A tale of bad combustion

Ken C.

I was sent to an apartment to clean a gas-fired hot water boiler this afternoon, and the tenant said I was the fourth serviceman there. She called the gas company a couple weeks ago because of a strange smell when the boiler was running. She said the gas company serviceman knew immediately from the smell that the boiler needed a cleaning. An employee from the company that was first called for the cleaning saw that it was a Vaillant boiler and refused to work on it, she told me. The next company's employee did perform a cleaning, but the "bad smell" remained. The boiler was shut off when I arrived. An inspection mirror in the burner compartment revealed a heavy, white coating of crud (not sure from what) in the flueways. I lit the pilot, fired the burner, and sure enough, there was severe rollout and a yellow-orange flame. I also got a good dose of that "smell," which I presume was from aldehydes, which I've read is an indicator that CO is being produced. I've never smelled aldehydes before, but this odor was very acrid and made me cough and gag after only running the boiler for 60 seconds or so. Needless to say, I shut the boiler down, turned off the gas supply and recommended that the landlord get a new boiler. The tenant seems to think it hasn't been cleaned since it was put in about 12 years ago. I've heard that Vaillant boilers are more susceptible to sooting up due to small flue passageways. Anyone else experience similar problems with the Vaillants?
Ken C.

pperkins

I work on gas boilers for a gas company,the white coating is from the by product of the gas pilot that stays on all year long.once i had a gas boiler that was making high co,just needed a brushing of the boiler sections.co dropped to a low level.good luck to you...

pperkins

I work on gas boilers for a gas company,the white coating is from the by product of the gas pilot that stays on all year long.once i had a gas boiler that was making high co,just needed a brushing of the boiler sections.co dropped to a low level.good luck to you...

Steamhead

Never heard

of Vaillants being more susceptible to this than other boilers. But with that smell I'd say you're generating major CO for sure.

With the flame rolling out like that, you may have a blocked chimney or flue passages. This reduces the air supply to the burners enough that they roll out and make CO. The same thing can happen if the burners are over-gassed.

I saw a classic case of this a couple years ago. Small Repco gas boiler completely sooted up. Turned out some bricks had fallen into the chimney flue, and the gas regulator was screwed all the way down causing a flame that was way too high. This combination produced a very dirty flame that soon sooted up the boiler, and set off a CO alarm. After a brush-and-vacuum and resetting the regulator and air shutters, it ran like a champ with about 50 PPM CO if I remember correctly.

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Unknown

The white stuff

is the result of a breakdown of sulphuric acid, carbonic acid and other residue which results from a poor air environment and the very tight sections of the Vaillant boilers. They are difficult to clean with out a good soot sword and some long thin wire brushes. I use the same type used to clean the rifling on guns.

A real good cleaning will solve this problem. The smell is sulphuric acid mixed with impingement odor (aldehydes), it can be pretty acrid.

I would also check the venting and air for combustion in the area. Make sure there are VOC's (volatile organic compounds). Lacquesr, thinners etc in the area.

Mark Wolff

Flame Rollout

Check the boiler passageways to see if the cleaning was thorough, then check the stove pipe and chimney. Most likely the stove pipe or chimney is plugged. Check for rain soaked soot (it's like lava) or an extreme buildup of loose soot in the chimney where you are connected.

Mark Eatherton1

Tim...

I think you meant "make sure there are NO voc's in the area of combustion", dintcha?

I've seen VOCs dissolve cast iron burners, and turn steel burners into trash in 30 days!

You don't want to know where or why...

ME

Mark Hunt

Some day


we should have a discussion on "plugged chimneys".

I have lost count of the number of times that I have entered homes where there were elevated levels of CO. Without my testing equipment I never would have known.

Anyone that enters a home without some sort of CO testing device, enters at their own risk.

Last year a 63 year old woman perished from CO poisoning in Queensbury, NY. FIVE of the people that entered her home, including a State Trooper, had to be taken to the hospital for CO exposure. They were all breathing death.

You NEVER know what you're walking into.

Mark H

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