Issue with furnace - smell un-burnt propane

tentcamper · 10-21-2014, 12:57 PM

This last time out we had nights in the low 40's. One night we came back to the camper after being out for 5+ hours and the camper was very cold. I turn on the electric heater and then fired up the furnace to warm it up quickly. All seem to work fine except it took several try to fire up the furnace. I did get a brief smell of un-burnt propane.

The furnace heat output was very low. Later via thermostat demand when it tried to fire up, it would get the spark but no flame. I had a little smell of un-burnt propane.

I figured out the issue and made the repair to the furnace not lighting. I inspected the combustion chamber and all seals. They all look good. It was a clogged orifices. All work well after and there was no smells.

My concern is that I could smell the un-burnt propane??? Since the furnace is a closed combustion chamber and only vented outside and I could smell the un-burnt propane inside???

I think what took place is my furnace vents are about 12 inches to the forward side of the door and with all the air movement from the fan it created a slight vacuum bringing in some of the gasses through the leaky seals around the door. Since you can not smell CO, i'm now concern how much of the CO is leaking back into the camper. I going to take a CO tester out next time and run the furnace.

Any body have this issue or any thoughts on it???

**wbmiller3** · 10-21-2014, 02:07 PM

That's definitely a valid concern. On our fall trip to New England, we ran the heater a lot. I took along a CO detector. It sorta seems like overkill with propane, smoke, and CO detectors, but oh well.

10-21-2014, 02:49 PM

An easy fix if anyone is concerned would be to replace the battery-operated smoke detector with a smoke/CO detector. Available at the hardware stores.

tentcamper · 10-21-2014, 06:55 PM

MisterP I like that idea. Just as long as I can find one that easy to remove. It seems like our smoke detector go's off every other trip either fro a camp fire or starting to cook with out the fan running.

**ShrimpBurrito** · 10-21-2014, 09:46 PM

Quote:

Originally Posted by tentcamper

I think what took place is my furnace vents are about 12 inches to the forward side of the door and with all the air movement from the fan it created a slight vacuum bringing in some of the gasses through the leaky seals around the door. Since you can not smell CO, i'm now concern how much of the CO is leaking back into the camper. I going to take a CO tester out next time and run the furnace.

Any body have this issue or any thoughts on it???

Hmmm....I'm not so sure about this theory. Even if a vacuum force were created, which I'm not seeing how that would happen exactly, there are so many leaks in the TM that I don't see how it could ever build up to create negative pressure. I suppose it could just blow in, and maybe even very small amounts could be easily detectable.

I think I would give Suburban a call and talk with tech support. Absent the gas coming in the door or window, I too am confused as to why you would be smelling propane with a sealed combustion chamber. Even if your vacuum theory is right, how do you fix it? And if that's the problem, why doesn't everyone with a blowing furnace have this problem?

Also, propane is odorless. What you are smelling is an odorant, probably mercaptan. I'm not sure if that has any relevance here, since its sole purpose is to alert you to the presence of propane, but I have read that mercaptan can be absorbed into certain materials (like tank linings, pipes, masonry, etc.), so it sometimes can be detected in the absence of propane (although I seriously doubt that here).

Dave

Padgett · 10-22-2014, 09:32 AM

"I could smell the un-burnt propane" Propane itself is odorless. For safety reasons aeromatic hydrocarbons are added that you can smell in ppm (parts per million) - very low concentrations.

That said, ANY leak should be fixed.

oldstick · 10-22-2014, 10:30 AM

I'll go on record and say I knew exactly what TentCamper meant by "smelled propane".....

TrailManorMan · 10-22-2014, 10:39 AM

^me too

tentcamper · 10-22-2014, 10:54 AM

i'm going to look at it more in the spring. I just put the camper in the garage to hibernate.

The other thought I have is, when I took up the panel under the seat, while the furnace is running there is a good vacuum in the furnace cabinet. Almost like there is not enough cold are return. There is more air flow without the cover. So maybe the leak is around the actual vent tube to outside fixture. It does not take much propane to smell it.

**ShrimpBurrito** · 10-22-2014, 01:11 PM

Quote:

Originally Posted by tentcamper

i'm going to look at it more in the spring. I just put the camper in the garage to hibernate.

The other thought I have is, when I took up the panel under the seat, while the furnace is running there is a good vacuum in the furnace cabinet. Almost like there is not enough cold are return. There is more air flow without the cover. So maybe the leak is around the actual vent tube to outside fixture. It does not take much propane to smell it.

Yes, there could be something obvious that Suburban could suggest looking at. There has to be seals of some sort around that combustion chamber, and a leak at the vent tube/outside fixture junction as you suggest sounds like an even more likely culprit. Definitely would like to hear what you find come spring.

Dave