What is a HID Fixture?
A HID fixture is a lighting device that consists of a fixture, a HID bulb, a ballast, reflectors and a mount. HID is an acronym for High Intensity Discharge, and applies to a family of high lumen bulbs. Mercury Vapor, Metal Halide.
Ceramics, Sodium Vapor and Xenon based bulbs are all considered to be HID bulbs. All HID bulbs need a ballast that converts AC line power into energy used to power the HID bulb.
The bulbs are omni-directional in nature, and they create light in all directions. To focus HID lights, adding reflectors and lenses to the fixture to direct the light where its needed. HID bulbs are very bright, but required a long strike time to produce greatest levels of light. If you switch off a fixture, the amount of time it takes to re-cycle the fixture is considerable. The two most common HID bulbs are metal halide bulbs and sodium vapor bulbs. Both bulbs are distinctive. Sodium bulbs are orange in color, metal halide are whiter.
Applications for HID Fixtures
HID fixtures are for high lumen applications. Indoor applications like gymnasiums, warehouses, bay fixtures, recessed lights and factory lights. Outdoor applications include parking lots, stadiums, street lights and area lights. HID bulbs come in a variety of wattages for different applications.
- Large fixtures with high wattage bulbs use 1000W, 1500W and 2000W HID bulbs.
- Smaller bulbs used in bay fixtures and parking lit lights use 250W and 400W bulbs.
- Smaller wall mounted fixtures with less lighting requirements, 100W and 150W bulbs.
High-Pressure Sodium (HPS) Lamp
The high-pressure sodium (HPS) lamp is widely used for outdoor and industrial applications. Its higher efficacy makes it a better choice than metal halide for these applications, especially when good color rendering is not a priority.
HPS lamps differ from mercury and metal-halide lamps in that they do not contain starting electrodes; the ballast circuit includes a high-voltage electronic starter. The arc tube is made of a ceramic material which can withstand temperatures up to 2,372°F. It is filled with xenon to help start the arc, as well as a sodium-mercury gas mixture.
The efficacy of the HPS lamp is very high (as much as 140 lumens per watt.) For example, a 400-watt high pressure sodium lamp produces 50,000 initial lumens. The same wattage metal halide lamp produces 40,000 initial lumens, and the 400-watt mercury vapor lamp produces only 21,000 initially.
Sodium, the major element used, produces the “golden” color that is characteristic of HPS lamps. Although HPS lamps are not generally recommended for applications where color rendering is critical, HPS color rendering properties are being improved. Some HPS lamps are now available in “deluxe” and “white” colors that provide higher color temperature and improved color rendition. The efficacy of low-wattage “white” HPS lamps is lower than that of metal halide lamps (lumens per watt of low-wattage metal halide is 75-85, while white HPS is 50-60 LPW).
Life of a HID bulb
HID bulbs have different lifespans, between 12,00 hours to 20,000 hours. During this lifespan, light out degrades with the age of the bulb. It is not uncommon that after 1/2 life of the bulb, the HID bulb has lost over 50% of its effective lumens. A bulb that has used 80% of its life is only producing 20% of its initial lumens. Thus, it is not uncommon to replace bulbs well before complete End of Life.
A phenomenon associated with HID lamp wear and aging is discoloration of the light. In whiter based HID bulbs, this means the shift is to a blue or violet shade.
Converting HID Fixtures over to LED
So why are users of HID Fixtures converting to LED? When LED was in its infancy 11 years ago, LED barely produced enough light to replace HID bulbs. LED was inefficient, and expensive. Today, LEDs have matured, and mass production has brought down the cost of the product. LED options now produce enough lumens to compete against their HID counterparts. LED offer several advantages over the HID fixtures.
- LED is energy efficient, using 25% of the energy that a HID bulb uses to produce the same amount of lumens.
- LED’s life spans are longer than HID bulbs. A 20,000 hour HID bulb has a L50 of 10,000 hours. Some LED fixtures currently have a L70 exceeding 100,000 hours.
- The purity of LED light is better than HID lighting. Some metal halide bulbs have a high Color Rendering Index (CRI), but most LED products have a high CRI. Sodium Vapor bulbs have a horrible CRI.
Replacing HID fixtures or Retrofitting HID Fixtures
There are 2 options that are available converting HID to LED: replace or retrofit. Replacement means removing the fixture and a installing a new LED fixture. Retrofit is removing HID components from the fixture and replacing with LED components. Both options have pros and cons. Which one to use depends on circumstances unique to the fixture and installation.
LED Kits for HID Fixtures are a series of 11 kits designed to replace all HID bulbs ranging from 150W to 1500W. HID Retrofit Kits are a certified retrofit solution. As part of the installation process, remove the reflector as it is not required. Expect energy savings around 75% over their HID counterparts. Life span should exceed 10+ years under normal operating conditions.
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