I live in the Arizona desert and am looking to upgrade the original 21 year old AC/furnace systems in my home. The house has 2 split systems with AC and gas furnaces. A heat load analysis has been done indicating that one system needs to be 4 ton, and the other 3 to 3.5 ton. I plan to stay in the house long-term, so I've been looking mainly at high-efficiency systems with dual-stage heating and cooling and variable blowers. I'm only looking at 80% efficiency furnaces due to the low heating needs. I plan on sticking with the standard 1" filters.
So far I've gotten quotes on Trane, Lennox, and Amana, which seemed to be the most recommended brands based on my Internet research. Relative pricing ranks as follows: Lennox HSX-19 (highest), Trane XL19i (few hundred less), Amana RSG Ultron 16 (another few hundred less). These quotes were from established reputable contractors and I didn't see any reason to prefer one over another. So the choice comes down to the equipment. Since the initial cost differences are relatively small, my primary selection criteria are efficiency and reliability.
Note that I've pretty much eliminated Carrier from the running due to the comments I've read about coil leaks.
I'd appreciate any comments about these equipment options, or any other suggestions I should consider. Here are a few specific questions:
- What payback period should I expect on these high-end systems? I've read other posts saying they'll never payback, but keep in mind that I live in area with lots of 100+ degree summer days.
- There seem to be conflicting opinions on whether the refrigerant lines have to be replaced when upgrading from R22 to R410a. Is this really necessary? In my case replacement may be difficult since they run under the house. The quotes I have assumed that the existing lines are reusable.
- Some posts say that the main benefit of the dual-stage compressors is humidity control and not efficiency. Is that true? Humidity control is not a big concern where I live. Improved efficiency and temperature uniformity are more interesting potential benefits to me.
Thanks in advance for any info!