I have a 23 YO two story home in SE PA, about 4000 sq ft. Currently serviced by two 3 Ton carrier heat pumps. I am new to the home (and the area), so I have no idea how it performed last winter.

The upper unit (in the attic) uses strip heaters for second stage heat. The lower unit (in the basement) uses fuel oil for second stage heat. The lower unit works great (heat and cool). The upper unit, not so much, but I'll address that in a separate thread.

The chimney sweep has indicated that my chimney (for the fuel oil) is not in good shape and needs to be lined, to the tune of about $1500. I've also discovered that fuel oil is about $3.50, while propane (which I require for other appliances) is about $2.50. I know propane has less energy than fuel oil, but that the furnaces may be more efficient, and require less maintenance.

So I'm considering replacing the lower system from HP + fuel oil to HP + propane with direct vent. I figure this gives me a $1500 "advance" on a new system, by NOT spending it to line the flue, which I won't need with a direct vent unit.

The outside unit (a 697CN036) is about 12 years old. The inside unit appears to be original (though I did not check the coil). While it all works fine, it's not exactly new.

So... I am NUTS for wanting to convert from fuel oil to propane?

They gave me several options -

#1 25HBC536A + CNPVP3621A + 58MVC080-14 + Infinity Stat = 10K

#2 25HCB636A + CNPVP3621A + 58MVC080-14 + Infinity Stat = 12K

#3 25HNB636A + CNPVP6321A + 58MVC080-14 + Infinity Stat = 11K (after rebates)

He also mentioned combination #1 with a 58MCB080-12 for 7500 or #1 with a 58MEC080-12 for 9300 when I asked how often the propane would even be running with the HP.

I don't want to drop to the 80% furnace, because I don't believe they are direct vent, and them I'm back to the same flue problem.

Do I need a variable speed fan? Do I need a 2-speed heat pump? Should I just fix the dang flue and live with it for now?