[JDKeebler]

Our home heat pump/AC breaker [20 amp double] keeps tripping after 15-45 minutes of use.
It seems to be happening only when the unit is stepping down, or turning off after temp is reached. This problem began in the last 24 hours. When unit fan is spinning, and until it trips the breaker, the AC works great. Our inside HVAC unit and outside Heat Pump are Payne make, and were installed brand new in January of 2009. We took laser thermometer readings of the compressor [which were between 108 and 160 degrees], and the fan-which is warm [think comfy mid-soak bathwater temp-comfortable to leave my hand on fan plate above for indefinite period w/o discomfort of any kind] but not hot. No insects stuck in outside unit controls, contacts are clean and wire connections checked and found to be good. Had electrical panel examined, wires good properly installed, right materials, and not warm, have no signs of insulation or heat issues. Breakers are cool to touch. Replaced older breaker with brand new Square D of same spec, and still having same issue.