While dimming options are limited, time-switches and multi-level controls can contribute to savings.
There are significant limitations to using control systems with HID lamps, given they do not start instantly. HID lamps are also very difficult to reliably dim, in terms of maintaining constant colour and colour temperature.
In high activity areas make sure:
- The lighting level is constant when the building is occupied
- When it's unoccupied, use a time-switch control or computer system to ensure all non-essential lighting is off.
And in medium activity areas:
- Reduce light levels in unoccupied areas, rather than complete darkness (this will help maintain acceptable contrast ratios)
- Switch fixtures to a lower light level on occupancy or operator-activated systems.
In terms of specific equipment:
- New ballast technology for fluorescent lamps significantly improves the life of lamps that are switched frequently
- Two-level controls work well for metal halide systems - when the high level is switched on, the lamps ramp up quickly and return to optimum colour and light output
- Photo-sensor controlled fluorescent dimming systems or high/low metal halide systems are effective and comfortable ways to