Yes Natural Gas Furnace for Heating along with the AC condenser. I have read up a lot on zoning, it seems to me like there are not a lot of installers in the industry that really know how to set them up properly. There also is a lot of negative information on zoning as it relates to the troubles a by-pass can cause to your systems efficiency. That is why I was leaning towards the two unit system, however need to figure out the proper size for each level. I know the best thing to run is a Manual J on the place however as a starting point what is the general rule based on square footage in determining the tonnage and BTU for a heating and cooling system? That along with how does the rising of hot air and the dropping of cool air determine the size you would go with? Any help would be appreciated.

After some long discussions with York reps and with Honeywell (who does the zoning equipment), I think (if the HVAC guy doesn't come down on price) I may have them run 2 trunks in the basement, and feed the appropriate ducts into each. i.e. have all the 1st floor ducts go into the trunk for the 1st floor and the 2nd floor ducts into the trunk for the 2nd floor. Then have them put in a manual damper near the beginning of each trunk, and have them run a thermostat wire upstairs for future use. I can't imagine this would be much more work than what they're planning on doing anyway. Remember the main plenum/trunk isn't even run yet. That way I can go the first year and see how bad the temp differential is between floors. And I could simply manually adjust the dampers each season (likely close off the 1st floor by a certain percentage) so that more or less air flow goes where I need it. If it doesn't work out, or if it does but my manual adjusting is too much work, I can do the zoning in the future without too much more cost, since the trunks are already done. I figure at that point, they'd just have to add the zoning panel, hook up the 2nd floor thermostat, add the auto dampers etc. And at that point, I could at least have some other HVAC guys come in and get some competition and different ideas. Thoughts on this approach?

Hi Tiger, thanks for chiming in! The current Lennox G-14 is a 80,000 Btuh (I think...from reading the model numbers in the cabinet G1403-80-03. Plus another company quoted us an 80) The current AC is Goodman CKT30-1, which a quick google tells me it is 2.5 ton. We do plan to seal the duct leaks in the accessible areas of the basement, have installed interior storm windows on our huge windows, and with the addition of the R35 in the back of the house, I feel it is reasonable to go down in size. We do have considerable humidity, so for the unit to be running longer is a good thing. Returns: The current return is in the most central part of the house. There are no other hallways, so those returns will need to go on room walls. The main question is.....should we do the zoning? There isn't much room to work with in the furnace room, and they would need to do that during the install. I suppose it depends on the ducts. There's 3 main trunks, one to the bedroom portion, and two for the cathedral portion. One of those wraps around the fireplace & water heater chimneys, he did mention that that isn't ideal. We can have them come look at the ducting next week once we get the ceiling tiles down. The tax credit is listed on all three options. That does help the cost....but of course not up front. Hmmm.....not sure on the coil. It says: "Coil Type: Cased" for all three. Anything I should ask specifically about that, or which type (Looks like N or A) is better? The middle thermo is just listed as Programmable Thermostat, and is included. (quoted as $65) We could get the Thermidistat for $115....would it make much difference with the 1 stage AC? We are having the humidifier removed, we haven't needed it. It does not specifically mention the air filter cabinet, but on the last install they did for us, it was the 5 inch pleated. He did mention it when taking measurements for the quote. Again, thanks for your thoughts. Definitely helpful and giving me fodder for the next conversation with the contractor.

What is 2nd stage cfm delivery? 800 cfm for 2 tons. what happens when any one zone goes high stage. with no damper bypass the velocity will be extreme.Ive done it both ways. oversize duct by 60% is great for 2 zone application but never tryied it on 4 zone. Im all about efficiency and hate bypass for this reason however you must accept bypass rather then problems with noise and velocity.that 8x16 bypass is wayy to big and I would go 8" round ( 400cfm) The smallest zone 350 cfm +byass of 400 = 750 . carrier moves air at 350 per ton so 700 cfm wil be ok. I would check to see what 2nd stage heat cfm is gonna deliver as well.