There are many types of control method utilised in compressed air systems. Over the last 20 years a number of different control methods have been developed, so identifying the right technology for each individual site can result in significant gains in efficiency and reduction in operating costs.

Common control methods include:

  • Start/Stop
  • Load/Unload
  • Modulation
  • Variable Speed Drive (VSD)
  • Variable Displacement

To determine the control method that will maximise efficiency and minimise your operating costs requires a thorough and detailed usage profile to be established. A usage profile consists of reading and analysing your plants demand for air over time. This is usually collected through the use of an auditing device that can be configured to your compressed air system to measure the air demand in the plant over an extended period. Once a detailed usage profile has been determined it can be analysed and the control method that will deliver the greatest efficiency identified.

Generally there are 4 distinct types of profiles identified in most plants:

1)    Constant Demand

Constant demand occurs when a plant typically requires a consistent amount of air delivery to the plant during all shifts. A plant with a constant demand benefits most from a fixed speed, load/unload controlled air compressor with a correctly sized air receiver to minimise cycles and extend off-load time.

Air Compressor - Constant-Demand-Graph

2)    Widely Varying Demand

Widely varying demand occurs when a plants air demand fluctuates significantly during and between processes and shifts. VSD compressors offer the most efficient control method as a VSD can alter air production to meet the plants requirements at all times ensuring there is no wastage.


3)    Changing Demand

Changing demand profiles occur where there are different air demands between processes and/or shifts. For example a day shift may require a higher volume of compressed air where as a night shift may require only half the amount of the day shift. The best control method for changing demand levels is multiple sequenced compressors. Sequencing multiple compressors enables the system to automatically determine the most efficient operating mode to produce the amount of compressed air required in the plant at any stage during production.


4)    Short Term High Demand

Short term high demand occurs when a plant has specific times of peak demand in an otherwise constant demand profile. There are certain processes that only occur a few times during a shift but require a high level of compressed air. The best control method for short term high demand is generally a fixed speed, load/unload compressor with an engineered air receiver that has enough storage to handle the short peak demands.


Your plant may represent one or a combination of these usage profiles, it is critical an air audit is conducted on your plant to determine a usage profile and the best control method for your application is applied.

Implementing the best control method for your plant will reduce energy and maintenance costs leading to significant savings to your bottom line.

If you would like further advice on control methods or help in determining the best control method for your particular system, don’t hesitate to contact Southern Cross Compressors on 1300 098 901 or simply complete the ‘Enquire’ form on this page.