[scott2004]

I recently had a new AC/Heating system installed with all-metal ducts (insulation on the exterior) and all-metal boxes. I went with all-metal to facilitate cleaning of the ducts. The system includes a 3-ton Carrier condenser, 3-ton Carrier air handler, Ultravation UV filter, Ultravation Hepa filter, 4 air returns, all covering 1650 sq.ft. under air.

The problem I am having is that in the cooling mode, the system produces an air noise through the ducts which is VERY LOUD. The technician said the noise is created by an uneven/turbulent flow of air exiting the air handler, and reccommended interior insulation of the plenum--the duct-work just outside of the air handler. Will this reduce the air noise? Are all-metal ducts always noisy? The sound produced is a bit like the noise in the interior of an airplane... Thanks in advance for your comments.

 

[HVAC Doc]

A properly designed duct sytem can be quiet but I suspect that you had previously ductboard? Flex duct? A little of both? Comparing duct board/ flex duct to metal is an apples to oranges comparison. Yes, lining the plenum on the inside will help reduce some of the velocity noise but also making sure the proper air speed is set, dampners set in proper positions (if any are there and if there aren't maybe there should be), and air gaps in returns/suppys being sealed will also help. Also, depending on how old of system you had before, you may have gotten "used" to the sound it produced and are not used to todays higher airflow systems. What might be an unbearable "loud" nosie to one person might not be of any consequence to another. Not saying it is all in your head, just that there could be some other mitigating factors that we here on the net cannot hear or see in person.

 

[Glasshousebltr]

My grandmother had some noisy metal ducks, the wings would spin when the wind blew.:cheesygri

Bob

 

[mdshunk]

The sound produced is a bit like the noise in the interior of an airoplane.

I've never noticed any special irritating sound when on the interior of an airplane. Some noises drive some crazy while not bothering others. I suspect that if you go with the duct lining the tech proposes, and possibly adding canvas connectors on the supply and return at the AHU, you'll attenuate the sound enough to please you.

 

[scott2004]

Quick follow-up question

Thanks for the response. I appreciate your time. Could you kindly explain to me what a "damper" is and how it works?

 

[HVAC Doc]

Thanks for the response. I appreciate your time. Could you kindly explain to me what a "damper" is and how it works?

Sure. A dampner is like a water valve so to speak. It is a metal blade inside your ductwork usually in your main trunk lines or at the beginning of your supply lines that has a metal handle on the outside of the duct that allows you to move it to either cut down or direct more airflow to various parts of your duct system. Not all ductwork has them installed and you may or may not have these. You can also try adjusting the airflow with the "dampner" inside your registers although these are generally not quite as effective as ones installed in the duct system itself.

 

[747]

Glasshouse

LOL I like that :cheesygri

 

[Tomgeer]

I recently had a new AC/Heating system installed with all-metal ducts (insulation on the exterior) and all-metal boxes. I went with all-metal to facilitate cleaning of the ducts. The system includes a 3-ton Carrier condenser, 3-ton Carrier air handler, Ultravation UV filter, Ultravation Hepa filter, 4 air returns, all covering 1650 sq.ft. under air.

The problem I am having is that in the cooling mode, the system produces an air noise through the ducts which is VERY LOUD. The technician said the noise is created by an uneven/turbulent flow of air exiting the air handler, and reccommended interior insulation of the plenum--the duct-work just outside of the air handler. Will this reduce the air noise? Are all-metal ducts always noisy? The sound produced is a bit like the noise in the interior of an airplane... Thanks in advance for your comments.

Yes its common and insulating the duct work will help. However I've come across jobs where the duct work is undersised cause high level of noise as you discribed. Where are you by the way? I ask becuase of the system size compared to your house size. In chicago with new construction you could cool the same space with 2.5 ton. But only if the manual "J" alowed. Did they do a manual "j" ? ( load calc)