337rls Suburban furnace propane smell

[Randyv]

Used our furnace for the first time this week and we have a propane smell only while its running. When it’s off no gas smell so I have to assume it’s leaking past the valve or the valve itself. Have a appointment to drop off at the dealership later but it’s a long haul and we are doing some winter camping so who knows how long it take.
Has anyone pulled the furnace out of a 337rls? Looks like a pretty simple job. I have some HVAC background so crawling around in the basement looks like the hardest part. Any advice will be appreciated.

[Second Chance]

Is the smell inside or outside of the RV? The combustion chamber is vented externally, so no propane or exhaust fumes should make it inside unless there is a cracked or defective combustion chamber. If you're smelling propane outside, I would definitely have it looked at (no need to remove the furnace to do this). Are you certain it's propane you're smelling? RV furnaces typically put off a pretty strong smell the first 5 - 10 times they're used. This is burning off dust, heating the paint, etc. This happens at the beginning of each season for us, too - on every RV we've ever owned.

Rob

[Steven@147]

As @Second Chance says it's worth having your system checked out.
On our Rig, Only when the propane tank just runs out with the furnace running, On ours there is a faint smell of propane inside the RV(detected by my Wife's nose, but not mine). At no other time is there any smell of propane inside the RV. I believe its caused by the pressure getting so low just as the tank runs out and the furnace hasn't gone into error yet, and hasn't shut off yet, due to the sensor not detecting flame heat. With the exhaust port and the intake port on the exterior side of the RV only being an inch from each other, its plausible the unburnt propane comes out the exhaust and right back in the intake.

The furnace fan pulls the last little bit of propane smell into the furnace at flame out and out through the ducts, If I can catch it just as the regulator shows red and just before the tank runs out, to switch to the other tank, there is no propane smell inside. If I would allow the system to change tanks automatically there wouldn't be a problem with it.

For a new RV just running the furnace there will be a new burn in smell but its not a propane odor, its burning out contaminants in the combustion chamber and like a plastic smell through the ducts.

[Randyv]

As @Second Chance says it's worth having your system checked out.
On our Rig, Only when the propane tank just runs out with the furnace running, On ours there is a faint smell of propane inside the RV(detected by my Wife's nose, but not mine). At no other time is there any smell of propane inside the RV. I believe its caused by the pressure getting so low just as the tank runs out and the furnace hasn't gone into error yet, and hasn't shut off yet, due to the sensor not detecting flame heat. With the exhaust port and the intake port on the exterior side of the RV only being an inch from each other, its plausible the unburnt propane comes out the exhaust and right back in the intake.

The furnace fan pulls the last little bit of propane smell into the furnace at flame out and out through the ducts, If I can catch it just as the regulator shows red and just before the tank runs out, to switch to the other tank, there is no propane smell inside. If I would allow the system to change tanks automatically there wouldn't be a problem with it.

For a new RV just running the furnace there will be a new burn in smell but its not a propane odor, its burning out contaminants in the combustion chamber and like a plastic smell through the ducts.

Sorry for the delay in replying. Today was a travel day back home from camping.
And yes the next day we did run out of propane. Of course it happened while my wife was in the shower and we have a on demand water heater. That water sure is cold when it’s 29 degrees outside! That’s a summary of the things my wife said! I switched over to the other tank but didn’t try the furnace until we got home and read your replies and so far no smell. We started smelling LP inside the camper that evening, just a tiny hint but it went away. Only when the furnace came on. Then in the middle of the night my wife woke me up and the smell was pretty strong, especially in the bedroom. Turned it off until the next morning and when I turned it on again you could smell it in the camper. That was right before the LP ran out.
We have a appointment to leave it at the dealer Thursday so I figured we would run it for a couple days before we canceled.

You guys are awesome!

[Second Chance]

... we did run out of propane... I switched over to the other tank...

Are you not leaving both tanks open and using the auto-switchover feature of the regulator?

Rob

[Randyv]

Are you not leaving both tanks open and using the auto-switchover feature of the regulator?

Rob

Afraid I would run out completely not knowing the tanks had switched. Looking back my wife would probably have appreciated it!

[Second Chance]

Afraid I would run out completely not knowing the tanks had switched. Looking back my wife would probably have appreciated it!

If you check the tanks regularly, watch for the red indicator to flip when the first tank is empty and get that filled, there is no danger of that happening. I would never dream of not using the automatic regulator and having to run out in the middle of a cold night to manually switch tanks. That's what the system is there for.

Rob

[Randyv]

Well I pulled the heater this morning and found some oily substance had baked onto the heat exchanger and dripped under the heater. The exchanger doesn’t appear to be leaking and that stuff was baked on random spots on the sides and bottom. Maybe something got sucked up and cooked? I cleaned it up and ran it all afternoon and no smell. Will run it tonight and see for sure.

Also found the gas line on the burner side of the valve was not very tight. Snugged it about 1/4 turn.

[Second Chance]

Thanks for the update - good find! My guess is construction debris... maybe some foam or something.

Rob

[Steven@147]

Well I pulled the heater this morning and found some oily substance had baked onto the heat exchanger and dripped under the heater. The exchanger doesn’t appear to be leaking and that stuff was baked on random spots on the sides and bottom. Maybe something got sucked up and cooked? I cleaned it up and ran it all afternoon and no smell. Will run it tonight and see for sure.

Also found the gas line on the burner side of the valve was not very tight. Snugged it about 1/4 turn.

Thanks for getting back to us with what you found. That stuff would sure be smelly Did you have any problems getting the furnace out? I took the outside cover off our unit and cleaned out what I could and inspected what I could see. To get ours out I would have to remove the basement wall, crawl back in there and disconnect the ducts after disconnecting the gas line, then I could pull the unit out. Not looking forward to that.

Your post also reminded me I need to get off my butt and buy a back flow preventer valve and install it on the regulator where the factory removed it. Then reposition the regulator on the wall, then reposition the out flow hose. That way I could let the regulator do its magic auto change over to the other tank. The way it is now one tank back fills the other tank and we end up using both propane tanks at the same time till they are both empty. (if both tanks are turned on) One of these days I'll get around to it/