I am installing a bathroom vent fan with fan motor, nite lite, and 2 compact fluorescent room lights. The room already has fluorescent tubes over the vanity. I am looking at the Leviton 1755 to operate everything independently but the fan motor, which I will put on a timer. I just discovered that the installation document from Leviton contains a notation I have not seen elsewhere "incandescent only". Is this true? Why? It also recommends installing the 3-gang switch in a double-gang wall box, which seems to defeat some of the space-saving advantage of this product. Is this also necessary?

Yes, the device likely has electronic switching using Triacs. These cannot be used for devices that use magnetics or other non-resistive devices. Fluorescent and motors are in this category and MOST CFL lights. The magnetic devices keep the current flowing due to the inductive properties so the controlling device never sees the current go to zero to turn off for next cycle, hence they lock for the whole cycle and are locked on. Some of the controlling devices can be damaged due to transients from the inductive spikes.

Hello sam. the incandescent only notation is there so that you do not use it with fluorescent or the newer compact fluorescent or LED bulbs. The reason for the double-gang wall box is the wiriing code. you aren't supposed to have more than 4 wires in a single-gang box. Often, the double-gang box is used with a single cover plate top plate. Please do follow the electrical code as not doing so can be a hazard and can void your fire insurance. Joe