Even it’s passed all those test but I’m still nervous about safety issues for home owner. How do you guy checked for cracked heat exchanger, please share...!

Using a combustion analyzer, a large crack or hole in the HX might look something like this:

O2 (%): 10 - 10 - 10 Blower ON: 8 - 7.9 - 7.8 - 7.7

CO (ppm): 5 - 5 - 5 Blower ON: 10 - 15 - 20 - 30

Seeing numbers that were stable before the blower came on, then they are unstable, is good reason to do a visual inspection of the HX, it is not a confirmation of a crack/hole.

Leaky blowers or burner compartments can cause the same reaction, and the reason you don’t assume the HX is cracked.

Looking at O2, CO and draft might give you reason to expect a crack, but it is not foolproof.

The CO and O2 can go either up or down with a large crack or hole in the HX, and the above numbers were just an example.

If the Combustion analyzer shows good STABLE numbers, I would have no problem walking away and sleeping well at night.

Selling the customer a Low Level CO Monitor, would also help the customer rest well.

 

You're really not usually going to detect CO in the living space. The blower motor is more powerful than the burner motor, or inducer, so it's going up the chimney.
But you will see numbers similar to what @rundawg stated.

Also keep in mind there is a very large company (my area, orange trucks) who a very high pressure, hard sell. The offer a very cheap safety check (and one next year for free). They have almost never come across a furnace more than 10 years old that didn't have a 'cracked heat exchanger' and deadly Carbon Monoxide will leak into your home.

So if you don't see it with an analyzer, and don't see it visually, how did they dial it out?

 

A combustion analyzer is an awesome tool and this is only part of what it’s good for. Taking a reading is a lot faster then checking the HX visually, and although it won’t tell you for sure that there is a crack, it can usually tell you if there isn’t.
For a second opinion call though, I’d still feel obligated to do a visual check. If, as was your case, I can’t find anything. Make sure that they have working CO detectors and walk away knowing you probably saved them from a unnecessary purchase.


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Pull it and look.

 

In my experience, you’ll have an operational issue when there’s a crack large enough to be observable. Flame will typically be lazy on one burner, flame will rollout in your face (never sit in front of a furnace if it has a tripped rollout!), or flames will dance when the blower comes on. With either of these symptoms, I give a thorough visual inspection. Small cracks can be easily overlooked. I have a few pictures I can post as an example later when I get home.


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Sound like combustion analyzer is more accurate except you pulled it, visible Check is not easy on 90+, I don’t have a combustion analyzer now but thinking getting one, any recommendation for starter? At the meantime, hope to hear more experience from you guys. Thanks for responding.


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Back before analyzers & cameras the old guys would spray a saltwater mist into the flames & look for " smoke " from the vents. If it didn't smoke just come back in a few weeks and it would need a Hx :grin2:

 

Old guy,

Do you remember the old smoke tabs that you would light and they would smoke like crazy. Then look in the plenum for smoke. Move them from cell to cell or just leave them in the drum of the old tanks and let them smoke. Boy did you find out if the flue was not drawing though, it would fill the whole basement with smoke. If I remember right we only used them on old welded seam heat exchangers as clamshell pressed fit would always fail a smoke test due to the seams not being hermetically sealed.

Have not used a smoke bomb test in many years, don’t know if they still make the smoke tabs.

Oh the memories.

 

A company I was with 15 years ago was still using the smoke bombs. Tough seeing through all the smoke to even look into the plenum. Graduated to a camera eventually but still always made me nervous having to make a call one way or the other....

 

I remember the salt spray but don't remember looking for smoke. I don't know that it would. We would spray the salt water above the burner in a lite mist with the blower running then the other guy would check at the registers with a propane torch for a change in flame color of the torch, it would turn orange as I remember.

 

I use the Testo 310 it's the cheapo of their other models but works fine for what I need.

 

Testo 310 is around 620 on Amazon, little high for my budget right now, I was looking at fieldpiece sox3, anyone have any input on this?


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This isn’t something individual techs should have to buy. This is something your company should provide to you, just like reclaim machines, vacuum pumps, ladders and such.
As said previously it’s a tool that needs yearly calibration. Which just adds to the upfront cost.

 

Why are you buying it? That's a high ticket item that requires maintenance, the company should purchase it. Its for there benefit!

 

Well, been with the company for years now and haven’t seen anyone have it yet, but will bring up with the boss to find out, thanks for everyone inputs.


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I’m interested in a combustion analyzing kit also. So if anyone has any input on which to get or stay away from I’d love to hear.


(Just tryna get better)

 

If anyone is interested I have several old Bacharack and a Testo Combustion Analyzers. They are old and have not been used in years. They were replaced because they needed sensors and calibration and I decided to put the money into new rather than the old. If interested send me a PM and I can send pictures of the units and you can research what it may cost to get them running again.

 

I’m interested but can’t pm you, sent you an email.


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I’ve never worked for any company that supplied combustion analyzers. Never even heard of the tool until I started lurking on this site. I’ve always been required to take a picture of the crack to give to the customer. A good snake camera and some experience will show you where to start looking on different types of heat exchangers.

 

Just checking flame roll out and lazy flame can fool you. plugged secondary will show similar symptoms. use an analyzer and visual inspection. Though I guess either is a condemnation of the exchanger.

 

I was under the impression the only way to check a clamshell heat exchanger was to spray it with water. Can a combustion analyzer work?

 

A combustion analysis that shows high CO, or changes in CO and O2 when the blower comes on (70% and 80% furnaces), is a reason to look further for a crack or hole in the HX.

The reason you have to look further is, excessive duct leakage or leaky blower and burner compartments can causes this same symptom.

The only method that is 100% accurate is a visual inspection, and it should always be the final test.

 

Wait !
You just contradicted yourself 🤣

 

I don't mind old threads. The info is what's important.
I wouldn't bet on an instrument. I think they can be fooled and too much reliance on them. EZ way out.
It all depends too much on the tech, the instrument, calibration, placement etc.
Even cracks can be almost invisible. A combination will be more accurate.
No one wants to take a furnace apart if not necessary. But sometimes it is.
I've used lots of methods over the years. But w/o a visual I would never be positive. Even a visual could miss something. That an instrument didn't see it, does that mean it doesn't exist?
It's fortunate that they way furnaces are built with a positive blower pressure on the exchanger,
probably people are safe most of the time.

The most strangely unscientific I remember was oil of wintergreen in the exchanger and asking the HO to sniff the supplies. The smell of the oil will go everywhere with or without a bad exchanger.

 

I've never understood the meaning of "why we should not reply to an old thread."
I totally agreed with you " I don't mind old threads. The info is what's important."

 

How about having it become something like, it automatically turns into a ''as in reference to'' after a certain time frame. Kinda like when a lot of guys respond to a thread they provide that useful 'go to' link to an old thread. KindaSorta?

 

I am not an IT guy, but I would think there are options available that would reduce the number of bounced emails, like limiting a thread to a one year response time. After that, the thread becomes locked for added comments. This would force the member to start a new thread on the topic.

All would require modifications to our antiquated software that no one wants to tinker with at this time, because our we are suppose to be nearing the time when our site will be upgraded to the Xenforo software.

What can or will be done after that, is unknown.

 

I stick a bbq igniter into each tube and run the blower. It really is clear as day.

 

I’m remember the Salt Spray test. The Company I worked for bought the Blue Tinted Solution Cheap from the Gas Company. Some outfits decided to make their own solution, this was against regulations on the required testing. They got caught, as the Gas Company stuff changed color under UV Light.

 

wish my company would provide me with one I had to buy my own

 

Easy test is connect a magnehelic to port for pressure switch with blower running. There should be no pressure there if hx is good. Not definitive but one of many tools in the belt. Lit match in burner hole with blower running is good too.

 

I need to see the documentation on that.