Lighting, Fans and Small Domestic Electrical Fittings
Lighting, Fans and Small Domestic Electrical Fittings
Lighting, Fans and Small Domestic Electrical Fittings tests lamp types, lighting quantities, fan selection and small fittings such as doorbells, buzzers and indicators.
Core rules and concepts
- Lamp terms: luminous flux (lumens), illuminance (lux = lumens/m²), efficacy (lm/W), colour temperature (CCT, K) and colour rendering index (CRI).
- Incandescent lamps are resistive and simple but inefficient, about 10–15 lm/W. Fluorescent tubes need a choke or ballast and starter in magnetic circuits, or an electronic ballast. CFLs are compact fluorescents. LEDs use a driver and are often 80–120 lm/W.
- Ceiling fans use a capacitor motor; table fans may use a shaded-pole motor; exhaust fans use a capacitor or shaded-pole motor. Air delivery is stated in m³/min.
- Small fittings include doorbell push, buzzer, chime, indicator lamp, night lamp and extension board. Bell circuits often use a step-down transformer for safety.
- Choose CCT by use: about 2700–3000 K warm for homes, 4000 K neutral, 6500 K daylight for task areas.
Worked example
A 4 m × 3 m room needs 150 lux. Area = 12 m², so required flux = 150 × 12 = 1800 lm. An 18 W LED with 100 lm/W gives 1800 lm, so one fixture is sufficient in ideal conditions; allow for loss factor and use two 9 W lamps if light distribution is uneven. Reasoning: work in lumens, then convert to lamp wattage using efficacy.
Traps that cost marks
- Comparing lamps by wattage instead of lumens.
- Using a low-CRI lamp for colour-critical work.
- Fitting an LED to a dimmer not rated for it.
- Replacing a fan capacitor with the wrong value.