Came out to call for air handler we installed tripping a breaker when emergency heat is on. I checked the system over and found the main wiring going into the air handler breakers were flipped. 10kw of heat was on the 30 amp breaker and 5kw of heat was on the 60. 30 amp breaker had too many amps being pulled, overheated and tripped. Changed wiring around and checked operation. Advised customer about the breakers and what I had done, if the breaker continues to trip, I suggested having the 30 amp breaker replaced as it might have weakened from the high amps being delivered to it before.