Options for reducing noise out of this return
Posted Dec 3, 2023, 5:54 PM UTC
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You can consider some Dynamat style product stuck on the outside of the tin. What made mine nearly silent was a modern ECM blower furnace, and switching to a round return duct.
1
Oh interesting, I hadn't considered sticking something to the outside. That would be a lot easier to get more coverage. I may start there, thanks.
Our new Lennox system has a variable speed blower, the furnace model is EL296UH090XV48C. I'm not sure if variable speed always means ECM though? Regardless, it definitely gets loud when both zones request heat/cooling.
If we end up replacing the duct to mitigate the issue, I'll have to ask about making it round.
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Yeah variable is and other name for ECM. The round duct won’t make it silent, but it did help. The box duct resonates like a drum skin. Round is stiffer. But if your fan is just a few feet away you are gonna hear it.
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If the return air duct is insulated internally (ductliner) , then that will kill a lot of air noise from the blower. I'd start there. Your hvac contractor won't want to take your existing ductwork out & insulate it & re-install it, so plan on it just being replaced. There might be other options, but I couldn't say unless I was looking at how it is configured. Be sure to explain the goal to whoever looks at it & see if they have a good solution.