I have a 2,000 sqft house. I suspect the heating system (Trane) is
not working properly because it takes one hour to raise the
temperature four degrees.

The service man from the company which installed the unit last
summer told me the system works fine. He said the supply air is
105 degree and return air is 71 degree and usually he only gets
101 degree for supply air.

I don't have much experience with gas heat and wonder if a supply
air of 105 degree is normal. Any thoughts?