I have a 2000 sq foot ranch house in Phoenix, built in the early 70s.
Until a few weeks ago the house used the original Carrier split system
for cooling. I believe it was a 4 ton unit. The duct work in the
house is the large bent metal type, large enough for a small child to
crawl through. The air handler blows up from a closet in the hall to a
"T" of duct work that goes down two hall with ceiling registers in each
room. The old system was quite--as is our large Master Cool Evap
cooler that also feeds into the duct work. The new Trane air handler
has a large amount of air noise coming from the registers. There is
little noise at the intake. The new system measures between 69 and 72
dB noise at the registers, the Evap cooler noise level is below 60 db.
The squirrel cage blower from the old Carrier system was about 13"
across and was belt drive, the new Trane blower is about 9" across. It
looks like the old low velocity/high flow blower was replaced with a
high velocity/high flow blower and this is causing all the noise.
Does anyone have any ideas on how to quite down this system? The big
open ducts transmit the noise very well. I've been told by a number of
AC companies that no one makes a low velocity high flow blower anymore.
The blowers are all designed for the flexable duct work that most
homes are now built with.
So far we've tried insulating the inside of the duct work where the air
handler connects but this had little effect.