"Doug Warner" wrote in message
...
"HL" wrote:

Compared to a 20 year old furnace how much does each design improvement
increase AFUE:

Draft inducer fan
Ignitor vs pilot
Faster fan startup (is this due to the draft inducer)
Hx design chages?
Anything else?


Second heat exchanger, Extracts so much heat from the exhaust that
the water vapor in it condenses and runs out a drain (my condensate
pump runs summer AND winter) The inducer fan is needed because the
exhaust gases are too cool to rise up a chimney. Instead, they're
pushed out through a 3" PVC pipe that barely gets warm.

He's talking about the 80%, not the 92% stuff. The flue gases will rise up
the chimney, but will condense real bad and rot out the chimney quick

Other than that, you're correct....