Hello,
Does anyone know of an affordable way to dim 120volt 4' fluorescent fixtures?
Thank you,
Jim
What's affordable?
Why are you trying to dim?
How much dimming range do you need?
How many fixtures?
There are two major categories. power-line phase control dimming or auxiliary control dimming.
If you're installing or retrofitting using existing two wire system and you're not doing too many, then the power-line phase control(i.e. Advance Mark 10 or Lutron Tu-Wire ballasts) is the most affordable type.
If you have a lot of fixtures or this is a new install, 3-wire dimming that uses dimmed hot as third rail for control purpose(best dimming range) or low voltage control 0-10v(industry standard, best control system selection and the wire pair can also be used for DALI in the future).
Below 10% is more or less useless for energy savings. You hit the floor at 25% or so energy consumption @ 10% output and anything below has negligible effect on power usage and it is mostly for aesthetics. Ballasts that dim below 10% cost more.
So, keeping 25% energy consumption floor in mind....
square root of measured light output is perceived output
or perceived^2 is measured output.
Ballasts are rated in measured output.
10% measured output ballasts are the ones spec'd for incentive and energy saving work. They "feel like" they dim to 32% (sqrt 0.1). Some newer ones go down to 5% (feel like 22%), but whatever you do, don't mix and match ballasts. No harm, but the fixtures will look like cow patches if you do. They don't feel like they dim anywhere near as much as incandescent lamps.
You can get 5-10% ones in 0-10v, Lutron style (3 wire) or power line phase control.
The only 1% ones I know of are Lutron Hi-Lume and they only come in 3-wire control or 3-wire/DALI hybrid and they dim to feel like 10% of full output.
Whatever you choose, you have to get a special dimmer. You can't use an incandescent dimmer even with the 2-wire type and expect each dimmer to cost $50-100 ea.