System and methods for controlling rotary screw compressors

An electronic control apparatus for protecting an air compressor connected by a sump to an air pressure system, the sump having a pressure sensor measuring pressure in the sump, comprising:

• input means for receiving an instruction to start the compressor;
• blowdown valve means for releasing pressure from the sump in response to a control signal;
• processing means, operatively connected to input means, pressure sensor, and blowdown valve means, for detecting the start instruction and starting the compressor;
• storage means for storing a predetermined maximum starting sump pressure value;
• and
• starting prevention means, operatively associated with the processing means, for preventing starting of the compressor against a load by automatically determining pressure in the sump using the sump pressure sensor, and when the determined pressure is greater than the maximum starting sump pressure value, automatically actuating the blowdown valve means to relive the pressure in the sump and delaying starting of the compressor until the pressure in the sump is below the value.