I have a new 90% + furnace and there is a constant hissing/static noise in the ducts.
The hissing noise is coming from the heat exchanger of the gas furnace of the new unit. With the unit off and listening in the ducts a light tap on the exterior of the furnace unit leads to a metalic vibration sound that fades away in a couple of seconds. I imagine when the fan is on this vibration is amplified a great deal. The sound is louder as the fan speed goes up.
The contractor says nothing can be done to stop this sound in the heat exchanger, it is normal. Is it?
They want to start duct modification to damper the sound, I don't plan to go this route as we can hear the hissing in five to six ducts. Are there quiet high efficiency furnaces out there?