Can you quiet down cold air return

Old 04-01-03, 07:37 PM
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Smile Can you quiet down cold air return

I just had my HVAC replaced with a new natural gas York 94% 2 stage upflow with 3 ton AC. My cold air return is just upstairs from the unit, and as it comes on the slow speed of the fan is very quiet, but as it speeds up the noise of the fan echos up the return. Add the higher volume of air being moved by the grill, and we turn up the TV just to hear it. My dealer is not sure how to make a change here. Duct size appears to be proper for the size of the unit. We have more of an echo problem.
Old 04-02-03, 05:00 AM
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A return air grill is the most quiet when it is far from the furnace. Also depending on the construction of your house there should be several return grills.
A main return line should be run for a good portion of the length of your house and then tap off to all the different rooms.
Old 04-02-03, 05:49 AM
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For a 3 ton system, you need to be able to move at least 1200 cubic ft. per minute. That is a lot of air. I suspect that your duct system is undersized. Maybe the trunk is adequate. 22 X 8 would suffice at the unit. But you should count up the total number of returns. You would need 12- 6" ducts or 8- 7" ducts or 6- 8" ducts. A stud bay with a 14 X 6 grille counts as an 8" duct. How do these rules of thumb stack up to what you have in your home?
A properly sized duct system is very quiet.

Old 04-02-03, 11:43 AM
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COLD AIR return

I have found lots of times on the cold air return if they made it big enough .We take scrap fiber glass duct board and line the cold air duct some with it. This helps a lot. Then theres the grills that resonates this you have to do by just bend the grills a little ED
Old 04-02-03, 05:14 PM
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i am with ed

down where he lives there are a lot of units sitting on a return box with a through the wall return. i lined my dad's in palm beach last summer with ductboard and reduced the noise a lot. this may not apply to you, as i am not real sure what you have, beware that lining a plenum will reduce its inside volume and cut down on airflow capacity.
Old 04-03-03, 05:51 AM
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Thumbs up Problem solved - ->> solution

Two things took place to correct the noise. First and most importantly, the installer had not adjusted the fan speed. The variable setting was defaulted to it's highest speed. Secondly we cut in another cold air return near the unit itself. Shazam, problem went away. I can hear the unit as the controler turns on the second stage of heating or cooling, but it is nowhere the DB reading we had before. On low speed, you must really listen to even hear it run. Same thing with the unit outside - low sound levels. The exhaust gasses going out the PVC appear louder than the condenser / compressor.

Thanks for all the input!


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