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mantione
Dec 22, 2015, 07:42 PM
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

ma0641
Dec 23, 2015, 03:00 PM
Check this link.

Online Manual J load calculator (http://hvac-talk.com/vbb/showthread.php?989491-Online-Manual-J-load-calculator)