Most modern screw compressors have electronic controllers built into the compressor.
Built in controllers are able to monitor the function of the compressor, such as fault codes, running times, loaded & unloaded running times, key temperatures etc. It will also allow the user to change some key running parameters of the compressor such as cut in cut out pressures.
Generally, on bigger machines, these controllers as well as controlling the logic of its compressor can also be connected to other compressors. The ‘master’ controller can then control multiple compressors, for example deciding which compressor should be made to run when certain demand is observed. Connecting the various controllers between compressors of the same make is generally fairly easy, only requiring a control wire to be ‘daisy chained’ between the machines. However, there are restrictions. Usually, only machines of a similar age and brand can be connected in this way. Additionally, the functions and logic available to these linked compressors may be limited.
A better and more flexible alternative is to fit a separate controller. Most manufacturers offer separate controllers that can be connected to multiple compressors, normally of different makes and styles (such as fixed and variable speed). It is often necessary to fit a conversion module to the compressor to allow the controller to talk to the different compressors.
The standalone controller gives you much more flexible and powerful way of controlling multiple compressors. The controller can, for example, be programmed to maximise efficiency of the complete system, prioritising the most efficient compressor or group of compressors to meet current demand. This will often be a fixed machine(s) for base load and topped up using a variable speed machine. Controllers can also be programmed to equalise the running hours of compressors over time, they will also make sure that every compressor runs for a period every day, meaning none of the compressors end up collecting dust in the corner and never getting used.
Electronic controllers certainly add another dimension to energy conservation and efficiency particularly if they are set up to manage a range of fixed and variable speed compressors.