We had a new Maytag Heat Pump installed last year, and shortly after installation I noticed a pretty loud (you can hear it everywhere in the house) groaning noise coming from the Heat Pump. The noise seemed to occur when the heat pump would cycle into defrost (or at least that is what I think it was doing). It seems freon related, and I think the noise is carrying through the lines.
I called the installer, and he had the factory rep come out and he did get to hear the noise. The rep said that all scroll compressors make the noise, and it had to do with the heat pump going into defrost mode. We went on to say it was 'normal', and nothing to be concerned about.
Once summer came, and we switched to A/C we never heard the noise again. Now that it's winter again, the noise is back - and it seems like it is louder than last year (although that could be my mind playing tricks on me). Also, it seemed like it would only occur once per heat cycle last year, and this year it seems to be occurring twice as often (2 times in a cycle).
What I would like to know is if any of the professional installers on this site are familiar with such a groaning noise being 'normal' operation on a scroll based heat pump. I don't want to start a fight with Maytag if it's really true that this is normal operation... but I just can't believe this is by design. To me it sounds like a $5,000 piece of junk (with all that groaning).