Motor Overload Protection Setting Reference
Calculate NEC 430.32 maximum motor overload trip current from nameplate FLA, service-factor or temperature-rise markings, and overload-device type.
Nameplate and protection device
This reference covers continuous-duty motors rated above 1 HP with a separate overload device.
Use the motor nameplate current. Do not substitute NEC table full-load current.
The 125% limit applies if either qualifying nameplate condition is met. Otherwise, use the 115% class.
The conditional increase in 430.32(C) applies to a separate overload relay, not a fuse or circuit breaker.
Select only when the normal setting is insufficient. Verify the motor and relay manufacturer's instructions.
Maximum overload trip current
The normal maximum is based on the selected nameplate class. Use the higher 430.32(C) limit only when its conditions are met and the overload device is a separate relay.
About this calculator
Calculate the maximum overload trip-current reference for a continuous-duty motor rated above 1 HP with a separate overload device. Enter the motor nameplate full-load current and select the motor's service-factor or temperature-rise class.
The calculator distinguishes the normal maximum from a conditional 430.32(C) adjustment. It does not select an overload relay, heater, fuse, circuit breaker, or actual device dial setting.
Method and assumptions
Under the separate overload-device method in 430.32(A)(1), the normal maximum trip current is 125% of nameplate FLA for a motor marked with service factor 1.15 or greater, or temperature rise 40°C or less. For all other motors, this reference uses 115% of nameplate FLA.
Section 430.32(C) permits a higher overload-relay trip setting only when the normal setting is not sufficient to start the motor or carry the load. The conditional ceiling is 140% for the qualifying motor class and 130% for all other motors. This adjustment does not apply to a fuse or circuit breaker in this reference.
The calculated amperes are maximum trip-current references. Overload relay trip curves, calibration, sensing element ratings, and dial markings vary by manufacturer. Follow the listed starter and overload-device instructions for the actual setting.
This page covers continuous-duty motors above 1 HP with a separate overload device. Other motor sizes, duty ratings, integral protectors, and special equipment may use different provisions.
Example
A motor with 20 A nameplate FLA and a qualifying service-factor or temperature-rise marking has a normal maximum trip current of 20 × 1.25 = 25 A. If that separate overload relay will not start the motor or carry its load, the conditional ceiling is 20 × 1.40 = 28 A.
For an otherwise identical motor without either qualifying marking, the normal maximum is 20 × 1.15 = 23 A and the conditional relay ceiling is 20 × 1.30 = 26 A. These values do not establish the correct setting for a particular relay or driven load.
Interpret the result
Use the normal maximum as the starting reference for overload-device selection. Select the conditional adjustment only when the normal setting cannot start the motor or carry its load, and use it only with a separate overload relay.
Verify the motor nameplate, load behavior, relay trip class, starter instructions, ambient conditions, and locally adopted code. Coordinate overload protection separately from branch-circuit short-circuit and ground-fault protection.
FAQs
Why does this use nameplate current instead of table full-load current?
Motor overload protection uses motor nameplate full-load current. NEC table full-load current is used for other motor branch-circuit calculations, including conductor sizing and short-circuit/ground-fault protection.
When does the calculator use 125%?
The 125% normal maximum applies when the motor is marked with a service factor of 1.15 or greater, or a temperature rise of 40°C or less. All other motors use 115% in this reference.
When can I use the higher 430.32(C) setting?
Only when the overload device selected at the normal setting is not sufficient to start the motor or carry the load. The higher limit is conditional, not a routine starting point. Confirm the motor, load, relay, and manufacturer instructions.
Can a fuse or circuit breaker use the higher setting?
No. This calculator applies the 430.32(C) increase only to a separate overload relay. A fuse or circuit breaker remains at the normal overload limit shown here; other motor branch-circuit protection rules are separate.
Is the result the number to dial into a relay?
No. The result is a maximum trip-current reference. Relay dials and heater selections use manufacturer-specific calibration and trip curves. Use the starter and overload-device instructions to set the actual device.
Which motors are covered?
This reference is limited to continuous-duty motors rated above 1 HP with a separate overload device. Motors 1 HP or less, motors with integral thermal protection, noncontinuous-duty motors, and special equipment use other rules.
Sources
- NFPA 70, National Electrical Code, 2026 edition — Sections 430.6(A)(2) and 430.32(A)(1), (C). Verify the edition adopted by the authority having jurisdiction.
- NFPA Code-Making Panel 2 Second Draft Report, preliminary report — public code-development source for the conditional overload-relay increase; it is not a substitute for the adopted final code text.
- Use the motor, starter, and overload-device nameplates and current manufacturer instructions for the actual relay setting.