Mercury Vapor Lamps

Marijuana Horticulture

by Jorge Cervantes

The mercury vapor lamp is the oldest and best known member of the HID family. The HID principle was first used with the mercury vapor lamp around the turn of the 20th century, but it was not until the mid 1930s that the mercury vapor lamp was really employed commercially.

Mercury vapor lamps produce only 60 lumens per watt. A comparison of the spectral energy distribution of the mercury vapor and the photosynthetic response chart will show this is a poor lamp for horticulture. It is expensive to operate and produces a spectrum with a low PAR value.

amps are available in sizes from 40 to 1000 watts. Bulbs have fair lumen maintenance and a relatively long life. Most wattages last up to three years at 18 hours of daily operation.

Bulbs usually require separate ballasts, however, there are few low wattage bulbs with self contained ballasts. Uninformed growers occasionally try to scrounge mercury vapor ballasts from junk yards and use them in place of the proper halide or HP sodium ballast. Trying to modify these ballasts for use with other HIDs will cause problems.