How to Wire a 3 Phase Air Compressor - Ask the Electrician Wiring a 3 Phase Motor for an Air Compressor. The Basic Requirements for Wiring Electric Motors. Every motor should have a name plate which is typically attached on the side or end of the motor. The information found on the label tells all about the motor size and electrical requirements. How to Connect Wiring to an AC Compressor | Hunker Step 1. A single-phase compressor has three slide-on terminals. The terminals are normally marked, either by the terminals, or on the terminal cover. They will be marked as R, which is the run line; S, which is the start line; and C, which is the common line. In a few cases, the terminals might not be marked.