Equipment for General Use
What to master
Articles 400 through 480 cover the equipment you install every day: flexible cords (400), switches (404), receptacles (406), switchboards and panelboards (408), luminaires (410), appliances (422), motors (430), A/C and refrigeration (440), transformers (450), and batteries (480). For motors, use 430.6 to select table values rather than nameplate current for conductor and short-circuit protection sizing; 430.22 requires branch-circuit conductors at 125% of full-load current; 430.52 sets the standard breaker at 250% of FLC for inverse-time devices; and 430.32 overload protection is set from the nameplate. For hermetic refrigerant motor-compressors, 440.22 allows 175% of rated-load current (225% if the unit will not start).
Traps
Sizing motor branch conductors from the nameplate amps; confusing overload protection with branch-circuit short-circuit protection; forgetting the 125% continuous-load factor on appliances and EV charging; and applying the 175% A/C rule to the conductor instead of the overcurrent device.
Worked example
A 10 hp, 460 V, three-phase motor shows 14 A in Table 430.250. Conductors: 14 × 1.25 = 17.5 A, so 12 AWG copper at 75 °C works. Inverse-time breaker: 14 × 2.50 = 35 A, which is a standard size, so a 35 A breaker is acceptable even though it exceeds the conductor ampacity - that is exactly what 430.52 permits.