Our house is 6mo old. No choice on HVAC contractor.
House is 2800 SF on two floors in Central NY. House has 4 zones with 7 and 3 vents on 1st floor and 5 and 4 on the second floor. The ducting is 6"; supply plenums are 8x14; two taper to 8x12 for last duct at end of runs. Ducts do considerable meandering...
Furnace is a Rheem RGRL 90k BTU input (2 stage). Fan will run at two speeds in heat mode but only on High in cool mode. Zonex controls for the zoning. The fan speed can be tweaked a bit but I have no idea if that was actually done or not.
NOTE: I had a discussion with owner of original mechanicals company and was told that with a zoned system, a variable speed unit (or modulating one) would be a waste of $$. That lead to the Rheem unit cited above.
Amongst 5 outfits which I have talked to to put in central air; one said the furnace should have been a var speed fan type but simply quoted a 2 stage 16 SEER Carrier unit. All said a TXV value would be used. Three said nothing about current configuration.
Now enter #5 in the "who-will-install-the-AC" contest. At a minimum, they feel that I need a barometric bypass installed (and it should have been done in the first place) and with that, would offer a 15 SEER single stage 3.5T AC unit.
The bombshell was that, even with the minimum fix proposed, I will likely face premature component failure (blower fan, possibly compressor especially if 2 stage) and a less efficient operation. Suggests that Furnace be replaced along with a coordinated control system along with adding a 2 stage AC unit (4T/2T). (Carrier Infinity systems.)
Price to do the full fix will be about double the "get by" fix. (I do possibly have someone I can sell the existing furnace to moderating my $$ hit)
I am PO'd at the original mechanical outfit for apparently giving completely wrong advice as to using a modulating furnace. I honestly don't think they wanted to have to deal with more complex systems...
Oh, since this is the retirement home it's not like we are planning on leaving in 3 years to stick the next guy in line. It also means that efficiency is very important - I don't calculate cost benefit on today's prices as I believe they are only going to continue to rise.
Advice? I simply do not know what to do.