I just installed a new grill for my return vent on a forced hot air system and noticed that the noise level has increased. It's the same grill pattern as the old one. If I take the grill off while the fan is going, there's very little noise. But when I put the grill up, it's almost whistling because of the volume of air being sucked in.
Any tips on how to cure this problem?
Return vent size: 6x20
Home is approx. 1200 square feet.
Home built in 1995
Also, on the 2nd floor near the attic door, there is a large vent, maybe 20x20, I assumed it was a return air vent also, but there's no air movement. It has large ductwork hooked up to it and it appears that it would tie into the same duct as the other return vent that has lots o' air movement. Anyone know what the deal is?