I've read a number of posts regarding return air that emphasize the need to correctly size the amount of return air. A contractor recently stated: "a system can only put out what it takes in" . He was pointing out that each of our units had less than adequate return air and if we expanded the return air we would likely see a significant improvement in performance. (This was a side note and not a selling point).
Each of our 4 systems have only one return air that is typically an opening in an adjacent wall and in one case the wall goes to an adjacent closet with a louvered door. The largest return air opening we have is 8" x 20" on a 3 ton system with a 16" x 25" filter. The rest of the return air openings are smaller and that includes a 5 ton unit. The house was built 35 years ago and is located in northern Texas.
My questions: If we increase the vent openings to match the size of the filters, what performance gains might we see. ie: overall percent increase in system performance, increase in EER or SEER, shorter runs times ...etc. I am interested in some kind of qualified measurement.
Also, the three ton unit I mentioned has the loudest return air noise of all the systems even though it is identical to one other system. So if we increase the return air openings will that increase our interior noise levels?