420 Magazine Background

Does the Bulb have to match my Ballast?

Smokin Moose

Fallen Cannabis Warrior
Yes Ballasts and Bulbs Should be Matched.

HID bulbs generally need specific ballasts, and any given ballast can usually safely and effectively operate only one type or a few types of HID bulbs.

The bulb wattage must be matched to the ballast. A smaller bulb will usually be fed a wattage close to what the proper bulb takes, and will generally overheat and may catastrophically fail. Any catastrophic failures may not necessarily happen quickly. A larger bulb will be underpowered, and will operate at reduced efficiency and may have a shortened lifetime. The ballast may also overheat from prolonged operation with an oversized bulb that fails to warm.

Even if the ballast and bulb wattages match, substitutions can be limited by various factors including but not limited to different operating voltages for different bulbs. Examples are:

Pulse-start sodium lamps often have a slightly lower operating voltage than metal halide and mercury lamps of the same wattage, and ballasts for these sodium bulbs provide slightly more current than mercury and metal halide ballasts for the same wattage would. The higher current provided by the pulse-start sodium ballast can overheat mercury and metal halide lamps. Mercury and metal halide lamps may also "cycle" on and off in lower voltage sodium ballasts, such as many 50 to 100 watt ones.

Metal halide lamps have an operating voltage close to that of mercury lamps in many wattages, but have stricter tolerances for wattage and current waveform. Metal halides also usually need a higher starting voltage. Most metal halide lamps 100 watts or smaller require a high voltage starting pulse around or even over 1,000 volts.
175 to 400 watt metal halide lamp ballasts can power mercury lamps of the same wattage, but the reverse is not recommended.

Mercury lamps 50 to 100 watts will work on metal halide ballasts, but hot re-striking of mercury lamps 100 watts or smaller on metal halide lamps may be hard on the mercury lamp since the starting pulse can force current through cold electrodes and the starting resistor inside the mercury lamp.

1,000 watt mercury lamps come in two operating voltages, one of which is OK for 1,000 watt metal halide ballasts. A few wattages of pulse-start sodium (150 watts?) come in two voltages.
A low voltage lamp in a high voltage ballast will be underpowered, resulting in reduced efficiency, possible reduced lamp life, and possible ballast overheating. A high voltage lamp in a low voltage ballast will usually cycle on and off, operate erratically, or possibly overheat. This will usually result in greatly reduced lamp life in any case.

One class of sodium lamps is made to work in mercury fixtures, but these only work properly with some mercury ballasts, namely:
'Reactor' (plain inductor) ballasts on 230 to 277 volt lines.
'High leakage reactance autotransformer' ballasts, preferably with an open circuit voltage around 230 to 277 volts. NOT 'lead', 'lead-peak' nor any metal halide ballast!

These sodium lamps may suffer poor power regulation and accelerated aging in the wrong mercury ballasts, especially after some normal aging changes their electrical characteristics. Also, these lamps may overheat and will probably have shortened life with pulse-start sodium ballasts.

Many sodium lamps require a high voltage starting pulse provided only by ballasts made to power such lamps.

To prevent dangerous accidents please keep remote ballasts away from tap points and on an elevated position (approx 5 inches off the floor) using a block or shelf.


New Member
Well BWC BayArea I will soon find out, I order a 600 watt Elec. Ballast and can only find Conversion Type MH bulbs for 600 watt ballasts. They make every wattage but 600 MH Bulbs:50:. I should of done more homework:idea:. Or went 1000 :30:.

Purple Goose

On Vacation
Any opinions on the SS 10 econo switchable ballast 1000w comes with 5 year warranty but is one big ballast entier thing is 50lbs and like 14" x 6" x 6" have only used 400w ballasts before and they were not even 1/3 the size of this monster which I assume is so large because of the ignitor circuits and its a magnetic induction ballast I beleive they are called not digital but only costs 140$ for a brand new one with Artemis hps bulb 145000 lumens initial 2100k and a ushio metal halide bulb 105000 lumens 5000k temp. Wondering though which is a better temp hps the 2100k or the 2700k bulbs I have seen?


Plant of the Month: June 2010 - Nug of the Month: July 2010
What's your opinion on conversion bulbs? Like a metal halide conversion that can be used with an HPS ballast.

other than the cost, conversion bulbs perform well. i have talked to people that have modified their hps ballast by adding a switch to turn on/off the ignitor circuit (used by hps bulbs), but i have not attempted it myself.


New Member
I picked up a 400 watt switchable ballast, 400 watt standard MH and a 400 watt standard HPS bulbs for my grow and after changing from MH to HPS "low and behold" I forgot to throw the switch.
It ran for four days (48 Hours ) like this. I got my light meater from my camera case to check the lighting. It read the same even after throwing the switch to HPS.
Q. So all I did was take some of the life from my bulb ??


Plant of the Month: June 2010 - Nug of the Month: July 2010
The only difference between mh and hps as far as the ballast is concerned is that in hps mode, it enables the ignitor circuit. Hps normally requires a higher voltage to strike the arc than the operating voltage. Doubtful that any harm came to your lamp.


Plant of the Month: June 2010 - Nug of the Month: July 2010
Top Bottom