I am in the process of replacing ducts and need a to do something with the noise coming out of the furnace at the same time.
Right now its all flex duct with sheet metal plenums, Carrier Infinity 96 is mounted vertically, sits on a slab floor.
At 1500CFM noise is horrible, the whole unit and plenum vibrates, The problem is my office is across the wall, i can feel vibration on this wall with my hand!!! And unit does not even touch the wall, 1" air gap
The ducts will be replaced with sheet metal ones, maximum supply trunk velocity 700 fpm, branches 600, on the return 600/400 fpm respectively.
I consider the following solutions:
1. Add a flexible connection in between the unit and the main trunk
2. Add anti vibration pads under the unit
3. Pull the unit another couple inches away from the wall
4. Add sound dampening foam to the underside of the blower compartment
5. Add sound absorbing foam to the underside of a 90 degree main trunk elbow to attenuate transmitted noise
6. sound proof the wall with a low density polyurethane foam.
Any advice is highly appreciated! I have only one chance to get it done right