Thread: Correct term for flame extended beyond side of burner?

What is the correct term for the condition where the flame in a GFAF extends past the side of the burner and impinges on the sheet metal burner housing, and what is that housing properly called?

(Yes. I know the furnace is toast. You can feel the roll out at the draft hood when the blower kicks on. I just want to know how to properly describe that flame impingement.)

- Thanks

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I would call it flame roll out. Chance are though that your client would not understand that term so I might simply just say that the burner is not burning properly.

I've never heard anyone in the trades call it anything but 'flame rollout'. Like Scott said you'll probably have to do some splaining to the client.
Flame rollout can occur from several reasons such as back drafting flue, negative pressure in room from other appliances and rusted out heat exchanger.

I had a similar situation a few years back. Talked to HVAC guy at coffee shop the next day and he says it is really a breach of the heat exchanger. Talked to the buyer in the spring as I went back to check his exterior GFI'S as there was 3-4 feet of snow. He said the Furnace guy he had look at it says it is fine. I told him I find that hard to believe and could be safety issue. He said I am going to change it out this year anyway. Hard to believe furnace guy would give ok.

Thanks.

I've always though of "flame rollout" as often intermittent condition occurring at and beyond the front end of the burners. This is a continuous, steady flame at the side of the burner where it enters the inner sheet metal casing of the furnace. I don't intend to get that detailed with the client "This furnace is beyond the end of it's expected and safe operating life and requires immediate replacement" is what they need to know. I just wanted to know if there is a specific term for that steady flame-to-the-side so that I can accurately describe it to HVAC service personnel if I ever need to.

Originally Posted by Michael Thomas

Thanks.

I've always though of "flame rollout" as often intermittent condition occurring at and beyond the front end of the burners, this is a continuous, steady flame at the side of the burner where it enters the inner sheet metal casing of the furnace. I don't intend to get that detailed with the client "This furnace is beyond the end of it's expected and safe operating life and requires immediate replacement" is what they need to know. I just wanted to know if there is a specific term for that steady flame-to-the-side so that I can accurately describe it to HVAC service personnel if I ever need to.

I often wondered that myself Michael.

I seem to be attending having a bad heat exchanger festival this month - likely, two out of three in this house alone! - other times I can go months without encountering anything suspicious.

And all these houses have been occupied, and none of the occupants are reporting adverse health effects.

Of course I'm going to continue to call out every one.

But I am beginning to wonder if compromised HEs are anywhere near as dangerous as disconnected vent pipes or situations where exhaust is entering the cold air return stream - I've read account of injuries and deaths from the latter two, but i don't remember ever reading of the same from a HE leak.

Originally Posted by Michael Thomas

I seem to be attending having a bad heat exchanger festival this month - likely, two out of three in this house alone! - other times I can go months without encountering anything suspicious.

And all these houses have been occupied, and none of the occupants are reporting adverse health effects.

Of course I'm going to continue to call out every one.

But I am beginning to wonder if compromised HEs are anywhere near as dangerous as disconnected vent pipes or situations where exhaust is entering the cold air return stream - I've read account of injuries and deaths from the latter two, but i don't remember ever reading of the same from a HE leak.

I think your right. Most heat exchanger leaks I have seen pics of are small rusted holes/cracks.

One of the reasons folks don't suffer from the effects of a cracked heat exchanger is that it takes a good size hole or crack for the flue gases to enter into the air stream. Most of the time and one of the reasons that the flame is wavers or fluctuates is that air is being sucked into the heat exchanger and not the other way around. The outside of the heat exchanger is under positive air pressure so it will push air into the crack on the heat exchanger.

At some point the crack or hole will be too large and the reverse will happen, and then this is when folks die!

Quite a bit of misconceptions and assumptions about heat exchanger cracks and CO poisoning being posted on this thread.

The scenario you are encountering in your first picture Michael is due to the gas crossover of the inshot burner allowing the gas to burn outside of the last burner on the manifold.
It is not a rollout condition.

This is usually found with a unit that has weak draft in the flue or a weak draft inducer.
Combustion testing of the furnace would help to identify any other problems.

If all checks out okay just clamp the crossover gap down on the last burner with a pair of pliers to stop the flow of gas outside of the burner.

Originally Posted by Michael Thomas

the sheet metal burner housing, and what is that housing properly called?

- Thanks

Are you referring to the heat shield or one of these others?

The burner on the left is defective, there is a built in gas path for the pilot flame to ignite on a call for heat. If you looked close you would see that the flame is coming from the stamp sheet metal of the burning.

Michael,

The term that you may be looking for is over-firing which would not be the same as rollout.

The easiest way to determine if that is occurring from an overfire condition is from combustion testing.

CO over 100 PPM, low O2, high stack temperature and a high supply plenum temperature combined are a good sign that overfiring is occurring is occurring in a furnace.

Seller had an HVAC tech out to look at a 25+ year old GFAF furnace I inspected last week, and the buyer forwarded me the following, forwarded from the seller's broker.

"They brought in Bart from American Weathermakers in Northbrook. His report (attached) states that they could not find cracks inside the exchanger with a fiber optic viewer. It looks like they found 2 cracks in the "face plate bisket?" (I couldn't read this part).

Therefore his recommendation is that it is safe to operate but is old and needs replaced."

Just wondering what the "face plate bisket?" could have been.

------------------------------------------------------------------------------------------------------------------------

IMO this furnace "is safe to operate but is old and needs to be replaced" in the same sense that that "a DC-3 with 80,000 hours on the airframe is safe to operate but is old and needs to be replaced".... but that's another story....

And thanks for all the responses.

Michael, the problem, as described here was regarding the burner ports--not the HX. Did he inspect the burners? The burners should have been removed, photographed and inspected. If still serviceable, they should be cleaned and reinstalled after the HX is then inspected along with the venting. Once put back together, he should have run a combustion analysis and observe the burners while firing. Cracked burners can cause a host of problems and must be corrected before this unit is fired again.

As for your terminology, since it has not been determined to be true flame rollout as from a vent obstruction, you could refer to it as "fugitive flame with impingement" or some such.

HTH,
Bob

Originally Posted by Michael Thomas

"They brought in Bart from American Weathermakers in Northbrook. His report (attached) states that they could not find cracks inside the exchanger with a fiber optic viewer. It looks like they found 2 cracks in the "face plate bisket?" (I couldn't read this part).

Therefore his recommendation is that it is safe to operate but is old and needs replaced."

Simply amazing!
The guy looks at the furnace and declares it safe because it has no cracks.
Still such a long way to go.

Might not be a bad idea Michael to state that the safety of the appliance has not been verified by the HVAC guy as this can only be done through a thorough combustion analysis and draft interference test.
I wish I was good enough to determine how safe an applince was with just a visual.

Bob,

Thanks as always for your response.

The furnace in the post above is a different unit, different house. This one is old (illegible plate) short-cycling Singer 120 series heating a house of around 1600 sq/ft and venting into an unlined chimney. With the blower on the flames danced around 3/4" of an inch, but that may well have been because the blower bearings were shot, and the furnace felt and sounded like a WWI tank with a bad transmission.

What I want to know is: Did the service tech put a combustion analyzer on this beast?

DavidR,

I've not see the service documentation, and I don''t know for a fact that no combustion analysis was done.

My clients understand the situation, and if they buy the house the furnace is going in any case - for one thing the chimney needs to be rebuilt from the roof and possibly the attic floor on up and a liner installed (its currently unlined, and had been for the entire time of the Singer's operation, with the expected result) - so it's going to be less expensive to move on to a CAT IV sidewall vented unit than to straighten out the chimney problems.

Fugitive flame, That's a gooooooooooooood one. I can't wait to throw that one out at a broker and hear the brain cells start to pop pop, popopopopoppop.
On a serious note. All good info on this post.

OK, here's deal.

The service tech says that he did what the seller asked - inspected the portions of the heat exchanger accessible with his borascope and without disassembly - for free, and that the seller did not want to pay for disassembly or a combustion test or anything else. Per the tech he does NOT know if the entire heat exchanger is free of cracks, he cannot certify that a furnace at least 35 and possibly 40 years old is safe, and he recommends its replacement.

"Disingenuous" was the clients' term for the way the tech's report had been presented by the sellers.

This service tech sounds like he's was turned down for a job as a foot operated land mine sweeper's position for being over qualified. Talk about liability. Either you do it properly or not at all. Since when do we rely upon the skill and expertise of the lay public to determine what and how to service? This must be one of those guys that pets the zoo animals thinking he's safe behind the fence...

I think Davidr will agree with me, a visual inspection alone of a heat exchanger (HX), is not worth nearly so much as performance testing. Also, the presence of cracks in a HX does not guarantee CO entry into the home. Only testing can prove that. It simply means further investigation by a pro is warranted. For the home inspector, you spot something fishy and call it out for a pro to check out.

Yeah Wayne, technically fuel gas from a 'gas leak' is referred to as "fugitive gas" so I borrowed the term. ;-)

For the record, there is no such thing as the absolute term "safe". Safety is a relative term. Fireplaces are much saf-er if you don't build fires in them. Cars are generally saf-er if you don't drive them on the road. Anytime you bring fire into a home, there are inherent risks of hazards. The installer and service tech have a duty to ensure the installation is reasonably free from risk of hazards that would be apparent to a person under similar circumstances with similar training and qualifications based upon the Standard of Care for that community. If you ask for a tech in the Philly suburbs, you're lucky he has two opposable thumbs and speaks english. You go to a certain community in Kentucky and you can expect your tech to insist on including combustion analysis, inspection and performance testing on all calls with proper documentation of same. The tech who performed a negative price job (no such thing as free--it cost HIM) and allowed the client to force him to cut corners is insane. All he had to do was insist on doing a complete thorough job of it or walk away.
Bob

Originally Posted by Bob Harper

Fireplaces are much saf-er if you don't build fires in them. Cars are generally saf-er if you don't drive them on the road.

Bob,

This is just a good opportunity to throw in what I read today in my NFPA Journal:

Related to fires and cars, that's the tie-in here.

There are 33 highway vehicle fires reported across the US *PER HOUR*. Data covers from 2002 to 2005.

Originally Posted by Michael Thomas

"Disingenuous" was the clients' term for the way the tech's report had been presented by the sellers.

I love it. Perhaps the BUYER should have arranged for the furnace technician.

Perhaps others see this stuff more often than I do, but I thought is morning's furnace was kind of a classic:

Far beyond the scope of a home inspector other than suggesting replacement. An HVAC company should be called in for pricing. Do not use the system until a complete system evaluation has been performed by a competant licensed and issured HVAC company.

I will only go so far with any HVAC system. If it looks like a complete disaster I state what I stated above. I am not going any further with an inspection at that point. I inspected a home yesterday where none of the three system functioned nearly at all. Two of the units were rusted out. One system was electric and worked half azz. I told the seller immediately upon entering the home of the gasses in the air. It was hard to breath in the home. Honestly I am surprised (if there is not) that the family living in this home did not already have serious permanent injury from these rotted out units, disconnected flues etc. etc. He shut the 2 gas units down and immediately called an HVAC company. He has been complaining to the investor that leased them this home for months and nothing has ever been done. I can see the legal end now.

Honestly. If anyone should be dead this family should be. I was not kidding about the instantanious, hit you in the head, obvious combustion concerns in the home. As I said the air was so heavy it was hard to breath. They have been living in the home with the heat on and the windows open. They may very well have been brain dead before moving in because it actually took someone like me to convince him to do something about it now or move out.