Cracked Heat Exchangers and Furnaces

Last Updated on Monday, 01 February 2010 16:12 Written by Richard Friday, 29 February 2008 17:40

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The Dangers of a Cracked Heat Exchanger

A Cracked Heat Exchanger

Everyone wants heat when old man winter arrives in the fall. Many times we take it for granted that when the temperature falls all we have to do is go to the thermostat and turn the heat on. Usually, this is not a problem. We turn the thermostat on and the heat comes on. Whether we have boilers or a furnaces at the beginning of the season when we do first turn the furnace on we have a slight burning odor which comes from the system. Usually, many of us ignore this odor because it does eventually, usually, go away. This is normal and is usually dust particles that have accumulated on the furnace's heat exchanger burning off. How many people actually think it is carbon monoxide and called a professional HVAC technician to make sure it is not a problem? There are some people who do call but a majority of people just ignore and enjoy the heat being produced by their furnace. After all, carbon monoxide is a colorless and odorless byproduct of burning fossil fuels so even if an unsafe condition existed with their furnace they would probably never know it. This is why it is important, before old man winter arrives, to call a professional, qualified furnace technician to inspect the furnace. First, the furnace technician can make sure that the furnace will start and second of all the furnace technician can make sure you will have a safely operating furnace. You want to make sure the furnace does not have a cracked heat exchanger and a good qualified HVAC technician will look for a furnace cracked heat exchanger. Heat safety is paramount so have your furnaces inspected immediately. Have a safe heating season.

Carbon Monoxide Detectors

Heat safety is important. A carbon monoxide detector installed in the home is a very good idea. In fact, many believe it should be a required item to go along with any type of fossil fuel burning appliance including a furnace. Remember, carbon monoxide is a colorless and odorless gas which is highly toxic to humans (and animals). You will never see it or smell it but you will feel the effects of it. It can make you physically ill and while it may happen all at once and possible incapacitate you, chances are it can also happen very slowly. At first the effects of carbon monoxide poisoning can seem mild but as time goes on and you absorb more of the gas into your system the effects can be crippling. If you have a fossil fuel burning appliance, including a gas or oil furnace, it is important that you install a carbon monoxide detector so that you can enjoy a safe and healthy heating season. Gas furnaces can be safe for providing heat safely to you and your dwelling but let us not take it for granted.

Anyone who has an oil or gas boiler, oil or gas furnace, gas logs whether they be propane or natural gas, a gas stove or oven, any wood burning appliance or fire place, or appliance or heating device that burns fossil fuels you need a carbon monoxide detector installed in your home or business. Tragedies including death and severe sickness occur every year because of carbon monoxide poisoning. It does not have to be from a fossil fuel burning appliance that causes the carbon monoxide danger. It can be from someone starting their car in a garage without opening the garage door. The person may get by with this for a while but eventually the carbon monoxide infiltrates the house and a build up can occur. There was story reported on the news after a hurricane. A man set up a portable gas generator because the electricity was out because of the storm. He set the generator up next the house too close to a window. The wind blew all the exhaust gases from the generator into the room where the window was open and the carbon monoxide killed his daughter. There are too many tragic stories to tell about the dangers of carbon monoxide. Take necessary precautions when dealing with any fossil fuel burning appliance or device and get a carbon monoxide detector. Play it safe so you don't make the news.

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Not Enough Information
written by Paul S Person, September 04, 2008

Here we have a section labled "The Dangers of a Cracked Heat Exchanger", which I am interested in because my heating oil company claims my furnace has one, and it says NOTHING WHATSOEVER of what those dangers might be.

Given the second part of the article, carbon monoxide would be a good bet. But the stack temp came up higher than before, and it is fairly stable, so I was wondering if there was a fire/explosion danger as well. I'll keep looking ...

Former Member of American Society of Home Inspectors.
written by Robert Shideler, December 16, 2008

Cracks can open in any heating cycle. If cracks are so dangerous, shouldn't heat exchangers be inspected after each heating cycle instead of once per year? I have inspected thousands of furnaces (mostly the 70% efficient type). What I have to say here may not apply to furnaces above 80% efficient. Using a 1 part per million CO tester, I could not get any detectible reading of CO in the air stream near the heat exchanger. Most older burners did not produce more than 25 or 30 ppm CO. Newer burners much less. Even if the crack created a venturi effect that drew CO from the burner into the air flow, that small amount of CO distributed with the blower air would have undetectable amounts of CO. If the burner is well tuned and there is proper venting, there is almost no chance that CO will build up. Every reported death I am aware of had poor venting.
An exception is a rusted out heat exchanger. Flakes of rust can fall on the burner causing poor combustion and an increase in CO. When I checked a furnace, I taped the air inlets to the burners which produced about 500 PPM of CO. I still could not get a detectable reading on the air stream even with a cracked heat exchanger. My recommendation is: take your time repairing the cracked heat exchanger, but by law, the crack must be disclosed to a new buyer who may demand the heat exchanger be replaced.

-3

Sorry I assumed.........the authors response
written by Richard the Author, December 16, 2008

In response to Paul Person - Sorry I assumed people knew that combustion appliances produce carbon monoxide which is very hazardous to ones health. Carbon Monoxide is not explosive.

In response to the home inspector - just because you could not get a furnace to produce 25 or 30 PPM of CO does not mean that CO will not build up in spaces that have poor ventilation and accumulate to very dangerous levels of CO. ASHRAE contends, and I agree that a short term exposure to 9 PPM is allowable (they do not define what short term exposure means in the documents I have but I assume it is less than 8 hours). 10 to 24 PPM can have hazardous health effects to humans to humans and animals exposed to that amount. Regardless of the data and documentary evidence about the hazardous effects of CO - CO does accumulate and the 25 or 30 PPM you measured builds into 100 PPM and higher over time in spaces with poor ventilation. Try measuring CO in a garage where people start their cars even with garage door open. CO levels can be measured in poor ventilated areas of the garage at toxic levels to humans even if they just start their car and immediately move it outside. I personally have seen the ill effects from a cracked heat exchanger. I believe your intentions are good but you just didn't carry it through and think about the cumulative effects of the build up in poor ventilated areas.

Former house inspector
written by Robert Shideler, December 17, 2008

If the furnace is vented properly, and the burner is properly tuned, it is probably impossible to have significant CO build up. Houses have a complete air exchange with outside air in about an hour. The tightest houses have an complete exchange in about 3 hours. The American Gas Association allows holes in the heat exchanger up to 3/8 inch diameter or larger depending on the BTU capacity of the furnace. Heat exchangers are not hermetically sealed and some even have small holes created by the manufacturer. If the furnace is dangerous, then a gas stove is more so. A gas stove with all burners on produces about half the heat of most furnaces. Most gas stoves are not vented to the outside and many houses use recirculating hoods over the stoves.

Consistantly, the main problem with furnaces is poor venting of combustion gasses followed by poorly tuned burner. Again, I do not personally know of any significant CO build up due solely to a cracked heat exchanger. A rusted out heat exchanger with gaping holes could be a different matter.

-3

Sing the Song
written by Richard the Author, December 17, 2008

And beat the horse...........you can sing that song until the cows come but I have seen firsthand carbon monoxide poisoning from cracked heat exchangers in multiple instances. A cracked heat exchanger, while it may not induce CO into the airstream, is dangerous!!!!! Period! I'll tell you what, you give me your phone and the next time I run across a cracked heat exchanger where the people are sick or have been sick because of it I will give you a call and you can explain to them that it WAS NOT the cracked heat exchanger that gave them the headaches, nausea, and lethargic feelings. Have a good day))))

BTW
written by Richard the Author, December 17, 2008

By the Way, those systems you describe with holes in the exchanger are by design. Ventless gas logs are by design. The cooking stove you describe is by design (notice the solid blue flame on most cooking stoves). They are design for maximum combustion of the gas to prevent CO. Ventless gas logs have an O2 sensor on the pilot so if there is a build up of CO the gas logs will not fire because the O2 sensor prevents the pilot from burning when no O2 exists. A typical gas furnace is not (IS NOT) designed for a crack in the exchanger and when this happens it can possibly be dangerous. Yes I said possibly. I said this because sometimes the pressure outside of the heat exchanger is greater than the pressure inside the heat exchanger so the air from the airstream outside of the exchanger mixes with the air inside the exchanger. This makes the problem worse and produces more CO. Hopefully if the occupants are lucky the crack won't get any bigger. Unfortunately it often does get bigger and eventually some of the excess CO gets into the airstream and the people get sick. I was working a furnace a few years ago and I started to get dizzy. I left the house and went to my truck and got my Bacharach CO detector (Bacharach is the best by the way) and sure enough the CO was over 80 PPM. I condemned the furnace after finding a crack in the exchanger. The homeowner had called about something altogether different and wasn't aware of a cracked exchanger except he was sick. He had been to different doctors to find out why he was feeling bad over the last few months before I found the cracked heat exchanger. I didn't write the article by reading things from a book. I wrote the article because people need to be aware of this danger. I've seen this firsthand and it is no joke.

Former House Inspector
written by Robert Shideler, December 17, 2008

To Richard the Author. You are saying that a 70% GFA furnace with proper venting and properly tuned burner produced 80ppm CO in the house with a small crack in the exchanger? Is that correct?

-1

Impressions
written by Richard the Author, December 17, 2008

I get the impression you are the type of person who would argue with a fence post. This is not a forum for debate or arguing back and forth based on supposition of some tests someone came up with and think these test are final and proof. This is real world advice and quite frankly I do not remember what kind of furnace it was. At the time it was normal for me to see anywhere from 15 to 40 furnaces a week. I was in the field at the time and now I am in the field only on a limited basis as a consultant and sometimes in a training capacity. I am a professional licensed HVAC Master with many years of experience in the field working on HVAC equipment. I have been to many, many classes about HVAC including classes on CO and CO poisoning. I am highly respected in my trade both locally and nationally. I am not right 100% of the time and I certainly do not know everything. I am glad you have experimented with gas furnaces and hopefully it was your own gas
These are real world occurrences and not a supposition or from a book or a test which I think is appropriate
furnace and not someone elses. I truly wish more Home Inspectors took an interest as you have in gas furnaces and other HVAC subjects. There is one of your colleagues out in Phoenix (I think) who makes videos which are posted on YouTube and other video posting sites that call HVAC techs murderers. He is promoting his business at the expense of HVAC technicians based on the exact subject we are discussing right now (maybe you can talk to him and give him the same conjecture you offer here). I don't think there are any HVAC Techs out there who have any malicious intent on harming anyone. In fact, many have advised people of dangerous situations, including myself, and have been ignored including advising people on this very subject. If I find a cracked heat exchanger I condemn the furnace whether it is spewing CO inside the dwelling or not. I also turn the gas valve of and sometimes disable the controls so the furnace has no way of firing. I then write it on my ticket and make the homeowner sign the paper saying they are aware of the cracked heat exchanger and that the gas heat has been disable and condemned because of the crack. I have returned a few days later an observed the condemned furnace running. I can only shake my head because I have seen the DANGERS OF A CRACKED HEAT EXCHANGER firsthand. In the photo I posted in this article.....the woman was in a wheel chair because of the harmful affects of CO. So what if it was a 70% AFUE furnace properly tuned? It doesn't matter does it? The fact of the matter is the man had CO in his house and was sick from it. So therefore, all these tests you have done and your very own opinion you are promoting on this forum really do not make any difference to me at all because in my world these are real occurrences where I visually observed sick people and the problem was fixed and these people went on to lead otherwise healthy lives after the furnace was replaced or the heat exchanger was replaced. By the way, a heat exchanger should never be repaired unless you are metallurgist or a furnace manufacturer.These are real world occurrences and not a supposition or from a book or a test which I think is appropriate. People get sick from cracked heat exchangers and thank God I have not found anyone who lost their life because of a cracked heat exchanger but I am almost certain it has happened and this is why I say people need a CO detector in their home if the have any type fossil fuel appliance in their home including furnaces of any kind except an electric furnace.

Former House Inspector
written by Robert Shideler, December 19, 2008

I applaud your passion to do the right thing. You have made some good points. I also have some. When I was trained as a house inspector, I learned about the "dangers" of cracked heat exchangers. I found that cracks were not easy to detect. I was worried about how I sould feel if someone died because I did not detect a crack in a heat exchanger. I became an expert at finding cracks. At times, I was finding cracks between 10 and 20% of furnaces inspected. Often, HVAC contractors claimed there were no cracks, but I would go out and show them. I got tired of being second guessed so I began leaving my my business card showing where the crack was. For a time, I was very proud of myself. I remember a couple of more reputable contractors indicating maybe I was going too far with the naturally vented GFA furnaces. Cracks tended to occur in the same places on different models and the cracks rarely opened up more than a hairs width. In my city alone, probably tens of thousands of homes had cracked heat exchangers. There should have been an epidemic of health related problems. After that, I taped shut burner air intakes of every furnace I inspected and tested for CO (with a Bacharach CO detector) in the air stream near the heat exchanger and at a nearby register. I never once got an elevated reading in the air stream (yes, I had the detector calibrated periodically). With the air intakes shut, the CO level at the burner was in the neighborhood of 500 ppm. With the intakes open, most burners had between 5 and 10 ppm. The lack of readings in the air stream of the thousands of furnaces I checked indicates that the situation where the blower airstream will suck air above the burner into the air distribution system is very rare. The next time you remove a furnace from an empty house, try getting CO into the airstream through any normal crack. When you are able to get some CO into the airstream, remove the tape from the burner air intakes and see if you can still detect any CO.
I will guarantee you that the house with elevated CO had a venting problem. The tuning of the burner probably was not the problem. My contention is that with a properly tuned burner, proper makeup and combustion air, no cracked heat exchanger (I am not talking about gaping holes) will cause a CO problem.

When a small crack is detected on a furnace with prober venting, and combustion air, the homeowner does not need to pay overtime wages to replace the furnace that cold winter night to prevent pipes from freezing. The homeowner has time to get his finances in order and think about the furnace and contractor he wants.
My questioning about heat exhanger cracks got a boost when I followed a fellow inspector in an empty house. The water heater was turned off. He lit the burner and removed the draft diverter so the exhaust gasses went directly into the basement. All windows in the house were closed. We could detect no CO in the basement when we returned about 30 minutes later. The other inspector reminded me that the 40,000 BTU water heater puts out about as much CO as a gas stove with all burners on. I also found out that, in older houses, the total volume of air in the house is replaced with outside air about every 1/2 to 1 hour. In other words, CO will reach a maximum build up in about 1 hour in older houses and about 3 hours in very tight houses. The only way the CO can increase after those times is if interior air is used for combustion air faster than outside air can replace it (i.e. poor or no venting).
Since these "extremely dangerous" cracks (even wide ones) can occur in the next heating cycle after the last inspection, why is it industry standard for these dangerous cracks to go undetected for a year until the next inspection?
On the other hand, I have found CO in gravity furnaces with cracked heat exchangers. I will not argue with you about the need to replace them. I also cannot comment on the enclosed high efficiency furnaces.

Contention = Assumption
written by Richard the Author, December 21, 2008

Your contention equals an assumption that every furnace is properly tuned. The water heat where you left it it not hooked up to the flue - I was in a mechanical room one time. This mechanical room has a large chiller, a large steam boiler, and a small 40 gallon water heater tucked away in the corner. I was there to service the steam boiler. I carried my tools in the mechanical and started working. After about 10 minutes I started to get dizzy. Red flags begin to go off and I removed myself from the mechanical room ASAP. I returned 15 minutes later with my CO detector and refrigerant leak detector. Both CO and refrigerant will make you dizzy. I don't remember what my CO detector registered for PPM but it was enough to make me look around. I checked the steam boiler which I had shut down for maintenance purposes but everything there seemed to be fine. I found the water heater over in the corner and the flue was rusted through and it was spewing CO into the mechanical room and thus the reason for me getting dizzy. When it comes to safety never assume things. With CO poisoning you may never have another chance to assume. I would never ever ever under any circumstances leave a furnace with a cracked heat exchanger in service. Assuming can have deadly consequences and I will sleep good at night knowing I always did the right thing and not worry if the homeowner is still alive after running the furnace with a cracked heat exchanger that I found and told them about - I can see myself in court right now being sued by the family - I'm sitting on the stand and the lawyer asks me, "So you let them run the furnace so they would have time to get their finances in order to buy a new furnace?" I will never be placed in the situation and will make an err on the side of safety versus a financial situation. I don't care if someone jumps up and down and holds their breathe for 15 minutes because they don't have heat - GO TO WALMART OR THE HARDWARE STORE AND BUY SOME ELECTRIC HEATERS TO GET YOU THROUGH UNTIL YOU GET THE FINANCES IN ORDER. Don't get mad at me I'm just the messenger. If they decide to make the furnace operational again then that is their decision but I did the right thing and condemned the furnace and documented it. How many people take the lowest bidder? How many people never have their furnaces maintained on a regular schedule? Too many go with the lowest bidder and end up with a system that is dysfunctional or becomes dysfunctional over time because it was never installed properly or tuned properly when installed. I am not saying that the lowest bid is always going to give you poor quality but the odds are you will get a poor installation with the lowest bid. The same with the people who don't have regular maintenance done to their furnaces.................there are millions of furnaces out there that need maintenance. I am not going to guess or assume especially when it comes to human life. If the furnace has a cracked heat exchanger I condemn and disable the unit. I go home to my wife and I have a good evening with her. Then I go to sleep and never have any worries because I don't assume or guess when it comes to safety and safety related decisions. I also hold a Masters license and this makes me more responsible. I will never intentionally endanger someones life and you will never see my name in the newspaper in a related incident concerning carbon monoxide unless it is an OpEd from a homeowner business person who was angered because I condemned a bad furnace. In that regard I will be happy to have my name in the OpEd.

Cracked Heat Exchange
written by Jake, December 22, 2008

HELP! I found your comments while researching what a HVAC Technician told me about my gas unit. I apologize in advance if my terminology is incorrect--I know nothing more than what I was told.
About a week and a half ago my gas furnace stopped working--blowing just cold air--even when I turned the furnace off. I called a technician out. The error code in the unit said a "roll out switch" failed. He said I had a cracked heat exchange. He said it would be ok to run the furnace, but to make sure we had carbon monoxide detectors. I have a home warranty, so they filed the paperwork to see what the warranty company was going to do. Since then, we've had warmer weather and no need to run he furnace. Last night, colder weather came in--and the unit was running, what seemed normally early in the evening. At 5am, I got up and the house was filled with the smell of an electrical fire. I searched everywhere in the house and found nothing. I decided to call the fire department as the smell continued to worsen. 3 trucks and 6 firefighters later--they believe they traced it to the gas furnace outside the house. We "aired out" the house--and the smell did go away. In what I've read above, no one mentioned anything about a "burning smell" associated with a cracked heat exchange. Are the two related. The technician said they might replace the heat exchange--but also mentioned potentially replacing the entire unit. Again, this would be covered by a home warranty--what should I expect? More important--from what I read--it seems very dangerous to even have the unit running (no, I don't have it on--we're just bundled up!).

CO
written by Richard the Author, December 24, 2008

One resource for my opinion is located at http://www.cpsc.gov/library/co05.pdf - Please have a look at page 7.

How do I replace my cracked heat exchange?
written by Michael Hall, January 02, 2009

More of a question than a comment. I own a 1966 era home with a propane gas heater that was upgraded in 1989 with a central AC unit/furnace. Last year I had it inspected and saw cracks in the heat exchange. I would like to upgrade the system again due to more rooms becoming functional, but the cost is beyond our budget at this time. My thought was to replace the heat exchange, but I'm not sure if that is possible or what the expense is. Could you help me with that and put me in the right direction to resolve this issue? Thanks.

...
written by Josh, January 04, 2009

To the home inspector. Im now a operations manager of a local heating co. For 15 years I was a service technician dealing with these same issues of cracked heat exchangers. I believe that if there is a substancial crack to not take any chances with the furnace. Remember that you are liable if you touched it last. I was not about to take any chances and be liable for some little kid sleeping at night. I've learned that co can become very dangerous very quick. Some the best co information I've seen is from Jim Davis. Maybe you should take a look at the articals.

Homeowner
written by Bob Vanderberry, January 12, 2009

Just had a new load of propane delivered. Have smelled the odorant(mercaptin)since. The technician could not find a heat exchanger problem.I got a new CO and gas detector. The highest CO level is 12PPM. There has been no gas detection. Is it possible there was too much mercatin put in the latest propane batch?

Home inspector
written by Peter Sherwood, January 20, 2009

I am a home inspector in Virginia. My time is split between inspections, marketing and learning. I am always looking for good material to better myself at my profession. I was hoping that Richard the Author could recommend a good book to help me better inspect gas furnaces and more importantly how to identify problem hazardous cracks. Thanks

No CO measured in the airstream? Ok, that means nothing!
written by Greg Hunsicker, February 02, 2009

99% of the heat exchangers one would encounter today operate under a slight negative(natural draft) or definite negative(induced draft) pressure inside the chambers. That said, when a crack or hole develops in the chambers and you have positive pressure on the outsides of the chambers from the main blower motor forcing air around the chambers it is highly unlikely you will get combustion products delivered into the supply airstream ductwork. Yes, in certain situations it can happen such as when you have multiple cracks or holes in the same chamber or in low pressure areas where a venturi effect could suck for lack of a better word combustion products out of the chamber. Most cracks or holes will allow the blower to push house air into the chambers which then dilutes and pushes your combustion products out the flue (if you are lucky) while reducing operating efficiency and putting owners in high risk of burner or combustion product rollout as well as venting rollout. Air being injected into the chambers by the blower can also create improper combustion which can cause soot to buildup blocking heat exchanger passages which then can create some highly deadly CO levels due to incomplete combustion.

The bottom line is this..if cracks or holes were ok then there would be no reason for manufacturers to have extended warranty on them. The only time a furnace with crack(s) or hole(s) should be left operating is if you get a statement from the manufacturer who built the furnace on their letterhead that acknowledges the failure you found on the product they built and that they take responsibility for it to continue to operate safely after you leave it on. If anyone ever gets one of those statements from the manufacturer please forward it to me though I will not be holding my breath. I will not be arguing with anyone on this thread and if your response is headed that direction it will be ignored. I have over 25 years in this field with many credentials and provide training on this subject for some of the largest well known manufacturers dealer base.
http://www.furnacesafetyconsultants.com

Active home inspector
written by Ken Bates, February 08, 2009

I agree with Robert Shideler. It is not easy to create CO except with an internal combustion engine. Auto exhaust in a garage has a lethal potential.

It is a rare gas furnace that has its flame(s) impinging upon a sufficient amount of metal that the flame will be cooled enough to create high amounts of CO.

gas ovens do create a lot. Mine creates hundreds of ppm while the top burners create less than 9 ppm. Do we get groggy at thanksgiving due to too much turkey or too much CO from the oven and too many guests?

Whenever my Tif 8800a or my CO detector went into the red zone it was due to venting.

If we can survive hours of an unvented oven generating up to 500 ppm we can survive heat exchanger cracks from a furnace that flames on half the time that an oven is cooking a turkey.
(half the btu's for twice the time during a 4 hour period.)
Breast or leg?

The Difference
written by Richard the Author, February 08, 2009

An oven used for cooking is designed for that purpose. 500 PPM will put you in a coma in less than an hour. You will become dizzy from CO very quickly at 500 PPM so if you do stay conscious during that period and can serve up that Turkey I'll take a breast but I won't be staying in your house to eat it. Ventless gas logs, ovens and stoves are designed for operating inside structures and they produce little if any CO. They do produce a lot of CO2 though and too much CO2 will make you drowsy.

...
written by lisa, June 14, 2009

I have to disagree with you people that say it IS safe to keep using a furnace with a cracked heat exchanger, i just found out mine has 3 cracks and the past 6 months i have been very sick prolly due to this heat exchanger being cracked and not knowing. I have looked up many many things and this is very dangerous and can produce CO in the home and can KILL. Since we had the furnance off now i have been getting a little better each day! I am worried that you people are sending the wrong messages out to others saying it wont produce CO. People wake up this is very dangerous!!!
A heater exchange to weld is about 1/2 the price of a new furnance. It takes quite a few hours for the welder to get to it cause everything is attached to this heater exchange, i will be getting a new furnance soon as mine was already 18 years old.

HVAC Service Technician
written by Gary Reecher, August 24, 2009

First ---CO Detectors --- Read the instructions on your co detector. Unless the detector that you have is a low level monitor it will do nothing at protecting your health at CO levels below 30 ppm. The major manufacturers of CO detectors write in their instructions that if you have a heart or breathing conditions, are pregnant, have a baby or infants you should consider a low level monitor. Yet these same manufacturers do not make a low level monitor. ??????? If you want a low level monitor you have to purchase them on line. CO Experts and NSI3000 are the only low level monitors available.

Someone mentioned leaky houses as reduced co potential. Maybe. Dr. Thomas Greiner, Iowa State University investigated a co incident where the furnace was not leaking. It was producing high levels of CO. It was vented side wall. The dynamics of the house were such that the co was entering the house through the sill plate and siding, old farm house.

Have your furnace inspected annually. Make sure they test the flue gases with an electronic combustion meter from furnace start up to shut down. A trained technician can in most cases determine that your furnace has a crack or perforation doing this test as well as determining if the furnace is burning properly. If the company that you use does not have a meter tell them you would like your furnace tested with one.

...
written by Charles, October 02, 2009

I have a question. I was having a problem with the A/C and called my home warranty company to have someone come out and check it. the a/c guy found that the furance was unplugged and the gas shut off. I just bought this house as a rental and had a home inspection done. the inspection report read no problems with heating system/furance. while the a/c guys was check my system he found a checked heat exchanger due to rust in the back of one of the chambers. now I am being told that the whole furance has to be replaced. My home warranty is not covering $1075.00 worth of work. Why did the home inspector not find this a couple of weeks ago during the inspection? What should I do about this? Why would I have so much extra cost in going from old unit (10 siers) to new unit (13 siers) sorry if I didn't spell "siers" correctly. any thoughts or commments would be help

i have a question
written by audra, October 12, 2009

i had my yearly service on my carrier furnace and they did a test and told me my heater exchange was cracked. the man used a liquid in the exchange and then used a light and wore glasses and showed that one had a green crack down the seam and the others did not. my brother who is in construction for 25 years tells me the guy just wants my money and that i can use the system that his heating guy looked at the flame and said it was fine? how do i know who is right?

Timing of Crack
written by Eric, January 19, 2010

Prior to purchasing my new home, the inspector mentioned the furnace was working fine. The gap between the inspection and moving day was 6 weeks. Upon moving in we immediately noticed an odor when the heat kicked on. It took a couple of weeks to figure out the problem - cracked heat exchanger. We immediately installed a new furnace and discovered a 4+" gash in the exchanger. How long does it take for an opening like that to form? I'm seeking compensation from the inspection company for the oversight.

...
written by Nancy Fay, February 01, 2010

I have a cracked heat exchanger and I am waiting for the part to come in. The fumes are bad. I am told that I am not in danger unless we put our faces up to the vents. How true is this? I think it impossible that these fumes would not effect us.... even my dog is drinking alot more water I dont think its a coinsidence...