Recently have hit “logger heads” with a homeowner over the installation of a 3ton AC unit in his home. The home,located in southern Ontario, is approx. 4000sqft,two storys, and equipped with a venmar active HRV system. Owner is claiming that according to 1998 CSA revisions, the current unit is insufficient. Somebody PLEASE clue me into these “revisions” and/or the process for determining such !