trane weathertron heat pump

[Kevcules]

My trane heat pump had its compressor replaced after about 18 years of service.Since then the main breaker in my house has tripped after a month of running.The power resumed when I powered everything up except the heat pump.Then 6 hours later I powered on the heat pump and a day later, the heat pump breaker tripped.What is happening, why is it drawing so much power?? It has been -40 with the wind chill lately so hopefully it's just the cold!!!Any help would be appreciated..