Outboard Lighting Circuits and Luminaire Types
What the candidate must know
Outboard lighting includes navigation lights, deck and working lights, searchlights, floodlights, and emergency or escape lighting. Candidates should recognise luminaire families (incandescent, halogen, fluorescent, LED, HID) and their electrical behaviour: inrush current, power factor, dimming compatibility, and heat output. Know the difference between a circuit (the conductors and protection) and a luminaire (the fitting). Understand switching arrangements: single-pole, two-way, and relay or contactor control where a small switch operates a large load. Navigation lights carry strict requirements for visibility sectors, colour, and independence from other circuits.
Traps that appear in questions
- Ignoring LED inrush: many small LED drivers on one circuit can trip a breaker rated well above the steady-state current.
- Assuming a dimmer rated for the wattage suits every lamp; leading-edge and trailing-edge dimmers are not interchangeable with all drivers.
- Forgetting that a switch is not a protective device; it must be rated for the load and for the environment.
- Mixing up series and parallel switching in two-way circuits, producing a lamp that cannot be turned off.
- Overlooking heat clearance around halogen and HID fittings.
Worked example / rule of thumb
Twelve 20 W LED floodlights draw 240 W total, about 1 A at 230 V, but each driver may pull 10-20 A for a few milliseconds. A 6 A type B breaker may trip on start-up. Rule of thumb: sum the inrush of the largest group that can start together and choose a C-curve or higher-rated breaker, or stagger switching, then confirm the steady-state current still protects the cable.