On 3/11/2013 11:38 AM, nestork wrote:
It's like so many other things... it's possible to replace a furnace
heat exchanger, but that's not an economic alternative. The cost will
be close to that of replacing the whole furnace, and everything else in
that furnace is 15 to 20 years old and can go at any time. So, better
to spend more and get a new high efficiency furnace rather than keep the
old one alive only to have to spend more on repairs as it gets still
older.

Note that if you get a high efficiency "condensing" furnace, that means
that so much heat will be taken out of the flue gas that it won't rise
up your chimney any more AND corrosive condensate will precipitate out
of that flue gas. So, typically, the flue from a condensing furnace
will just be vented out a side wall with a blower blowing the flue gas
out and drawing fresh air in.

Also, some jurisdictions require that the condensate from high
efficiency boilers, furnaces and water heaters be treated before being
dumped into the sewer. That means you have to buy or build a pH
neutralizing filter to neutralize the corrosive condensate, and that's
not hard to do. There's a company in Saskatoon, Saskatchewan called
Axiom Industries that provides the filter media for $40 for a 40 pound
box. It's called NMD-25, and it works very well at neutralizing
corrosive condensate providing your filter is large enough. It's most
common to just run the condensate through the filter and into a sump
pit, and then let the sump pump pump it out along with any ground water
in the sump pit.





I had a $600 control board fail on a 14 year gas old furnance and
instead of replacing the board elected to go with a brand new and here
are the results:

80% to 96% effeciency, which is $25 dollars a month in winter in gas
savings(Canada) from what I can see in my bills (1800 square foot home)

$650 in government refunds for replacing old furnance with new high
effiecency

$250 government refund for installing a variable speed blower fan.

Variable speed blower appears to be saving $1 a day in Air conditionting
costs (June July August usages)


Just some things for the OP to consider.