I don't know what temperature your furnace flue pipe should run, but an 80%
efficiency furnace is not very efficient, so I would expect that the flue
pipe would run quite hot. You would have what is called a mid-efficiency
furnace, basically a regular non-efficient furnace that has a flue damper
and sometimes a power exhaust added to reduce some heat loss.

You cannot reclaim most of the heat from your furnace flue as it requires
the heat to create the draft that will lift the exhaust up the chimney and
out the house.

Furnaces that run cool exhausts are the high efficiency ones that run 92% to
98% efficiency. They have a heat exchanger then run the exhaust through a
condensing chamber then power exhaust through a 2 inch plastic pipe the
outside. They need a drain line to dump the acidic water that they condense
from the exhaust.


wrote in message
ups.com...
Okay, last stupid question about my stupid Amana furnace.

I keep forgetting to use my IR thermometer on the exhaust pipe, but it
seems awfully hot to the touch. You can't keep your hand on the pipe
for more than a second or so. I don't think it'd burn, but it is beyond
the human threshold of pain.

It's an 80% efficient furnace, so I'd expect the pipe to be somewhat
warm to the touch. But, it's got a power vent too. Exhaust goes up a
conventional chimney and out the roof, along with at least 20% of my
gas bill

Should it be that hot? Understanding that some is radiating off the
pipe into the basement, is there a way to reclaim more of that heat?

Thanks for all the info!