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.

If you are buying Carrier equipment, then it is best to buy from a factory authorized dealer. They are supposed to install the equipment to your satisfaction or remove it and refund your money. They should also have better training than the typical Carrier dealer. The Comfort series is Carrier's entry level product. I would be a good idea to upgrade to the Performance equipment. It is a little better built and quieter. I think upgrading to the 2-stage Infinity furnace is expensive, but worth the money in my opinion. I hope your upgrade price includes the Infinity controller. The ECM motor is reliable, but is expensive to replace if it ever goes bad. If you get a labor warranty get it through Carrier. I have the Carrier warranty and I am not forced to have maintenance. But you do have to take care of your equipment and not abuse it. I suggest having maintenance done once a year. You should not pay more than 10% of the total price for the labor warranty. You are already covered by a 10 year parts warranty.

Gotcha. I will pass this along to the builder for him to have hvac guy do. I spoke to hvac guy about the $400 overrun vs the over-the-phone/options fax estimate (turns out it is not $1k -- $600 of that is the builder's problem for the 13 SEER base upgrade). He said that $200 of that came from needing to add 120v wiring to the power humidifier since it does not run off the furnace fan. We didn't specifically get to the other $200 as he stated that FILCAB was $450, and EZXCAB was $275. FILCAB is what was in the quote. So after a $40 MERV10 filter for EZXCAB we're now at $10 less than the upgraded quote. Interesting, especially since he previously said FILCAB was $225 -- and I had to set him straight that FILCAB could only take MERV8 filters from what I understand. I'll make sure the builder also gets a competing quote. And I am getting the complete model number of the coil in writing, of course.

Tigerdunes brought up demand defrost versus timed defrost. For the past 18 years, I have dealt with my Lennox defrost scheme. The only times I heard it go into defrost mode were when the unit was first running in heat mode. The unit would switch over from heat to defrost, the defrost cycle would complete and everything would turn off. I never heard it run a defrost cycle when it was not first heating. I rarely heard it go into defrost. I never heard it defrost on a fixed cycle such as every 90 minutes. Am I to understand that a Carrier will just go into defrost mode every X minutes whether it needs it or not and is not in a heating cycle; just turn on and defrost itself? I found this information in the Carrier 25HNB6 heat pump installation instructions: AUTO defrost adjusts the defrost interval time based on the last defrost time as follows: When defrost time When defrost time 3-5 minutes, the next defrost interval=90 minutes. When defrost time 5-7 minutes, the next defrost interval=60 minutes. When defrost time >7 minutes, the next defrost interval=30 minutes. The control board accumulates compressor run time. As the accumulated run time approaches the selected defrost interval time, the control board monitors the coil temperature sensor for a defrost demand. If a defrost demand exists, a defrost cycle will be initiated at the end of the selected time interval. A defrost demand exists when the coil temperature is at or below 32_F (0_C) for 4 minutes during the interval. From that description, if the time interval elapses and the coil is not at 32 degress, then no defrost will take place. That, to me, sounds like a form of demand defrost. Is Baldloonie saying that the coil could be at 32 degrees or less without frost and, therefore, a defrost cycle would be unnecessary? What kind of ambient sensor detects presence or absence of frost? Neohioheatpump asked, "When your old A/C would run, was it producing water?" It was producing water and I saw it dripping from the condensate drain. One weekend I went out of town and came back to find water on the floor around the return box that the fan coil sits on. I opened up the access and found the interior insulation of that box soaked. Turns out the condensate line was plugged. Took awhile for that to dry out. On the other hand, this past summer I did not see water dripping from the condensate drain. The drain line was not plugged and the drip pan seemed dry. I thought it was because I had dried out the air so much with the two dehumidifiers that there wasn't enough remaining for the A/C to remove. Cooling was normal. Running the fan on manual started with the installation of the Lennox and an associated Honeywell Electronic Air Cleaner. The house suddenly became dusty and I blamed the EAC for not doing its job. The Honeywell zone representative came to my house, sized up the situation, and told me to run the fan on manual so that the dust would remain suspended in the air and available to be captured by the EAC. I did that and it was of no help for the dust situation but it did help reduce the temperature differential between the first and second floors during cooling so I kept doing it as a matter of routine. Thus, I cannot say that not running the fan reduced the humidity. Though I complained about humidity, the heat pump contractor never told me that I was humidifying the house by running the fan (on orders from the Honeywell rep). I will continue to run at least one dehumidifier in the completely below grade basement during the summer because I want that area to be warm and dry to avoid mold and mildew. I've been in the basements of other houses in the area that don't use dehumidifiers and they stink. Mike Home said, "You stated in an earlier post that you run the fan in the summer because the upper floor is 2-3 degrees hotter than the lower floor. I think adding the attic insulation will help this." I agree that adding attic insulation could help. But, having a Dutch Colonial house with a barn-like roof that is covered in dark shingles on the east and west sides causes a lot of heat gain through the second floor walls. I'm not keen on opening the walls to determine the amount of insulation or add to it. Changing to a light-colored roof would make the house look out of character with the neighborhood. There are newer shingles that reject heat gain that I will investigate. Mike Home also said, "You could also zone the first and second floors, but this is expensive and probably not feasible with your current duct work." There is but one main feed duct and it runs through the basement. There is no way to segregate the room feeds in this scheme without doing each one individually. I'll leave that expense to the next owner.