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StumpedTechy 10-09-2007 06:40 PM

Newish larger A/C unit much louder? What can be done?
Okay this has been driving my family buggy. When we first bought this house 5+ years ago I think it had a 3 ton unit for a 1,800 sqare foot house. At the time A/C was not that noisy. We knew we were having to do an addition to the house but in the intrum we had the A/C conk out on us about 2 years ago and we decided to go for a 5 ton unit that would be able to support the addition as well (which has not been done and probably is about 2 years off from architect to conception).

Since this new unit the A/C has been LOUD. I am not taking mechanics or ratteling or anything it is just pure wind velocity noise. If I close the vents in any of the room the partial closing makes the vents whistle. On a few of the older vents they actually just can stay open or if I put it 1/2 way it just snaps shut (I assume to the force of the air as this will only happen when the air is running).

Its great to have a cold house but how do you get it so you don't feel llike your in a wind tunnel every time the A/C turns on?

I read somewhere to get bigger vents? but what size should I go to most of my vents are already 13x13 square and quite large....

ON a side note if it is purely the tonnage of the unit an the square footage it can handle can I assume since were adding 1/3 the square footage the noise level will also reduce about 1/3rd?

I am so frustrated with this noisy house.

glennjanie 10-09-2007 08:16 PM

Hey StumpedTechy:
Yes, you are correct about the larger capacity being the reason for the noise.
When the addition is in place and takes its share of the air, the noise will subside considerably. Meanwhile, I would not recommend closing vents or restricting the air in any way for fear of damage to the fan motor.
The unit is simply oversized and sounds like it. Some things you could do to reduce the noise are, 1. insulate your return air duct inside to lower the fan noise, 2. insulate all your ducts on the outside and only on the inside of the boot that holds the register. The external insulation should be 2" fiberglass with a foil outside, while the internal insulation is more like a pressed fiberglass board 1/2" thick turn the black side in to the opening to help hide the insulation it must be glued to the duct and should be pinned to the duct with a spot weld process.

CraigFL 10-10-2007 05:26 AM

Maybe move your fan motor speed tap one step slower???

glennjanie 10-10-2007 09:40 AM

Slowing the fan will cause icing on the evaporator coil. There must be good air flow over the coil.

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