What type of control should not be used as a speed control for ceiling fans?

Using a light dimmer as a speed control for ceiling fans is not advisable because dimmers are designed to regulate the voltage and current for lighting loads rather than for motor loads commonly found in ceiling fans. Ceiling fan motors generally require a specific type of speed control mechanism that can vary the fan's speed effectively without damaging the motor.

Dimmers can cause the fan motor to overheat or malfunction due to inadequate power supply regulation when set to lower speeds. Unlike ceiling fan speed controls that adjust the phase angle of the current to provide various speeds safely, light dimmers can introduce unwanted noise and flickering, and can potentially lead to reduced efficiency and lifespan of the fan motor.

In contrast, other controls like toggle switches, smart switches, and remote controls are specifically designed for fan operation. They either allow for simple on/off functionality or incorporate integrated speed control functions that are safe and effective for ceiling fans.