HeatMan wrote:
"HL" wrote in message
news:tNurd.223772$df2.120623@edtnps89...

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?




Yes.

The biggest improvement, IMO, is the ignition vs. the standing pilot.



You may be right about the biggest improvement, but the improvement
can't be much. My lowest gas bills in the summer are about $10 for
heating water with a water heater has a pilot light. I doubt that
the pilot accounts for more than 10 percent of the gas usage, so the
pilot probably cost about $1 per month or $12 per year.

BTW, I elected to install a water heater with a pilot light and am
glad that I did because operation is nearly silent. I would hate to
listen to an inducer fan every time the water heater burns; the damn
inducer fan on the furnace makes a lot of noise. More over, the pilot
light means that you continue to have plenty of hot water during
electrical outages. None of this applies to a furnace since you can't
operate it without electricity and the burner makes as much or more
noise than the inducer fan. But, it does go to suggest that the
benefits of electrical ignition is minor.