Eigenvector wrote:
I have just a basic question about the vents for my gas furnace.

There is one large vent that leads directly to the furnace main
ducting - its located on the floor and is probably about 18" x 30". What
is the vent, is it a return vent, a heater vent, or something
else?

Likely the return duct. Turn on the fan and see if air is going in or
coming out.

--
Joseph Meehan

Dia duit