My fan motor for a Rheem Ruud condenser seized up. I called around and found a replacement. I wired it up according to the wiring diagram and even added a new capacitor like it said. It started fine and cold air started to come out of the vents. After about 20 minutes of it running it shut off. The motor was real hot and it tripped the reset button. I reset to button and it tripped again after just a couple of minutes. The original motor was 850 rpm and the replacement was 825 rpm. Everything else is the same. Can anyone tell me why it might be overheating?