Will it be advantageous to have dual return?

[kathuat]

I have a 3 level house. Square footage of the top 2 levels is 2604 sq. ft and basement is another 1100 sq. ft. The basement is finished with HVAC as well. The house is serviced by a single 80% furnace (20 Year old) (Input BTU: 140,000) and a 4 Ton 10 SEER AC (6 Year Old). The furnace has a single return. The basement return ties into the return coming from the 1st and 2nd floor. My question is that is there an advantage to separate out the basement return and have 2 separate returns. One return will be on the LHS side of the system (1st and 2nd floor) and then the other return of the basement on the RHS. Is this a recommended arrangement or will it improve efficiency than having a single return? If the answer or recommendation is yes, the follow up question is that if the 2 returns are unbalanced i.e. have unequal amount of air coming will that effect the furnace. Why? Appreciate your help.

[amickracing]

Assuming the return you have now is sized properly, from a technical standpoint you won't gain much by having other returns.

But.. (there's always one of them), it will probably make your house more comfortable by allowing the air to circulate better and help keep the temps more even.

Ideal situation is to have a return in every room on every floor (except the kitchen and bathroom). Not always possible, but one on every level would help too.

Might be harder to do than it seems, so cost might prohibit it. About the balancing question. In a perfect world, ever return would suck the exact ammount the supplies pumped into that room. Of course we don't live in a perfect world, so getting a close is usually good enough. If for example the basement ends up pulling 2/3's of the air and the other is pulling the other 1/3, you'd probably be fine.

[kathuat]

Other comments please

[contactor]

Most manufacturers recomend 2 returns on sides,or bottom plenum on 4 ton systems and larger,and so would I. An air flow imbalance will only draw more or less air from the basement level. Adding this should increase furnace and Ac efficiency by increasing airflow distribution and utilizing both sides of the blower better. Generally speaking,adding more return slightly improves overall efficency and evens temps.