It looks like:

- heat exchanger failure
- dirty burners caused by propane usage
- VOCs in the combustion air (if indirect vented/80% unit)
- exhaust gas recycling problem (if direct vented/90% unit)

any one or more of those can be the culprit. A tech can verify that easily

 

Thanks for the reply!!! I am sure this forum is sick and tired of homeowners writing in with Goodman issues.

I'll try and snake a camera in there and see what I find. It is a 95%, variable speed, two stage upflow furnace. It's approx 70k BTU on the high stage. I run it 66 F at night and 72F during the day.

If you have time, could you point me to some info on what "exhaust gas recycling problem" means?

I'm super grateful for any info. I did register the furnace so I should be OK with a warranty. I'm having a Goodman-website-listed contractor come out in late March to take a look.

Any further opinions welcome! More pictures coming.

 

Goodman is OK equipment when it is installed correctly. Exhaust gas recycling happens when the exhaust gases get sucked back into the intake outside. They are acidic and when reburnt they chew up anything metal quickly. Additionally, if it gets really bad, the flame quits and you have a no heat problem.

Sometimes high snow levels can cause this. Improper terminations are a more likely scenario.

 

And again AOP delivers. Thanks for the response! May your phone ringeth.

The furnace intake is in the room. Only the exhaust is piped to daylight. The fresh air intake is nearby.

Also nearby is the water heater, which used to be an updraft vent model. I put in a power vent WH in October.

Does this change anything?

 

you might have a lack of combustion air. I cant tell that from here, though. But you're definitely burning VOCs from the laundry area and/or whatever else is around the house. On a higher tech furnace such as yours it SHOULD be piped as direct vent (intake and exhaust from outside).

 

Brian, did not mention where you are or the location of the furnace, but if you are in a humid environment and in a basement and running on low fire a lot, you might have condensation forming on/in the HX... Just thinkin' out loud.

 

Do you have A/C with the furnace, if so is the coil mounted upstream or downstream of the HX?

 

Hold on boys.

That rust on the faceplate is NOT PART OF THE HEAT EXCHANGER.

That's a sacrificial plate, installed to protect the heat exchanger.

The discoloration indicates that your overfiring.
The plate is replaceable if wanted.

Whats your temperature rise aross the unit?
Next would be to get someone check your gas pressure.

 

Short cycling can cause that. Possibly oversized furnace.

 

Gap a little too big in the crossovers will do that.