In California Title 24 energy code for commercial buildings requires multilevel lighting control. A simple way to achieve this is to switch individual ballasts in multi ballast fixtures separately. Many call this A/B switching because of the switch notation architects use. Any fluorescent fixture with two ballasts can be A/B switched. Dimming is also allowed.

dim4fun, is there a particular source you can suggest, for two-ballast fixtures? How feasible/expensive might it be to rewire a single-ballast fixture with two smaller ballasts? I suppose it would shoot the UL listing...

What kind of fixture are you looking for?

It is standard industry practice to retrofit ballasts in fluorescent fixtures. The individual components are UL listed and the instructions for the ballast purchased separately show that this is the intended use. I've never heard of an inspector questioning this. Not all fixtures are designed to hold all types and quantities of ballasts so there are limits to what you can do. Ballast casings come in standard sizes and fixtures are designed to accept a specific size of ballast. Manufacturers have fixtures that can be configured with two, three, four or more lamps and the channel where the ballast goes can accommodate one or two ballasts. Some fixtures are designed better than others in terms of controlling temperatures that can affect ballast life span.

The latest electronic ballasts are getting so smart that they automatically adjust for input voltage between 120 and 277. ItÂs easier to stock the right replacements and no more wrong voltage order problems. Digital addressing is an option now. You teach the ballast which switch to listen to and you can re-teach as office spaces are changed so that you don't have to rewire to accomodate a new floor plan layout.

There are companies that specialize in fluorescent fixture upgrades and they may retrofit new ballast, lamps and reflectors into old fixtures.

All of that above is for commercial type fixtures that you see in the ceiling of a typical office space since the industry evolved with that intent. Are we talking about houses here? If so it is probably more common to dim the fluorescents rather than A/B switch them. IÂve not experienced residential fixtures other than 8Â tandem fluorescent strips in garages and similar lens wrapped fixtures in studios, garages, home offices that can be retrofitted in this way.

It would probably be less expensive to purchase a new fixture with two ballasts than to retrofit your old one. About 20 years ago when I was doing our kitchen I installed two 4' fluorescent fixtures with four bulbs in each. Each fixture had two ballasts so I had two separate switches put in. One switch turned on the outer lamps and the second switch turned on the inner lamps. This was pre-dimming ballasts and allowed me to have 50% lighting in the kitchen. I usually only use one of the switches since it is enough light.

You can go to an electrical supply house or a lighting showroom and ask if they stock or can order any fluorescent fixture with two ballasts. At that point it is just a matter of the wiring to the switches. You can do this with electronic ballasts also, since we just did this in someone else's house.

Need to put in a motion sensor for a inboard/outboard fixture. The module has 4 wires, 2 reds a black and white. Need your help for hookup.

Need to put in a motion sensor for a inboard/outboard fixture. The module has 4 wires, 2 reds a black and white. Need your help for hookup.

Need to put in a motion sensor for a inboard/outboard fixture. The module has 4 wires, 2 reds a black and white. Need your help for hookup.

Need to put in a motion sensor for a inboard/outboard fixture. The module has 4 wires, 2 reds a black and white. Need your help for hookup.