Controlling the CFM (Cubic Feet per Minute) output on an air compressor primarily depends on whether it's a variable speed or fixed-speed model and is closely linked to the operating pressure.
Understanding CFM Control by Compressor Type
The method for influencing or "controlling" CFM varies significantly between different types of compressors:
- Variable Speed Compressors: These compressors can adjust their motor speed based on air demand. This allows for some degree of control over CFM output.
- Fixed-Speed Compressors: These compressors run at a constant speed when active. Their CFM output is largely fixed.
Controlling CFM on Variable Speed Compressors
For variable speed compressors, the key factor influencing available CFM is the pressure setting.
- Increasing pressure in a variable speed compressor will reduce the available CFM. When the compressor needs to reach a higher pressure, it becomes less efficient at delivering a high volume of air flow.
- Decreasing the pressure will increase the available CFM. By setting a lower target pressure, the compressor can deliver a greater volume of air (CFM) more easily.
Therefore, on a variable speed unit, adjusting the pressure up or down is the primary way to influence the CFM being supplied at any given moment, within the compressor's operational range.
Controlling CFM on Fixed-Speed Compressors
Fixed-speed compressors always produce the same amount of air (flow) when they are running. You cannot adjust a setting on a fixed-speed compressor to change the CFM it is capable of producing. Its output is constant based on its design and horsepower.
Increasing Maximum CFM Capacity
Regardless of the compressor type (variable or fixed-speed), there's a fundamental limit to how much air it can produce.
- You can't increase the CFM without providing more horsepower (HP). If you need a higher maximum CFM output than your current compressor provides, you would typically need a larger compressor with a more powerful motor (higher HP). Adjusting settings like pressure allows you to access more or less of the compressor's available CFM in a variable speed unit, but it doesn't increase the compressor's maximum potential CFM.
In summary, for direct control over CFM flow at a given pressure on a live system, a variable speed compressor allows adjustment via pressure settings. A fixed-speed compressor's CFM is constant. To increase the total potential CFM output of your system, you generally need more horsepower.
