Update. The new flame rollout sensor did not trip and interrupt the furnace until Sunday around noon. So I went from Friday afternoon through Sunday noon. Now I am back to resetting the flame rollout sensor as needed.
I had an HVAC tech come out and take a look at it. He pulled the hose off the condensate trap, smelled it and said I had a plugged secondary heat exchanger. He noted the rust stains on the concrete floor near the area where the condensate trap is located and said the rusty smell of the water in the condensate trap and the stain on the floor were telltale signs.
He cleaned out the condensate trap, a lot of stinky black gunk came out. He replaced it and we cycled the furnace on. He said that my gas flames looked good and predicted that the metal box with the sight glass that surrounds the burners will become hot, which should not happen. This indicates a poor air flow through the system, caused by the rusted secondary heat exchanger.
Sure enough, the box got hot and one end of the box was hotter than the other, which happens to be the end where the flame rollout sensor is located. He predicted if we could see the rust on the secondary heat exchanger it would be heavier on the side of the exchanger corresponding to the side of the burner box that gets hotter.
My particular Carrier furnace has a known issue with this problem of the secondary heat exchanger becoming clogged and rusted. Carrier has even issued a service bulletin and are offering a $900 credit towards the installation of a new Carrier furnace if a homeowner has this problem. My furnace model number is on the list of the models affected.
So it looks like it's time for a new furnace.
