Maximum demand
The realistic peak an installation will draw, worked out from the connected load with applied. It is the figure the supply arrangements are sized against — tails, main switch, distribution equipment — and the first number a designer needs before any circuit-level decisions make sense.
Where Maximum demand fits in the learning path
The Installation section covers these units:
- Wiring Systems & Enclosures
- Cable Selection & Circuit Design
- Earthing, Bonding & Consumer Units
Curriculum mapping: C&G 2365 Units 203/204/305.
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The design allowance for the fact that connected loads never all run flat-out at once. A kitchen's sockets, oven and kettle sum to a huge figure on paper, but the realistic simultaneous demand is far lower. Applying diversity turns the connected load into a sensible maximum demand, keeping supplies, switchgear and cables from being absurdly oversized.
Diversity
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Diversity
The design allowance for the fact that connected loads never all run flat-out at once. A kitchen's sockets, oven and kettle sum to a huge figure on paper, but the realistic simultaneous demand is far lower. Applying diversity turns the connected load into a sensible maximum demand, keeping supplies, switchgear and cables from being absurdly oversized.
Read the Diversity entryCurrent-carrying capacity — Iz
The current a cable can carry continuously in its installed conditions without its insulation exceeding the temperature it was designed for. Tabulated values assume reference conditions; the real, installed capacity is what remains after correction factors for temperature, grouping and insulation have taken their share.
Read the Current-carrying capacity entryElectrical power
Electrical power is the rate at which electrical energy is transferred, measured in watts (W) or kilowatts (kW). A 1 kW load transfers energy twice as fast as a 500 W load. In a DC circuit, power equals voltage multiplied by current. For AC loads, real power also depends on power factor, so multiplying voltage and current alone does not always give watts.
Read the Electrical power entryElectrical energy
Electrical energy is the amount transferred over time, measured in joules (J) or, on electricity bills, kilowatt-hours (kWh). A load drawing a steady 1 kW for two hours uses 2 kWh. Power describes the rate of transfer; energy describes the accumulated amount. A battery capacity quoted in kWh is therefore different from its power rating in kW.
Read the Electrical energy entryA definition is a start. Using it in a real question is where it sticks.