#1 is just oversizing the furnace and not looking out for your best interests. Newer furnaces need to move more airflow, and if the ducts can't handle the added air (and likely can't), could get loud.

I'd pick the properly sized and installed American Standard before the Carrier Infinity system installed by an incompetent dealer any day. 15 year parts and labor warranty isn't through Carrier, so I hope the dealer is around in 15 years.

60,000 btu furnace x .95 efficient = 57k btu's
75,000 btu furnace x .80 efficient (when it was new) = 60k btu's

If they did a Manual J, they should be able to guarantee its performance and comfort at certain temperatures.

You are right, the last 5 years are through the dealer. However, they have been around here for awhile and have a good reputation (except for this sizing issue.) I am meeting w/ them in their showroom tomorrow and will attempt to get an answer.

As to the Manual J calculation. The guy who says he did one measured the exterior of the house, noted the orientation, asked about the insulation and that was it. Maybe that's all you need, but I thought it was a little more involved. If it is, then I guess I have a mini-Manual J. I did tell that guy that the existing unit has trouble cooling the second floor on hot days. He said that was more likely an issue of ductwork sizing instead of AC sizing, but left it at that. He did guarantee the sizing would be correct.

What about all this coil/airhandler stuff? Is that an issue or if it is a matched system, no problem.

I just talked to the Lenox guy who quoted a G71P 90K unit. He said the high effeciency units don't blow as hot as the unit I currently have so he sized 90K as a comfort issue. Does that make sense? (Not interested in his quote b/c of price and poor Lenox warranty.)

"I am meeting w/ them in their showroom tomorrow and will attempt to get an answer."

Don't let them try to say because it will run on low stage most of the time. The furnaces need to be sized for their high stage capacity. The idea is it will run longer in low stage, not short cycle, using more gas and causing less comfort.

"I did tell that guy that the existing unit has trouble cooling the second floor on hot days. He said that was more likely an issue of ductwork sizing instead of AC sizing, but left it at that. He did guarantee the sizing would be correct."

He is correct. Most cooling issues are due to ductwork when one level doesn't cool as well. There are things that can be done, including balancing the system with dampers. Did he measure the windows? Did he use a laptop or a chart to calculate the size (Manual J)? If he guarantees it will keep it at the temperature you want it to be on the hottest or coldest days, then this is the most efficient way to go, and the most comfortable way--with properly sized equipment.

"What about all this coil/airhandler stuff? Is that an issue or if it is a matched system, no problem."

An air handler is used with a heat pump or just an air conditioner and includes the coil and a fan (often called a "fan coil"). Your furnace is acting as the air handler, and has a coil sit over the furnace.

The Lennox equipment should have a 10-year parts warranty and limited lifetime warranty on the heat exchanger. 15 years is not standard, if that's what you're comparing other manufacturer warranties to. See if that 15 year warranty requires an annual maintenance contract, and read the fine print. Sounds too good to be true. The G71MPP comes in a 70k size, which is probably more correct and would have even more output capacity than your current furnace. The 90k would probably work fine as long as ductwork is sized appropriately because it is a modulating furnace and would more than likely never use the 90k fire rate.

He did none of those things. He noted the answers I gave him on paper. I left while he was measuring the outside so I suppose he could have estimated the second floor window sizes. The only room of the house he was actually in was the kitchen. I have doubts I really got a Model J, but he at least tried harder than the other guys. I would have thought he would have followed up his ductwork response with some suggestions, but no.

The Lenox does have a 10 year parts warranty. The quote said 5 year parts and labor, so I assume the dealer is throwing in the 5 year labor part. (The sales guy has penmanship issues.)

I will check the fine print. I have a copy of it at home.

I should have mentioned that the furnace is in the garage and of course there are upper bedrooms at the farthest distance from the furnace. Any dampers would have to be installed in the crawlspace, but that could be done. Again though, not suggested. I'll ask him.

15 year warranty requires a maintenance agreement for the duration. I believe the current price is around $160. Of course the claim is that is cheaper than paying for the separate annual heating and cooling check. Of course the first 10 years of parts are on Carrier since they don't appear to have a labor warranty either.