Many decades ago, after the development of fluorescent lighting in general, lighting engineers realized that they would need fluorescent bulbs to work outdoors or under cold temperature conditions.  There were several issues to overcome, but the most important were starting the lamp in cold temperatures and maintaining a high light output as well.  The ballast is critical in this system and you can't have one without the other, HO lamps or ballasts.  The development came into what are called generally high output fluorescent ballasts.  These have the ability to start the lamp at a lower starting temperature than standard ballasts and creating a higher lumen output too.  The typical applications are outdoor lighting, sign lighting and coolers and freezers which need a lot of light maintained regardless of the cold temperature.  The most common type of these are still the T12/HO, but there are also T8 and T5 HO choices in today's market.  One of the ways that these are abbreviated is with the two letters HO.  If you ever see HO as part of the code number, you will know that they are high output fluorescent light bulbs.  You will find these in almost any length as they have many different lighting applications so they can be as little as 2 feet long and as much as 10 feet in some special cases.

As with all fluorescent bulbs, they rely on particular ballasts in the fixtures for proper operation. The ballasts for the HO lamps are usually much larger than the standard types, and put out a lot more heat.  These ballasts are very heavy too!  Some of that is changing when it comes to electronic ballasts as they have a size that is almost the same as the standard electronic ballast.  The old style HO ballasts are very heavy as they have large windings inside.  The ballast is important because it is specific for each type of lamp.  You can't change from one type of fluorescent to another without changing the ballast in most cases.  Most of the time the ballast and the lamp are matched electrically and so it's good to make sure the ballast you have is the right one for the lamp you choose.  In the case of magnetic high output fluorescent ballasts, you will find that many of these will operate various lengths within a certain range.  Such as the 8 foot and 6 foot lamps sometimes use the same HO ballast.  Almost every manufacturer makes high output fluorescent ballasts, among them are Universal ballasts and many others. There is always a choice when it comes to the voltage to operate the ballast.  Most of the time, you will find them in 120 or 277 volt, which are the most common.  Sometimes on a rare occasion you might see a 480 volt in a VHO lamp system.  That's a little different than the lamps we're talking about here, but is similar and almost obsolete.  It's important to get the voltage right or else the ballast will not work or the high voltage can instantly burn out the ballast.

Keep in mind that there are many ballasts for high output fluorescent light bulbs, we describe some of the general characteristics here.  We have a large inventory of high output fluorescent ballasts for nearly every type of light fixture in the field.  It's never a problem to get what you need since Universal is our preferred brand of this type of lighting.  If you need help identifying a ballast, our customer service representatives can help you determine which one it is by the code number on the label.  We have extensive cross references which will tell us exactly what you have, no problem!