Overcurrent Protection

1Code & System

Code basis NEC 2026 (NFPA 70) CEC 2024 (CSA C22.1) System phase

Single-phase Three-phase

System voltage / configuration (for device voltage rating) 120 V 208Y/120 V (slash) 240 V 480Y/277 V (slash) 480 V (straight / delta) 600Y/347 V (slash · CEC) 600 V (straight · CEC) > 1000 V (medium voltage) Slash systems (e.g. 480Y/277) require a slash-rated OCPD unless a straight-rated device is used.

2Load Nature & Rating

Load type - sets the governing sizing rule General load (continuous / non-continuous) Motor - branch-circuit S/C & G-F protection Transformer Listed equipment (nameplate MCA / MOCP) Capacitor

3Conductor (Protection Check)

Corrected ampacity from Conductor Sizing tool (A) - optional Enter the final derated ampacity (after ambient + CCC) from the Conductor Sizing (AC) tool. If blank, the 75/90 °C table value below is used per the termination rating.

4Device & System Protection

Device type Recommend (compare fuse & breaker) Fuse Circuit breaker Breaker trip type Thermal-magnetic (inverse-time) Electronic trip (LSIG) Instantaneous-only (MCP - motors) Available fault current at device (kA) - optional Coordination requirement None Coordinate with upstream device Selective coordination required (emergency / legally-required / COPS) Upstream device rating (A)

5Suppliers

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