Reason for rusting on new HE furnace

[Egbert Jager]

Certainly beyond the scope of my home inspections to dictate repairs, but for my own knowledge:

What causes would result in the burner flames impinging on the sides (top) of the heat exchanger firing tubes? Only two of five so affected (#3 and #5 from the left). One of the locations has rust (pic coming when I figure out how to shrink to them)

2018 Goodman
Model GMSS921004CNAA
Serial 1808181182
100,000 BTU

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[Gunnar Alquist]

Certainly beyond the scope of my home inspections to dictate repairs, but for my own knowledge:

What causes would result in the burner flames impinging on the sides (top) of the heat exchanger firing tubes? Only two of five so affected (#3 and #5 from the left). One of the locations has rust (pic coming when I figure out how to shrink to them)

2018 Goodman
Model GMSS921004CNAA
Serial 1808181182
100,000 BTU

Egbert,

Pics would help. In order to shrink pics, I sometimes use MSPaint if I'm only doing one or two, but it's clumsy to do multiple images. There are also free online services that you can use to shrink multiple images.

[Egbert Jager]

rimg4257.jpg

Worst tube: rimg4264-gimped.jpg
One other (barely) affected tuberimg4265.jpg

All others unaffected :rimg4263(2).jpg

[Gunnar Alquist]

E,

I am not sure. I see that fairly often. My guess would be improperly adjusted burners. Hopefully someone who knows more about furnaces will post a more educated answer.

[Mike Clarke]

Have done some installations not as much experience on the repair diagnostic part as much and not in a while, only few HE installations before so not a lot experience diagnosing these models so this all is just for reference
Basically need a certified HVAC tech to take a look but here are some things that can cause what would may be checked when they service.


Also said new, was the unit installed and verified proper operation by a certified HVAC tech and was known to be operating normally before?
sometimes shipping can bump hard enough to move things


So there are checks needing to be made before operation and then while in operation
really hard to tell until actually see the flames while running, on an HE models should have a sight glass to look through while running.
covers must be in place, good seal for the air to be pulled into the chambers properly while running, if not then may can cause an improper burn, draft inducer fan is working properly, no air leaks, etc


some non operational checks
Check intake, exhaust, proper sizing and no blockage, not too may turns. Where is the Intake located have seen improperly use inside air, attic installations where intake was in the attic, verify no negative pressure
May include verifying gas pressure not too high (using a manometer), not too much moisture in the gas, etc. Verify gas supply is sized properly. IF running on LP most come with NG configuration and conversion parts to be done in the field (new orifices) may need to be checked was done/properly if the case.


can get the installation instructions for that model as a quick check was done per them but still needs to be checked by certified HVAC tech


some things they may check related to the issue while operating (HVAC tech) but not limited to these
Watching while in operation before and after main blower kicks in
would observe any changes in the flame pattern
Floating flames
Flame roll out
Flame distortion
Flame discoloration (yellow, green, purple)
for instance, if flame roll out after blower kicks in can be caused by cracks/leaks in the HX or connecting parts causing blow back into the combustion chambers(s), also cover not in place and sealing properly, gasket materials, inducer fan, physical damage to burner/chamber and/or connecting parts


Flame impingement does not always indicate a heat exchanger issue, can be caused by burner/orifice alignment or in some cases, air leakage maybe around the hot surface igniter.

Diagnosing these properly takes some experience.

[Richard Bushong]

rimg4257.jpg

Worst tube: rimg4264-gimped.jpg
One other (barely) affected tuberimg4265.jpg

All others unaffected :rimg4263(2).jpg

Acouple things can be happening, #1 unit needs a good cleaning , burners removed and brushed out. #2 the burners could be slightly misaligned by the person that last cleaned it. #3 Gas perssure at the manifold needs to be checked and made sure to be in spec. Most likely cause is 2 dirty burners and this is caused in these HE furnaces that take combustion air from within the structure and you get a dust buildup in some or all of the burners. Why these 2 particular ones is a gues but depending on what air currents are created when the unit is running could pull more dust to them . I used to get this question a lot and our codes and standards engineers and AGA personnel would say it just happens. So back to #1 , cleaning cures a lot of ills on a furnace or boiler, after that it needs to be checked to make sure it is not creating excessive CO or soot.

[Mike Clarke]

Acouple things can be happening, #1 unit needs a good cleaning , burners removed and brushed out. #2 the burners could be slightly misaligned by the person that last cleaned it. #3 Gas perssure at the manifold needs to be checked and made sure to be in spec. Most likely cause is 2 dirty burners and this is caused in these HE furnaces that take combustion air from within the structure and you get a dust buildup in some or all of the burners. Why these 2 particular ones is a gues but depending on what air currents are created when the unit is running could pull more dust to them . I used to get this question a lot and our codes and standards engineers and AGA personnel would say it just happens. So back to #1 , cleaning cures a lot of ills on a furnace or boiler, after that it needs to be checked to make sure it is not creating excessive CO or soot.

Dang! completely missed mention burners could be dirty, something interfering with the flame, cleaning the orifice, etc.

[Richard Bushong]

Dang! completely missed mention burners could be dirty, something interfering with the flame, cleaning the orifice, etc.

It's all fun until your hand gets caught in the fan

[Egbert Jager]

some non operational checks
Check intake, exhaust, proper sizing and no blockage, not too may turns. Where is the Intake located have seen improperly use inside air, attic installations where intake was in the attic, verify no negative pressure

Hey there, thanks for the very detailed list of things that can go wrong during an install or service.

What really caught my eye was the attic intake. Have you got a more source for this being incorrect. I've seen it once or twice and called it out as non-standard: might be working for now but expect to have it changed. But if you can show me where it is not allowed that would be great.

- - - Updated - - -

Acouple things can be happening, #1 unit needs a good cleaning , burners removed and brushed out. #2 the burners could be slightly misaligned by the person that last cleaned it. #3 Gas perssure at the manifold needs to be checked and made sure to be in spec. Most likely cause is 2 dirty burners and this is caused in these HE furnaces that take combustion air from within the structure and you get a dust buildup in some or all of the burners. Why these 2 particular ones is a gues but depending on what air currents are created when the unit is running could pull more dust to them . I used to get this question a lot and our codes and standards engineers and AGA personnel would say it just happens. So back to #1 , cleaning cures a lot of ills on a furnace or boiler, after that it needs to be checked to make sure it is not creating excessive CO or soot.

Thanks, these are certainly logical reasons for the specific problem of flame not being centered. Cleaning is a part of good maintenance!

[Richard Bushong]

Hey there, thanks for the very detailed list of things that can go wrong during an install or service.

What really caught my eye was the attic intake. Have you got a more source for this being incorrect. I've seen it once or twice and called it out as non-standard: might be working for now but expect to have it changed. But if you can show me where it is not allowed that would be great.

- - - Updated - - -



Thanks, these are certainly logical reasons for the specific problem of flame not being centered. Cleaning is a part of good maintenance!

As long as the units are getting proper combustion air I have never seen a code regarding the quality of the air on the combustion intake side, if it is a dusty attic because of wind or some other anomaly creating dust to the combustion air as long as it ir recieving the required cubic footage of air there is no reason you could not filter it , have never seen it done except in a lab but as far as I know there is no code against it. Yearly cleaning and adjustment recommendations are your best bet. I know after 30 years in the gas industry they say clean a gas furnace every 2 years , but I clean mine every year, too cheap not to do it.