Building services electrical loads, demand and energy management
Domain 2: Building services electrical loads, demand and energy management
This domain tests load assessment and the commercial consequences of demand. You must distinguish connected load, maximum demand, diversity and energy use, and show how metering and control reduce both peak kVA and consumption.
Core rules
- Connected load is the sum of nameplate ratings; maximum demand is the coincident peak after diversity and demand factors.
- Diversity factor = maximum demand / connected load; demand factor = maximum demand / connected load for a specific group. State which definition you use.
- Apply diversity by realistic groups and operating patterns, not a blanket factor to the whole building.
- Convert kW to kVA using operating power factor; add harmonic distortion where applicable.
- Use sub-metering, tariff analysis, load shifting, power-factor correction and scheduling to manage peak demand.
- Check that energy targets use annual kWh, not peak kW; report both.
Worked example
Forty flats have 8 kW connected each: 40 × 8 = 320 kW. Apply a 0.40 diversity factor: 128 kW. Common services add 25 kW, giving 153 kW. At 0.90 power factor, demand is 153/0.90 = 170 kVA. A 200 kVA supply has 15% headroom; check future loads and motor starting before accepting it. The 8 kW nameplate is not the design peak.
Traps
- Adding nameplate ratings and calling the result maximum demand.
- Applying diversity twice.
- Ignoring power factor when sizing kVA.
- Using peak demand as the energy baseline.