I've been getting a few quotes on a new forced air furnace and AC. I have been reading these forums and trying to educate myself on how to pick an installer, since that seems to be the key. The only thing is I wish is that the installers came out to give the estimates and not the salesmen. Seems like they all have their own selling points and none has even included a Manual J. I do have a specific question though.

I have been told my return is to small for the AC and would have to be enlarged, which made sense. However, the last guy just came in and said my return trunks did not provide the necessary airflow either. He recommended adding 2 more returns to increase the returns by 600-700 CFM as well as increase the size of the return.

My existing system is 16 years old and has an 8x20 return with 2 trunks (8x10 and 8x14)coming in. The house is 2400 sq ft and has 2 6x30" returns and 5 6x15" returns in the rooms. The supply trunks are 8x8 and 8x18 at the plenum and feed a total of 13 18" floor vents and 2 12" floor vents.

The existing system has been fine over the years.

Does this make sense, is it important to increase the ductwork in my system or is there sufficient airflow as is and this is a non issue. Thanks for any help.