[A/S] furnace

[a9464@xxxxxxxxxxx]

I have a 78 31ft. Excella rear bedroom. The furnance is located on 
the curb side on your left as you walk in the door. If you sit down 
in front of the furnace, there is a heat vent to the left (front of 
tlr) The next one is a rectangular sheet metal vent that follows the 
curb side wall thru the galley, behind the shower, under the bath 
room sink and terminates in the rear bedroom. Also at about the 
shower area, there are two silver round flexable hoses that (approx 
2" dia.) are taken from the main heat run. One of them goes to a 
small heat vent at the base of the shower and the other goes below 
the floor to keep the plumbing warm on cold days. Now here is my ? 
There is one more of those silver round flexable heat vents at the 
furnace. It also goes down under the floor,but is no where near the 
plumbing. It goes straight down inside the furnance cavity. What the 
heck is it for? . Thanx ..Arnie