 35 A minimum ampacity.
• Inverse time breaker: 28 A × 250% = 70 A, a standard size.

Use 28 A for the overload and you get 35 A, the most common wrong answer.

Example 2: 5 hp, 460 V, three-phase, SF 1.0, 50°C rise

Nameplate FLA is 7.0 A. The service factor is under 1.15 and the rise is over 40°C, so it falls under all other motors. Table 430.250 lists 7.6 A.

• Overload: 7.0 A × 115% = 8.05 A maximum. If it won't start: 7.0 A × 130% = 9.1 A.
• Conductors: 7.6 A × 125% = 9.5 A minimum ampacity.
• Inverse time breaker: 7.6 A × 250% = 19 A, so the next standard size, 20 A.

Example 3: 3 hp, 230 V, single-phase, 40°C rise

Nameplate FLA is 16 A, SF 1.0. The 40°C rise earns the 125% column. Table 430.248 lists 17 A.

• Overload: 16 A × 125% = 20 A maximum. If it won't start: 16 A × 140% = 22.4 A.
• Conductors: 17 A × 125% = 21.25 A minimum ampacity.
• Inverse time breaker: 17 A × 250% = 42.5 A, so the next standard size, 45 A.

Exam traps on 430.32

• Table current for the overload. If the question gives both a nameplate FLA and a horsepower, the overload answer comes from the nameplate.
• Jumping straight to 140%. 430.32(C) is only for a motor that won't start or carry its load at the (A)(1) setting. A plain maximum-overload question means 115% or 125%.
• Rounding up. The next-standard-size rule belongs to the breaker in 430.52(C)(1) Exception No. 1. 430.32 has no round-up. 32.5 A means 32.5 A.
• Missing the 40°C rise. An SF 1.0 motor still gets 125% if it's marked 40°C rise or less.
• Using 2020 table numbers. 430.32 didn't change, but the conductor tables did. In the 2017 NEC you size the motor conductors from Table 310.15(B)(16), which the 2020 edition renumbered Table 310.16. Tennessee, Nevada, Arizona and Kansas score the 2017 number.

430.32 practice quiz: 5 questions

Work these with your 2017 NEC open, write down your answers, then open the explanations.

Question 1

A continuous-duty motor has a nameplate FLA of 40 A and a service factor of 1.15. What is the maximum rating of a separate overload device under 430.32(A)(1)?

1. 46 A
2. 50 A
3. 52 A
4. 56 A

Question 2

A motor is marked with a service factor of 1.0 and a temperature rise of 50°C. Its nameplate FLA is 20 A. What is the maximum overload rating?

1. 23 A
2. 25 A
3. 26 A
4. 28 A

Question 3

The motor in Question 1 won't start with an overload sized at 125%. What is the most 430.32(C) allows?

1. 50 A
2. 52 A
3. 56 A
4. 60 A

Question 4

Which current does the 2017 NEC require you to use when sizing separate motor overload protection?

1. Full-load current from Table 430.250
2. Motor nameplate current rating
3. Locked-rotor current
4. 125% of the table full-load current

Question 5

A 25 hp, 460 V, three-phase motor has a nameplate FLA of 32 A and a service factor of 1.15. Table 430.250 lists 34 A. What is the maximum overload rating?

1. 36.8 A
2. 40 A
3. 42.5 A
4. 44.8 A

Answer key with 2017 NEC sections

Motor overload sizing FAQ

Do you size motor overloads from the nameplate or the NEC table?

The nameplate. 430.6(A)(2) requires the motor nameplate current for separate overload protection. Conductors and the branch-circuit breaker use the Table 430.248 or 430.250 value.

What is the maximum overload for a motor with a 1.15 service factor?

125% of the nameplate full-load current under 430.32(A)(1). If that setting won't start the motor or carry the load, 430.32(C) allows up to 140%.

Do you round motor overloads up to the next standard size?

No. The next-size-up rule is for the branch-circuit breaker or fuse in 430.52. The 430.32 percentages are maximums.

Did 430.32 change between the 2017 and 2020 NEC?

No. The 115%, 125%, 130% and 140% values are the same in both editions. The tables around it, like the conductor ampacity table, were renumbered in 2020.

How do I calculate motor overload size?

Multiply the nameplate full-load amps by 125% if the motor is marked SF 1.15 or more or 40°C rise or less, or by 115% for any other motor. Pick an overload device or setting that trips at or below that number. Go to 140% or 130% only if the motor won't start or carry its load.