Maximum Demand - As3000

This post is intended for electrical engineers, trade professionals, and advanced students. Most electricians size a circuit breaker for the cable. Fewer truly master the art of Maximum Demand (MD) . In AS/NZS 3000, MD is not a worst-case guess; it is a calculated engineering decision that dictates the economics and safety of the entire installation.

| Load | AS3000 Rule | Calculation | Result (A) | |------|-------------|-------------|-------------| | Lighting | C5: First 10A @100%, rest @50% | 10 + (10×0.5) | 15 | | Sockets (2 circuits) | C6: 10A + 50% of remaining (16 outlets = 16A assumed total) | 10 + (6×0.5) | 13 | | Cooktop | C8: (0.4 × 27.8) + 10 | 11.1 + 10 | 21.1 | | Oven | C8: (0.4 × 20) + 10 | 8 + 10 | 18 | | Hot water | C7: No diversity (storage) | 15.6 | 15.6 | | AC | C9: Largest unit 100% | 16 | 16 | maximum demand as3000

Example: EV charger + AC + cooktop + dryer → a controller can stagger operation so the measured 30-minute MD never exceeds 63A, even though the sum of breakers is 150A. This post is intended for electrical engineers, trade