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Why do Metal Halide Lamps Need an ANSI Coded Ballast?

Posted by Lamar Guzman on October 19, 2015

In the lighting industry there are many important components that the average lighting buyer is unaware of, or simply doesn’t think about. Many of my customers don't know how high intensity discharge lamps like metal halides are powered. I certainly didn’t prior to joining the lighting industry.

A major component to powering metal halide, high pressure soium & fluorescent lamps is the Ballast. High Intensity Discharge lamps carry a large amount of electrical discharge to create light. The job of the Ballast in this case is to drive and sustain the power output toward the lamps. Here is a quick run down on how a metal halide ballast operates.

First the line voltage goes into the ballast. The most commonly used line voltages in the U.S. are 120, 208, 240, 277 or 480V. You will notice that most metal halide ballast operate on 120-277V. These 4 tap ballast as they are called operate 120/208/240/277V. You will also see 120-480V ballast which we call 5 tap ballast. These ballast operate 120/208/240/277 & 480V. Each voltage has it's own specific wire that is to be used depending on the voltage you have in your facility. The others are not used. So if you have 120V in your building operating the fixture you would choose the 120V wire and leave the other wires alone. In the picture below the 4 wires in the rubber band are each of your "taps", one of the wires would be chosen and they are all appropriately labeled. The operating voltage of the lamp is defined by the ANSI(American National Standards Institute) and noted on the lamp and ballast. Here are some examples of 400W M59 probe start ANSI metal halide ballasts. The M59/400CWAH/4T/K is a 4 tap ballast, notice the 4 in the part number, the M400ML5AC4M500K is a 5 tap ballast, the 5 is highlighted as well in the part number. Typically 5 tap ballasts have more copper coils so they cost a bit more.

Once you have your voltage specified the ballast takes over all the heavy lifting. The input voltage enters the ballast and then the main control circuits convert the power into an AC signal and senses resistance within the lamp being operated. The ballasts provide the starting voltage and ignition pulses (pulse-start lamps) that are necessary to ignite the lamp. The ballast keeps a steady set flow of electricity flowing to the lamp once the lamp has been started. 

Once in operation, the resistance can be detected over one thousand times per second while adjusting the output. An important feature to pay attention to is the Ballast Efficiency. This determines how much of the power is actually being used during output. For example, if a ballast has an efficiency rating of 80% (0.80) this means that for every 100 watts, 80 watts is actually powering the lamps. The other 20 watts are lost in heat transfer. Another great feature is that some ballasts have EMI shielding. EMI shielding prevents things such as radios, TV’s, cell phones, etc… from interfering with the signal inside of the ballast.


A question I’m asked daily by customers is “How do I know what ballast I need to run these lamps?” Fortunately for all of us the manufacturers use an ANSI code system. For metal halide lamps the ballast and the lamp will have a unique identifier on them. They will all start with an "M" and then have a number such as 57, 58, 59 or 110. After that number there can be an "E" or "O" these have to do with the lamp being open rated or close fixture rated. The typical ballast kit sold by will include a capacitor and/or an ignitor(depending on the ANSI system) 2 screws, 2 new brackets and a new core and coil transformer like the one pictured above.

A popular ballast we sell is the Halco M57/175CWAH/4T/K. If you go to the website and look up this product, you will notice there is an ANSI code M57. This is a guide to finding all lamps matching this ballast. When searching this ANSI code you will find a lamp such as MH175/U/MED/IC PROLUME, in the description you will see ANSI Code M57. It is imperative to match up the ANSI code on your ballast with the ANSI code on the lamp. If you do not have a match the system will not operate properly. 

If you still need help trying to figure out what metal halide ballast you need please give us a call at 1-888-988-2852 or send us an email!

We are here to help!

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