I have a dual unit setup for my home, which is 3200 sq ft, ~2000 down, ~1200 up. The downstairs unit failed a couple of weeks ago. The downstairs is 10' throughout, except the entryway which is 19' for a 15' x 10' area, and a vaulted ceiling to about 12' in the master bedroom.
I currently have a 5 ton Carrier for the downstairs, but curiously the house was quoted in all the builder's paperwork as having a 3.5 ton downstairs. (The 5 ton is the original unit, so that's the disparity.) I've had a feeling for a while that the unit was oversized. I've read several threads in here, and I've seen several setups similar to mine, even southern setups (I'm in Texas) that I've never see sized to 5 tons.
Well now that unit has failed, and I'm starting to get quotes. The problem is, I'm getting a WIDE disparity, based on assumptions of what has to be done to the duct work. Nobody has done a full load calculation - not that they won't, but the initial sales guy won't.
I did a map of all the duct work, and noticed some peculiar runs (I'm not an HVAC guy, so who knows). Can I tell from the size of the ducts whether the number of supplies and returns matches the 5 ton unit? I realize you cannot tell if 5 ton is the right size without performing a load calculation, but I'd at least like to know if the current duct work is properly supporting a 5 ton unit.
For supply, I have 1x10, 2x9, 3x8, and 1x6. For return I have 3x14.