Duct dampers or just partially close registers?

[Garyl53]

Hi,
I have several floor registers that are really blowing air and I am keeping them partially closed. Is it better for the distribution system to put dampers in the ducts near the main plenum or does it not matter?
Gary

[big johnson]

Best to install a balancing damper at the branch where it exits the main trunk.

[sktn77a]

Partially (or more) closing the register will produce wind noise. Closing the dampers at the branch will do the same at the damper but it won't be as audible in the room. As to whether it makes any difference to the performance/reliability of the system as a whole, I'll let someone more experienced answer that.

[dash]

Partially (or more) closing the register will produce wind noise. Closing the dampers at the branch will do the same at the damper but it won't be as audible in the room. As to whether it makes any difference to the performance/reliability of the system as a whole, I'll let someone more experienced answer that.

Makes no difference except as noted above.


However closing register or duct dampers too much canraise the static
(resistance to air flow) too high and damage the equipment.The better the duct system was designed and installed the better you will be able to balance it with either method.

[motoguy128]

Audible noise around a round butterfly valve (assuming we're talking about round supply ducts), should produce much less noise than the flaps on a register.

Also restricting flow at the register can increase loss at any leaks on that supply branch. Using a damper upstream essentially creates a pressure drop across it.

Balancing issues from inadequately sized branches or trunks can definitely be a problem. Imbalance because of too little size reduction at the end of the main trunk, would increase static, but shouldn't cause any problems.