Grow Light Ballasts

MH and HPS lamps both require special ballasts. Each ballast contains a transformer and a capacitor, and regulates the voltage for the lamp. Since more HID bulbs come in either 250, 400, or 1000-watt versions, make sure the ballast you use is designed for the proper lamp and wattage. Using the wrong ballast could result in a burned out lamp, or worse!

There are dual systems, where you can switch the ballast from MH to HPS, and all you have to do is switch the bulb. Ballast configurations are different between MH and HPS. That's usually the X-3 wire on your ballast configuration, you just put a toggle switch in there and basically all you're doing is you're shutting off the ignitor. The MH bulbs have an ignitor built into the base of the bulb, the HPS don't. So the HPS require an external ignitor in the ballast configuration. If you're going to switch back and forth between the two of them, you have to switch off the ignitor and then put in an MH bulb. It's usually more expensive, but if you factor in the additional ballast cost, it's much cheaper.