I have a new HVAC 90 Plus high efficiency upflow gas furnace that was installed 3 days ago. It makes a high pitch noise that sounds like a very small hairdryer on high which I assume to be the fan blower. It starts up the same time as the fan so that must be it. It reaches a constant pitch and stays on as long as the fan is on. I have metal ductwork. The noise seems to be coming out of the return. You can hear it from every room on this floor but it doesn't seem to be coming out of the vents. You also can hear it in front of the gas furnace and in the basement in general.
They have tested every vent, the static, and other things, and decided to replace the blower today. The blower they took out was very hot so we were hoping that was it. The noise still is there.
I have read some of the posts on this forum that sound similar to mine, but I can't find where anyone came back to the forum and said what resolved this problem. If you know of a resolution, please reply.
Someone on this forum said to try this to someone else but I don't know if it worked.
Surely other people have installed high efficiency units on metal ductwork and gotten rid of this air blower noise.