National Electrical Code 2011 (Handbook)Ģ. NEC 210-22(C) = Over-Current Protection Device shall be calculated as 100% of non-continuous load + 125% of the continuous load.ġ. NEC 430- 52 = The size of the branch circuit protection for motor loads shall not be greater than 250% of motor full load current for CB and 300% for non-time delay fuses on full voltage starting.Ĥ. NEC 430 -22 = The size of the wire supplying motorized load shall not be less than 125% of the rated full load current of the motor.ģ. NEC 210-9a - Maximum to be served by branch circuit must not be less than 80% of the ampacity of the condutorĢ. Note: 10 kAIC is just an assumed value, we need short circuit calculation to determine the right specs of the OCPD to be used in this exampleġ. Use 50 sqmm TW cable as main feeder or service entrance wire Read: How to Select Proper Type of Miniature Circuit Breakers MCBsĬontinuous loads = 9,963 VA or 45.29 A 220V (lighting loads and ACU) Wire = 22.71 / 80% = 28.41 Amperes, Use 8.0 sqmm TW wire or #8 AWGĬircuit Breaker = Use 40 A Circuit Breaker VA = 5000 W / 1.0 pf (heating load is a resistive load w/ 100% pf) Note: since the breaker is 30 Ampere, we need to increase the cable size to 5.5 sqmm (rated 30 amps by NEC ) to maintain the coordination of cable and the circuit breaker. Wire = 10.60 x 125% = 13.24 Amperes, Use 3.5 sqmm TW wire or #12 AWG Ĭircuit Breaker = 5.45 x 250% = 26.5 Amperes, Use 30 A Circuit Breaker All things remaining equal in the 2020 NEC, that 1,260A. If the service supplying the building is 480Y/277V, 3-phase, this adds a total of about 1,260A of capacity to the required electrical supply for the building. Read: What are the Different Electric Current Symbols According to IEC Standard In the 2017 NEC, the lighting load would be calculated at 300,000 ft2 × 3.5VA/ft2 for a total load of 1,050,000VA on the service.
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