Pinhole crack in heat exchanger - opinions needed

[sitandspin]

Hi,

I just bought a new house and figured I should have the 15 year old furnace cleaned up and inspected before we ran it for the first time. I live in Buffalo, NY, and it gets pretty cold here, and it's difficult to live without heat in the winter. Anyway, called a reputable company, had a service guy come out and clean it up. He showed me a pinhole size crack in the wall of the heat exchanger and started talking about Carbon Monoxide. I looked through some flexible scope at what looked like a bloody pimple on sheet metal. He told me that it was risky to run it, and if the gas company knew about it, they would come out and cut the gas line to the furnace because of the CO risk. He said installing a new heat exchanger would be about $1500 after labor. He wrote me a $3000 estimate for a new unit. I'm under the impression that this guy wants to sell me a new unit/unnecessary service.

I have CO detectors in my ~1200 s.f. house. I didn't plan on replacing the furnace for at least a few years, but is his opinion worth its salt? Is the risk of CO that much greater with a pinhole sized crack?

Thanks in advance.

[htrguy]

Get a second opinion.
CO is invisable and it can be serious. No reputable company would leave a furnace running if it was truely cracked.
Disreputable companies will scare you into a new furnace. There are shades of gray were one says bad, one says good.

[Edited by htrguy on 10-12-2006 at 02:16 PM]

[HVAC Pro]

Pinhole crack? Sounds like an oxymoron to me. I think of a pinhole as round and a crack pertaining to something involving length.

In either case you saw this "pinhole sized crack" while the heat exchanger was cold. It's possible if it is a crack that it can open up once heated due to expansion, creating a potentially more serious situation.

How old is the furnace? Did the tech check the warranty status? Most modern furnaces come with a 20 yr. heat exchanger warranty while older ones carried a 10 yr. warranty. In that case you would only need to pay for labor assuming the remainder of the furnace is in good shape and/or is relatively new.

If in doubt call someone else for a second opinion. This isn't something you want to take lightly even with CO detectors.

[t527ed]

in nj the gas co will shut off heater with ANY crack or hole in the hx. as others said get a second opinion, check for warranty but if it is cracked get it fixed or replaced. don't count on your co detector to protect you, most are not sensative enough.

[smokin68]

There's no such thing as an O.K. crack in a heat exchanger. That said, get a second opinion, and before shelling the big bucks, see how much a new high-efficiency will run you, could be money well spent in a cold climate.JMO

[hvacer12345]

Pin-holeing or just plain pin-holes are another way of describing pitting action.

Badly maintained furnaces will get this along with heavy soot on the burners.

Could be the furnace was cleaned up before you moved in.

As far as turning off the unit, many techs just note it on the invoice and don't turn off the furnace because it creates hard feelings.

With us, we tell th HO he has a crack. If he chooses not to take remdial action we write out the bill, document said furnace condition, and lastly we send a copy of the invoice to the local building authorities who file it with the HOs address.

One time I turned off a furnace with the HO standing by me.
He became angry and picked up a hammer and threatened me.

[sitandspin]

Thanks for all the great responses so far. I guess a "pinhole crack" is a bit of a misnomer. It was a small puncture. I've been doing some research, and it appears that the heat exchanger has a 20 year warranty even though I'm not the original owner. I need to make some calls and find out the deal.

It's a Tempstar furnace, model # NUGE475BG01. I'm definitely weighing the options, but I don't have the cash at the moment to replace the unit.

I'm definitely getting a second opinion. In other news, we got about 2-3" of damp snow in Buffalo today. Winter hath arrived.

[lonny]

Inthe Detroit area we are required to turn the unit off and cap the gas line, per gas company. Now, if you want to leave the unit opperable YOU will be held responisable when the coustermer says he got sick after you left. I tell the coustermer to call the gas company after I leave for A second opion.

[coolguysfl]

Well lets see -- if it's just a little crack... you'll only be a little dead. The tech may have just saved your life.

Get a second opinion B4 you hurt some one. If the second opinion confirms the heat exchanger has lost it's integrity - get a new furnace.

[bonafide]

You have been worned, get an second opinion from a senior certified tech

[2hot2coolme]

A crack is a crack, it won't get smaller, it will only get ......ah whatever, why bother. Good luck with your cracked heat exchanger...I have no idea what I'm doing in this goofy forum anyhow....some of you folks are just plain ole wacked!!

[hvacjamie]

A reputable service company told me that there is a crack in the heat exchanger and showed it to me so I could see it. He said it would kill me. He wants to sell me a new furnace. How dare he?!

[brettln]

If it was me, the gas would of been shut off there at unit.
If customer wants to take a chance and turn it back on, that would be their decision. That is our companies policy.
CO2 is nothing to mess around with. This is why we force the customer to make a swift decision, rather it be a 2nd opinion or repair.

[cem-bsee]

unless you paid about $100 for your CO detector, it is just an indicator -- = poor --

[cphc]

I agree you need a second opion. Never seen any pin hole crack. Did he do a co test at the registers?

[wptski]

Originally posted by cem-bsee
unless you paid about $100 for your CO detector, it is just an indicator -- = poor --
And what is the over $100 CO detector going to give you? PPM too?

[m kilgore]

You called a good company to check your furnace for safety and when you found out it wasn't safe you think he's just trying to sell you somthing? I can't believe folks like you. You need a new heat exchanger or furnace period. It dosn't matter if you "can't afford it right now". Whats more important, money or your life. I guess its your life but don't put the tech down for doing exactly what you hired him to do. I'm not so sure you even need a second opinion if you actually saw the hole. A hole is a hole and your furnace should not be running until repaired.

[markwolf]

Originally posted by cphc
I agree you need a second opion. Never seen any pin hole crack. Did he do a co test at the registers? That would be a dangerous way to determine weather or not to run a furnace.

[markwolf]

The guy showed you the hole with a camera.you have some serious issues....Metal expands and contracts each time it is heated.Did you ever see someone bend a piece of metal back & fourth until it broke in two?Now go back to the fact that you have a heat exchanger in a comprimised condition.Are you begining to understand that no one can tell you when it will break in two pieces?We can tell you it is in a weakened contion that warrants immediate attention!Is your family worth $3000.00

[mark beiser]

Originally posted by cphc
Did he do a co test at the registers?

What would be usefull about checking for CO at the registers?

Since the supply air around the HX is under much higher pressure than the pressure inside the HX, CO won't leak out of the HX into the supply air.
The only exeption I can think of is Pulse furnaces.

The danger from a breach in the HX isn't CO leaking out the breach into the supply air. The danger is supply air leaking into the HX, interfering with the combustion proccess and/or venting, wich can cause CO and other combustion products to spill out of the front of the furnace, sometimes even fire.
It isn't until CO is spilling out of the furnace, instead of being vented, that it will get into the conditioned space.

Hopefully someone will have caught the problem well before it progresses to the point that there are any measurable levels of CO in the conditioned space.

[davidr]

Originally posted by wptski

Originally posted by cem-bsee
unless you paid about $100 for your CO detector, it is just an indicator -- = poor --
And what is the over $100 CO detector going to give you? PPM too?

If it is an over $100 CO detector that detects low levels of CO it may just be the only detector that really works.

Any CO detector with a UL 2034 stamp on it is unreliable for providing any true protection to anyone.

For those thinking a store bought CO detector is going to make them safe, think again.

[davidr]

Originally posted by mark beiser

Originally posted by cphc
Did he do a co test at the registers?

What would be usefull about checking for CO at the registers?

Since the supply air around the HX is under much higher pressure than the pressure inside the HX, CO won't leak out of the HX into the supply air.
The only exeption I can think of is Pulse furnaces.

The danger from a breach in the HX isn't CO leaking out the breach into the supply air. The danger is supply air leaking into the HX, interfering with the combustion proccess and/or venting, wich can cause CO and other combustion products to spill out of the front of the furnace, sometimes even fire.
It isn't until CO is spilling out of the furnace, instead of being vented, that it will get into the conditioned space.

Hopefully someone will have caught the problem well before it progresses to the point that there are any measurable levels of CO in the conditioned space.





Mark nailed this one, CO testing at a register is useless in most cases.

If there is CO in the duct system it is because the fan is recirculating it through the ducts.

CO could be in the thousands of PPM in the furnace before it ever registered in the ambient air.

[wptski]

Originally posted by davidr

Originally posted by wptski

Originally posted by cem-bsee
unless you paid about $100 for your CO detector, it is just an indicator -- = poor --
And what is the over $100 CO detector going to give you? PPM too?

If it is an over $100 CO detector that detects low levels of CO it may just be the only detector that really works.

Any CO detector with a UL 2034 stamp on it is unreliable for providing any true protection to anyone.

For those thinking a store bought CO detector is going to make them safe, think again.
How about naming a few that are good?

[davidr]

Originally posted by wptski

Originally posted by davidr

Originally posted by wptski

Originally posted by cem-bsee
unless you paid about $100 for your CO detector, it is just an indicator -- = poor --
And what is the over $100 CO detector going to give you? PPM too?

If it is an over $100 CO detector that detects low levels of CO it may just be the only detector that really works.

Any CO detector with a UL 2034 stamp on it is unreliable for providing any true protection to anyone.

For those thinking a store bought CO detector is going to make them safe, think again.
How about naming a few that are good?

NSI 3000 & CO Experts Model 2004 are the only two I would even consider.

http://www.nationalcomfortinstitute.com

http://www.coexperts.com

[wptski]

Originally posted by davidr

Originally posted by wptski

Originally posted by davidr

Originally posted by wptski

Originally posted by cem-bsee
unless you paid about $100 for your CO detector, it is just an indicator -- = poor --
And what is the over $100 CO detector going to give you? PPM too?

If it is an over $100 CO detector that detects low levels of CO it may just be the only detector that really works.

Any CO detector with a UL 2034 stamp on it is unreliable for providing any true protection to anyone.

For those thinking a store bought CO detector is going to make them safe, think again.
How about naming a few that are good?

NSI 3000 & CO Experts Model 2004 are the only two I would even consider.

http://www.nationalcomfortinstitute.com

http://www.coexperts.com


Thanks!

[xv80satisfiedcust]

sitandspin,

If you get a Goodman 90 afue furnace you may find that your total monthly cost (after utility savings) is very minimal.

My xv80.... username is a TRANE furnace model. I am in no way affiliated with Goodman.

HVAC Talk does not allow specific pricing discussions, so don't post any.

To estimate your monthly cost/utility savings, I used the EPA HVAC Investor Software with a location of Buffalo, NY and a low heating BTU need of 60,000 btu with 15.8% annual percentage rate interest for 7 years loan term. (15.8 for 7 years was the HVAC investor default). This is using a $1 per therm natural gas cost estimate.

After the 7 year loan, the $19 dollar a month utility savings (90 versus 80 afue) would continue without the payments.

Shop around with your contractors. Some of the Goodman furnaces have a 10 year warranty (see http://www.goodmanmfg.com).

Unfortunately, the HVAC Investor software is temporarily unavailable on the EPA website (www.energystar.gov)

One of your HVAC contractors may have the software. Inputting the ACTUAL installed prices of what they are bidding will make your monthly cost/benefit more accurate.

The following menus should be updated for your location and utility cost:

Utility, Gas (therm rate), Options, Heating Region

A high efficiency furnace is less expensive than you may perceive.

In addition to the repair tech second opinion, I would get at least 4 bids for a replacement furnace.

Remember, the HVAC Talk Pro's have no financial benefit of you getting a new furnace. I have seen many threads where they have objectively told homeowners that a repair is more practical financially.

If you get a free warranty heat exchanger and you keep your furnace 10 years, you lose at least $1900 in higher utilities.

The $50 homeowner trial version of HVAC-Calc is good at ensuring you don't get a furnace too large for your house. It would help refine the data for the HVAC investor cost calculations too (higher btu number than 60,000 probably).

[htrguy]

Originally posted by davidr

Originally posted by mark beiser

Originally posted by cphc
Did he do a co test at the registers?

What would be usefull about checking for CO at the registers?

Since the supply air around the HX is under much higher pressure than the pressure inside the HX, CO won't leak out of the HX into the supply air.
The only exeption I can think of is Pulse furnaces.

The danger from a breach in the HX isn't CO leaking out the breach into the supply air. The danger is supply air leaking into the HX, interfering with the combustion proccess and/or venting, wich can cause CO and other combustion products to spill out of the front of the furnace, sometimes even fire.
It isn't until CO is spilling out of the furnace, instead of being vented, that it will get into the conditioned space.

Hopefully someone will have caught the problem well before it progresses to the point that there are any measurable levels of CO in the conditioned space.





Mark nailed this one, CO testing at a register is useless in most cases.

If there is CO in the duct system it is because the fan is recirculating it through the ducts.

CO could be in the thousands of PPM in the furnace before it ever registered in the ambient air.

I have seen (in more than one case) where the air traveling over the heat exchanger causes a low pressure area that induces the exhaust gasses out of the heat exchanger. This also is what caused the hot spot to begin with. Careful with assumptions.

[cphc]

If the man showed him a hole in the furnace. We use the Flute Co220 and it works great in the home area and when even held over a vent. Flute rep showed us that trick. This meter is extreamly sensitive in this area. We've got reading in air streams even when inspection were questionable and went back and rechecked again. However I can see your point here also but do what works. We also take them at the furnace, cover all the bases.

[Edited by cphc on 10-16-2006 at 12:09 PM]

[wptski]

A bit off topic but my sister was getting headaches and finally figured out that they only came after doing her laundry! The furnace, water heater and dryer are all gas in that room. They had the window right over the dryer open. The problem went away when the window was closed.

I used a Fluke CO-220 around the furnace, water heater and the dryer. Nothing but a zero reading. Went outside and caught the dryer exchaust in a plastic bag and still nothing!

I can only guess that she's allergic to her soap which she has used for twenty years or maybe the Bounce sheets she uses.

[tinknocker service tech]

if the tech showed you the hole and you admit you saw it and belive him it is there. why are you here. The hole isnt going to go away and the time you spend questioning something you have seen with your own eyes is time waisted

No one here is going to say it is ok to use your furnace because it can be very dangerous and your family health is at risk

15 year old furnace imo isnt woth a heatexchanger replacement because all the other parts are 15 years old

look into financing or a wood stove

what ever you do plaes DONT USE THAT FURNACE THE RISK IS TO GREAT

[slims]

If that furnace is what I think it is... 75kbtu upflow I would get a 2nd opinion. I take it the visual on that scope wasn't very clear. Here in Southern California I have never seen an older Heil-tempstar or Sears upflow with a cracked hx. Horizontals-heat/cool gas paks and multipos are a different story

[markwolf]

Originally posted by slims
If that furnace is what I think it is... 75kbtu upflow I would get a 2nd opinion. I take it the visual on that scope wasn't very clear. Here in Southern California I have never seen an older Heil-tempstar or Sears upflow with a cracked hx. Horizontals-heat/cool gas paks and multipos are a different story This is funny!You live in s.cali!This guy is in buffalo ny they already got hammered with snow.I am betting that his unit gets almost double the run time that any unit you have seen!I live in wisconsin where we use our furnaces too & found more than a handful of these with failed primary heat exchangers.I change out the secondarys by the dozens each year.I have however not seen one with pinholes that did not have a cracked tank on the secondary too.

[markwolf]

I am shocked at some of the responses here.A thread started by someone that was shown pinholes in thier primary heat exchanger WITH A CAMERA has no business with talk of C.O. detectors in it.This gives out the impression that it is ok to run a furnace with heat exchanger problems if you just install a C.O. detector.This shows not only a lack of common sense,but gross negligence IMO.!!!!

[slims]

Markwolf I know we dont get your runtime or weather thats why I posted where I live. One man sees A pinhole not pinholeS and one man sees a pimple.Tech said it would be risky to run it. Thats what made me think 2nd opinion because I would have shut the furnace down and documented my work order. Come to think of it old Heil upflows with standing pilot never seen those hx fail here.Not one post here gave me the impression that it was ok to run a furnace with a cracked hx.

[icyflame]

Originally posted by hvacjamie
A reputable service company told me that there is a crack in the heat exchanger and showed it to me so I could see it. He said it would kill me. He wants to sell me a new furnace. How dare he?!


You hit this one square on the head!! I read this stuff and shudder at it all! Sometimes I can't tell who is asking and who is answering the questions!! :D

[davidr]

Originally posted by htrguy
Careful with assumptions.

If it's one thing I try not to work off of it's assumptions.

If the air was stratifying that badly over a HX there are some other issues that need to be addressed as well.

If I see changes in the CO & O2 readings in the flue gas after the fan energizes or after an extended period of run time I know to further investigate.

Either way a breech would have been identified through analysis of the flue gas as the culprit instead of wondering what if by testing the registers.

[beckservmngr]

Originally posted by markwolf
I am shocked at some of the responses here.A thread started by someone that was shown pinholes in thier primary heat exchanger WITH A CAMERA has no business with talk of C.O. detectors in it.This gives out the impression that it is ok to run a furnace with heat exchanger problems if you just install a C.O. detector.This shows not only a lack of common sense,but gross negligence IMO.!!!!

You definetly got that right.

and I tell ya, there is no way I would let myself, nor one of my guys leave a furnace goin after it has been prooven to be failed. with that said different companies have different policies. none the less, don't you dare run that, you can't smell it, you can't see it, you just don't know it till your dead, children are suseptible first, smaller bodies. if you want a second opinion then get one! But for God's sake, don't run it till you do!! Believe it or not there are other ways to heat a home, espeacially temporarilly.

Tomarrow, High 57*F, for Buffalo, Tell me how you could justify runnin that thing?

[swnoel]

I'm starting to wonder if there ARE many professionals on this board.

I also can't believe some of the responses.

CO can and will infiltrate your ductwork if the HX is cracked, before the fan energizes, then it becomes distributed throughout the home.

CO is a silent odorless killer and any gas appliance needs to have an annual service performed by competent technicians. (any here?)

If you have a cracked HX... get rid of the furnace.

A second opinion is fine, but if you already have seen the problem you don't need one.

If the furnace is older, I'd suggest getting a entire new unit, not just the HX.

Yes... most of the time you can just replace the HX, but you probably be changing other parts soon, on that still old furnace.

And I'll bet ya, you won't have saved a thing.

[7X]

Wptski posted:

"A bit off topic but my sister was getting headaches and finally figured out that they only came after doing her laundry! The furnace, water heater and dryer are all gas in that room. They had the window right over the dryer open. The problem went away when the window was closed.

I used a Fluke CO-220 around the furnace, water heater and the dryer. Nothing but a zero reading. Went outside and caught the dryer exchaust in a plastic bag and still nothing!

I can only guess that she's allergic to her soap which she has used for twenty years or maybe the Bounce sheets she uses."

This certainly has nothing to do with the original thread, but I couldn't help but think about this. If CO was really the problem and closing the window actually fixed it, then where was it coming from? Maybe the other appliances are vented near that area and the negative pressure in the room with the dryer running was pulling flue products through the open window. Checking the flue products for CO on the furnace and water heater would be a good idea. Maybe closing the window didn't really fix it and it is coincidental timing thing - the water heater backdrafts with the dryer running regardless of whether the window is open or not and it just hasn't been running much since the window has been closed. (My utility room is -8 Pa with my dryer running and the little window open) Anyway, I think I would take another look at the room pressures and the actual combustion characteristics of the other appliances.

I just can't wrap my mind around believing that closing a window fixed an allergy problem.

P.S. - swnoel, there are some very intelligent and competent professionals on this board. Stick with it, you will learn something.

[hvacer12345]

Good thread. Lots'a good stuff for everybody.

[swnoel]

7X... I know there are, but this isn't a site to debate whether the HX have a crack or a hole... who cares.

The unit is compromised and needs to be replaced.

I have learned alot, and don't plan on leaving, but have also been surprised at some of the responses.

[7X]

swnoel - I agree and wish you well.

[wendel]

You might find this study interesting. It's about documented causes of CO poisioning. I couldn't find any heat exchanger crack issues mentioned. I think those documented causes are very self-evident as to what usually happens in CO poisioning.

http://www.extension.iastate.edu/pages/communications/CO/co_cases.html

[davidr]

Originally posted by swnoel
I'm starting to wonder if there ARE many professionals on this board.

I also can't believe some of the responses.

CO can and will infiltrate your ductwork if the HX is cracked, before the fan energizes, then it becomes distributed throughout the home.

CO is a silent odorless killer and any gas appliance needs to have an annual service performed by competent technicians. (any here?)




Curious as to how you have arrived at these statements here.

How many times have you measured CO infiltrating into the ductwork from a crack in a heat exchanger before the fan energizes?

How can annual service performed by a "competent technician" insure that an appliance is safe?

A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.

That being said I am talking about small cracks not huge gapeing holes.

[swnoel]

(How can annual service performed by a "competent technician" insure that an appliance is safe?)

Your kidding... right? If you don't think an annual preventative service is valuable, that's you opinion, many technicians do.

Many potential hazards and problems can be found and corrected prior to damage, injury, or death. That's what competent technicians do, find those problems if they exist.

Gas pressures set incorrectly, units producing high levels of CO, safeties not functioning, compromised heat exchangers, I've even found systems that were wired wrong, where the case to the unit was energized.

(A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.)

I understand that after the fan energizes, combustions gases usually don't infiltrate the ductwork, but, they certainly can prior to the pressurization of the ducts.

Could they lead to poisoning?

You may think that it would be the last likely source, but, I don't want to be the one going to court to try to defend myself that it didn't cause the problem.

[davidr]

Originally posted by swnoel
(How can annual service performed by a "competent technician" insure that an appliance is safe?)

Your kidding... right? If you don't think an annual preventative service is valuable, that's you opinion, many technicians do.

Many potential hazards and problems can be found and corrected prior to damage, injury, or death. That's what competent technicians do, find those problems if they exist.

Gas pressures set incorrectly, units producing high levels of CO, safeties not functioning, compromised heat exchangers, I've even found systems that were wired wrong, where the case to the unit was energized.

(A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.)

I understand that after the fan energizes, combustions gases usually don't infiltrate the ductwork, but, they certainly can prior to the pressurization of the ducts.

Could they lead to poisoning?

You may think that it would be the last likely source, but, I don't want to be the one going to court to try to defend myself that it didn't cause the problem.



Never said I didn't think annual maintenance has no value, my question was how do they insure a piece of equipment is safe?

What procedures do you use to verify equipment safety & what type of measurements do you take during a maintenance call to verify safe operation?

Any specific testing equipment you use?

How have you determined that combustion gases enter the ductwork prior to the fan energizing?

Don't be so focused on looking for cracked heat exchangers as the cause for CO that you miss the main causes of CO poisoning in a building.

[swnoel]

Originally posted by davidr

Originally posted by swnoel
(How can annual service performed by a "competent technician" insure that an appliance is safe?)

Your kidding... right? If you don't think an annual preventative service is valuable, that's you opinion, many technicians do.

Many potential hazards and problems can be found and corrected prior to damage, injury, or death. That's what competent technicians do, find those problems if they
exist.

Gas pressures set incorrectly, units producing high levels of CO, safeties not functioning, compromised heat exchangers, I've even found systems that were wired wrong, where the case to the unit was energized.

(A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.)

I understand that after the fan energizes, combustions gases usually don't infiltrate the ductwork, but, they certainly can prior to the pressurization of the ducts.

Could they lead to poisoning?

You may think that it would be the last likely source, but, I don't want to be the one going to court to try to defend myself that it didn't cause the problem.



Never said I didn't think annual maintenance has no value, my question was how do they insure a piece of equipment is safe?

What procedures do you use to verify equipment safety & what type of measurements do you take during a maintenance call to verify safe operation?



I believe I answered most of that already. Check draft, inspect flue and chimney, it also depends whether the fuel is oil or gas(natural or propane), usually takes minumum of 2 hours to complete. I always finish with a combustion test and print 2 records of readings and document what I do.


Any specific testing equipment you use?


Manometer( don't remember the name), Testo 330, Fluke multimeter, transformer tester, pump tester, etc.



How have you determined that combustion gases enter the ductwork prior to the fan energizing?

Many customers complain of odors so I focus on the most obvious.
Found many problems while doing steady state co2 reading...
fan energizes, reading will usually drop if HX or clean out is problem.


Don't be so focused on looking for cracked heat exchangers as the cause for CO that you miss the main causes of CO poisoning in a building.

Again, I will say that I don't want to be the one in court, trying to defend myself that it wasn't and I don't dispute what you say.

Now it's your turn... how bout you answering your questions.

[Freezeking2000]

What CO levels do you look for in the exhaust of an 80 % furnace?

I had one the other day at 35PPM, is that ok?

[davidr]

Originally posted by swnoel


Now it's your turn... how bout you answering your questions.





I would be glad to but first I am glad to see that you are combustion testing & documenting what you find.
It is a win win for everyone in this case.

Now to me answering my own questions.

You already got the safety part of a maintenance call that is through combustion testing & draft interference testing.
If a combustion test isn't done the safety of an appliance is purely a guess.

The combustion test & proper interpretation of those numbers is critical as to what an appliance is doing & if it is venting or not.

Test instruments I use are a TSI CA-6130 analyzer & a Dwyer 460 air meter for draft testing.
TSI Velocicalc Plus for room pressure testing along with a smoke puffer.

I don't measure CO in the ducts because I can watch the readings from the flue gases & pretty much tell what is going on.
A draft measurement is also taken if working on induced draft or atmospheric equipment.

[davidr]

Originally posted by Freezeking2000
What CO levels do you look for in the exhaust of an 80 % furnace?

I had one the other day at 35PPM, is that ok?

Acceptable readings for CO are less than 400 PPM on light-off & less than 100 PPM during the run cycle & stable.

What you really need to watch is the action of the CO as the furnace runs.
If the CO numbers continue to climb over any period past five minutes there is more than meets the eye.


Just for kicks lets say we see these numbers on a combustion analyzer, is this furnace safe?

CO - 24 PPM, O2 - 8.5% after four minutes of running

CO - 24 PPM, O2 - 8.4% after six minutes of running

CO - 24 PPM, O2 - 8.3% after eight minutes

[Freezeking2000]

Originally posted by davidr

Originally posted by Freezeking2000
What CO levels do you look for in the exhaust of an 80 % furnace?

I had one the other day at 35PPM, is that ok?

Acceptable readings for CO are less than 400 PPM on light-off & less than 100 PPM during the run cycle & stable.

What you really need to watch is the action of the CO as the furnace runs.
If the CO numbers continue to climb over any period past five minutes there is more than meets the eye.


Just for kicks lets say we see these numbers on a combustion analyzer, is this furnace safe?

CO - 24 PPM, O2 - 8.5% after four minutes of running

CO - 24 PPM, O2 - 8.4% after six minutes of running

CO - 24 PPM, O2 - 8.3% after eight minutes





I will say it looks good to me.............but i know i am in a trap.

I always check for co in the home or around the furnace. I have not noticed a drop on any unit as you show, but I would have to believe we have a fresh air problem.

[tinknocker service tech]

although i think everyone have made good points but imo
pin hole or hole the size of my fist is still a hole and poses a dangerous enviorment

a hair line crack or a wide open crack same thing dangerous enviorment

there is no inbetween the hx or furnace needs to be replaced
and should be shut down for saftey

[davidr]

Originally posted by Freezeking2000

Originally posted by davidr

Originally posted by Freezeking2000
What CO levels do you look for in the exhaust of an 80 % furnace?

I had one the other day at 35PPM, is that ok?

Acceptable readings for CO are less than 400 PPM on light-off & less than 100 PPM during the run cycle & stable.

What you really need to watch is the action of the CO as the furnace runs.
If the CO numbers continue to climb over any period past five minutes there is more than meets the eye.


Just for kicks lets say we see these numbers on a combustion analyzer, is this furnace safe?

CO - 24 PPM, O2 - 8.5% after four minutes of running

CO - 24 PPM, O2 - 8.4% after six minutes of running

CO - 24 PPM, O2 - 8.3% after eight minutes





I will say it looks good to me.............but i know i am in a trap.

I always check for co in the home or around the furnace. I have not noticed a drop on any unit as you show, but I would have to believe we have a fresh air problem.

No trap Freeze just an example of why you can't depend solely on CO readings in the flue gas to insure if that appliance is safe or not.

The CO readings are stable at 24 PPM but the Oxygen readings are steadily falling throughout the whole cycle.
This is what is referred to as a deteriorating condition.

Once that O2 level drops to a certain point those CO readings are going to skyrocket.

When you add additional readings to CO & O2 like draft, stack temperature & delta T you can make a pretty good stab at the problem.

These readings have to be recorded over the entire run cycle to be of any value though, a one time readings does not offer much information.

Thinking about investing in a combustion analyzer now Freeze? :D

BTW kudos on checking the air for CO in the buildings you are entering, your safety is #1 priority.

[dougfamous]

How many times have you measured CO infiltrating into the ductwork from a crack in a heat exchanger before the fan energizes?

I have, several times. While it's usually a lower PPM at the registers, it can and does infiltrate.


How can annual service performed by a "competent technician" insure that an appliance is safe?

Are you for real? Well, for one, it can help find "pinhole cracks" in the heat exchanger that you didn't know were there until your kids didn't wake up in the morning.


A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.

Do you have any facts to back this up, or just talking out your ass?


That being said I am talking about small cracks not huge gapeing holes.

Where do you suppose the huge gaping holes get started?

To the OP: The heat exchanger is cracked. QUIT BEING CHEAP AND FIX IT BEFORE SOMEONE DIES.

Jesus, what's wrong with you people?

[davidr]

How much combustion testing have you done Doug?

In case you aren't aware of it every new heat exchanger leaks.

When was the last time you saw a welded heat exchanger in a new furnace?

[beckservmngr]

Originally posted by davidr


When was the last time you saw a welded heat exchanger in a new furnace?

Ever seen a tubular HX?? Believ it or not, welded.

[davidr]

Originally posted by beckservmngr

Originally posted by davidr


When was the last time you saw a welded heat exchanger in a new furnace?

Ever seen a tubular HX?? Believ it or not, welded.

Look at how they mount to the collector box, not welded.

[tinknocker service tech]

Originally posted by davidr

Originally posted by beckservmngr

Originally posted by davidr


When was the last time you saw a welded heat exchanger in a new furnace?

Ever seen a tubular HX?? Believ it or not, welded.

Look at how they mount to the collector box, not welded.

this is true most are reamed or pressed in and should seal quite well. pose no real problem

as has been stated with a crack or hole there is minamal chance of co being in the duct after the fan comes on. The minor amount that does get in if any before the fan most likely wont get detected after the blower comes on

the biggest danger is what the crack or hole no matter how mynute it may be is in the cobustion chanber. The added air blowing on the burners and causing incomplete cobustion or flame roll out. This is where the threat of co is.

to debate this is futal because sooner or later that crack or hole will be bigger and will cause co to enter the living space of the house imo

[mark beiser]

Originally posted by dougfamous

[quote]A cracked HX is a defect & needs to be replaced but it is usually the last likely source to cause CO poisoning in a home.

Do you have any facts to back this up, or just talking out your ass?

I have never run a CO response where a failed HX was the direct cause of the CO in the home. 100% of the times I have found a bad HX when on a call for CO, there was a venting problem keeping it from venting properly, or air blowing on the flame causing combustion products to escape from the furnace. The only time I have found a CO level in the ductwork that is higher than the ambient CO in the house is when there are return air leaks pulling it in from around a furnace that is spilling CO.

The only place I have seen where the numbers were collected reainto something that could be reliably checked out was in a provence in Canada.

CO poisoning from cars left running in garages outnumbered all other sources combined.
Unvented appliances is a distant 2nd, but still outnumbers all others combined, exept cars running in garages.
The bulk of the rest of them are mostly vent system problems on furnaces and water heaters.
I don't remember seeing any that were directly caused by a failed HX. A number of the venting problems that caused a CO poisoning likely have a failed HX as the root cause.

I have never seen a report of a failed HX causing a CO related death by directly leaking CO into the supply air. Not even a Pulse furnace killing anyone due to a HX leak, and those do leak directly into the air supply when they leak. The only Pulse furnace related deaths I know of was due to an incorrectly installed exhaust that leaked CO into the neighboring unit of a duplex.

I'm not trying to minimize the danger of a breach in a HX, I'm just saying that the danger isn't CO leaking through the breach.

[cn]

I have never seen a report of a failed HX causing a CO related death by directly leaking CO into the supply air. Not even a Pulse furnace killing anyone due to a HX leak, and those do leak directly into the air supply when they leak. The only Pulse furnace related deaths I know of was due to an incorrectly installed exhaust that leaked CO into the neighboring unit of a duplex.

I'm not trying to minimize the danger of a breach in a HX, I'm just saying that the danger isn't CO leaking through the breach. [/B]

Your post is interesting. My HVAC tech says the same thing.
I agree with the pros, when there is a HX crack, replace, replace and replace the HX (or the furnace if it is old).

However, when the furnace is running, the blower causes an increase on the non-combustion side of the HX, and with combustion side heat drawing the heat up the flue, the Law of Physics says air moves from HIGH pressure to LOW pressure side, which is from the Non-combustion side to the combustion chamber and up the flue.

This is why when dealing with a cracked HX, there is little if any CO that enters the house. I mention this strictly for the sake of discussion.

But back to above, SAFETY FIRST. REPLACE THE HX OR THE FURNACE.

[Edited by cn on 10-21-2006 at 02:09 PM]

[davidr]

I thought we made it pretty clear that we weren't condoning leaving a cracked HX in place or operation.

Just trying to stress the point that there are many other sources in a home that will produce CO over a crack in a HX.

Many times the forest gets missed by focusing on one tree.

[gospelgrunt]

For everyones information a breached HX with air rushing by the hole is not necesarily safe. The air moving past the hole can actually pull the low pressure atmosphere out of the HX into the supply air (Venturi Effect). I hope only Pros are reading these posts because bringing clear cut standards like a compromised HX must be replaced into debate could give some a false sense of security to uninformed homeowners.

[cem-bsee]

I only brought up the issue of the CO detector quality because it seemed that the HO wanted to rely upon it for continuing to use the furnace --