Hi All... my neighbor's carbon monoxide alarm goes off, she shuts down
her 1996 Carrier Weathermaker 58TUA hi-efficiency furnace, calls in
Frank the HVAC guy, and after a peek inside (from the top), Frank
concludes that the heat exchanger is cracked and a whole new furnace
Is this possible? Common?
How can you tell if it's cracked (it looks like new haha)?
What else might be the matter?
Carrier had a 20yr warranty on those things back then... shouldn't a
suggestion be made to use it?
This was an expensive furnace... wt*?
Thanks for all of your help,
Yes its possible, especially if it wasn't installed and set up correctly.
Was it serviced every year like its supposed to?? You wouldn't buy a new car
and try and run it for 12 years without ever having it serviced, would you??
Why would you do it with the single most expensive appliance in your home??
The tech should have *SHOWN* the home owner the cracks
Its broken... there are several reasons it could have set off the CO
detector... cracked HX is a likely culprit, as well as over-firing,
partially blocked vent pipe, etc.
Replacing the HX will cost almost as much as a new furnace...even if Carrier
warrantys the HX.
Expensive is relative... If it was the cheapest price, then all bets are
off. If it wasn't installed by a *competent*, licensed, insured,
professionaly trained, Master HVAC Tech, then all bets are off.
You should [listen to kjpro]. Get a second opinion. Find a service company
with a "Gas Analyzer" to check for CO coming from the appliance. They can
also check for a crack by checking the CO level before, during, and after
the furnace is in operation in the flu. Your local utility may offer a free
inspection to confirm the HVAC service tech's opinion.
Just a slight correction. A CO detector will NOT always find a crack
in a heat exchanger. Many furnaces with cracks support proper
combustion just fine. I wouldnt want that furnace in my home but a
crack in a heat exchanger doesnt always burn "dirty" and cause carbon
Im just restating that but Im sure thats what you meant. :-)
Not necessarily so. The ventor fan sucks ad does not blow.. And the
crack is usually on the top side out of the airstream of the indoor
blower. An infrared camera can spot it when still hot. Or sometimes
smoking it right after shut down There are many furnaces that are
diagnosed with cracked exchangers when all that is wrong is a clogged
chamber in the seconfdary exchanger. This most oftern occurs on propane
furnaces and is due to improper firing. This can be crappy tuning or a
wide variance in the BTUH of the fuelgases. In the winter moisture is
either added or condensed into the gase to make it easier to shove up
the pipelines. This moisture is what causes a tarring effect in the
chambers when the mix is bad.
Most here are updated to the high efficiency ones. I guess I thought you
folks would be more into Heat pumps. As for your take on 80% furnaces..
I concede.. That is the main way of diagnosing cracked exchangers.
Im just sayin.....I had a Tempstar a few years back (90%er) that I got
a call on no heat. It was the main limit (the little camstat POS) that
failed open. I finally looked in and the plastic collector on the side
of the secondary had a hole in the top of it big enough to put a
tennis ball in. The burner roll out never did trip. His CO detectors
never went off (most of them wont though but thats a whole nother
story). Ive had many Tempstars and Janitrols that I found popped rings
on that were burning just fine. Its a bit harder to condem someone's
furnace when they call for a "tune-up" and you have to give them the
"good" news about their working defective furnace.
Using a CO gas analyzer can measure the CO from the flu. Generally
something less than 18 ppm for most gas fired furnaces. When the indoor
blower comes on and forces positive pressure into the heat exchanger [a
rupture] will in most cases show the CO going down. [An increase in
unburned gases [air] getting into the firebox will show a decrease in CO
because of dilution.] When you see this condition, it warrants pulling to
blower and / or burners for further investigation.
The Carrier of a 1996 vintage will have an aluminized heat exchanger, albeit
it's installed correctly would have a good life span, but if there's
insufficient air... well you know. :)
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