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  1. #1
    Join Date
    Feb 2006
    Posts
    5
    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?

    Specs:
    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?

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Likely not the same exact pattern,or something else changed,like the other grill moving little or no air.

    Bend the fins open a little to reduce air noise,or get one with wider spacing between fins,IF nothing else is wrong.

    Are you sure the 20X20 moves no air,any dampers in the duct system???

  3. #3
    Join Date
    Feb 2006
    Posts
    5
    Thanks Dash.

    The other grill did take air in, but not with this hushing sound. I did do one thing different- I installed some wood blocks behind the wall so I would have something to screw into other than the drywall.

    The weird thing is if I cover some of the slats with my hand or a piece of paper, the noise level DECREASES.

    Should I consider making the opening larger and getting a bigger grill? Any risk in making a return larger?

    The 20x20 grill on the celing of the second floor has no air movement. There are cob webs on the grill. I don't see any dampers on the ductwork in the attic for that return.

  4. #4
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,517
    straghten the fins on the grille a little more
    the noise is harmonic
    the fins are at a angle so as the air crosses it it acts like a whistle. move each fin and the noise should go away

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    The blocks you added likely restricted the space a little,causing the same amount of air to move faster,faster equals mor noise.

    I'd look at how the ducts are routed to that second floor return.Air generally follows the "path of least restance",which means if it can get all the return air required from closer grille it will.There could be dampers in the duct to "balance" this.Likely will need a Pro to check it out,and advise of the best course.

  6. #6
    Join Date
    Feb 2006
    Posts
    5
    Bending the fins back a little took care of it. Never would have thought that the angle they are manufactured at would need to be modified.

    Thanks!

  7. #7
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Please understand ,if the ducts are properly designed and installed and the grilles are properly selected,you wouldn't need to bend them.


    It's an indication that all is not "just right".

  8. #8
    Join Date
    Jan 2006
    Location
    Near Atlanta, GA.
    Posts
    14,630
    I've ran into this too and the problem was the air sucking between the grill and the wall. Try putting a strip of adhesive backed 1/4" foam tape on the back of the grill before mounting to the wall so it will have an airtite seal. Plus it will stop any vibration against the wall.

    Why don't all registers/grills come with seals on the back anyway? I added it to all the supplies and returns in my house.

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by k_fridge
    I've ran into this too and the problem was the air sucking between the grill and the wall. Try putting a strip of adhesive backed 1/4" foam tape on the back of the grill before mounting to the wall so it will have an airtite seal. Plus it will stop any vibration against the wall.

    Why don't all registers/grills come with seals on the back anyway? I added it to all the supplies and returns in my house.


    If the register box/boot is not sealed tightly to the back side of the drywall,adding a seal as you have,will increase the duct leakage at that point.Just FYI.

  10. #10
    Join Date
    Jan 2006
    Location
    Near Atlanta, GA.
    Posts
    14,630
    Originally posted by dash
    Originally posted by k_fridge
    I've ran into this too and the problem was the air sucking between the grill and the wall. Try putting a strip of adhesive backed 1/4" foam tape on the back of the grill before mounting to the wall so it will have an airtite seal. Plus it will stop any vibration against the wall.

    Why don't all registers/grills come with seals on the back anyway? I added it to all the supplies and returns in my house.


    If the register box/boot is not sealed tightly to the back side of the drywall,adding a seal as you have,will increase the duct leakage at that point.Just FYI.
    True, but the boots should be sealed too. I caulked all of mine so I'm not air conditioning the stud cavities.

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