Can anyone tell what the size of the suction line is for the trane xr13 model?

Usually 3/4 OD on the 13 SEER units. Sometimes you can get by with a 5/8 OD on a short line set 10 to 15 feet.

The size of the refrigerant lines are dependent on the tonage of the unit and the length of the line set ( this can range from 1 1/2 to 5 tons)