I have been reading for several months, learning a lot from the professionals on this board. Everyone agrees that most problems come from poor installation. I am going to install a dual fuel system with 13-14 SEER HP with probably 90%+ gas (2-stage, VS) furnace back up.

So, my question is this: What are the key considerations an informed homeowner should pay attention to when the installation is underway? Should I insist on all metal pipes, or is some flex OK? Is mastic tape OK or should I insist on something else? What about the connections at the unit? If any of you guys would like to give me your top five or top ten things you see done WRONG, then I'll know what to watch for during install. I've remodeled houses for 15 years and had several heating systems installed over this time. I worked for an HVAC company in college, but just for one summer. I'm by no means an expert, but know more than the typical homeowner. Again, thanks for all the great information and responses to previous posts. One other question: In a relatively mild winter area like East Tennessee, would I be better off putting more money in a higher SEER HP (say 15,16 or so rather than 13,14)and saving a little money by going to an 80% two-stage VS gas furnace rather than spending more money on a 90+ gas furnace and lower SEER HP?

Responses would be greatly appreciated.

Jim Pryor