I know you are double checking your new job but do not worry. The company
who installed it would not put themselves in a situation where they need to
go back under warranty.
They are right about the sound. When I use to install I would add extra flex
duct in the attic to cut down the sound of the blower assembly. I like to
increase my size of return, By code you would use 14" flex for a 2-ton
system but I would use 16".
I am assuming that the duct you are talking about is flex. Here in South
East Texas flex duct is used allot.
HVAC Service Technician
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