Grow Lights in hydroponics gardening – Metal Halide (MH) grow lights
Generating between 65 to 115 lumens of light per each watt of consumed electricity, metal halide grow light lamps are considered to have high efficiency. MH lights produce light, which is very close to the natural sunlight with the rich blue spectrum. Due to this, MH lamps support vegetative growing in the most desired way – when plants have many leaves on the stem with short internodes.
Structurally, metal halide lamp is a vacuum glass tube. There is also an arc tube inside, filled with mercury and other metals in iodine form. Under the influence of electric current, those metals start to generate light and heat intensively. Though metal halide bulbs can be either transparent or coated with phosphorus, the first type is more preferred for the indoor gardening, since it produces very bright light.
There are different sizes of metal halide lamps, starting from 70watts and finishing with 1500 watts. However 250w, 400w and 1000w are modifications, most commonly used in hydroponics systems gardening. In order to make MH light to work, it is necessary to use a ballast, designed for a particular bulb size. Ballast is, in fact, a transformer, which decreases voltage to some predefined amount.
The lamps can work only in the positions they were designed for. Those marked with BU or BD should be used only in vertical position; while those lamps, which carry HOR sign, are for horizontal application. Besides, there are also universal (U) lamps, which can operate in either position.
There are also many different styles of metal halide lamps available on the market today. Along with typical or regular MH bulbs, there are also Super Bulbs, which can produce up to 10-12% more light than ordinary bulbs.
Regular metal halide bulbs should be replaced after about 18 months or 9500-10000 hours of use. Super bulbs are less durable and should be replaced more frequently – approximately after 12 months or 6500 hours of use. These recommendations apply if grow lights will work 18 hours daily.