Unlike incandescent lamps, which generate lighting by heating a filament, discharge lamps ionize a vapour to produce light. Metal halide high-intensity discharge (HID) lamps that provide an intense cone of light are widely used because they are about three times as efficient as incandescent lamps.
Traditional probe-start metal halide lamps do not use an igniter and require three electrical contacts to ignite the gas and remain lit. Recently developed pulse-start metal halide lamps use only two contacts and use an igniter located inside the ballast pod.
Pulse-start lamps offer several benefits:
- higher light output per unit of electric power
- higher light output as lamps age
- longer lamp life
- more stable colour rendering as lamps age
- quicker startup – pulse-start lamps can reach full brightness in two to four minutes instead the five to ten minutes needed by probe-start lamps
A 250-W pulse-start bulb costs 20 percent more than a probe-start bulb (2004 comparison).
How Does Pulse-Start Metal Halide Lighting Save Money?
Compared with probe-start lighting, pulse-start metal halide lighting saves you money in four ways:
- Brighter light – Pulse-start lamps produce more mean lumens per watt of electricity.
- Lamp light output is maintained – Because the light output of lamps declines as they age, the design of the lighting system must be based on the “maintained” or end-of-life light output. The bigger the decline (lumen depreciation), the more excess-initial-lighting must be provided. Pulse-start metal halide lamps are about 6 percent better than probe-start lamps in maintaining light output over their service life, so fewer lamps are required.
- Lamp life is long – Some pulse-start metal halide lamps last longer than probe-start lamps. For example, 250-W pulse-start lamp can have a 15 000-hour life, compared with a 10 000-hour life for a probe-start lamp of the same wattage.
- Lamp replacement is less frequent – Replacing burned out lamps is a significant labour cost. Pulse-start lamps last longer, so they don't need replacing as often, thus lowering labour costs.
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