Thank you for your response Tigerdunes. I will definitely check with the bidder on the third party evaporator coil. I specified matched systems having read your prior posts to others extensively, but didn't catch that this evaporator coil wasn't a matching Trane. Thanks. The boiler was sufficient in heating the entire 1200 square feet main floor living space with AND without all the radiators in place. I don't recall the size at the moment, but will check. The HVAC people were all pleased with its size when they looked at it. Because the house is without electric and water service as yet, we are not totally sure the boiler is still in working order. It was not fire damaged, but water from the fire fighters and heat from the fire might have caused some unknown problems, which was another reason to hedge the bet by adding a gas furnace. The second reason for considering a gas furnace, not just A/C is that a realtor who knows the house and its value, - which is considerable for a small house, given its location and craftsman, cedar shingled cottage charm - suggests that some buyers don't like radiator systems, and feels the addition of an alternate heat system and the addition of A/C will be worth it, which is another reason I got the bid for it. The third reason for considering a gas furnace is code compliance, and the cost to do so. The cost of adding hydronic units to the sunroom, pantry, dining room and bath areas to meet code are unnecessary if I install the gas furnace. Anyone wanting to use the radiator system only for heat would have to add these units, or live without them as I did, but code is met with the addition of a furnace. No furnace, and I have to add radiators in the areas mentioned above and detailed below. I agree that a heat pump would be the way to go if we knew for sure that the radiator system was going to be the primary source of heat as it was when I lived in the house. New owners might opt for a forced air system. My question on this is, can a gas furnace be added into the system as cost effectively later as it can be added now with the A/C going in. The new heating system, if installed, l would heat/coo the 1200 sq ft main floor with its 9 ft ceilings, with two registers in the open 950 sq ft unfinished basement. The basement stays cool in summer and warm in winter without additional heating and cooling. The attic space, if developed later, will be heated and cooled with an in-wall, Mitsubishi type system. Trying to run ducts and vents is a problem, which is why we don't have the new proposed system sited in the attic. It would make the attic fairly unusable in a future development as a master suite and sitting room. The ducting layout using the in the basement location has worked well, and the location of cold air returns well placed and spaced. So the attic will not be heated or cooled with this system. In the past, with the boiler, the heat loss from the main floor was enough to keep the attic above freezing, but does not warm it significantly. The attic has 4 large double window sets, 3 large Velux skylights and a 4.0 french door set, and the roof is black, so it stays warm enough on sunny days, and is well ventilated in summer.. The attic floor will be re-insulated at this time, but not the walls or ceiling. The new insulation in the attic floor will be far better than the old, and as I said, the new windows throughout, from basement to attic are a vast improvement in energy efficiency over what the boiler used to have to handle. The 950 sq ft basement is unheated at present, though I believe two registers will be added to this space with the new furnace The basement stays comfortable in winter when the boiler is in operation simply from the hot water pipes to the radiators and hot water heater and warmth of the up stairs. It is is open space, unfinished and only used for laundry and workshop space/tool storage. The dining room radiator was removed from under a south facing bump out window. That window was removed and replaced by an exterior double french door when a new deck was added at the time of the new boiler. The heat loss to this room was noticeable but not enough to be a problem for me, though it would be for others, and it is for code. Each room has to have a heat source, so I either have to put in a register or add a radiator. The bathroom is only 6x7 and is now warmed by the heat/fan which is not sufficient for code. I have a not yet installed hydronic towel bar that gives off 1500 BTU, enough to handle the bath and the small hall adjoining the dining room, bath, bedroom and parlor. If I do the gas furnace, this is unnecessary. At same time the new boiler was installed, a kitchen was installed in a 11x12 ft space that only had a sink and refrigerator with a radiator. An adjoining but separate 6x8 pantry at the south end of the kitchen had a stove and a cabinet. The pantry is also an access corridor to the basement stairs. So in installing a kitchen, I removed the radiator and replaced it with a toe kick radiator under the sink base the fully fitted kitchen. Base and upper cabinets were added to the pantry on the load bearing exterior wall that separated the pantry from the screen 8x8 screened back porch at the other half of the kitchen south wall. The fire that started at the electric service connection into the house was located on the east wall between the kitchen and screen porch, so this area and the attic above it were severely impacted by the fire. In rebuilding this area, the screen porch got a solid foundation, was mostly opened to the kitchen, and serves as a sunroom breakfast area. It is,fully windowed from ceiling to 36 inches above the floor with a door that opens to the deck. The load bearing wall separating the sunroom from the pantry still exists, but the pantry is now open to the kitchen rather than walled off with a doorway. The kitchen toe kick puts out 5,600 BTU and has to handle the kitchen sunroom and pantry area now. If I do not add a furnace, code will require me to heat the sunroom and pantry areas, which I would do with toe kick units under the pantry base cabinets - one venting into the sunroom through the wall and one venting into the pantry. If I add a furnace, this will not be required, we will simply use those areas for the forced air registers. If I do not add a furnace I will have to provide hydronic heat sources for both areas. So, to answer your question 4, the only addition to the heat load that the boiler has covered adequately (1200 sp ft) is the 8x8 fully weatherized and insulated sunroom. If I go with a gas furnace we will add the register(s) for the unfinished basement. I don't know if code requires the basement to be covered. I do know the non living space attic does not need to be covered. Sorry for all the detail, but I find that sooner or later the information is needed, so I am trying to give it all upfront.

Ryan, thank you so much for the feedback. This is such an great informative forum and I'm glad I found this site. Yes, they have to over-size the furnace to just be qualified for the tax rebate. Blame on Trane for their current lineup I guess. Not best situation to be an honest Trane dealer if you have to either over size something or use a third party products to take advantage for the tax rebase. The load calc says "Total Heating Load = 61506" so 120-140k BTUH sounds way too much. Plus, I'm concerned now you pointed out the furnace will likely need to move much more air than your current ductwork can handle. What's my alternatives if I want to stay with Trane 3 ton Heap pump either XL15i or XR15? Regarding the IAQ may not be used to trigger to slow down the blower when combining with zoning. Where do I check to be sure? Also, does the triggering even possible with XR15 like it does with XL15i? I think the reason I try to go with a Hybrid system (duel-fuel) is that over here in central NC it does get pretty chilly during Jan and Feb with temprature down to single digits at night for a few weeks. It seems to me it will be prudent to have some sort of back-up heating during this periold. And if adfing a heap-strip with Heat pump/Air handler, I think I have to add a circuit break or something. At least that what I had been told. To other folks on the forum, do you have your advice on choosing a dual-fuel hybrid system vs just heap pump + heap strip? Specifically, anyone in the same area that has done this before? Today the Bryant dealer came and spent only 15 min looking at my attic. He took away my drawing of the 2nd/3rd floor plan with window and room sizing and said he would run it over the weekend through a load calc program to see what's the corect size and propose some setups for me. I guess I won't know any details for a few days. Again, thanks for the feedback. If I don't get to talk to you again here, have a very nice weekend Ryan!

Thanks for the feedback everyone. I've decided to go with the Carrier Infinity system. It seems like a nice product and I like the contractor (and they are required to follow SCE guidelines). I did ask him again about a Carrier coil, but it wasn't an option. That might be the case, or it might be a cost issue, but he isn't going to budge. HVAC Calc actually suggested raising the outdoor summer temp by 5 for the safety factor. I doubt if they'll be able to do that for me on Manual J though. HVAC Calc was useful since I had the chance to play around with some of the settings. Going from r6 to r8 ducts makes a big difference as suggested. It's much easier and probably less expensive than going from R30 insulation to R38. This contractor also mentioned that he uses R8 normally. Thanks again everyone.

Thanks for all the messages. When I first got this quote, I hadn't priced furnaces ever. I had told the contractor that I did not need the Rolls Royce of furnaces because we do not expect to live here more than another 5 years, and he came back with this quote. After talking with some other contractors the past couple of days, I am realizing that there are less expensive options than the Infinity model (including the Performance series from Carrier, which can also qualify for the current tax credit). I am now getting bids on similar efficiency models from contractors that use Rheem, Goodman, Carrier/Bryant/Payne, and other models. Thanks for the help on this question. After this weekend, I'll probably have another question asking for help in comparing models and their prices. I have to act quickly on the furnace because ours was diagnosed officially yesterday and the primary heat exchanger is cracked, which didn't surprise me. Have a good weekend everyone.