Homeowner reported a tankless water heater displaying error code 29, indicating a condensate drain issue. Upon inspection, the condensate line was found to be frozen due to improper installation, including undersized ½" piping and back pitch. The condensate drain line was corrected by upsizing to ¾" piping, properly pitching the line, and shortening the run. These corrections will help prevent the condensate line from freezing in the future and restore proper operation of the unit.