Eliminate "flutter" noise at register? - http://www.hvacmechanic.com/ Forums
Original message
| PoorJohn
 |  "Eliminate "flutter" noise at register?"
, posted Wed 29 Oct 02:05  
Apologies for a home-owner question - I know the pros get tired of them - but Google didn't give me an answer to a hopefully simple problem.
In SoCal the nights are usually cool so some time ago I put in a "night air" system that simply used a duct fan in the attic (near a vent) that sucked air in and delivered it to a separate register in each of the two bedrooms. Wife happy.
Recently decided that filtering the air would be a good idea and learned about back pressure and propeller fans, so bought a nice box with a centrifugal fan and incidentally more airflow - about 300 CFM.
Now the register in our bedroom makes a "flutter" kind of sound. Not particularly loud except in the quiet of the night. The other bedroom is quiet, period. At first I had a rattle due to the register vanes (12x6 adjustable) being loose. I bought a new register and the rattle went away so I could hear the low flutter noise. I then put some tape on the vanes on the old register so it wouldn't rattle, and found that it makes exactly the same flutter/rumble noise.
Air handling is 8" flex duct out of the ventilator box to a "Y" thence to the two registers. Thanks for your comments.
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Replies:
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| Schock Therapy
| "Re(1):Eliminate" , posted Wed 29 Oct 19:51
My first thought would be that the flex duct may be the problem. That stuff creates a huge amount of turbulence, and could very easily be causing the sound you are hearing. you could try replacing the flex duct with rigid metal duct. It really isn't that hard to work with, and has far better airflow characteristics than flex. You can still use the flex to connect to your diffusers, but do as much as possible in tin.
It's only a shock if your not expecting it!
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| | PoorJohn
| "Re(2):Eliminate" , posted Thu 30 Oct 00:22
Thanks a lot for the suggestion - I'll give it a try.
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