Tokai wrote:
I originally posted this on alt.hvac, but received a courteous
suggestion to post on this group.

I can either replace a heat exchanger for about $400 (part under
warranty, labor based upon actual time), or buy a new furnace installed
for a net price of $2,600.

Old furnace: 90% Carrier with a clogged secondary heat exchanger (still
works for about 15 minutes at a time until the limit switch trips, so
can maintain temp in current 30 degree weather). 88,000 BTU.
Manufacturing date of 1989, but some evidence suggests it was installed
in 1992. I replaced the motherboard a few years ago (did it myself for
about $125). The igniter was replaced a few weeks ago (free because the
service guy broke it during the tune & clean). Other than that, I think
all the parts are original. I think it has a lifetime heat exchanger
warranty (part only). Clogged secondary was diagnosed by: 1) Tripping
of Limit cutoff switch; and 2) Soot in exhaust pipe.

New furnace: 94-96% Carrier Infinity 96. 80,000 BTU. Net cost of
$2,600, which is $3,550 less: $150 Carrier rebate, $170 for paying cash
(rather than credit), $150 utility company rebate, $400 for replacing
a Carrier (bad heat exchanger program?), and $80 for tune and clean
performed 10 days ago. 10-year parts and labor warranty. Lifetime heat
exchanger warranty (part only). Because it is replacing a 90% Carrier,
it is a pretty direct swap-out. The new unit is a little shorter, so a
short collar to bridge the gap. PVC air supply and exhaust pipes are
fine.

Situation: South East Wisconsin. I'm guessing the new furance will save
$200/yr, but also make the house more comfortable because of the
multi-stage, and hopefully a little more quiet.

Because of rebates, a single stage 90% Carrier is only $300 cheaper,
and the other 2 stage Carrier is about $150 cheaper. The comparable
Lennox is about $500 more expensive (primarily due to the $400 Carrier
rebate). I have not priced a Trane or Rheem.

I currently have 2 furnaces, and the other Carrier is identical, except
for being a smaller BTU. If I replace the furnace, I would keep the old
one for spare parts.

Questions:
1) Any thoughts on replacing the heat exchanger, or the whole furnace
(seems like the age of the furnace is on the edge of being "old")?
2) Does the price seem reasonable?
3) How can I determine if they will install it right?
4) Did they cause the problem when they tuned the furnace (dislodged
rust that clogged the secondary)? Service man did say the heat
exchanger was rusting, but should last a few more years.
5) If they didn't cause the problem, should they have been able to see
the problem during the tune and clean (the problem arose when I set
back the thermostat 5 degrees when we were away for the weekend, and
the furnace needed extended run time to warm up the house)?

Thanks in advance for your help.

this is Turtle.

you want use to tell you about a problem here of furnases.

You have a 90% afue furnace that can be fixed for $400.00 + free parts.


You can get a new 94%-96% afue furnace for $2,600.00 which will save
you $200.00 a year.

The saving between the old one and buying a new one is $2,600.00 -
$400.00 = $2,200.00 to try to make up for with the savings of the new
furnace with $200.00 a year savings. At this rate , it will be 11 years
before you get your money back by way of savings of $200.00 a year.
then if you figure in if you took this money and put it CD's it will
double every 10 years. then this 11 years turns into 21 years.

how long are you going to be in this house ?

How Old are you ?

You will be looking for a new one about the time you get your money
back.

You tell me what you want to do after reading this.

TURTLE