I replaced an oil furnace with a gas furnace. When I needed to replace the A/C, the 2nd vendor said the fan was on high and would burn out in 5 years. He relocated the furnace to a central position that balanced the air flow. I really needed to replace the ductwork anyway. Long-term decision. Some are more savvy and knowledgeable than others. The recommendation could produce more efficiency. IDK. Just my experience. My return upstairs is 14×30 and the 2 downstairs are 12×20. ** Edited by TomTurkey at 5/24/2023, 10:05:42 AM