Flames shooting out of front of heater

This is a new Williams wall heater of a very common type in my inspection area. What could be causing the rather yellow flame? Most of them run a more pure blue.

Looks like delayed ignition… the ignition source is too far from the fuel source. As for the orange v. blue flame that could be from a lot of different things but it looks pretty normal once ignited and running.

Will tell you, after you tell me why my car won’t start.


Flame rollout and incomplete combustion can both be caused by inadequate draft. “The inspector recommends that a qualified HVAC professional service tech be consulted for further diagnosis of the wall furnace in the ____ room.”


Yellow-Orange in flame indicates insufficient / poor oxygen mixture.


Installed by flipper/homeowner and not properly adjusted/tuned when installed!


Moring, Bryce.
I forgot to mention. If this is Natural Gas - NG, a yellow and orange could be cause for concern. Why? At times excess **moisture in the air can change the color of your flames in your furnace usually due to the use of an unbalanced humidifier or even wet NG or combustion balancing.
Ribbon burner?
Model number?
Might need oxygen mixture adjustment.

I could detect no difference between this furnace, and an identical model in the same building… the position of the pilot relative to the burner area looked identical.

There was a white powder, typical my area when the pilot is too high, on the thermocouple.
I wiped off that powder but the behavior did not change.

Here’s the flame burn from the comparable heater one floor up:

Not in this case. The service records indicate it was installed by a professional,
and as far as I can tell no adjustments are even possible, certainly none are mentioned in the user manual. The flue length is roughly 40 feet straight up. My inspection scope was limited so I did not examine the rooftop end.

For @ryoung7


I don’t see how “insufficient air” could have been present.
The furnace was in a large enough room, and a sliding door was open. Maybe maybe there was a pressure differential from the roof to the lower floor (40 feet). But not a lack of air, and on the video it’s clear the flame does not lift off the ports, it’s just yellow.

I would call it “lift”, when there is a flame rollout for the first 4 or 5 seconds of ignition before the burners re-light blue. :laughing:

Something tells me the installer didn’t use the correct oval B/W vent and oval-to-round adapter. Times being what they are, the damn thing might not have been available and somebody decided to improvise.

And always keep in mind that you are playing with a “gashed-burning appliance”. Something was obviously lost in the translation.

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I don’t necessarily see those as the same cause. The rollout is violent enough it could do almost anything. It’s the ongoing flame quality that concerns me more.

It’s related. It’s a combustion air flow problem. They probably even used the existing flue pipe to the roof since it was such a long run.

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Certainly. And while the wall heater is new, that means a 53 year old pipe for this 1969 era building.

Incomplete combustion and carbon monoxide emissions.
Might be low NG pressure.

What did the flue at the crown look like?

Identical heaters in the same building and same floor showed normal flame. Flue crown was inaccessible under scope of inspection. Pipe is likely about 40 feet, installed 1958 when building was constructed.

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