Getting quotes for a complete new central gas heat & a/c, no two quotes alike so far and I'm really getting discusted. Some give quotes on the phone, some on site want to replace ducts & copper lines, some say only the copper lines, some say they can use the current ducts & lines, some say R410a only, others say R22 or R410a. All of them say we have to add a disconnect on the outside and a plug-in on the inside but that's Not included in their quotes. All of them say the 8" vent has to replaced.

It seem like no matter what I tell them we want, they quote what they want and how they want to install it. I argued with one guy for 20mins about not wanting a variable speed motor, I gave up and let him quote it to get rid of him, total waste of time.

I understand if I want a 90%+ afue furnace they will have to replace the vent with a plastic one to handle the condensation, which equals more labor and most are hesitant to quote that system, the ones that do have it at $2k over the 80%. This area's avg heating days are 62 and temp avg is 35 degrees. Avg cooling days are 172 and avg temp is 95 degrees. The house is single story, 2500 sq ft, 4 returns, 11 windows, 16 registers. Old system gas furnace is 160k input/128k output, a/c 5 ton, it's kept us comfortable.

The old system's relay controls have finally given up and I haven't found someone talented enough to rewire it. There are no leaks in the ducts, there have never been any leaks in the a/c and the lines from the a/c are the larger size that is installed on current units. If we go with an 80% afue furnace, do I have to disturb the roof with a smaller vent? Somehow I don't think their quotes will include fixing the roof either. Comments?

Good luck getting one solid uniform answer on this one. Everyone does things differently and every company has it's own guidelines as far quotes are concerned. I would like to give you this one piece of advise though regarding variable speed motors: RUN FAR AND RUN FAST! When, not if, they fail they are very very expensive to replace.

Get a 90% plus unit and vent it out the side of the house. MarkwithaK is correct about the variable speed motors. They are DC units and are two piece. The end bell contains part of the electronics and the other part the actual motor. Most servicemen do not have the proper tools or knowledge to check one out correctly which causes a lot of motors to be replaced when they are not bad.

If you want variable speed then have your installer install a Fan Handler control. Been using them for over 20 years with no problems and they are automatic in operation.