"I did not feel the difference between stages." If you can't tell the difference between the two stages then you still have a problem. Either the furnace never changes stages, or your duct work is so bad that a majority of the air is lost before it reaches the registers. The Bryant 925 100K BTU furnace puts out 63,000 BTU in the low stage, and 97,000 BTU in the high stage. That is a 50% difference in air flow. You should at least hear this when you stand next to the furnace. If you can't call Mr. Bryant with his 20 years of experience back ASAP. The furnace is sized for the high stage. The low stage is used either to maintain the set point once it is reached and on mild temperature days. I find it strange this contractor has no problem swapping out your furnace but does not want to install a true 2-stage thermostat.

National Company! I'll guess Delta Mechanical. It all depends upon the guy doing the work. You should not have 5" on the vent connector. You should have 4" B-vent. The inch diameter you pick up will allow for proper grading of the flue. Your best bet on liner will be to install B-vent all the way down. You should have a bottom capped tee at the bottom of the stack as a drip leg. Yours is the worst condition for a Category I furnace, long vent connector and exterior chimney. If you go with a chimney sweep for the liner, as I said, chick out the Chimney Sweep Guild for a "real" contractor. You are correct about getting taken on this. There has been all kinds of fraud in this field. Perhaps it would be best to make the installing company come through on this. MAKE SURE, if you have them do it with B-vent that they screw the joints together with screw that does not penetrate the inner aluminum liner. A seemingly small but important detail. Also have them use a metal tape on the joints. They can drop the tee and vert portion into the flue and work back to the furnace, finishing with an adjustable length at the furnace. I am glad that you liked the salesman, but I would not let him off the hook on this. If he is a good guy you can help him become better by insisting that he come out and look at the system. You never install a Cat I furnace where a masonry chimney is going to be used. It is "the" reason to go to the condensing furnace using PVC for the side wall venting. As well, you pick up another 15% efficiency. You will be helping this man if you have this conversation. Nationally, once you cross the Mason-Dixon condensing furnaces are 95+% of the market. As you move south, the view is the heating load is not as high so, why buy the more expensive (efficient) equipment. Net/net, regardless of intent, you got stiffed here by nice but not well informed people and your inspector pencil whipped the permit. Perhaps that is a bit tough. they did fail the inspection initially. Salti, heck, we don't argue. I enjoy reading your posts. In my experience, if you were hitting 80% with the old furnace you "grabbed the brass ring", unless it was an oil furnace and the better brands have almost always hit the 80% mark. Is it oil? If it is gas and old, I really am surprised. The reason the codes changed since '91 is that by being mandated to deliver a min efficiency of 78% up from those 60% figures is that by putting the heat into the house there was less energy available to drive proper venting of the new appliances in masonry. Proper venting meaning getting the flue gases out as a vapor and not having them condense (approx 3.2 Ph) on the walls of the flue. You can hide a lot of design issues with a high stack temperature. With high exhaust temps you gained velocity. With 78% you didn't have a chance. Even at that, it was interesting seeing the code changes over the years. Every four years with the new edition of NFPA 54 the restrictions became more and more stringent until about 10 years ago they finally said, "masonry chimneys do not work and do not use them". Also, be aware, if you are hitting the 80% combustion efficiency" that is not remotely close to system efficiency. You have probably seen my fairly frequent posts on googling, "doe duct leakage". If you want to get the best out of your heating dollar, seal the duct system. Residential duct systems in the US are terrible. It is the "crazy aunt in the back room" that no one in the industry wants to talk about. It is a big deal and it is finally coming to light. What I have always said is the unitary manuf (Carrier, York, Lennox, Trane, etc) can put all the technology they want in the box. They simply cannot deliver it…due to duct leakage Happy Heating!

For Rayball Obviously, you were not paying attention to my posts and recommendation. The main purpose of the Greenspeed is the low temp feature and the HSPF heating efficiency. That's what you are paying for. While the 003 air handler is an AHRI Directory match, it is not the best match as far as HSPF. There is a significant difference from a 10.5 HSPF to a 12-13 HSPF. See below for comparison. I posted same on July 4th.. 4616892 Active Systems CARRIER AIR CONDITIONING INFINITY SERIES HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4AN(B,F)003+UI 1200 875 705 33400 13.00 19.00 35600 10.50 29200 1 HRCU-A-CB 218 662 Yes 7021746 Active Systems CARRIER AIR CONDITIONING INFINITY SERIES HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4AN(B,F)003L+UI 1200 875 705 33400 13.00 19.00 35600 10.50 29200 1 HRCU-A-CB 218 662 Yes 4616934 Active Systems CARRIER AIR CONDITIONING INFINITY SERIES HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4AN(B,F)005+UI 1200 875 705 35000 14.00 20.00 33400 12.00 31000 1 HRCU-A-CB 217 579 Yes 6938465 Active Systems CARRIER AIR CONDITIONING INFINITY SERIES HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4AN(B,F)005L+UI 1200 875 705 35000 14.00 20.00 33400 12.00 31000 1 HRCU-A-CB 217 579 Yes 4539517 Active Systems CARRIER AIR CONDITIONING INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4ANB006+UI 1200 875 650 35000 14.50 20.50 33400 13.00 31600 1 HRCU-A-CB 212 535 Yes 7017320 Active Systems CARRIER AIR CONDITIONING INFINITY 20 HP WITH GREENSPEED INTELLIGENCE CARRIER AIR CONDITIONING 25VNA036A**30 FE4ANB006L+UI 1200 875 650 35000 14.50 20.50 33400 13.00 31600 1 HRCU-A-CB Yes 212 535 Yes You will need to decide whether it is worth changing the air handlers out from the 003 to 005-006. Probably not but plan on higher operating costs in the winter. The 2 areas that take a hit are the cooling BTUs and the HSPF heating efficiency. Dealer should be able to give you some est operating cost differences. IMO This post was edited by tigerdunes on Mon, Aug 4, 14 at 6:03

Haha, well now this makes sense. I'm in Silicon Valley and have more than enough exposure to engineers and tech types who think they can understand and improve just about anything with homespun whizbang. They far too often fail but have trouble admitting that. Usually the damage isn't too costly. That may not be so here. JoeQ, your clever "system" may bring your furnace to a premature end of life. Or may have already. And that can lead to carbon monoxide emissions in your home. Or may have already. A new furnace may be a few thousand dollars. Health damage from carbon monoxide, hard to quantify. Your "system" isn't performing its most basic requirement, which is to properly control the furnace without damaging it or risking your health. Declare your experiment over and call an HVAC company to get your stuff working right, the traditional way. Good luck.