Finnicky I generally agree with the remarks from the previous post. It should be noted that on a BTU basis, the operating cost between HP and nat gas is basically a wash. See below. Cost per 100,000 btu of useable heat Heat pump: $1.10 Natural gas:$1.09 Like the other posters, I am surprised about the price of the XL16c and I also prefer the Trane over the Carrier package units. I would recommend a new lineset. What thermostat has been proposed? It makes a difference.plus I would want an outdoor thermostat to control the switch point between HP and nat gas. What size furnace is available for the 3 ton dual fuel unit? I would add the Ext warranty and a whole house air filter cabinet. Perhaps you might ask about the HW Mdl 200. If you have any hot/cold spots within home, now is the time to address. How many returns does your home have? You want to be certain they are sized correctly, located strategically for best airflow and overall comfort. IMO

I've been doing some reading, lots of reading, LOL, and came across an article saying that home designs like ours, two stories with a vaulted entryway and staircase are a nightmare for HVAC. It recommended two systems: one up, one down for real comfort and said it was really more economical than a two-zone single system. We've thought about putting a second unit in the attic, but it's something that probably has to wait until the house is paid off. In the meantime, I've been thinking and finally realized that there is a place we could put another supply duct. It would be on the far side of the door into the garage. The current duct trunk is on the other side of that door. It's right above the closet in the guest room, so we should be able to go through there and straight up to the attic--hope the attic joists aren't in the way. The run would be about 10"-11" x 24" in size and approx 58' long with 2 right angle turns. We're thinking it could handle about 900 CFM and hoping we could take our master bedroom and vaulted ceiling bath off the current duct and supply them with that. Our bedroom gets a little, but our bath is at the end of the current run and gets basically no air. With our master suite off the main trunk, I'm pretty sure the other upstairs rooms would have plenty. Does that sound like a duct that would work? Hubby is also thinking that if we did it with ductboard, he'd be able to do most of it himself, except for the connection to the plenum. He's pretty good with carpentry, plumbing and electrical, but has only worked on a/c in cars. And if I hadn't mentioned it, after measuring our house, we're really around 2,600 sq ft, not the 2,400 sq ft we had thought we had. Sorry, one more thing, if we have 1410 CFM now and add 900 CFM with another duct, going to about 2500 CFM, does that mean we'd need any certain blower size? Or do we just go with what the manual J says, assuming I can find the manual or a tech to do the calcs for us?

They're all just guessing without a load calc, which is sometimes hard to get done. 3 tons sounds crazy for just over 1000 sqft, but only a load calc will tell for sure. The old ducts probably need plenty of attention to get get the airflow needed for the new system. That's step 1.

is the trunk line insulated internally? what about the supply ducts from the trunk line? I'd be looking inside the trunk line into the ducts to see if the were wet on the inside also. I wouldn't trust without verifying myself. who puts in a trunk line before the roof is on? and if the trunk line was installed...why wasn't it mastic sealed? if duct system is properly sealed..it doesn't get rain inside of it. pics would help. best of luck