42 (A), the general rule of thumb is that the circuit breaker size should be rated at 125% of the ampacity of the cable and wire for continuous loads (lasting for 3 or more hours continuously, such as a water heater) that. According to NEC 210. ” The core principle is that the breaker, or Overcurrent Protective Device (OCPD), must protect the conductor from excessive current. The process. Common NEC standard breaker sizes are 10, 15, 20, 25, 30, 35, 40, 45, 50, and 60A. A 16A continuous load screens to a 20A review point, and 12 AWG copper still stays capped at 20A on a general branch circuit. Full-load current or calculated branch-circuit load in amperes For project context only;. Proper breaker sizing protects your electrical circuits from dangerous overcurrents while ensuring your electrical loads receive adequate power to function correctly. Reminder: This is a sizing aid. Always confirm with local codes, cable ampacity tables, and equipment manufacturer guidance.
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