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Mucluk 02-17-2012 05:49 AM

Air Return Vent
In my family room, I have 2 air vents and 1 air return vent. When the furnace is on, the return vent is drawing air in as it should, but when the furnace is not running, I can feel cold air coming out of it. This is only happening to the return vent in this room. Why would this be happening?

gregzoll 02-17-2012 07:05 AM

First question, where is the furnace located? Second, are all joints taped & sealed? Third, if you are feeling cold through convection currents, I would look at insulating the duct work. Another thing could be happening, is that you have enough air leaks in the home, that it is pulling air through the system through chimney effect.

Also, do you have a fresh air inlet into your hvac system? That can cause problems, if the damper is not closing after the furnace stops. And where are you located, location helps in diagnosing.

bobinphx 02-17-2012 07:10 AM

there could be an air leak in the return duct system. This would allow cold air from the unconditioned spaces to enter into the return duct. Because cold air falls and warm air rises, the cold air is flowing out the return.

as to why it does not happen in other rooms... the leak maybe near that return and not the others.

I would suggest an inspection of the return air duct system. You can do this yourself or have a pro do it for you. Ill bet that you find there is a leak. If there is, you will have to repair it with mastic or tape or someother standard hvac repair product. I would also suggest that if there is a leak that you inspect the evap coil and the blow wheel for dirt and dust. The leak could have been pulling all sorts of crap into the system and this will cut down the efficency of the system.

Post back what you found and include pictures if you can!!!

Mucluk 02-17-2012 07:43 AM

thanks for the suggestions. The room that this is happening in has a fire place in it, could this be pulling the air from the vent? The furnace is located in the basement. Basement is finished and has a drop ceiling. I will inspect the return duct for any leaks. thanks

gregzoll 02-17-2012 10:05 AM

Yes your fireplace can be causing it.

REP 02-17-2012 03:08 PM

A fireplace with no damper or a stuck damper is literally like a vacuum cleaner pulling money ( warm air) out of the house.

how 02-17-2012 03:23 PM

And one more possibility to add to the mix.
I don't know how old your system is but in my neck of the woods it was common to duct the fresh air supply into the return air duct and open a plenum grill above the furnace for atmospheric furnaces. One of the downsides of these type of instalations was cold air spilling from the return air when the furnace wasn't running. I'd check if you still have a fresh air grill (usually 4") on the outside of the house that connects with your return air ducting..

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