Last fall, I had the following dual fuel system installed:

American Standard Heritage 16 Heat Pump (2 step compressor)
AS Freedom 80 2 stage VS furnace
Honeywell IAQ thermostat

I was quite pleased with the system performance over the winter months. However, during the summer, it is not cutting it in cooling of the 2nd floor. After reading this board, it seems like this is quite common in a 2 story home and I need to look at zoning to correct my problem. While I have read just about every thread on the board about zoning I have a general zoning question as well as a few system specific question to ask this group before I start getting quotes from the pros. BTW, if anyone is in the northern Colorado area and would like to bid, please let me know.

My basement is finished with most of the trunk lines of the HVAC system “hidden” behind drywall down the center of the basement ceiling. However, the runs off of the trunk lines for the first floor run above a drop ceiling and are easy to access as they run to the vents. The runs that come off the trunk lines and go straight up for the 2nd floor are visible, but nearly impossible to access without major work. My plan is to just have 2 zones. I want the basement and the first floor to be zone 1 and the 2nd floor (bedrooms) to be zone 2.

General zoning question

All of the conventional zone systems I have seen illustrated basically have a controller, plus damper(s) and a thermostat for each zone. I had an idea about an unconventional system. With my plan for 2 zones, I never expect the 2nd zone (upstairs) to be satisfied and the 1st zone unsatisfied. And the fact that the ducting to the 2nd floor is so difficult to access, would it be possible/reasonable/a good idea to have a system with a zone controller, thermostat in each zone, but only one set of dampers that control only zone 1?

Specific system questions

I read in another thread about zoning a Trane XL16i (same as AS Heritage 16, right?) and the difficulties that people were having with it.

1) Can an AS 16 be properly zones without loosing a lot of the features that I paid for (VS, staging, etc.)?
2) It seems that if I zone, the zone controller takes over a lot of the functions that the IAQ now performs. Is that correct?
3) If 2 is yes, do I still need the IAQ and do I need an IAQ for the 2nd zone?
4) If I keep the IAQ, does the EIM no longer get used or does the EIM connect to the zone controller?
5) Also looking at the different companies control boards, there don’t seem to be a lot of choices to match with the AS 16 dual fuel system. What controllers can handle my system? The only one I found that can handle 4 stages of heat is the EWC UZC-4. Is that correct? Are there others?