Basement returns

[PVR]

My basement is 1500 sq. ft. The furnace is down there. There are four registers into the basement, all directly on the plenum (correct word?). I cannot find any air returns as exist in the rest of the house. There are plenty of returns in the basement leading upstairs but none of these opens to the basement.

How does air into the basement get returned to the furnace?

Peter.

[Jim Sullivan]

In the last house I was in with a basement, there was a return on the main cold air return as it came down from the upstairs. Just a 6" hole with a plenum (?) in it.

[nospam_coloradotrout]