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On 1/7/2012 2:39 PM, L. H. wrote:

Subject: Myth #1

I've read your info stating that this myth is wrong....carbon monoxide released into the home if heat exchanger has a crack. That is what I want to believe, but I read several other sites that agree that carbon monoxide does get into the home with a cracked heat exchanger. We recently had a furnace inspector tell us that our heat exchanger is cracked and that we would need a new furnace. It seemed he was pressing a bit too hard.

We called another authorized inspector and he told us that he would rebuild the heat exchanger, that carbon monoxide goes out the exhaust pipe....consistent with you. Please give us more backup on this issue. Thank you.

D. and L. H.

1/10/12

Dear D. and L.,

Your second inspector is correct. However, it is usually more cost effective in the long run to replace the furnace versus replace the heat exchanger.

My argument with the industry is with the scare tactics they use, mis-information they circulate and dis-service they do to customers.

1. The heat exchanger is an empty metal shell sitting inside a bigger metal shell (the outside of the furnace) with a blower pushing a lot of air through it. The air passes from the blower, over the heat exchanger and out through your duct work. The same pressure that pushes air out of the duct vent (register) also forces air INTO any cracks or holes in a heat exchanger. The first tell-tale sign that there is a heat exchanger issue is that the main burner flame wavers (is blown around and changes shape) inside the heat exchanger when the blower comes on. This indicates air moving INTO the heat exchanger.

2. Heat exchanger cracks need to be dealt with. In most cases it makes more sense to replace the furnace. Sometimes heat exchangers are not available. Usually a new furnace will be more efficient and will carry at least a 10-year, more probably a 20-year exchanger warranty.

3. My issue is that service contractors put folks against a rock and a hard spot and will force them to shut off working equipment in the middle of the winter. Many times the cracks or holes that are discovered have been in the equipment for years, yet the furnace ran correctly and presented no hazard. Families are inconvenienced and their property is put at risk of pipe freeze ups because of a false sense of urgency. The family budget is destroyed by the need for an immediate furnace purchase. At the same time the ability for the owners to get competitive bids is almost eliminated. Folks are stuck with the prices and equipment offered by the contractors who are at hand and have equipment in stock.

My suggestion would be to replace the furnace. I would get at least 4 bids and make sure the contractors give you prices for their "standard" equipment (similar to the furnace being replaced), their "upgrade" model and their top of the line model. Also get prices on extended parts and labor warranties. Most new furnaces come with control boards that cost $400 to $1,000 to replace when they fail. The electronics usually come with a one-year to 5-year warranty.

If you want to delay the replacement, get a carbon monoxide detector and put it in the bedroom area. Note that carbon monoxide detectors are not 100% reliable, but they will give you a good margin of protection until the furnace is replaced. The waiting period should be days. It will give you enough time to get competitive bids, but I wouldn't wait for an entire season. What appears as a small crack or split today, may become a large gaping split tomorrow.

Regards,

Gus

1/14/12

Subject: Question About Flue Gas CO Level

Gus,

We have a hydronic hot water system (radiant heat) in our home and recently had an HVAC company come out to service it. They took a CO reading directly in the exhaust flue of the boiler with a probe (measures O2 and CO) and alerted me that the furnace needs replacing because of high CO levels. I am assuming that there is always some level of CO in the flue. What would be an acceptable CO level in the flue stack?

Thanks,

Mike

(76x) 4xx-9xxx

1/14/12

Mike,

Get a second opinion. Check Angie's list for a reputable contractor.

High CO level in the flue gasses means "keep looking for a problem". Most of the time high CO is due to a correctable problem like dirt, rusted passages, blockage from soot or other foreign matter contained in the products of combustion. It can also be caused by incorrect adjustments or bad automatic gas valves. If it is an oil system, then burner adjustment, poor pump performance, partially clogged nozzle, blocked fuel filter or contaminated fuel may be issues.

I'm not familiar with acceptable CO levels for oil burners, however for gas systems, anything over 10 ppm (parts per million) would indicate the need for a closer look at the system. Anything over 100 ppm usually indicates an issue that needs to be addressed. Natural gas burns clean so any amount of CO over 9 or 10 ppm is suspect.

In most cases, the issues can be handled without replacing the equipment. However, if the equipment is old, 15 years or more, then it may be economically more practical to replace the system versus try to fix the problem.

A qualified HVAC contractor familiar with boilers should be able to help you in that area.

Gus

I was experment in gwith natrual gas two years ago becouse I was thinking of natrual gas stoves adn how thay are not vented out side.
I had bought a house and just lost my job money was not tight until going into the second year of unenployment. I have a gas fire place upstairs
I opend the frount of the fire place and blocked off the flue to see if it would set off the co2 or the fire alarms in the house and it did not the gas fire place is on a thermastate
so i would set it to 70 deg. F. Using the princible that warm air travels to cold I let it heat the basement that way since it was only being used for Laundry
and stuff like that. I know co2 is heavy than air but gets mixed in with air but the co2 detectors down stairs did not even go off.
 
I think the furnace (natrual gas) is harmless. I have herd stories on the news of a family get together barbacue and the weather turning bad and barbacuing in the garage with th edoors closed and everone
in th egarage died from co2. but the barbacue was propane.
 
And outher people using propane heaters in a tent while deer hunting and died of co2 again Propane or butane.
 
I can not find any news about deaths caused by co2 (natraul gas) in a home.
 
When I started looking about Mythe of natrual gas on the web today I found your artical. Question in a cracked heat exchanger the return air is at a higher PSI
wich would eather blow out the combustion or add to the combustion air am I thinking along the wright thought process.
 
By the way i really like your web page..
 
 
Please le me know If my thought process is messed up in any way thank you.
 
 
 
Jxxx
 
Jxxx.jxxxxx@live.com 

11/7/2011 2:25 PM

From: zxxxxxxx@rxxxxxs.com

Subject: Great site and question

Hi,

I like your site and will buy your book. I have a question for you.
I have 17 year old furnace , maintained annually, last inspection showed no problems. There was no issues
with heat exchanger or CO leakage. Then this so called consult tells me that due to age of my furnace
CO could be leaking ...etc. This does not seem logical. Do you have any facts to dispute these statements
as it looks like he is just using sales pitch to sell furnaces.

Thanks

---

 I get a visit from so called "Certified Energy Management Consultant " and told the following -

---

The composition of the heat exchanger will degrade over time. As it begins to crack, carbon monoxide is leaking and becomes part of the air flow in your house. Once a level of 100 parts/ million is detected, the gas has to be shut off to the furnace and it is "red tagged". Any contractors insurance plans does not cover the heat exchanger of any furnace they don't carry. Manufacturers warranty their own heat exchangers for a limited time and we will replace them, but at a labour cost of approximately $1500-$2000. You can call Rheem and see what their warranty is, but at this age of a furnace, it's hardly worth repairing. But that would be up to you. 

 

Hope this helps. 

Certified Energy Management Consultant
Ottawa

---

f I could tell you how long your furnace would last, I'd buy a lottery ticket for the both of us, and we wouldn't have to worry about cost. :) 

Seriously, at that age, the composition could change over the course of the season and potentially leave you with out heat....or it could last. 

I just don't understand how anyone could say, emphatically, that something will last "X" number of years. My personal opinion. 

So, I'd prefer my clientele to benefit for piece of mind and not have to worry, and receive rebate money while it's available. 

 

Great questions. Look forward to your response. 

Certified Energy Management Consultant

11/9/11

Sorry Zxxxxr, I've been out of town and missed your email.

Heat exchangers develop cracks over time due to thermal expansion and contraction. If there are excess moisture issues, they may also rust to the point of being paper thin. Moden day furnaces rarely introduce carbon monoxide into the home's air stream even with a crack or a number of cracks. Typically the force of the blower pushes air into the the heat exchanger and causes problems with ignition and combustion efficiency.

At 17 years old, I'd say you've gotten good value from your equipment and I agree with your consultant that you should consider replacing the furnace. I seriously doubt that carbon monoxide would become an issue simply due to the furnace's age, but consider this:

As backward as many communities are, there are currently ordinances on the books that dictate that furnaces be red-tagged and disconnected if they have heat exchanger cracks. So, in the interest of saving yourself some money, you run an extra two years and the furnace finally develops a crack. Now you have to go into panic mode, get estimates, and have the system replaced.

If you replace the equipment "on your terms", at a time of your choosing, you are much better off. You can negotiate better prices, have more time to review and select equipment, and can schedule an installation around your family's schedule.

The point of my book is to highlight the mis-information surrounding furnaces and carbon monoxide and to let technicians and homeowners know there are more things that need to be checked besides the furnace.

Good luck,

Gus

On 11/9/2011 7:16 AM

Re: Myth #1 - A furnace with a cracked heat exchanger will definitely produce carbon monoxide and poses an immediate danger.

Dear Gus, 

I recently called an HVAC to my house because my furnace wasn’t blowing cold air.  I attached a picture above taken by the service technician that told me that my family is in immediate danger.  He shut down my system and gave me an estimate for about $3900 to replace my furnace and A-Coil.  After he left I did some checking online and was able to diagnose my problem myself.  I replaced my pressure switch and my furnace is working again.  When the technician followed up with me he was alarmed that I had turned my furnace back on.  He encouraged me to go on the internet and Google “cracked heat exchanger” which I did and now I’m concerned.  Your article “Myth #1” matches more closely to what I was told by a friend who has been in the industry for 30 years.  My furnace is old (14 years) but I have CO detectors in my house.  Should I call the gas company out to measure the CO levels?  I’m just wondering if I can make through the winter before purchasing a new furnace. 

Thank you  

C.....

11/9/2011 11:51 AM

Hi C....,

Resign yourself to the fact that at some point in the near future you will have to replace the furnace, or at least the heat exchanger.

Typically a small crack like the one in your picture does not represent a problem and will not introduce CO into the home. Generally the crack allows air from the blower to be pushed INTO the heat exchanger which can upset combustion efficiency, blow the burner flame around, cause delayed ignition, create problems with ignition sensing on start-up or cause the flame to roll out the front of the furnace.

If you have working CO detectors that are less than five years old, you will be warned if CO becomes an issue. Detectors that are over 5 years old should be replaced.

Your gas utility might come out and measure for carbon monoxide, but my guess is that they would also red-tag and shut down your furnace. At least that's what they do in the mid-west and most areas of Canada.

My suggestion would be to start getting competitive bids on a replacement furnace and potentially the air-conditioner if it is also 14 years old. In the long run, you'll be money ahead.

Best of luck,

Gus

On 8/1/2011 3:57 PM, Mike Beeton wrote:

Hi
I only have one thing to say. Standard eff furnace,Mr squirell
builds a nest in the chimney,furnace has a cracked heat exchanger,
products of combustion come into the living space. Hope those people
didn`t spend the 40 bucks on your book instead of a co detector, cause
if they did they are dead.

Bud,

You obviously have NO idea how a furnace works. You might as well be Mr. "squirell" or squirrel. (I can tell spelling and English are not your strong suit.) I'll just bet you have the equipment and knowledge to check for the proper draft through a heat exchanger or water heater and can detect reduced volume through a flue when it is partially blocked.

And I'll bet you already know that If you TOTALLY block the flue, the products of combustion will roll out the draft diverter of a "standard efficiency" (assuming you mean atmospheric burner) furnace. If the furnace is equipped with roll-out sensors, then in theory, they will trip. All draft-induced furnaces have roll-out sensors, most atmospheric-burner furnaces do not. But you already knew that, right?

But, I'll bet you didn't know that If the furnace blower is operating there is absolutely 0 (zero - that mean nada, nothing, zilch) CO or any other gas going to come out of a heat exchanger into the indoor air stream.

Geez louise, pay attention.

The furnace blower is positively pressurizing the duct, moving air at over 700 feet per minute through the furnace. The first thing the air hits is the air-conditioning coil, which causes static pressure inside the furnace cabinet. So, you have .2" WC pressure surrounding the outside of the heat exchanger cells, and 0" WC on the inside of the heat exchanger. Which way will the air go? The products from the flue get into the house by being sucked in through cracks in the the return-air system or the furnace is already inside the home in a closet or utility room.

Whether the heat exchanger is cracked or intact makes no difference. (That's the point of my book. HVAC guys condemn furnaces because of a small hole or hairline crack and NEVER check the flues. In 60-70% of the cases there's a gas-fired water heater teed into the same flue. With a partially blocked flue and a draft-induced furnace and gas water heater teed into it, where do the products of combustion go?)

If the indoor blower creates enough pressure to push air through an a-coil and out a register (creates static pressure in the duct work), which way do you think it will push air if there's a hole in the heat exchanger. What, you think it "sucks" as it pushes air around the heat exchanger cells?

By the way, there are 100's of THOUSANDS of CO detectors being used by home owners at this very moment that won't alarm when high levels of CO are present. They've been contaminated with paint or other petro-chemical fumes or refrigerant gasses or they are just old. Electrically they are intact, but chemically they are dead. Based on past random testing, around 1 in 5 detectors would not alarm at lethal CO levels. The CO detector manufacturers say replace the detectors every five years. Beyond that time, the sensors die a natural death due to age.

So, a CO detector is no substitute for a technician that knows what he is doing.

I feel sorry for the customers that get you, though -- their survival chances will not improve.

Gus

PS: I know these are big words and science is a foreign concept to you, but don't trust me. Take an old furnace and figure it out. Make sure there is an a-coil on it, drill a bunch of 1/2" holes in the heat exchanger, and watch which way the wind blows.