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OpenSpecEngineering

Open data for a field built on precision

Circuit Breaker/Fuse Sizing

Minimum standard overcurrent device rating for a load, per NFPA 70 (National Electrical Code) Article 210.19/210.20 — continuous loads (on for 3 hours or more) require the device to be rated at least 125% of the load current; non-continuous loads only need 100%. The result is rounded up to the next standard rating from NEC Table 240.6(A).

15A 20A 25A 30A required min (17.4A) selected breaker
Standard sizes are discrete — round the required minimum up to the next standard rating.

Solution

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