I find it interesting you have searched for a three year old thread in order to post your comment. There is some elemement of a scare tactic in tagging and shutting down a furnace. The contractor does want you to buy a new furnace from him. But the dangers of a cracked heat exchanger are very real. There is a legal liability that an HVAC contractor shut down a furnace which show signs of being dangerous. There thousands of furnaces in use at this moment that have cracks and the homeowners don't know it. These furnaces continue to operate until they eventually fail for some other reason. This is not a reason to ignore the issue. Heat exchangers crack due to excessive heat. This could be caused by not changing the filter or poor installation. There is a high heat limit switch that will shut down the furnace, but it does not guarantee it will prevent the heat exchanger from cracking. There is no detector which can signal a crack in metal. I suppose a carbon monoxide detector could be built into the furnace. The detector would probably have many false positive readings as the furnace cycled on and off. If an HVAC technician says you have a cracked heat exchanger, then get a second opinion if you doubt his findings. It is better to be safe than sorry.

The DOE has worksheets that can help you calculate the relative cost of heating and cooling with different systems using your current energy costs. Of course you need to predict the relative costs over the next decade or two to really tell what is best. How is your crystal ball working? I would like to clear up a couple of common misconceptions. One type of heat does not dry a house in the winter any more than another. Leaky house envelopes dry houses. Heat by flame of some sort might dry a house more because they draw more outside air in if there is not a source of outside combustion air. That would be the only mechanism. There is nothing special about heat pumps in poorly-insulated, leaky homes. No heat or air conditioning source works as well in that situation as well as they do in tighter, well-insulated homes.

San Francisco Airport has a winter design temperature of 38 degrees F. If you have reasonable insulation and windows you need an 80,000 Btu furnace like an earache. The smallest Bryant 2-stage variable speed blower furnace is 40,000 Btu. That size would be my recommendation. This is the only furnace Bryant makes that is 96% AFUE. It's physically large and may not fit into all locations. Each furnace size (Btu input) has it's own efficiency rating. Ask for a Heat load calculation (Manual J) to be performed. That is the only way to size equipment. If the furnace is too large the system will short cycle and never reach the published efficiency ratings and you may not be comfortable. I cannot comment on pricing. I live on the East Coast, our outdoor design is 11 degrees F. Most homes have R-11 walls and R-19 in the ceiling. I cover a 2000 sq' house with a, 92+% AFUE, 60,000 to 75,000 Btu furnace. Most of our housing only need 45,000 to 50,000 Btu on a cold day and will average about 75% of that number for the winter. 2-stage heating is nice way to go. The furnace will operate on low most of the time, less air noise, better air mixing, filters filter longer, humidifiers humidify longer, all the good stuff. Bryant is Carrier with a different paint job. Trane and American Standard are the same sans paint, Rheem and Ruud sans labeling etc. Good luck.

Oh, no way, a failure by you, someone who's helping folks in your spare time?! No way! (I hope you were joking.) By "not a single person mentioned", I meant like installers when they came to give estimates, not anyone here. No trouble, it's all a learning experience. Yes, I had a media cabinet installed, but it was a Honeywell. I couldn't convince my installer to get the official Ruud cabinet. I wouldn't even call the condensate issue a failure necessarily by my installer, because he is right that my sump pump should work in freezing weather. Just these furnaces still aren't common in my area, so I'm surprised there aren't more words of caution out there. (In fact, my emergency handyman who came out that night cause I thought something had burst -- services rental properties as his full-time job -- turned to me and said "I haven't seen this before but your furnace is discharging water.") My installer is considering a condensate pump and there's a slight issue where the outdoor temp isn't being read. But overall, I'm super happy with my 96% Ruud and EcoNet thermostat. The thermostat tells me whether it's running high or low stage, I've been told I'm spending too much time with it. I can't thank everyone here enough. In the end, I was able to find a great HVAC team. It's been quite the adventure. I'll post pictures soon. The duct work is a masterpiece, everything was turned 90 degrees because otherwise code required I create a service opening in the wall.