In my venue we have 480 ETC Sensor3 dimmers, and due to an upcoming opera production I wonder:
We want to use regular LED roof panels that fit old office roof structures, where fluorescents where used.
All the best,
1. Yes, there is. The lower limit will depend on exactly what model of dimmer you have, but it's generally somewhere in the 50-100W range for SCR dimmers (ED15, D20, ...)
2. Not always. At the bottom end of the dimmer loading the electrical characteristics of the load will begin to matter. In general if the load is below the threshold required to latch the SCRs it won't come on at all; or it will flicker.
Usually the best thing to do is test the load if you can get one. The most common technique for working around this in productions is add some "dummy load" somewhere (a load on the same channel to increase the wattage) - this can be anything resistive you have around, such as a tungsten lamp, electrical heater, etc).