Conversion, or retrofit, bulbs increase flexibility. One type of conversion bulb allows you to utilize a metal halide (or mercury vapor) system with a bulb that emits light similar to an HP sodium bulb. The bulb looks like a blend between a metal halide and an HP sodium. While the outer bulb looks like a metal halide, the inner arc tube is similar to that of an HP sodium. A small igniter is located at the base of the bulb. Other conversion bulbs retrofit HP sodium systems to convert them into virtual metal halide systems.
Conversion bulbs are manufactured in 150, 215, 360, 400, 880, 940, and 1000-watt sizes. You do not need an adaptor or any additional equipment. Simply screw the bulb into a compatible ballast of comparable wattage.
HPS + Reaction
Conversion bulbs operate at a lower wattage and are not as bright as HP sodium bulbs. Although conversion bulbs have less blue, they are up to 25 percent brighter than metal halide systems and their lumens-per-watt conversion is better than that of super metal halides. The 940-watt conversion bulb has a lumens-per-watt rating of 138. Similar to the HP sodium lamp, the conversion bulb has a life expectancy of up to 24,000 hours. Unlike most high-pressure sodium lamps which flicker on and off near the end of their lives, conversion bulbs go off and remain off at the end of their lives.
Although conversion bulbs are not inexpensive, they are certainly less expensive than an entire HP sodium system. For gardeners who own a metal halide system, or who deem metal halide the most appropriate investment for their lighting needs, conversion bulbs offer a welcome alternative for bright light. In the United States, CEW Lighting distributes Iwasaki lights. Look for their Sunlux Super Ace and Sunlux Ultra Ace lamps.
Venture, Iwasaki, and Sunlight Supply manufacture bulbs for conversion in the opposite direction, from high-pressure sodium to metal halide. Venture's White-Lux and Iwasaki's White Ace are metal halide lamps which will operate in an HP sodium system. The 250, 400, 1000-watt conversion bulbs can be used in compatible HPS systems with no alterations or additional equipment. If you own a high-pressure sodium system but need the added blue light which metal halide bulbs produce, these conversion bulbs will suit your needs.
Many gardeners have great success using conversion bulbs. If you have a metal halide system but want the extra red and yellow light of an HP sodium lamp to promote flowering, simply buy a conversion bulb. Instead of investing in both a metal halide and an HP sodium system, you can rely on a metal halide system and use conversion bulbs when necessary, or vice versa.
HP Sodium to Metal Halide
The Sunlux Super Ace and Ultra Ace (Iwasaki)
and Retrolux (Philips) produce an HP sodium spectrum with a metal halide system. These bulbs make it possible to use a metal halide ballast and get the same spectrum as an HP sodium lamp. Lumens-per-watt efficiency is traded for the convenience of using these bulbs. A 1000-watt HP sodium bulb produces MO,000 initial lumens. A MH to HPS conversion bulb produces 130,000 initial lumens. If you only want one lamp, a conversion bulb is a fair choice.
Continue reading here: Mercury Vapor Lamps
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