Cracked Heat Exchanger


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Old 11-17-13, 07:24 PM
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Cracked Heat Exchanger

During the yearly maintenance on my furnace the tech told me I have a cracked heat exchanger. System is a 13 year old natural gas high efficiency condenser furnace. He showed this by turning on the blower fan only and holding a lighter in front of the intake vent for the combustion chamber. The flame did flicker a bit and looked like it was blowing away from the intake vent. Tech said this proves a crack. He took CO measurements at the supply vents and read 0ppm.

He said he would need to shut furnace down if he detected 8ppm, crack could get much worse at any time, CO detectors don't pick up until 200ppm, I need to replace the furnace ASAP.

Only been in the home 1 year and using this HVAC company for the first time. Trying to figure out if this a scare tactic or if I have a legitimate concern.

Not sure if a cracked heat exchanger would make the flames dance on a condenser style furnace or if that's only on standard furnace, but the flames do not jump or dance at all when the blower comes on.

So - does a draft out of the intake vent of the combustion chamber when the blower fan is on definitely indicate a cracked heat exchanger and a need for a new furnace ASAP or is there something else I can do to confirm or rule out a cracked heat exchanger?
 
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Old 11-17-13, 08:00 PM
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is there something else I can do to confirm or rule out a cracked heat exchanger?
I believe I'd get a 2nd opinion from another company, preferably a company you can find on referral from someone you trust.
 
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Old 11-17-13, 08:10 PM
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Get a second opinion. Its common to use scare tactics to get a sale ... The right way to verify a crack from how my old company did it was insert a camera and inspect the heat exchanger visually.

If he did not offer this ( and he may not even have a camera) then it may be hogwash..
 
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Old 11-18-13, 12:14 AM
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Some crimped clamshell heat exchangers may only be airtight when hot.

That's not a valid test.
 
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Old 11-18-13, 04:05 AM
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I agree.
You should be able to see the crack by either an inspection camera or removing parts to allow you to see it.
Besides, he should have offered a quote to replace just the heat exchanger.
 
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Old 11-18-13, 06:21 AM
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With that vintage of furnace there were some brands that experienced premature failure of the heat exchangers.

Not saying you do or don't have a cracked heat exchanger , but, I absolutely agree with the others ----- get a second or third opinion.


During the yearly maintenance on my furnace the tech told me I have a cracked heat exchanger. System is a 13 year old natural gas high efficiency condenser furnace. He showed this by turning on the blower fan only and holding a lighter in front of the intake vent for the combustion chamber. The flame did flicker a bit and looked like it was blowing away from the intake vent. Tech said this proves a crack. He took CO measurements at the supply vents and read 0ppm.
The lighter trick doesn't prove a cracked heat exchanger, considering the CO reading of 0ppm doesn't support his story.


He said he would need to shut furnace down if he detected 8ppm, crack could get much worse at any time, CO detectors don't pick up until 200ppm, I need to replace the furnace ASAP.
Again, since his CO measurement showed 0ppm and doesn't support his claim of a cracked heat exchanger.

It's not unusual to have a crack present in a heat exchanger only to be noticed when it's cold. Once the heat exchanger becomes hot the crack closes due to expansion of the metal. In which case a CO reading will register at a higher value initially and decrease indicating this scenerio.

Only been in the home 1 year and using this HVAC company for the first time. Trying to figure out if this a scare tactic or if I have a legitimate concern.
Getting a second or third opinion is the best option.
Yes, it's a legitimate concern but it's not an immediate one otherwise the gas would have been shut down and the furnace *red tagged* ( as we call it around here ). Arrange to line up other HVAC professionals to verify whether or not there is cause for concern ( in short order mind you ).

Around here we can contact the gas utility and they would send out a professional to inspect the furnace and give an unbiased evaluation.

Not sure if a cracked heat exchanger would make the flames dance on a condenser style furnace or if that's only on standard furnace, but the flames do not jump or dance at all when the blower comes on.
It can still be a visual refrence. Regardless of the type of appliance the heat exchnager(s) are in the air circulation path .

A crack in the heat exchanger would allow the air being moved by the circulation blower to infiltrate into the combustion chamber and creating turbulance. This causes the flames to move eractically along with introducing a yellow color to the flames instead of a nice consistant blue color.

Subsequently, this also allows some of the combustion gases ( CO ) to escape into air circulation stream and distrubited throughout the home.

Now, this is not a definitive test but is is a good visual referance to investigate further.

So - does a draft out of the intake vent of the combustion chamber when the blower fan is on definitely indicate a cracked heat exchanger and a need for a new furnace ASAP or is there something else I can do to confirm or rule out a cracked heat exchanger?
If this is a direct vented furnace with both the exhaust and intake direct vented outdoors -- not necessarilly a definitive test.

Unlike the exhaust , which is power vented with a blower , the intake is in part a natural draw from outside. There can be turbulance at the intake by natural positive and negative air pressures from outside --- how windy is it outside for example.

As far as what you can do -- not much other than getting other expert opinions.


2 cents worth.
 
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Old 11-18-13, 03:43 PM
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A crack well downstream of the burners may not increase co production, in theory.
 
 

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