Dampers in air return duct?

[Exterous]

Was doing some work and noticed that what looked like a piece of sheet metal near the base of the floor on a second floor air return. Took off the grill on another and same thing. A damper I assume? Poked at it with a fish stick and it moved easily but went back to its 'closed' position when I was done prodding.



Not super easy to see it but you get the idea.

Why would you want a damper on an air return? Even though it opened easily to my poking I would think you would need pretty decent suction to force it open to allow reasonable flow of hot air back down. A google search doesn't show anyone recommending you have one in place but there isn't a lot of discussion on it which leads me to think having one is wrong?

 

[Exterous]

As an update I opened up two more of my air returns and one had a damper while the other didn't. Not sure why the difference. Both of the new ones I opened were dedicated air returns for that room tying into the main line in close to the same location. It does get a little warm upstairs still so I am wondering if removing the dampers will help with removing the hot air?

 

[Carson Dyle]

Reason it out... What could be the purpose? If it was DIY, what was the thinking of whoever installed them?

How about: What if someone wanted to save on heating/cooling costs by shutting off a room? They can easily shut a register, but the return remains open. Would having the damper further isolate that room? I could see some logic there. Without it, heated or cooled air would enter the room to some degree. Although you'd think that if the room was closed off, back pressure in the room and a lack of airflow would mostly prevent it.

How about: Warm air rises. So if you're cooling the house, the A/C shuts off, the dampers close, warm air has less ability to rise through the returns to upstairs rooms.

Both ideas may be completely wrong, but there had to have been some twisted logic to it.

 

[Exterous]

Reason it out... What could be the purpose? If it was DIY, what was the thinking of whoever installed them?

How about: What if someone wanted to save on heating/cooling costs by shutting off a room? They can easily shut a register, but the return remains open. Would having the damper further isolate that room? I could see some logic there. Without it, heated or cooled air would enter the room to some degree. Although you'd think that if the room was closed off, back pressure in the room and a lack of airflow would mostly prevent it.

How about: Warm air rises. So if you're cooling the house, the A/C shuts off, the dampers close, warm air has less ability to rise through the returns to upstairs rooms.

Both ideas may be completely wrong, but there had to have been some twisted logic to it.

I'm not sure. There is no way to operate them manually as they are completely behind drywall and about 7' down from the air return grill. You can kinda poke at them with a fish stick but they dont appear to stay open.(Just flop back closed) No signs of cuts in the drywall (from the inside of the duct) and the previous home owner was really bad at DIY so I doubt thats the situation here. Still confused about why the rooms are not handled uniformly.

 

[herm0016]

they open when the pressure below them goes down? so they do not do any damping, just a check valve to prevent air going the wrong direction. Looks like some kind of fire block to me. you mentioned a 2 story house, usually the walls have to have blocking to prevent fire jumping floors inside the walls.

 

[Exterous]

they open when the pressure below them goes down? so they do not do any damping, just a check valve to prevent air going the wrong direction. Looks like some kind of fire block to me. you mentioned a 2 story house, usually the walls have to have blocking to prevent fire jumping floors inside the walls.

Thanks - its not something I've seen before and the inconsistency surprised me