Flame rollout

John McArthur_2 · October 2006

Thanks for the tips. The findings were placed into writing and given to the H.O. The boiler with the CO issue was taken out of service until it can be replaced. I believe it is too far gone for cleaning/repair.

Unfortunately, I only got a CO reading on the first boiler and was unable to do any substantial testing on the second because my analyzer is now in for repair. CO sensor went out I believe.

The second boiler is in a house that is currently unoccupied and in escrow. The first, and by far the worst, boiler is out of service and a fireplace is being used for heat until replacement. I hope to have my test equipment back soon. The (natural) gas pressure measured about 3.5" at the manifold though.

I was really suprised by the amount of soot on the boiler heat exchanger and inside the flue.

I'm curious if anyone can tell me how much soot is too much on a gas appliance? I've searched and googled but only find a few vague references. What I've found seem to indicate that it only takes a little to cause flame rollout to occur.

John McArthur_2 · September 2006

I have looked at a couple of boilers in the last week that have flame rollout problems. Both are about 30 years old and were in dirty environments and were nat gas atmospheric units w/o rollout or blocked flue safeties.

How much soot can build up inside the flue and heat exchanger before roll out begins? It seems obvious that the more soot that builds up the worse the draft will become and consequently, the worse the flame will become.

How much soot would be acceptable inside a nat gas flue?

I also noticed about 30ppm of CO spilling from the front of the combustion chamber on one of the boilers. I shut the boiler down.

Any enlightenment would be appreciated.

clammy · September 2006

roll outs and soot

Most roll out switches espically mounted on the draft hood or divertor are there for blocked flue or blocked or restricted chimmies ,or and bad draft or a down draft from the chimmey ,spark ingition and no estabished draft in a cold chimmey as for soot build up and a roll off i am not sure but i have only see 2 or 3 gas boiler soot up and in 2 cases it was caused by no combustion air and another from a bad gas valve not closing completly and burner half hearted sooting the boiler and chimmey.I believe that for the roll out switch near the burner would go off if the boiler was plugged but have seen it go on electronic inginition and outside chimmey and also b vent ran in chases which where not insulated or internally finished run into those calls on replacement boilers with indirects and electronic inginition .Hope that helps peace and good luck clammy

Robert O'Connor_12 · September 2006

Rollout

I'd say you have a dangerous condition on your hand that needs to be addressed immediately. Remember, YOU worked on it last. I'd find out why these boilers are sooting up and fix the problem. There are three ways I know to address this.

1. Lack of combustion air

2. incorrect gas pressure

3. Blocked flue

You may be experiencing #1 because possibly the field conditions changed. An example would be that replacement windows were installed/basement finished off and the structure went from loose to semi-tight construction thus periodically creating a negetive pressure in the space. Maybe a modern clothes dryer was installed thus stealing the combustion air away.

What ever you do, do it now!

Robert O'Connor/NJ

John McArthur_2 · September 2006

Both of the boilers I looked at are so old they do not have any safeties. The worst of the two is located in a mud room adjacent to a door with a large dog door. The room itself was pretty dirty and I suspect that at one time there was a washer/dryer in the room also. There is a huge amount of soot and what appears to be lint on the inside of the B vent. I advised the homeowner that the boiler was a fire-trap and that the CO spillage was endangering his family. He had a el cheapo CO detector that will not alarm at the 30 ppm level.

The owner is planning to have the flue cleaned and the boiler replaced.

The second boiler is located in a closet adjacent to the downstairs living area. The closet has solid wooden doors that remain closed. I suspect that the lack of adequate combustion air over a period of many years has lead to poor combustion and a build up of soot.

Both boiler areas were very dirty and it appears as though neither has had any routine cleaning or service.

The really scary part is that both units have relatively new expansion tanks. Whoever serviced these systems last must have missed some really obvious danger signs. The H.O. on the first boiler told me that he has had 3 or 4 people work on the boiler in the past few years and no one mentioned any of the problems I described above.

Thanks for the input, I just wanted to reassure myself that I wasn't coming across as a con artist just trying to sell the H.O. new equipment. It's a shame that a cast iron boiler is shot in about 30 years because of a lack of basic cleaning and service.

EBEBRATT-Ed · September 2006

I would suggest putting the boiler deficiencies in writing and have them signed by the homeowner.

If the units are dumping co or are otherwise unsafe to run they should be red tagged and shut down immediatly.

You don't need to read about them in the newspaper. Just IMHO.

ED

David Richardson · September 2006

Did you get a draft reading in the flue?

What about blocking off the draft hood temporarily to see if it made any change?

What were your combustion readings in the undiluted flue gases?

frank_25 · October 2006

roll-out/spill

[Flame] roll out switches are placed onto or on top of the burner plate in the boiler vestibule, above the burners. They will prevent the gas flame from "licking" out of that opening when the boiler flue passages are plugged w/ carbon deposits, or other materials, thereby causing the flame having no where else to go but out. This is not a good scene man. The "spill" switch is mounted at the flue diverter and will prevent the burner from operating if the chimney is clooged, no draft, etc. It senses the flue gas temp. leaving the boiler and not being drawn up the chimney. The gases sort of "spill" out the diverter opening. That is not a good scene man. Lock 'em off, disable 'em by disconnecting a wire or two. But don't leave'em as is. The carbon build up can be caused by many things that go bang in the night. A gas valve that doesn't shut down 100% is a famous cause of carbon [ not enough air mixture in that small flame]. Blocked or otherwise obstructed venturi tube or dirty burner faces with stuff like animal hair, itsy-bitsy spider webs, rust, etc. ya get my drift? Sounds to me that you aren't really qualified to handle this job due to the question..."what are these for?" Get a gas burner guy or check "Find a pro", or call the utility for a recomendation. Me thinks that you gotta property and life threating condition here. bwdik?ijap

Mitch_6 · October 2006

Sounds like you are having the same problem I use to have

I felt sorry for the H.O. and did not want to shut equipment down. But found I could not sleep if I did not.

Remember were there is soot there is incomplete combustion and high c.o.

I just had one this week, in-law suite with a direct vent hydro therm boiler (I always find High co on them) Like you my analizer is out for seasonal calibration (jim if you read this post asap back would be great. The boiler was direct vent with single wall smoke pipe with some silicone on it and in a tight room. The boiler was 124mbh in (Load was only 30mbh) and the room could only handle 40 mbh. The boiler was full of soot so just based on looks I condemned it the H.O. was begging me to try to fix it. As I started to disassemble it I found more problems, the smoke pipe "single wall galve" had not been properly sealed and above the ceiling was leaking into the joist bays and soting them up.

Grandmas bed was in the room just above and she is ill, Gram-pa died just recently.

Needless to say out went the old and in went the new new sealed combustion direct vent CGs boiler that also uses outside air and vented in UL approved stainless.

I have come upon several boilers this year that had high or unstable co readings. Got my sweep in and also found what I could not see, compromised flues above.

Looks bad or unsure shut it down, have doubts have the utility come by to cover you.

You are testing for a reason.

Mitch S.

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Steamhead (in transit) · October 2006

How much soot can be there?

NONE!

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John McArthur_2 · October 2006

Steamhead and Mitch,

Thank you, that is exactly what I wanted to confirm. It seemed to me that with a clean burning gas appliance there should be little or no soot. I understand that the combustion air is not always perfectly clean and that any dirt in the air will not completely combust and that is why I asked "how much soot is too much?"

Mitch I know what you are talking about. Bids have been given to replace both boilers and have the flues professionally cleaned.

As I stated prior, neither of the boilers have safety switches.

The boiler with the less pronounced problem (my analyzer is being serviced so no combustion readings just observations) I looked at on behalf of a potential home buyer. He agrees with my assessment that the equipment needs replaced but is concerned that the seller will find someone else who will come in and say that it's OK and he will have to pay for it once he buys the house. I believe his concern is valid since I know that the boiler was serviced several times recently with no mention of any safety problems.

Thank you all for your responses. I come to The Wall so that I can learn. It is always a treat to post a quetion and see how little I actually know!

Flame rollout

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