furnace burns rich , soot, any adjustments?

[batt]

Hi,
I have a 25' trade wind with a nt-22 surburban lp furnace. It seems to burn rich and was wondering if there are any adjustments that can be made.I noticed soot on the outside, is this normal? Pilot works good and goes through all the cycles fine. Just did not find anything in the service manual regarding tuning them.

[Siegmann]

This happened to me once when I cleaned the unit. The air mixing tube got knocked very slightly out of alignment with the gas jet. It has to be perfectly parallel. The misalignment was very slight, but when I adjusted, it solved the problem.

[idroba]

It is common for three things to happen to old Suburban furnaces which make them run rich.

1. Mud daubers have built nests inside the furnace restricting the flow of combustion air, either on the intake or exhaust side. This requires a dismantling of the entire furnace to find the problem and to clean it out.

2. The cast iron burner slots have rusted shut, and the gas/air ratio is then thrown off significantly. Again it requires a full dismantle of the furnace to see if that is the issue. The slots can be cleaned with a hack saw blade.

3. The rubber crossover tube is leaking, cracked open or missing altogether, so the combustion air from the combustion blower wheel is not reaching the burner. This was a major recall issue on all of the Suburban furnaces of the 70's. No recall parts are available now.

I always add this: The furnace is over 40 years old now. There are issues with rusting out of the combustion chamber as well as those mentioned above. Quite frankly it is time to replace it due to aging out. You or your family could find that significant CO poisoning is possible, making you very sick or even dead. I cannot recommend repair of the furnace.





3.