Hi,
A friend has a Kaussmann heat pump in her home. It produces a noticeable but not loud whine.
Heated air is dispersed by a centrifugal fan with squirrel cage about
80 cm long x 9 cm diameter. The blades are about 1 cm wide and 10 cm long. 10 cm x 8 segments = 80 cm.
One of the blades is missing from the rightmost segment of the squirrel cage and that may be the source of the whine.
According to the owner, Kaussmann is defunct. Any ideas about repair?
Thanks, ... P.