Start with the correct current source
- Conductors: table FLC
- Branch-circuit short-circuit and ground-fault protection: table FLC
- Overloads: nameplate FLA
- Disconnect and controller checks: continue the Article 430 workflow from the right source
Quick percentages electricians reach for first
- Conductors: 125 percent of table FLC
- Inverse-time breaker: often up to 250 percent of table FLC, subject to the actual motor rule path
- Dual-element time-delay fuse: often up to 175 percent of table FLC on the first pass
- Overload protection: tied to the motor nameplate current, not the table FLC
Correct sizing order
- Pull table FLC from HP, phase, and voltage.
- Size conductors from 125 percent of table FLC.
- Size branch-circuit protection using the correct device rule.
- Switch to the nameplate where overload protection actually requires it.
- Check disconnect, voltage drop, and short-circuit duty before you walk away.
What to verify after the first answer
The first sizing answer is not the last design decision. Confirm the actual nameplate, termination temperatures, line voltage, and whether long runs need a separate voltage-drop check.
Frequently Asked Questions
What current do I start with on a motor circuit?
Start with table FLC for conductor sizing and branch-circuit short-circuit and ground-fault protection. Do not start with nameplate FLA for everything.
What is the 125 percent motor rule?
NEC 430.22 requires branch-circuit conductors for a continuous-duty motor to be at least 125 percent of motor table FLC.
Why can the motor breaker be bigger than the conductor ampacity?
Because the breaker or fuse has to ride through motor inrush. Overload protection handles sustained overcurrent while the branch-circuit protective device handles faults.
Does this field guide cover DC motors?
No. This quick reference is for the standard AC motor workflow electricians usually mean when they ask for NEC motor sizing help.
Run The Motor Workflow
Motor FLC Calculator
Use the live workflow when you want the table lookup and the Article 430 sizing chain in one place.