This is not true. You can get a higher HSPF according to the directory with a different model Carrier coil with the same 60 K furnace. Now the question is whether that coil will fit your application. Only your dealer will know this as I can't see that far. I was just trying to bring this to your attention and help you out. I assure you I will not say anymore on the subject. Here are the listings for same model coil different size, same furnace. 4701908 Active Systems INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA024A**30 CNPV*3617A**+UI 59*N*A060V17**14 24200 14.50 18.60 24000 10.40 25400 1 HRCU-A-CB 154 456 Yes 4701910 Active Systems INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA024A**30 CNPV*3621A**+UI 59*N*A060V17**14 24200 14.50 18.70 24000 10.40 25400 1 HRCU-A-CB 153 456 Yes 4701915 Active Systems INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA024A**30 CNPV*4217A**+UI 59*N*A060V17**14 24400 14.90 19.10 23400 11.60 25200 1 HRCU-A-CB 151 409 Yes 4701917 Active Systems INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA024A**30 CNPV*4221A**+UI 59*N*A060V17**14 24200 14.80 18.90 23600 11.60 25200 1 HRCU-A-CB 152 409 Yes 4701922 Active Systems INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA024A**30 CNPV*4821A**+UI 59*N*A060V17**14 24600 15.20 19.50 23400 12.30 25200 1 HRCU-A-CB 149 385 Yes There are those that come on this forum seeking help but don't like what they hear. IMO This post was edited by tigerdunes on Wed, Apr 10, 13 at 15:17

tigerdunes -- thanks for your input! Much appreciated. That is the direction I'm heading, subject to final price, warranties, etc. (The last quote from Company 2 had the Infinity furnace with the Comfort A/C.) The tendency here seems to be the "1 ton / 500 sf" approach. I've been pushing the final two dealers to really be sure about their sizing by giving them as much info as possible (the number of windows in the house, no insulation, orientation, etc, etc.) vyasmk9 -- I'm on the Peninsula -- as are all of the contractors I've contacted. It just seems that people around here seem to service a smaller area (although I could be wrong), plus I like to support local biz whenever I can. Just FYI, I started by selecting a couple of well-known brand names (Trane and Carrier) and looking on their websites for local dealers. Followed that up with searches for reviews of those dealers on local.yahoo.com and yelp, as well as checks on the BBB. Also asked my electrician and utility company guy for their thoughts/referrals. Not sure what the forum rules are for recommending contractors, so I'd rather ask before naming names. Anyone want to comment?

I am not absolutely sure, but expect that it would. While the icomfort uses a proprietary protocol(there is no standard digital protocol in the industry--there was a standard for the old style predigital where single wires represented on/off for fan/heat/cooling cycles), it would be awkward for Lenox to change protocols. Their spare parts department would need to keep the old style around for a decade or so in case a thermostat failed. Generally, manufacturers of long life products try to maintain compatibility to simplify repair inventory. There is no reason to change the communications protocol. SLP98s are still relatively young in the product life cycle and the new ones have not gained any significant functionality other than being able to shift down as well as up. Make sure you have 4 (or more) thermostat wires in the wall for iComfort to connect to the furnace. This should not be a problem except in some homes with single stage heating and no A/C. The wires serve different functions than with an analog thermostat, but all that matters is that 4 are available. Wire quality requirements are quite loose and the distance requirement of under 300 feet of wire should not be a problem for any normal residential installation. On replacing the thermostat, work with power off to the furnace. You will likely need to change a DIP switch or jumpers on the furnace circuit board to reconfigure for iComfort operation before turning everything on. In two stage mode, certain wires carry power. In Icomfort mode the same wires carry data. So it is important that the furnace board be correctly configured before power flows through the thermostat wires.

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.