Metal Halide Fixtures
A metal halide fixture is a commercial or industrial light that has five main parts:
- The fixture type, such as high bay, shoebox, flood light, wall pack, and canopy light.
- The bulb, that screws into the socket of the fixture
- The ballast converts AC electricity to power the bulb.
- The reflector focuses the light energy of the bulb and directs it to where the fixture is aimed.
- The fixture mount is the means by which the fixture attaches or hangs.
Metal Halide belongs to a family of bulbs called High Intensity Discharge – or – HID. Other bulbs within the same HID family include Mercury Vapor, High Pressure Sodium, and Xenon. What is common across all HID bulbs is they all use a ballast to convert AC to power the bulb.
Metal Halide bulbs are omnidirectional. We are all familiar with standard home incandescent bulbs. They are also omnidirectional. Light is distributed in all directions. To focus Metal Halide bulbs, reflectors are added to the insides of the fixtures to gather and aim light.
As their name implies, reflectors are highly reflective and have mirror-like finishes. Metal Halide bulbs are initially very bright when new but fade rather quickly and require long strike (start-up) times to produce their maximum producible light levels. If the fixture is turned off, the bulb must first cool down before the long strike time starts again.
Metal Halide and High Pressure sodium are the most common HID bulbs in the family. It is easy to distinguish these bulbs apart. High Pressure Sodium bulbs create an orange light. Metal halide light is much whiter.
Applications for Metal Halide Fixtures
Metal Halide fixtures are for high-lumen applications. Indoor applications include gymnasiums, warehouses, high/low bay fixtures, shop lighting, factory lights, and recessed lights.
Outdoor applications include parking lots, stadiums and sport fields, street lights and area lights. Metal Halide bulbs come in a variety of wattages for different applications.
- Large fixtures use high-wattage bulbs. These include 1000-Watt, 1500-Watt, and 2000-Watt Metal Halide bulbs.
- Smaller bulbs are used in parking lot lights and high / low bay fixtures. They use 250-Watt and 400-Watt bulbs.
- Smaller wall-mounted fixtures with less lighting requirements use 100-Watt and 150-Watt bulbs.
Converting Metal Halide Fixtures over to LED
So why are users of Metal Halide Fixtures converting to LED? When LED was in its infancy, it barely produced enough light to replace Metal Halide bulbs. LED was inefficient and expensive by comparison.
LEDs have matured, and mass production has brought down the cost of the product. These days, LEDs produce sufficient lumens to compete with their Metal Halide counterparts. LED offers many improvements over Metal Halide fixtures.
- LED is energy efficient, using 25% of the energy that a Metal Halide bulb uses to produce the same number of lumens.
- LED’s lifespans are much longer than Metal Halide. A 20,000-hour Metal Halide bulb reaches half-life at only 10,000 hours and has already lost 1/2half of its initial lumens. Some LEDs currently have an L70 (70% of initial lumens) of 200,000 hours.
- The quality of LED light is better than Metal Halide lighting. Some metal halide bulbs have a high Color Rendering Index (CRI), but most LED products have a high CRI. High Pressure Sodium has a terrible CRI.
Life of a Metal Halide Bulb
Metal Halide bulbs have different lifespans, between 12,000 hours and 20,000 hours. During this lifespan, their light degrades with the age and usage of the bulb. It is not uncommon that after half of the life of the bulb, it will lose more than half of its effective lumens.
A Metal Halide bulb that’s utilized 80% of its lifespan is only generating 20% of its initial lumens. Because of this, it is not unusual to replace these bulbs well before the end of their life.
A phenomenon associated with Metal Halide lamp aging is discoloration of the light. In Metal Halide bulbs, this means the shift is to a blue or violet hue.