Single-phase systems use two legs (L1, L2) for residential work, while three-phase uses three legs (L1, L2, L3) for commercial units. Three-phase motors don't need start or run capacitors because their windings are already phase-shifted. Check voltage balance across all three legs instead of hunting for a missing capacitor.
Hey, are you new to the trades? Here's something you may not know about single-phase versus 3-phase power. Most residential work you'll see runs single-phase— 2 power legs labeled L1 and L2 on the schematic. But on bigger rooftop units or commercial refrigeration, a 3rd leg shows up— L1, L2, and L3. 3 lines in means 3-phase. On the diagram, you'll notice 3 fuses instead of 1 or 2, and motor terminals labeled T1, T2, T3 instead of just 2 wires. Here's the part that catches new techs off guard: 3-phase motors don't use a start or run capacitor. None. On a single-phase motor, that capacitor creates the phase shift needed to get it started. A 3-phase motor doesn't need that trick. Its windings are already spaced out electrically, so it starts strong on its own. No capacitor doesn't mean nothing's wrong. If you're hunting for a capacitor on a 3-phase compressor like you would on a residential system, stop— it was never there. Instead, grab your meter and check voltage balance across all 3 legs, because that's the fault 3-phase equipment actually gets. Now that you know, you can help someone else know.
