Had this unit installed in November. Immediately began hearing noise from the external fan. In the house it sounds like a single cylinder engine starting and running outside - my wife calls it the snowblower! It is mounted on aluminum brackets attached to the cement foundation, but the sound is produced by the fan blade. Outside the noise is very evident also - neighbours are complaining. The installer who has 30 years in business assures me this is normal noise for this unit. My contention is that if this is normal, I am not a happy customer and cannot believe Trane would design and manufacture such a product for residential use. The fan has 2 large sharply pitched blades. The noise is not from the motor but rather the blade slap against the air. Does anyone have a suggestion? Thanks!