Thanks mike_home. Glad to know that even the pros might have struggled with this problem. Adding the C wire was not a necessity, although it did fix the secondary problem (installing new batteries presumably would have done the same, but the thermostat did not even show a "low battery" warning, and I did not have new batteries handy). Adding the C wire will cut down on how often I will need to replace the batteries, and if for some reason weak batteries caused the secondary problem, then I should not have to worry about that again since it is getting power from the C wire now.

Thank you for the prompt reviews! Looks like Proposal #1 is the winner so far. Mike ��" the attic fan made a huge difference in second floor comfort. One of the best things I did. Glad your experience was the same. I will look into the 2 stage AC. I will not run the fan or put in an extra return for the humidity/temperature change issues. I will just continue to use my dehumidifiers. They do take care of the issue. I am going to plan on replacing the line set ��" it is easy to get to. What do you think about the drain pan/wet switch that will shut off the AC if there is a leak? Is it going to go off over nothing like a smoke detector I used to have and drive me nuts? Or is it a good idea? I might not have been clear about one thing. Both contractors told me to keep the old air filter set up (Spaceguard High Efficiency). It is the old Aprilaire humidifier that Contractor #1 said replace due to age/parts and Contractor #2 said keep it, parts are not going to be a problem and the only part that goes bad is the solenoid. Keep the old one or buy a new one? Contractor #1 is going to look into the Carrier early failure of heat exchangers settlement. It might only apply to the secondary heat exchanger. The primary one failed on my furnace. I meet with the last contractor tomorrow. I hope to have all the bids by the end of the week. My goal is all new equipment before I have to turn on the heat!

For using a chimney with no metal liner, the National Fuel Gas Code says: the flow area of the chimney cannot be more than 7 times the outlet of the smallest draft hood appliance. If the outlet of your water heater is 3", that's about 7 sq inches. Take that times 7 and you get 49. So the code says if the chimney is more than 49 inches (7x7 or some other dimension) then you must line it. That rule works for 80 & water heater or water heater alone. If 1 or more sides of the chimney is exposed to outdoors below the roof line, no question LINE IT! If an 80 alone is in a chimney, no question LINE IT! So really, the only way you could BY CODE not line the chimney is an inside chimney with 80 & water heater if the water heater draft hood meets the "7 times" rule. #1 could be OK if the rule is met #2 is a nut. The 80 alone needs a liner, the power vent water heater is expensive and inefficient. #3 is good though stainless steel unless required by local code may be an overkill. Certainly nothing wrong with it, would sure hold up better than the aluminum liners. Here is a link that might be useful: Liner info

Well the latest quote is in and it's the best so far. It's for two America Standard Freedom 95, two stage, variable speed furnaces. A 60k BTU system for the rental unit ( it gets a $600 rebate after installation) and a 100kBTU unit ($300 rebate) for the larger upstairs apartment. The quotes include everything; permits, thermostats, hard wired CO detectors, and removal of old oil tanks. 60k BTU cost $5500 100k BTU cost $5900 I will get $900 in rebates so the total cost for the install is $10500 I talked to the contractor as I believed that the units were oversized. The furnaces are purchased from the gas supplier and are the ones approved for rebates. He said a single stage 40k BTU unit will be fine for the rental apartment, but American Standard does not make a 40k BTU two stage unit and the 60k BTU unit will cost the same after the $600 rebate and it will be quieter, cheaper to run and will keep the tenants a bit more comfortable. I could get a 40k BTU Carrier Performance 96, there's a $300k rebate on that. He says an 80k BTU unit would be ok for the upstairs two floor apartment as far as heating goes, but from experience he feels that the larger fan capacity of the 100 kBTU unit is needed to get the air up from the basement to the top floor.