I have an AC sistem with inverter, it's working great on heating untill outside temperature drops below +3 degrees C, down from there external unit is starting to froze too often, i have a lot of defrost cycles, which reduces the yield considerably, in these condition inside i have only a maxim of +21, +22 Celsius(when is setted to +25), wich is not good.(in my country we have an average of -3 C, outside, with with minimum of -8 C)

I've got an ideea from someone that says it should work 100%.
All i have to do is to build a heat exchanger with the ground, in these way: heated refrigerant goes inside from outside unit in one pipe, and from another pipe refrigerant come back outside, this pipe shoult be cutted and taken into the ground at 1,5 m down(coil circulation), in there should be a coil with two rows (a maximum of 8-9 meeters of consumed pipe in total), these should be enough in order not to freeze the external unit coil.In ground at 1,5 meeters i should have +10...+14 Celsius, and like i will have a heat exchanger with the ground and also an electric energy saver.

A second iddea is exactly as the first, only the coil that is in the gound will also be introduced through another pipe, between those pipes i wil have antifreeze liquid recirculated with a small pump, in order to prevent excessive cooling and from there external radiator froze.(this iddea should be like a precautionary measure if the first will not work)

Perhaps the idea is uncalled.

Thanks, please excuse me if I posted in the wrong place, but i'm new in this forum, but I wanted to appeal to professionals that in my country lacks.