Given a lower BTU output and a slower flame speed (slower combustion air induction speed) I am promoting more heat residency time inside the heat exchanger galley and a lower flue stack temperature. My blower fan is pushing the same CFM through the exchanger, so when taken together my heat extraction efficiency is going up. By how much, I don't know.
Isin't it common knowledge that oversized furnaces were normal a few decades ago?
Actually, it's throttled back right now, to at least half of full flow. That's my point - even given my current outdoor climate (10 to 15f min and 20 to 25f max outdoor temp) I'm getting enough BTU's to keep the house at 71 - 72F all day and all night. And even then, my furnace is not running at 100% duty cycle. Maybe only 65 - 75%.
To be honest, the burner setting I have now is the lowest that gives me a consistent and even flame pattern and acceptible ignition roll-out.
Fall and spring don't last long enough to warrant their own lower burner-output setting, which as I just mentioned I probably couldn't achieve anyways.
Yup.
Tell me what a 120,000 BTU input, 96,000 btu bonnet furnace is designed for. What size house.
Tell me where such a furnace ranks today in terms of size (small, medium, large, extra-large, etc).
First thing, I'm in Ontario (Canada).
Second thing, in order to get gov't rebates, you need to contract for a home efficienty test by an acredited tester who will evaluate your current situation (air leakage, current furnace type and efficiency, maybe a few other things) and he will do it again when your new furnace is installed, and then he signs off on the tests and then the gov't will send you money. I don't know if it's "federal" or "state" money (or both). I also don't know if the local gas utility will kick in any of their own money.
One of my co-workers had this done, so I'll ask him how much of a kick-back he's supposed to get.
You've also got to factor in rebates for the heating vs the cooling components as well. I wouldn't be interested in replacing my A/C system.