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Can I Use a Mercury Ballast With a MH Lamp?
2014-03-27 16:17:29
You cannot use a
mercury ballast with a metal halide lamp. The power supplied by a mercury ballast for starting and for cycling is different from the metal halides requirements and the mismatch can cause explosive failure of the metal halide lamp. Metal halide bulbs must be run using matching
metal halide ballasts.
Metal halide (MH) ballasts are required to start the lamp, regulate the lamp starting and lamp operating currents, and provide appropriate sustaining supply voltage. (See "What are warm-up and restrike times for metal halide lamps?")
Starting the lamp: In MH lamps, ballasts provide the starting voltage and ignition pulses (pulse-start lamps) necessary to ignite the lamp. Probe-start
MH ballasts, however, can take as long as 10 to 20 minutes to restrike (re-start) a lamp. Pulse-start MH ballasts can restrike the lamp within 2 to 8 minutes of an interruption in current, because they provide high-voltage pulses to start these lamps.
Regulating lamp current and power: The ballast regulates the lamp operating current flowing through the lamp after the lamp has been started. The ballast is set to deliver relatively stable power to the lamp while regulating the lamp current despite typical line voltage fluctuations. This maximizes lamp life and ensures other performance characteristics such as color and light output.
Providing appropriate sustaining voltage: MH ballasts must maintain suitable voltage and current wave shape to the lamp. MH lamp voltage typically increases over time, and the ballast must continue to provide sufficient voltage to the lamp as it ages. In addition, the American National Standards Institute (ANSI) and/or the lamp manufacturers specify a suitable current wave shape to the lamp to achieve good lumen maintenance. Lamp current crest factor (CCF) is defined by ANSI as the ratio of the peak value of lamp current to the root-mean-square value of the current. A low CCF (between 1.4 and 1.6) contributes to good lamp lumen maintenance and longer life.
Uses
Because they provide a wide light spectrum, metal halide lamps are often preferred for use in reef aquariums which need bright, high intensity light sources. For the same reason they are also frequently chosen for the indoor growing of plants. Other uses include applications that require bright outdoor lighting such as baseball stadiums and
Metal Halide Flood Light Fixtures.
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