I have a 75,000 BTU gas furnace in the garage now. I want to replace it and add A/C at the same time. Two contractors have quoted me 4-ton A/C units. The third contractor, who seemed the sharpest of them, said that my house is limited to a 3-ton A/C unit because my plenum is only 14" and my return air grill is only 12" x 24". Do you agree that my house is limited to a 3-ton A/C units because of these dimensions? Thank you, Joe Mantione, San Diego
