bulges and "hot spots" inside 20 year old furnace...do I really need new one?

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I had my 20 year old Carrier forced air furnace tuned up today. The technician snaked a camera up the inside of the furnace. He did NOT find any cracks, but he found "bulging spots" which he also referred to as "hot spots", inside the furnace. He claimed the heat exchanger had these bulges and claimed that this is a sign that it is getting close to developing cracks, and showed me the bulges.
But I wonder if what he showed me really was the heat exchanger....can a camera can really be snaked up inside a heat exchanger?...or was what he showed me something else. I always assumed that a heat exchanger is a tremendously dense piece of metal and that you would not be able to "view inside it with a camera" only "view it from below with a camera". This same cavity could also be seen without a camera by looking into the furnace with flashlight (he had removed one of the panels above where the burners are) What he showed me was was a vertical cavity which had a couple of bulges on the sides of the cavity which were bulging toward the outside. Is that really the heat exchanger he showed me? What does the heat exchanger on a 20 Yr. old Carrier furnace look like and exactly where is it located?
There is also some rust present on the inside of the furnace.
The burners look like they produce a nice blue flame.
The technician is recommending a new furnace based on the age and based on the bulges and rust. Do I really need to be seriously thinking about getting a new furnace at this time because of the rust and bulges, or is it possible this furnace could last several more years? I believe they recommended a new furnace 3 years ago when I moved in although I don't recall anyone showing me the bulges before, but I'm suspecting they could have been present 3 years ago too.
BTW, the company I've been using prefers to install Goodman systems, although they would also be willing to give me a price on another brand that I have in mind which is Carrier. They say that they will warranty both the parts and labor for 10 years on the Goodman, but the warranty on the Carrier would depend on what their warranty is. Is a Goodman likely to last as long as a Carrier?
Thanks,
J.
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On Thu, 04 Oct 2007 22:38:58 +0000, snipped-for-privacy@verizon.net wrote:

I used to do furnace checks and was told to sell new furnace installs at any cost short of being fraudulent. The heat exchanger in you furnace is welded steel and is not known to crack or develop leaks at the welded seams. However at 20 years in service I would consider an upgrade if it is your budget to afford it. If it is affordable you would benefit from an increased efficiency in a high SEER rated furnace.
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I'm sure they love the idea of selling me a new furnace even if it isn't really necessary at this time.
Wondering if other metal inside the furnace were to crack and it weren't the heat exchanger cracking per se....would that require furnace replacement?
J ---------------------------------------------------------------------------------------------------------------------------------------

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On Thu, 04 Oct 2007 23:27:01 +0000, snipped-for-privacy@verizon.net wrote:

Main concern for safety is the heat exchanger. A crack or weld leak will allow CO from the combustion to mix with the heated air. Not much other metal that would crack or such.
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wrote:

the
replacement?
Maybe you need to look at a induced draft, inshot burner type of furnace. Things change over the years.
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snipped-for-privacy@verizon.net wrote:

The notion of a cracked heat exchanger being a hazard involves the leaking of CO into the living space.
Be aware that, for thousands of years, humans heated their dwellings without benefit of heat exchangers; some still do today.
I grew up in a home with natural gas heaters in every room. The only problem it ever caused me is the inability to tie my shoes. In all fairness, lately I have noticed a difficulty in using complicated mechanical devices (such as a spoon).
Nevertheless, a CO detector (or a canary) is far, far cheaper than a new furnace.
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wrote:

Furnaces are only built to last for 18 - 20 years. The new models use a fraction of the energy to run them. You can keep funneling money into repairs, and giving your money to the utility company if you want. Its been my personal experience that when I install a new comfort system in a customers home, there utility bills drop on the average of 60%, and the new system is so quiet, they are not even aware that its running. Its your choice....Keeping the old furnace will cost you more in the long run, and you'll *STILL* have to replace it...... its not a matter of *IF*, its a matter of *WHEN*
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Sorry Meat,
Paul is right. Furnaces don't have SEER ratings, that is an AC efficiency rating.
I manage several (around 20) townhouses that all have 16-17 year old Carrier furnaces. We have replaced 3-4, and are expecting to have to replace the rest of them over the next 2-3 years because the heat exchangers are failing. Granted, it is generally the secondary heat exchangers getting plugged with crud, but it isn't far fetched that the primaries are failing too, or if you have an 80% efficient model, the primary is all you have.
To the OP -
No, a heat exchanger is NOT a very dense piece of metal. Here is a link to a photo :
http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=HE
Your tech, from above or below, would be looking at the outside of this, getting the same view as you have in the pictures. Typically, on an upflow furnace, the heat exchanger is in the top of the cabinet, but we don't know what you have.
Like Paul said, get another opinion. If you decide to wait, do yourself a favor and spend $30 (or so) on a carbon monoxide detector.
JK
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wrote:

find
"hot
bulges
a
he
a
"view
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furnace
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outside.
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http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Cod e=HE
A 30 dollar CO detector is crap. Unless you spend a couple hundred dollars on a good one, it's a false sense of security.
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Heat exchangers do crack, yes you can look inside the exchanger, and usauly there will be a white area around the crack but not always, get a second if you want if he says the same buy it
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Would you have any evidence for this article of faith?
Nick
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On 5 Oct 2007 04:19:56 -0400, snipped-for-privacy@ece.villanova.edu wrote:

Nick, You can start right here. Its on the front page http://coexperts.com / The level that CO detectors DONT alarm at is the real problem. Happy reading. Bubba
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sense
Name one cheap $30 detector that protects against low level CO poisoning.
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hehe. 95% of the population (I made that percentage up on guesstimate) doesn't have a clue that an "average" CO detector might as well just be a dim night light plugged in the wall. At least you can tell when a night light goes bad. Bubba
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-- 95% of the population (I made that percentage up on guesstimate) ...
Did you know that 93.7% off all statistics are made up on the spot?
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It should be illegal to sell them without a disclaimer.
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They do have EERs, like ASHRAE bunnies: if a furnace moves 40K Btu/h with a 400 watt blower, the EER is 40K/(400x3.41) = 29.
If a 2K Btu/h car radiator with 36 W fans moves (140-50)2K = 180K Btu/h from 140 F solar heated water to 50 F air with a 170 W pump, the EER is 180K/(206x3.41) = 256.
Nick
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re: "No, a heat exchanger is NOT a very dense piece of metal."
Granted, I can't speak to a 20 YO Carrier, but the heat exchanger on my old gas fired unit was one heavy, honkin' mass of metal, looking somewhat similiar to an old water filled radiator. By far the heaviest component of the entire furnace.
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wrote:

The
find
as "hot

bulges
developing
exchanger....can a

what he

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an
It may be the heaviest, but it's not like its a 1/4 inch thick.
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- It may be the heaviest, but it's not like its a 1/4 inch thick
Dunno...it was a 1950-ish Perfection gas fired forced air. From exterior of the heat exchanger, it certainly appeared and felt, like the unit was pretty thick.
In an earlier post, someone said (about the 20 YO Carrier) "The burner tubes are inside the heat exchanger". On my perfection, the burner was below the heat exchanger in it's own compartment. The burner was, I don't know, about a 9" x 9" plate with over a hundred (?) flames.
The heat exchanger pictured towards the bottom of this site looks like an absolute wimp compared to the rough surfaced, solid looking heat exchanger in my old furnace.
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