Chevsky
Member
Nearing desperation with a furnace that's tripping flame rollout sensor. ICS/ComfortMaker RPJ-II LP gas furnace.
Well, it's working now, but that's only after I tore down the furnace to inspect the heat-exchanger for cracks, removed and cleaned the blower cage fan, and disassembled and reassembled the burner, gas manifold and igniters, and inspected the chimney and exhaust flues. Why it's now working is a mystery... (I think this furnace has it out for me)
Worth noting is that I have two LP gas furnaces (w/AC) and an LP hot water tank all on the same single-flue chimney. Primary 100K-btu LP furnace + H2O in the basement, and a smaller 75K-btu LP furnace on the second story.
It took me a couple weeks to finally realize the flame rollout had tripped. [Credit to "Word of Advice TV" and Greyfurnaceman.com YouTube channels: 10 reasons your rollout switch is tripping] I got it light but the flame rollout sensor/switch trips every 1-3 hours. I replaced the switch (seemed iffy -- have to push on it hard before a very faint reset click) but the new one keeps tripping too. (kept tripping -- 24 hours later and it's still working ok. I may have inadvertently fixed the furnace, or turning down the upstairs heat has stopped the problem reaction, or perhaps it's just taking a short vacation from mocking me)
Symptom is that the furnace is blowing cold and the burner isn't lit; I'd feel a cold breeze in the house; Go down to the basement, power off the furnace, reset the rollout switch, power-on the furnace, which would then ignite just fine and heat for a while; Eventually I'd get tired of watching the furnace waiting for some clue... I'd return to my sofa; Then 1-3 hours later it's blowing cold again. Rinse and repeat.
So I assume at some point the flame is indeed rolling out. (I've only actually witnessed it when I've reset the rollout switch without first powering off the furnace. In that case it happened because the furnace ignited just as the induction fan stopped)
Can anyone suggest things to check if this behavior starts up again?
Perhaps it is a bad heat exchanger, but maybe it's a chance startup (or just running) of the 2nd story furnace at the same time the basement furnace tries to startup. Or maybe it's while the basement furnace is running, AND the H2O is running, AND then the 2nd story furnace starts up and causes enough back-pressure to cause a rollout. One strange (seeming to me, but what do I know) behavior is that while watching the basement unit: it runs (heating) for some good long while, but then stops short of reaching the set temp... the burner stops; then a minute or two later the induction fans stops; then in a few minutes the blower stops -- BUT at that moment the induction fans starts, then the burner, and then the blower. This seems to cycle 2-3 times -- a heating cycle stopping and going immediately back into a heating cycle. Eventually it stops completely when the target temp is reached.
I tried my LP supplier for service, but over-the-phone response: "Your heat exchanger is cracked, blower is pushing air into the combustion chamber and blowing the flame to roll out. Furnace is junk. I can replace for $5K". Two years ago it was the Honeywell Smart-valve. $500 to replace. Last year the same symptom... but this time I took to it myself, and traced it down to a clogged pilot orifice -- a $3 part. Hmmm.
Yup it's an old unit, but I just want to buy some time to spec out a whole-system upgrade rather than throw money at this one furnace. I've posted another thread (here on my first day
) asking for thoughts on a two-system hybrid LP(s) + multimode heat pump(s) vs combining these two into a single zoned setup with some duct rework. Someday it will be like that scene in Office Space, out in a field with the printer...
Thanks all (long post, I know)
Well, it's working now, but that's only after I tore down the furnace to inspect the heat-exchanger for cracks, removed and cleaned the blower cage fan, and disassembled and reassembled the burner, gas manifold and igniters, and inspected the chimney and exhaust flues. Why it's now working is a mystery... (I think this furnace has it out for me)
Worth noting is that I have two LP gas furnaces (w/AC) and an LP hot water tank all on the same single-flue chimney. Primary 100K-btu LP furnace + H2O in the basement, and a smaller 75K-btu LP furnace on the second story.
It took me a couple weeks to finally realize the flame rollout had tripped. [Credit to "Word of Advice TV" and Greyfurnaceman.com YouTube channels: 10 reasons your rollout switch is tripping] I got it light but the flame rollout sensor/switch trips every 1-3 hours. I replaced the switch (seemed iffy -- have to push on it hard before a very faint reset click) but the new one keeps tripping too. (kept tripping -- 24 hours later and it's still working ok. I may have inadvertently fixed the furnace, or turning down the upstairs heat has stopped the problem reaction, or perhaps it's just taking a short vacation from mocking me)
Symptom is that the furnace is blowing cold and the burner isn't lit; I'd feel a cold breeze in the house; Go down to the basement, power off the furnace, reset the rollout switch, power-on the furnace, which would then ignite just fine and heat for a while; Eventually I'd get tired of watching the furnace waiting for some clue... I'd return to my sofa; Then 1-3 hours later it's blowing cold again. Rinse and repeat.
So I assume at some point the flame is indeed rolling out. (I've only actually witnessed it when I've reset the rollout switch without first powering off the furnace. In that case it happened because the furnace ignited just as the induction fan stopped)
Can anyone suggest things to check if this behavior starts up again?
Perhaps it is a bad heat exchanger, but maybe it's a chance startup (or just running) of the 2nd story furnace at the same time the basement furnace tries to startup. Or maybe it's while the basement furnace is running, AND the H2O is running, AND then the 2nd story furnace starts up and causes enough back-pressure to cause a rollout. One strange (seeming to me, but what do I know) behavior is that while watching the basement unit: it runs (heating) for some good long while, but then stops short of reaching the set temp... the burner stops; then a minute or two later the induction fans stops; then in a few minutes the blower stops -- BUT at that moment the induction fans starts, then the burner, and then the blower. This seems to cycle 2-3 times -- a heating cycle stopping and going immediately back into a heating cycle. Eventually it stops completely when the target temp is reached.
I tried my LP supplier for service, but over-the-phone response: "Your heat exchanger is cracked, blower is pushing air into the combustion chamber and blowing the flame to roll out. Furnace is junk. I can replace for $5K". Two years ago it was the Honeywell Smart-valve. $500 to replace. Last year the same symptom... but this time I took to it myself, and traced it down to a clogged pilot orifice -- a $3 part. Hmmm.
Yup it's an old unit, but I just want to buy some time to spec out a whole-system upgrade rather than throw money at this one furnace. I've posted another thread (here on my first day
) asking for thoughts on a two-system hybrid LP(s) + multimode heat pump(s) vs combining these two into a single zoned setup with some duct rework. Someday it will be like that scene in Office Space, out in a field with the printer...Thanks all (long post, I know)
