Knob Fan Speed Controller with Safety Cover

Manual fan speed controller with a covered knob, for AC fans within its current rating. Reduces speed and noise where full airflow is not needed.
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Overview

A manual speed controller for AC fans: a covered knob sets the voltage, which sets the speed. The cover prevents accidental adjustment in a panel or a public area.

It is not a dimmer. The controller has to be rated for the fan’s running current and designed for an inductive motor load; a lighting dimmer will overheat or damage the motor.

Where it fits

  • Panel and cabinet fans
  • Workshop exhaust with variable demand
  • Equipment where airflow is trimmed on site
  • Retrofit of fixed-speed AC fans

Selection and installation notes

Check the current rating against the fan, with margin for startup. A controller running at its limit gets hot and fails early.

Not every AC motor tolerates voltage control. Some hum or overheat at low settings; test at the lowest setting you plan to use.

FAQ

Can I use it with an EC fan?

No. EC fans need a 0–10 V or PWM signal, not a voltage controller.

Will it work with any AC fan?

Most, within the current rating, but some motors hum or overheat at low speed. Confirm the motor type.

Does it save energy?

It reduces consumption at lower speed, though less efficiently than an EC motor. The main benefit is noise and airflow control.

Can one controller run several fans?

Yes, if the total current including startup is within the rating.

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