Our house air conditioner went out last Saturday afternoon on a +100 F day. Was able to diagnose the problem itself as a problem with the starting circuit of the big compressor fan of the outside compressor unit. If I gave the fan a strong push with a stick to start it rotating, then the fan motor would start up and the air conditioning would work fine. An AC technician later determined that the compressor fan needed a new start-up capacitor, and now the AC works fine.
My question is this: Why are large 2-ton house air conditioners designed so that their compressor fans require start-up capacitors to turn on? The diameter of the compressor fan on our house AC appears to be roughly the same as that of an inexpensive box fan that I can get at Walmart, and the ac motors on those simple box fans don't require a start-up capacitor to turn on, do they? You just plug them in and they smoothly start revving up to speed all by themselves. So why do house air conditioners use compressor fans that need these trouble prone start-up capacitors, and why can't a simple self-starting ac motor like that of a box fan be used instead for the compressor fan?