Trane XL15i Heat Pump

[Pikanjoe]

I own a Trane 4TWX5048A (XL15i) Heat pump with electric auxiliary heats, all controlled with a Trane TCONT803 thermostat. This is my first winter with this unit and I’m having a problem with the compressor locking out when temperature goes below about 10F. Whenever this happens, I have to run of expensive electric heat until the temperature rises again above 10F, defeats the purpose of having an expensive heat pump, especially here in Alberta Canada.
I am looking for the cause of this “lockout”. I have set the thermostat for “no compressor lockout” or option “0” on installer setup number 0350. I am looking at resolving this problem, not sure if I’m overlooking something but would appreciate any suggestions.
Thanks
John P.

[hvacwiz]

why ,may I ask at 10 degrees is your outside unit wanting to running at all? Cutoff for heat pumps is usually 30 to 35 degrees.