General-use dimmer switches shall be used only to control which loads unless listed for control of other loads?

• A. Permanently installed incandescent luminaires
• B. Fluorescent fixtures
• C. Motors
• D. Receptacles

Answer: (A)

General-use dimmers are built to control incandescent lighting because they use a phase-cut method that reduces voltage for resistive loads. Incandescent luminaires are essentially resistive and tolerate voltage reduction well, so dimming them safely lowers brightness without upsetting the lamp.

Dimming fluorescent fixtures isn’t the same: their ballast electronics expect specific control signals and can flicker, hum, or be damaged if driven by a standard dimmer. Motors require a different kind of control entirely to manage starting and speed, not just reduced voltage. Receptacles are outlets, not fixed lighting loads, and dimming them isn’t appropriate or safe.

So, unless a dimmer is explicitly listed by the manufacturer for other loads, it should be used only to control permanently installed incandescent luminaires.