When I have my central Ac on the air coming through the registers is extremely loud. I have a Trane XL12 for an 1100 square foot house. My return is 12x24. Is this too small? Could that be the problem? Do I need to add more registers to large rooms like the living room? I only have 1 in the 12x16 living room which is a 12 inch square register.

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Originally Posted by KWP

When I have my central Ac on the air coming through the registers is extremely loud. I have a Trane XL12 for an 1100 square foot house. My return is 12x24. Is this too small? Could that be the problem? Do I need to add more registers to large rooms like the living room? I only have 1 in the 12x16 living room which is a 12 inch square register.

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Whenever you move air weather supply or return in a small or marginal duct size you will have more air noise than if the duct was a bit oversized. Here is a very simple duct chart so you can do your own homework. The CFM rate on this chart does not take into consideration the 25% loss at the registers due to the grill face.