I have a two story house approx. 2300 square feet. I have a 5 ton single unit. One contractor told be a need another air return. Currently I have one air return that hold two 16x20x1 air filters. I buy the more expensive 3M filters because they are a little more sturdy. The cheaper one tend to fold in from the vacuum.
How do I know how big the air return should be for a 5 ton unit?