In electrical design, a is used to estimate the largest current likely to be carried by an installation. Rather than simply summing all connected loads, these tables apply diversity factors (or "demand factors") to account for the fact that not all devices operate at full capacity simultaneously.
| Row | Circuit Description | Connected Load (W / A) | Diversity / Assessment Factor | Assessed Demand (W / A) | | :--- | :--- | :--- | :--- | :--- | | 1 | Lighting | | | | | 2 | Socket Outlets | | | | | 3 | Fixed Appliances | | | | | 4 | HVAC | | | | | 5 | Motors | | | | | 6 | | | | SUM | | 7 | Voltage (V) | | | _____ V | | 8 | Final Max Demand (Amps) | | | Row 6 ÷ Row 7 | | 9 | Safety Factor / Future Load | | | +25% (typical) | | 10 | Final Required Rating | | | Row 8 + Row 9 | max demand table
Max Demand Calculation: The BS 7671 Method Explained. Max demand is the starting point for every installation design. Get it wrong... www.elec-mate.com Maximum Demand Tables - ELEK Software After diversity maximum demand. Under normal operating conditions, not all the individual electrical equipment of an installation ... ELEK Software Show all Load Group Typical Calculation/Diversity Factor Reason for Factor Lighting First 20 points at 3A, then 2A per 20 thereafter Lights are rarely all on at once; modern LEDs use very little power. Socket Outlets 10A for the first 20 points, then 5A per 20 thereafter Most outlets are unused or power low-draw devices like phone chargers. Cooking Ranges 50% of the total connected load Ovens and hobs cycle on and off via thermostats once they reach temperature. Fixed Heating 75% to 100% of connected load Heating often runs for long periods during peak cold times. Water Heaters Often 100% (full load) for storage heaters These are "fixed loads" that draw full power until the water is hot. Methods of Determination While calculation via tables is common during design, regulations often allow four distinct methods to find maximum demand: Calculation In electrical design, a is used to estimate