I bought a new house with two 58STA units: one in the garage and one in the attic. They heat/cool the house well. THe unit in the garage drives air into ducts in my crawlspace. The problem is the retun come directly out the top 30 inches and then 90 degrees into a 14x20 replacable filter and grill in my living room. WHen the motor comes on for AC/heat you cannot hear the TV. When I remove the filter the noise is much louder so I don't think I have an air restriction problem. I can stand under the return on the second floor and I cannot hear it at all. In fact, the unit is so quiet I had to climb into the attic before I bought the house to convince myself it actually had a 2nd unit up there. I therefore assume I have either a duct problem or a motor speed problem with my first unit.

1. Will adding ductwork with a few 90 degree bends kill the aircraft engine noise this thing produces?
2. Would have a tech come out and adjust the motor speed be the right thing to do?
3. Is it possible to upgrade this furnace to a variable speed motor without replaceing the entire furnace?

Thanks
Robert

Hi. It sounds like the return is very small and you are getting the whistling/wind effect. I don't know the square footage of the area it is heating and cooling but out side of AZ consider 500 square feet per ton and in AZ 400 per ton. That's how you can get a good Idea what size you need. If it is over sized that happens because duct is to small. Find the size return air duct and grill you need by measuring the supply air duct. They should be the same it is that simple. Hope this helps. I accept tips. LOL.

The only way to make it quieter is going to be relocate the furnace or return air grill or replace the furnace with a variable speed. But for some reason I think you already knew that.

I would check and make sure you have a big enough duct system return and supply. Replacing unit will simply give you a new loud unit if duct work is to small and or return grill is simply to small. You have not said what size unit it is by the way.

The unit is a Carrier 58STX070-13112. IT has a 16 inch diameter circular top return. Neither the return or the unit can be moved. The house is 2,800 sqft with about 2000 sqft on the first floor which this unit services.
The suction on the return is incredible. I have to actually pull hard on the filter to get it out of the return after I open the return grill.

I read on the web that users cannot change the motor speed of the 58STX themselves. It appears that I am going to be stuck calling in a Carrier tech but I am afraid he is just going to try to sell me a new furnace.

Thanks for your help.
-Robert

The register is to small and the 16 inch may be pushing it as far as being to small. That is most likely a 4 to 5 ton and a 20x25x1 would do the trick. If you don't believe me take the return duct off the return grill and it will be quieter.

18-22 inch duct would make it very quiet. If it is not a very long run you can buy some say 20 inch flex at home depot and run it yourself easy and just leave the old grill there and get a new one the right size and put it by the t-stat is all.