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I'm glad you got your problem fixed. I just want to step in here and explain what the start capacitor actually does...
Electric motors need a rotating magnetic field to make the spinny parts spin. Single phase AC current does this, sort of. The motor is wound with "Poles". Lets say, in the motor in question, there are two poles, north and south. The alternating current in the magnetic field flips the direction of these poles at the frequency of the voltage. If the rotor part is spinning fast enough, the flipping of these poles keeps yanking the rotor in the right direction and the motor puts out torque. The problem is, though, when the rotor isn't spinning. These alternating poles may yank the rotor in the wrong direction or not provide enough torque to carry the rotor far enough to keep yanking on it as the field flips back and forth. Therefore, single phase AC induction motors have start windings to force a direction and provide additional starting torque. The start windings are in the "east-west" locations and make the rotor turn in the right direction and give it more torque. However, they have to be shut off once the rotor is past a certain speed or they draw too much current.
The start capacitor is what powers the start windings- the capacitor is wired in series between the AC power and the start windings. The start windings need to be energized out of phase from the main windings to make a rotating magnetic field in the required direction. Capacitors store energy, and essentially act as a phase shift by storing the energy at the peak of the AC waveform and passing it onto the start winding a bit afterward. Once the rotor is up to speed the start windings are disconnected. General purpose AC induction motors do this with a centrifugal switch, but a lot of AC compressors just use a timer.
A hard start capacitor is just a bigger, heavier duty start capacitor that can provide a greater phase shift for longer without overheating. It reduces the inrush current necessary to start the motor. It also costs more than the basic start capacitor, which is why it's a kit and not initially built into the unit.
We use polyphase (3 or more) current for industrial use... you don't need capacitors to start a motor with polyphase current because you get a built in rotation of the magnetic field. We use 3 phases because you only need 3 equally sized wires to implement it in a balanced system. 2 phase systems (one phase 90 degrees from the other) have been built but need a neutral wire that can carry more current than each of the power wires.
Split phase 240V is not a two phase system because there is no way to wire it as a rotating field without adding an intermediate device like a capacitor.
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Linear Mode
