Motors, HVAC Equipment, Luminaires and Power Production Sources
Motor circuits are the one place in the code where conductors, short-circuit protection and overload protection are all sized from different numbers and different percentages, which is exactly why the exam loves them. Once you accept that the table full-load current sizes almost everything except the overload, motor questions become routine arithmetic.
Motor Full-Load Current and Conductor Sizing
The full-load current tables in Article 430 are the required basis for conductor sizing, branch-circuit short-circuit protection and disconnect ratings, no matter what the motor nameplate says. This is deliberate, because the code wants a consistent installation even if the motor is later replaced with a different brand. Nameplate current is reserved for overload protection, where the goal is protecting that specific machine.
Overload Versus Short-Circuit Protection
These are two separate devices doing two separate jobs, and confusing them is the classic motor mistake. Overload protection responds slowly to modest sustained overcurrent that would cook the windings, and it is sized from the nameplate. Short-circuit and ground-fault protection responds quickly to a fault while still letting the motor draw its large starting current, so its percentages are far higher.
Air Conditioning and Refrigeration Equipment
Article 440 equipment is factory engineered, so the nameplate does most of the work for you. Minimum circuit ampacity sets the conductor and maximum overcurrent protective device sets the ceiling on the breaker or fuse, and neither number may be adjusted upward in the field. When you must calculate rather than read a nameplate, hermetic compressors use rated-load current with their own percentages.
Luminaires and Lighting Outlets
Luminaire rules concentrate on heat and on the specific hazard of clothes closets, where stored fabric can rest against a hot fixture. Recessed luminaires add the problem of blown-in insulation packed around a housing that was never designed for it, which is why the IC rating exists. Support requirements make sure the fixture weight is carried by the structure and not by the wiring.
Generators and Photovoltaic Systems
On-site power sources appear on the exam in small numbers but with predictable questions about conductor sizing and disconnection. Generator output conductors are uprated rather than derated because the machine itself limits the available current. Photovoltaic circuits apply the 125 percent factor twice, once to establish the maximum circuit current and again to size conductors and protection.
Last updated: July 2026