High Pressure Sodium
High pressure sodium (HPS) lamps are the most efficient member of the HID family where some degree of color rendition is important. Standard HPS lamps produce a golden white light when they reach full brightness. Many recognize them as the familiar golden light from street lights, one of their principal applications. There are versions of the HPS lamp designed for indoor use with improved color over standard HPS lamps, but the improvements come at the cost of shorter lamp life and lower efficacy. These lamps are now a readily accepted light source in industrial plants and also are being used in many commercial and institutional applications.
- Most efficient member of the HID light family, 7 times as efficient as incandescent and over 2 times as efficient as mercury vapor.
- Warm-up period is 3-4 minutes, which is somewhat less than that of a mercury vapor or metal halide lamp.
- Long lamp life -- 24,000 hours.
- Excellent lumen maintenance.
- Wide range of lamp types with wattages ranging from 35 to 1000 watts.
- Most HPS lamps can operate in any position.
- The light produced is a golden white color, which may not be appropriate for certain applications.
- Requires a ballast.
- Once started can take from five to ten minutes to reach full light output. They also require at least a one minute cool-down to re-strike.
- End of life is characterized by on-off-on cycling, and continued operation can damage the lamp ballast if not replaced quickly.
High Pressure Sodium lamps are recommended in a wide variety of applications including industrial, commercial, street, and security lighting. These lamps are extremely efficient when compared to incandescent and fluorescent and that makes them particularly suited for energy efficiency applications.
The wattage at which an HPS lamp operates will vary from its nominal rating depending on the ballast, the supply voltage, the lamp voltage and the fixture design. When planning an HPS installation, it's important to take these variables into account as the lumen output of the lamp varies with the wattage.
Regardless of operating position, High Pressure Sodium lamps produce the same lumen output. Position also has no effect on other lamp operating characteristics.
With appropriate ballasts, High Pressure Sodium lamps can start at ambient temperatures of -40F and even lower. HPS lamps are designed so that, once the arc has been established, they'll warm up to full wattage and light output at any temperature.
These lamps also provide high intensity light. This feature is useful for high mounting applications such as street lighting or industrial lighting where fixtures are mounted greater than 15 feet from the workplane.
Technology Types (Resource)
Recent technological advances have resulted in the introduction of a new color-corrected High Pressure Sodium lamp, which produces light with a dramatically improved color appearance and color rendering properties. In fact, the quality of light from these lamps closely approaches that of incandescent lamps.
Maintenance of lighting systems that are mounted on high ceilings or tall poles outdoors can be very cumbersome and costly. The 24,000 hour lamp life of High Pressure Sodium lamps reduces the frequency of lamp replacement and thus saves maintenance costs.
Compared with fluorescent lighting systems, High Pressure Sodium systems are rather expensive to purchase and install. However, the increased energy efficiency of these systems far outweighs the additional up front cost resulting in achieving payback in just a few years.
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