older air vents?

[michaelheerwald]

I have just purchased a home that originally did not have refridgerated air but did have central heat. The best I can tell all the air blows out on the lower vents close to the floor but above each one at the ceiling there is another vent which has a cylinder in it which stops just below the opening for the grate, the forced air is coming down inside the tube to the vent on the floor, but on the upper one there is a knob which can be pulled out or turned a quarter to open the tube. My main question is why does the knob pull out like it does what is its purpose? There are also the round vents in the ceilings in most rooms! The outside unit looks rather old, like 40 years or so but the inside unint looks fairly new.

[jadnashua]

It may be the duct work is set up for a/c. A/c is more comfortable if you drop the cold air from the ceiling, rather than try to push it up from the floor. The flap may be a damper to shut the flow off to the floor ducts.

[michaelheerwald]

Sorry wasn't clear on that but it does have a/c and the knob can turn about a quarter turn which does close the duct off from the ceiling, but the same knob pulls straight out about two inches and this is what I can not figure out the pupose for.

[jadnashua]

Regardless, they may have put in ceiling ducts to allow for better a/c operation if it was ever added. Try taking a picture of it and posting it...

If you turn the damper (I'm assuming it is a damper), then turn the thermostat's fan to on, does it block air to the lower registers and now direct it to the ceiling?