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Constant Speed Operation: Is It Right for You?


Constant speed operation is a configuration that allows an electric air compressor to run continuously, even when air is not being demanded. Unlike the typical start/stop configuration that is standard among most of our electric air compressors, constant speed models will continue to run after the top pressure setting is reached. All excess air that is compressed by the pump is released to atmosphere.

electric air compressor


The primary advantage to constant speed operation is that it promotes longevity of the motor. By allowing an induction motor to run continuously, it’s able to maintain an optimal operating temperature, limiting the potential for overheating that can occur with frequent starts. As an added bonus, the motor also maintains a steady amp draw, which comes in handy if a compressor is plugged into an extension cord or is hooked up to a circuit that has other equipment in line. In general, it’s an excellent option for crews that demand a lot from their compressor.


This configuration is available in two different forms – Constant Speed and Dual ControlConstant Speed comes standard on our two-stage portable electric models (3230K24CS), while Dual Control is an option available on our single-stage portable electric models. Both configurations are available as an option for our stationary electric models. Below we will look at how each one works.


Constant Speed

As described above, a constant speed air compressor runs continuously whether or not air is being demanded. When the tank(s) reaches top pressure, a pilot valve opens up and releases excess air to atmosphere. When the tanks are depleted, the pilot valve closes and compressed air is diverted back into the tank. Since there is no pressure switch in the system, an on/off switch (which looks like a light switch) is installed so the user can cut power to the motor.

constant speed air compressor

Dual Control

An air compressor set up for dual control utilizes a pressure switch and a pilot valve, allowing the user to switch between start/stop mode and constant speed mode. In constant speed mode, the pilot valve is in control and the compressor will run continuously, as described above. When in start/stop mode, the pressure switch takes over. It will cut power to the motor when the tanks reach the top pressure setting and restore power when more air is needed. When a model is ordered with this option, it will be factory set to constant speed mode. To switch between modes, the user must turn the knurled knob on top of the pilot valve. Rotating the knob clockwise activates start/stop mode and turning it counterclockwise activates constant speed mode.Dual Control


If you have any questions about how a constant speed or dual control model can benefit your crew, drop us a line. Already convinced? Contact your local ROLAIR dealer to get yours.