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I know there are probably answers to be had elsewhere, but I'm hoping someone is up and reading this now.

Going down to 8 degrees tonight and my five year old propane furnace is acting weird. It'll turn on, flame for a second or two, and then the flame stops.

There's a powered vent that seems to be working correctly. So too is the blower. There are no blockages in ducting, return air, etc

It seems like it's a gas supply issue, possibly a bad regulator, but I'm open to other ideas as well. I'm going to call the gas company first thing in the AM to come swap out the regulator, but I'm wondering if you all can think of any obvious thing I've missed...

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I’m running a coal boiler which is archaic but simple but if this is high efficiency I think there is a sensor that you can sandpaper to get going in a pinch, someone here will help more

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I assume LP furnaces have CAD cells (photo eye) to prove ignition, your symptoms in an oil furnace would be indicative of a dirty cell. Usually you wipe them off and go again. 

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Sure sounds like a flame sensor issue.  The furnace may be shutting down because it doesn't realize it is igniting.  We have 2 weil McClain eco boilers out there and have had this issue before.  On our specific boiler there was a work around until the part could be replaced.

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21 minutes ago, KWRB said:

I know there are probably answers to be had elsewhere, but I'm hoping someone is up and reading this now.

Going down to 8 degrees tonight and my five year old propane furnace is acting weird. It'll turn on, flame for a second or two, and then the flame stops.

There's a powered vent that seems to be working correctly. So too is the blower. There are no blockages in ducting, return air, etc

It seems like it's a gas supply issue, possibly a bad regulator, but I'm open to other ideas as well. I'm going to call the gas company first thing in the AM to come swap out the regulator, but I'm wondering if you all can think of any obvious thing I've missed...

I don't know squat but the one at my son's house will do that if there is the smallest of obstruction in the vent. Wasp nest or snow at the end will keep it from lighting. His has a 1 1/2" or 2" pvc from the vent fan to the outside with a rubber coupling. To diagnose his we uncoupled at the rubber hose coupling and tried it when it works we clean the pvc.

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25 minutes ago, KWRB said:

I know there are probably answers to be had elsewhere, but I'm hoping someone is up and reading this now.

Going down to 8 degrees tonight and my five year old propane furnace is acting weird. It'll turn on, flame for a second or two, and then the flame stops.

There's a powered vent that seems to be working correctly. So too is the blower. There are no blockages in ducting, return air, etc

It seems like it's a gas supply issue, possibly a bad regulator, but I'm open to other ideas as well. I'm going to call the gas company first thing in the AM to come swap out the regulator, but I'm wondering if you all can think of any obvious thing I've missed...

I would guess a flame sensor.   Looks like a metal probe.    They can get dirty and do funny things.    Use a Brillo pad or steel wool and clean it up.  

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Just going to throw this out there. 

My furnace is probably older than anyone elses on here. 

When my furnace won't stay lit, usually won't light at all, It is the thermocouple. 

it sits in the pilot light flame. 

I keep an extra one on hand because it always goes bad on the coldest nights. 

Sounds like a night to get under the quilts.

HOpe someone can help get you going again. 

Good luck

thermocouple.thumb.jpg.6210b35a96d7982b37e568204477857e.jpg

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If it has a draft inducer motor and a PVC vent pipe, chances are it is the flame sensor. You can find that on the opposite end of where the igniter is. Usually a quarter inch or 5/16 not driver to remove, sandpaper as clean as you can get it, reinstall. If the flame stays on longer than five seconds it is probably a pressure switch or another issue

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If it is only 5 years old it would probably have a self-diagnosis feature. Usually an LED or two that will flash in a pattern. There is usually a chart somewhere that will explain the code. As stated above, first and foremost clean up the flame sense rod. I would recommend against using sandpaper, but the idea is the same. Scrape with a knife, steel wool, or a wire brush to remove any residue or rust. The sensor rod is a steel rod approximately 1/8" diameter mounted in a porcelain insulator. Also clean up the area opposite the rod that provides the ground. Usually the burner or another rod without the insulator. The control senses the presence of a flame by attempting to pass electric current through the rod and flame to the ground. If the rod or ground is dirty enough to prevent the current flow the control thinks there is no flame and shuts off the gas flow. A flame is somewhat conductive. Air or the absence of a flame is not. You can use sandpaper but it may leave a residue on the rod that may cause the same issue or so I have been told. If you do use it I would recommend wiping the rod clean with a clean cloth. Good luck. 

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Just got done redoing our suburban furnace, now ours is an RV but your definition is the same as what ours was doing, thermostat would only turn on when cycled below the ambient temp line and turned up, this required a new thermonstat,  it would then not sense the need for heat so blow cold air and then cycle off, this required a new circuit board (dinosaur), then it would start the furnace but it wouldn't stay burning and shutdown, this required a new gas valve and a new igniter, with all the new parts and checking the heat exchanger, which was fine, the system is more fine tuned and responsive.

Good luck.

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Thanks for all the help guys.

 

It was indeed a regulator issue. Swapped it out and we're right up and running. House only got down to 50!!

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2 hours ago, KWRB said:

Thanks for all the help guys.

 

It was indeed a regulator issue. Swapped it out and we're right up and running. House only got down to 50!!

Yikes! Only one thing to do at that temperature... 

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I'll catch you all up on some details. Learning from other people's trials and whatnot.

 

The furnace is only 5 years old and I'd never had this issue before, so I was fairly confident it wasn't a furnace setup issue. It is a high efficiency propane furnace with powered vent.

Initially, my wife called and said that the furnace was short cycling and the temperature was falling fast in the house. Well, we had some rip roaring wind last night and I think "aha! the wind blew up the exhaust of the powered vent, and the furnace perceived it as a blockage and that tripped a safety cutout". I figured I'd reset it, then parked my wife's war wagon in front of the exhaust to block most of the prevailing wind and we'd be home free. Wishful thinking.

When I went to the basement to look, I was seeing that the burner would light and burn for a second, then go out. That means likely either the flame sensor wasn't seeing flame and thus shut off fuel, or I wasn't getting enough sustained fuel to maintain the flame. If it's the flame sensor, it could be corrosion. That's the scotch brite fix mentioned above. However, the control board was giving me a trouble code of "flame lost". That told me that the flame sensor was working, because otherwise it would never have seen the flame in the first place. So I was missing either fuel or air after the flame lit initially. None of the returns or vents were blocked, filter was not terrible, etc., so I ruled out air. Must be fuel.

I looked for a crimp in the line outside. We'd had some warm days recently and I thought maybe ice came down behind the tanks and pinched a line. Checked the tanks fill level. I've run out before, and it's always on these super cold nights. Always. Tanks are both still around 100 gallons. That pretty much leaves the regulator.

The biggest final tell for me that it was the regulator was this. Not only would it run for a second and flame out, but after the flameout, the behavior was different, depending on how long I waited before retrying. If I immediately tried to restart it, the igniter would click but no flame. If I waited a few minutes, I'd get that one second burn before flameout. Presumably, those few minutes allowed for the fuel line to repressurize through the bad regulator, but if done back to back, there wasn't enough time to build up pressure for the second attempt.

My furnace is fed by two 200 gallon LP tanks, but I think this summer I'm going to finally bite the bullet and put in in-ground 1500 gallon tank in. I hate LP tanks. They're an eyesore and the current tank location relative to my roof valleys and the two-tank setup I think contributes to the issue. I put an addition on this past summer and the snow really piles up all over them now. Even if I keep them shoveled, then icicles fall on it and I worry about them smashing the copper gas lines.

The last thing I want to add is this, in case it's helpful to someone else in the future. It works sometimes, but not always. Sometimes if it's real humid in the winter and just below freezing, a bad regulator will freeze up. This can also happen if the vent/drain holes in the regulator are not oriented down to allow water to drain out. Sometimes you can get temporary relief by taking a towel with hot water and wrapping the regulator. I have done this in the past with the other propane tank we use for the kitchen. Obviously it's not a great solution, because you're introducing even more moisture to the environment and it is likely to eventually re-freeze. Last night I tried a blow dryer on the regulator first and then tried the hot towel trick as a last resort. It didn't work last night I think because it was too cold. It may not have unfrozen at all, or I probably just made it worse, adding all that moisture. I stopped short of putting a torch to it ?. That being said, I don't know if the issue was the regulator freezing, or if it was some other failure. I'm just glad I troubleshot it correctly in that it was a regulator problem, so I didn't waste the propane guys' time in the cold this morning.

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Another thing to remember is the copper line from tank to regulator can start flacking off inside and block flow. I would guess 20 years or more but have seen it twice in the last 30 years.  The lines came with old tanks and regulators so they could of been 50 years old, I don't know. Could become more of a problem, I would guess if copper is smelted outside North America in the new stuff.

The flame on the kitchen stove would be weak, go tap the regulator. The other one flame would go out on the pilot of a water heater. After a new heater, and new thermal couple, it still went out. 

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