Good Morning. I have just finished the divisions and gyprock in my basement and I figure I'm going to have some problems since the only cold air return duct I have down there is in my son's bedroom. Right now I have 2 12X16 bedrooms, a 10X11 full bathroom/laundry room, and about an 18X20 open area which will be my family room. I also have a small area where the furnace/freezer/hot water heater are, as well as some storage under my stairs.

I was planning on installing a cold air return on the wall with it's back to the furnace room, since it's easy to get in there and do it without having to take anything apart. I plan to install the cold air return about 8" from the floor and connect it to the underside of the cold air return duct, since I cannot get at the top or side of that duct. Is installing it on the underside going to cause a problem or is that an accepted method? Also, I was going to use 4" round ducts...is that ok?

Please let me know...thank-you.

The first question to you....what size in input BTU's is your furnace ??? Look on the ID plate where the model number and serial number is written, and what make is it ??

Judging by the serial # tag on the side, it seems to be a Heil. The model number is
N9MP2075812B1. The Serial # is A051491824. It's less then 3 years old. I looked all around the thing but I can't seem to find a manufacturer's tag showing the details of the device. It was a rental from the gas company when I bought the house, and then I bought it outright. Maybe the gas company covered or removed the OEM tag.

Please let me know what you can find out.

Thanks!