Motors, Appliances, HVAC Equipment, and Dedicated Circuits
Motors, air conditioners, and appliances follow different sizing logic than general loads: conductors and overcurrent protection are sized from separate rules, and the nameplate frequently overrides the tables.
Motor branch circuits
Tables 430.248 and 430.250 give full-load currents. 430.22 sizes conductors at 125% of the table FLC, 430.32 provides running overload protection, and 430.52 provides short-circuit and ground-fault protection with limits such as 250% of FLC for an inverse-time breaker. 430.102 requires a disconnecting means within sight of the motor and its controller.
Air conditioning and heat pumps
Article 440 governs hermetic refrigerant motor-compressors. The nameplate gives a Minimum Circuit Ampacity and a Maximum Overcurrent Protective Device; those two numbers control. 440.32 sizes conductors at 125% of the largest load. 440.22 permits the branch-circuit device up to the nameplate maximum. 440.14 requires the disconnect within sight of and readily accessible from the unit.
Appliances
422.10 sizes appliance branch circuits from the nameplate; 422.11 sets overcurrent limits; 422.16 covers cord-and-plug connections such as the individual 20 A circuit permitted for a disposal. 250.140 addresses when frames of electric ranges and dryers may be grounded through the neutral, and those conditions apply only to existing installations.
Worked example
An outdoor condensing unit nameplate reads MCA 22.4 A and maximum fuse 35 A. Conductors must carry at least 22.4 A, so 10 AWG Cu THWN (35 A at 75°C) is adequate. The branch-circuit device may be a 35 A fuse or breaker; 240.4(G) and 440.22 permit that device to exceed the conductor's 30 A 60°C rating because the compressor's overload protection sits at the equipment. The disconnect is mounted within sight of the unit.
Traps
Using nameplate current where Table 430.248 applies, or table values for an A/C; sizing the A/C breaker by the conductor; omitting the disconnect; applying 60°C ampacity where 75°C applies; putting a 4.5 kW water heater on a 30 A circuit without checking 422.10 and 210.19.