Motor Full-Load Amps (FLA) Calculator

Enter horsepower, voltage, and phase to calculate NEC table FLA, minimum conductor ampacity, branch overcurrent maximum, and overload relay target per NEC Article 430.

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Tools for motor circuit work

Metering, troubleshooting, and termination tools that support Article 430 field work.

Clamp

Ideal Industries 61-757 Digital Clamp Meter

Measure live motor FLA without lifting conductors
Peak hold support for startup checks
True RMS readings for mixed motor loads

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Meter

Fluke 117 Electricians True RMS Multimeter

Verify motor terminal voltage during startup events
Trusted baseline meter for service diagnostics
CAT III safety rating for control-panel work

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Stripper

Gardner Bender GESP-70 Professional Wire Stripper

Fast prep for motor branch conductors
Improves termination quality at starters
Good fit for repetitive panel builds

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Insulated

Klein Tools 32584INSR 1000V Insulated Screwdriver Set

Safer torque adjustments in energized enclosures
IEC 60900-rated insulation for electrical work
Covers common terminal and lug drive styles

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Klein Tools ET310 Circuit Breaker Finder

Trace motor branch circuits at distribution panels
Speeds troubleshooting on retrofit jobs
Useful during lockout and labeling workflows

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Motor FLA: Why It Drives Every Motor Circuit Decision

Full-load amps (FLA) is the current a motor draws at rated horsepower and voltage. In motor work, FLA anchors the full branch design: conductor ampacity, branch overcurrent limits, overload settings, and disconnect minimums.

Unlike general branch circuits, NEC Article 430 separates these protective functions. That is why a motor breaker can look oversized while overload protection remains much tighter.

Field Rule Use the NEC table value for branch overcurrent sizing, then verify overload settings against the motor nameplate and service-factor details.

The Four Components You Must Size Separately

Conductor ampacity (430.22): minimum 125% of motor FLA.
Branch overcurrent (430.52): follows breaker/fuse multiplier limits for motor starting inrush.
Overload protection (430.32): protects windings from sustained overload.
Disconnecting means (430.110): minimum 115% of FLA.

Worked Example: 10 HP Three-Phase at 460V

Step 1: Table FLA = 14A.

Step 2: Conductor ampacity minimum = 14 x 1.25 = 17.5A.

Step 3: Inverse-time branch maximum = 14 x 2.50 = 35A.

Step 4: Overload target (SF 1.15+) = 14 x 1.25 = 17.5A.

Step 5: Disconnect minimum = 14 x 1.15 = 16.1A.

Inspection Failure Pattern Treating the branch breaker as overload protection is a frequent failure. Breaker sizing and overload relay sizing serve different functions in Article 430 workflows.

Frequently Asked Questions

What is the difference between FLA and LRA?

FLA is steady running current at rated output. LRA is startup inrush when the rotor is not yet moving, often many times higher than FLA.

Can the branch overcurrent device be less than 250%?

Yes. The multiplier limit is a maximum; if startup is reliable with a smaller setting, that is often preferred.

Do hermetic HVAC compressors use Article 430?

Typically no. Those are generally handled under Article 440 with MCA and MOP nameplate values.

Motor Full-Load Amps (FLA) Calculator