PLC does multitasks. If you want PLC to do all the tasks in an easy way like auto on/off, you can use Star Delta timer to manually turn on/off the compressor.
Problem to bhot par mostly Problem ye aata hai 1. Oil ka temperature high ho jata hai 2. Motor Overload ho jata hai 3. Air Build-up karna band kar deta hai Panel me 1. Contactor jal jata hai 2. Emergency ke NC tarminal kharab ho jate hai Or bhi kafi sara problem's aata hai