<strong>Yahoo Message Number: 111622</strong>I have two rooftop AC units and they are both Duo-Therm model 630516.321. The rear unit is very quiet but the front one make much more noise. The fan noise is about the same but if I had to guess I'd say the compressor on the front one is the source of the noise.<br/><br/>Anyone else have this experience?<br/><br/>Jim Coshow<br/><br/>2005 Inspire 51501