Hello and thanks ahead of time for any responses. I am the second owner of this home with a 13 year old Amana Distinctions furnace that has started to trip the flame blow back safety switch and throw a code of 6 blinking led. I have had the unit opened while running and also while viewing in the peep hole, I do not see the flame blow back that several youtube videos have shown. Exhaust pipe is clear the best I can tell (plenty of steam /exhaust when furnace is running). My initial assumption was the heat exchanger tube cracked or corroded out. We do have some corrosion in several areas and at times there will be puddles that form on the floor. So to test this with it tripped the furnace fan will continue to blow and I tried a match stick flame in each of the flame/heat exchanger tubes. The match stick flame did curve back but not violently as if being blown out due to a crack in the heat exchanger. So from my non-professional thoughts it doesn't seem to be a cracked heat exchanger issue. With the furnace running, I noticed that there appears to be flames coming out of the what appears to be crimped wing like side portions of the burners. I don't know the terminology or if this is normal flame behavior exiting the burner tube. I attached a picture of a burner with some hand drawn red flames at the place of where I see flames. These flames certainly are splashing out on the front surface of the exchanger but again I do not know if this is normal behavior. I will attach a pic of the actual flames. Sorry its a crappy cell phone pic. I am tempted to purchase new burners as these are original and a HVAC guy who inspected the furnace when we bought the house had said it appeared that the furnace had been running while propane tank was empty due to sooting on burner tubes. He pointed out the corrosion and said it was common with this furnace and believed there was some warranty on it but we were outside that timeframe. So any suggestions would be appreciated.
Suggestions solving flame blow back sensor tripping
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Fitter30
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The wing portion of burner is made for gas to come out. When checking for a bad hx with blower on and off is there a difference in the match flame? Best way to check is with a flue gas analyzer. A compromised hx doesn't have to have a gaping hole it could be a 1/2" hairline crack. Have you pulled the burners and with a mirror and flashlight look at where sections are welded together? Have you ever heard the burners making a loud noise burner could be burning back at the orfice and that would trip a roll out switch. 80% furnace should never have water on the floor they don't condense.
Fitter30, thanks for your reply. No difference in the match flame test with the blower on or off. The flame seemed to tilt back out the exchanger tube. I am thinking maybe the easiest flow of heat from the match? I have pulled the burners out and cleaned them. This year they do appear to have a bit more rust on them. If the issue is not heat exchanger related I will replace them. I did just look for any cracks in the welds and don't see anything obvious. The burners don't make any weird noises or have any flame blow back or anything that looks suspicious in the 20-30 minutes I have spent observing burns. The only thing that appeared suspicious to me was with the flame coming out of the winged portion. Which from viewing the flame I believe is how the 2,3,4 burners are ignited. I am leaning toward it possibly being the roll out sensor itself. I have a couple on order and it should arrive next week. I will have to evaluate what happens with that. Regarding the condensation on the floor it is when the AC is running. There is quite a bit of corrosion from condensation. The HVAC guy who did the install said he did pull a june bug out of the furnace once that clogged up the drain tube and made a mess on the inside. I believe he had to replace some electronics. It was before our time in the house. I have a maintenance routine to check the drains because of that. I also put screens on the intake and exhaust to keep the big bugs out. Both of which are clear right now. I will follow back with the results of the new sensor. Its -20 right now and the furnace is getting a work out.
Plumber69
In the Trades
Does it have a secondary heat exchanger. You can pull the blower and visually look for a rusty plugged secondary. Some times will rust out and leak water
