In HID lamps, light is produced by passing an electric current through a gas or vapor at a high pressure. The current produces a high intensity arc or discharge of light that is very efficient and has a longer life than the typical incandescent lamp. The exception is the Low Pressure Sodium lamp which passes an electric current through a gas or vapor at a low pressure. 

Mercury Vapor (MV), Metal Halide (MH), High Pressure Sodium (HPS) and Low Pressure Sodium (LPS) comprise the family of HID lamps.

Here are some other common characteristics of HID lamps:

• All HID lamps have a warm-up period that lasts from 3-10 minutes (depending on the type and wattage) before it produces full light output.
• It is important that an HID lamp have the correct ballast to operate properly (compare ANSI code on the ballast and lamp package)
• HID lamps have a restrike time which ranges from 1-15 minutes depending on type and wattage.

MV lamps feature low initial cost, but have higher operating costs then HPS or MH due to its lower efficiency (lumens per watt). The clear mercury bulb has a bluish green appearance and the Deluxe White has a higher color rendering. Mercury lamps get dimmer over time and rarely burn out, so it is wise to replace them and restore light level. Mercury lamps are used for landscape lighting, dusk to dawn fixtures, roadway, parking lots, floodlight, and security.

A MV lamp consists of a clear quartz arc tube enclosed in a gas-filled hard glass outer bulb which my be clear or phosphor-coated. The addition of a phosphor coating to the outer bulb, dramatically improves the appearance and color rendering of the light produced. The arc tube contains a small amount of mercury, together with argon gas, which is used to facilitate starting of the lamps.

Note: With the advent of the National Energy Policy Act of 2005, as of January 1, 2008 the ballasts required to run Mercury Vapor lamps, will no longer be able to be manufactured. There are far more economical and efficient light sources to replace this oldest of the HID family.

Common Mercury Vapor wattages and the related ANSI code equivalent:

• 50 Watts  (H46)
• 75 Watts  (H43)
• 100 Watts  (H38)
• 175 Watts  (H39)
• 250 Watts  (H37)
• 400 Watts  (H33)
• 1000 Watts  (H36)

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Metal Halide lamps are the fastest growing segment of the HID family due to their crisp white light, high efficiency, and good color rendering. Because of their good color rendering, MH lamps are used in interior as well as exterior applications. MH lamps are used extensively in shopping malls, retail, commercial buildings, roadway lighting, parking lots, airports, sports lighting, and building flood lighting.

A MH lamp consists of a clear quartz arc tube enclosed in a gas-filled hard glass outer bulb which may be clear or phosphor-coated. The arc tube contains mercury, together with other metals in iodide form, which serve to improve the color appearance, color rendering properties and lumen efficacy of the lamp in comparison to standard mercury lamps.

Common Metal Halide wattages and the related ANSI code equivalent:

• 150 Watts  (M107)
• 175 Watts  (M57)
• 250 Watts  (M58)
• 400 Watts  (M59)
• 1000 Watts  (M47)

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Considered the next generation of Metal Halide, as it improves upon the long standing Mercury Vapor and Metal Halide technology in new arc tube design, lamp life, efficacy and lumen maintenance. The primary difference in this lamp development was the addition of an ignitor with the proper ballast for the PS lamp.

This development saw improvements in the following criteria versus standard Metal Halide:

• Greater Efficacy (Lumens per watt) – 25-50% increases depending on lamp/ballast system
• Lumen Maintenance increased by 31%
• Longer lamp life increased up to 50%
• Color rendering increased up to 30% improvement
• Color shift was reduced by up to two-thirds
• Full light output in less then half the time of standard MH
• Quicker restrike time of 3-4 minutes compared to 15-20 minutes
• Colder starting temperature of –40 degrees F versus –20 degrees F

Common Pulse Start Metal Halide wattages and the related ANSI code equivalent:   

• 50 Watts  (M110)
• 70 Watts  (M98)
• 100 Watts  (M90)
• 150 Watts  (M102)
• 320 Watts  (M132)
• 350 Watts  (M131)
• 400 Watts  (M135)
• 750 Watts  (M149)
• 1000 Watts  (M141)

Marketing Names: Mastercolor

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HPS lamps are the most efficient HID lamps available. If color rendering is not critical and energy saving is important, HPS is an excellent choice. HPS lamps have a golden white color (2100K) and a Color rendering of only 21. Because of the color they have an added benefit in not attracting insects like other light sources. HPS fixtures cycle on and off when it is time to replace the bulb. Applications include security lighting, dusk-to-dawn fixtures, parking lots, flood lighting, roadway and Industrial/Commercial installations.

A HPS lamp consists of a translucent ceramic arc tube enclosed in a clear or coated evacuated hard glass outer bulb. The material used for construction of the arc tube in an HPS lamp differs from that used in MV and MH lamps because of the high chemical activity of sodium.

Common High Pressure Sodium wattages and the related ANSI code equivalent:

• 35 Watts  (S76)
• 50 Watts  (S68)
• 70 Watts  (S62)
• 100 Watts  (S54)
• 150 Watts  (S55)
• 200 Watts  (S66)
• 250 Watts  (S50)
• 400 Watts  (S51)
• 600 Watts  (S106)
• 1000 Watts  (S52)

Marketing Names: Ceramalux

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An HPS with two arc tubes mounted in parallel, enclosed in a hard glass outer bulb. The second arc tube provides instant relighting  capability in the event of a momentary power interruption. At any given time, only one arc tube is lighted. When power is restored after a momentary interruption, the second arc tube lights immediately and produces 3% to 5% of the lamps full light output, which is normally achieved within two minutes. The instant relighting and rapid recovery of a Dual Arc lamp eliminates the period of total darkness associated with the reignition of most HID lamps. This provides an extra measure of safety in applications where machinery or moving vehicles pose a hazard to workers.

In instant restrike applications, rated lamp life equals 24,000+ hours. When instant restrike is not important, rated lamp life is 40,000 hours.

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HPS lamps with an improved color rendering index of 65 and higher color temperature of 2200K; a significant improvement over standard HPS lamps typically rated 21 CRI and 2100K. These lamps provide improved color rendering in the red, blue and violet regions of the spectrum compared to conventional HPS.

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HPS lamps designed specifically to operate on all Mercury Vapor and Metal Halide single lamp ballasts for parallel type circuits. They are a direct retrofit product for MV and MH lamps as noted below. These lamps differ from other HPS sources in that they have a built-in ignitor to provide the high voltage pulse to start the lamp.

MH/MV Lamp		Retro Lux HPS Lamp
175-Watt		150-Watt
250-Watt		215-Watt
400-Watt		360-Watt

In terms of light output, RETRO LUX lamps represent a higher lumen package with lower power consumption as compared to the MV/MH lamps they replace.

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HPS lamps that have increased color rendering of 83-85 and color temperature of 2700K which is the color appearance of incandescent lamps. White SON lamps offer three times the efficacy of incandescent lamps and also feature a special base and socket to provide precise location of the source in optical systems. They are available in only two wattages 50 and 100 and 3 different base configurations.

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LPS lamps consist of a U-shaped arc tube constructed of sodium-resistant lime borate glass inside an evacuated clear outer envelope. The inside arc tube is a mixture of neon and argon gases, which are used to start the lamp, together with pure sodium metal. This mixture produces a golden yellow light that is monochromatic and hence does not have a color rendering index rating  to determine colors. LPS lamps are for outdoor and indoor use in areas where color is not a primary consideration. LPS lamps provide the lowest operating cost of any commercial source. They provide long lamp life with low operating temperatures and no ultraviolet output. Applications include roadway, bridge and tunnel lighting, security and area floodlighting.

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