Gas Furnace Operation

[jdcamp]

I have a recently purchased 2007 25 foot Safari Special Edition. Was using the gas furnace the other night for the first time and the first night everything was fine but the exhast was throwing a fair amount of smoke into the air. The second night which was completely still, you could smell exhaust in the trailer and it eventually set off the carbon monoxide detector. Of couse we immediately shut everything down and vented the trailer. On the night this occurred there was absolutely no wind to carry the exhaust away from the trailer. Any experience with this kind of thing? How much smoke is normal coming out from the furnace exhaust? Thanks for the help.

[Protagonist]

The first time you fire it up every winter the furnace has to burn off the dust from the heat exchanger that has accumulated.

As for the exhaust fumes getting into the trailer, while it's generally accepted practice to leave a window cracked open for ventilation, it's important that the window be on the opposite side, as far from the furnace as you can manage, to minimize the chance for fumes to enter through a window. Also keep your roof vents closed while running the furnace, not only to control exhaust fumes, but to prevent your heated air from escaping.

Propane is a very clean-burning fuel; after burning off the accumulated dust, the only "smoke" you should see is water vapor, just the same as when you can see your breath in the cold air when you exhale. If you're still getting actual smoke, there may be some kind of obstruction that's burning inside the furnace, such as spiderwebs or even wasp's nests. For some reason, some insect and arachnid vermin is attracted to the scent of propane and they will nest inside your furnace in the warmer months if the exhaust isn't screened.

[jdcamp]

Thanks, there is definitley a sort of dark smoke coming from the burner exhaust. It was on long enough to burn any dust so there must be something else burning. I opened the compartment door and blew out the compartment and there was was a piece of an old wasp nest in there which I removed. Will have to try to clean it out better but not sure how to get into the burner, etc.

[idroba]

I would agree that probably you have something like a mud dauber nest inside your furnace which is preventing enough combustion air from circulating through and creating incomplete combustion, CO and the smoke you see.

You will probably have to remove and disassemble the furnace to find the issue. I have taken them apart and found nests near the entry air point, but also deep inside the furnace. You may get lucky and only have superficial blockage, but if you are unlucky they will have gone farther inside. Since your furnace is not too old, it should be repairable, mostly at a cost of time to find the problem.

[mayco]

Bbq mouse

[jdcamp]

Thanks. I put my shop vac up to the exhaust pipe and vacuumed it out. Got a fair amount of soot and a piece of a wasp nest. I then turned the furnace on for awhile and it was better but still some odor and a little lighter colored smoke. I hope I don't have to get the whole thing pulled out and taken apart. Will definitely have to put a screen over the exhaust. Don't know why the don't do that at the factory.

[scamp]

There was a thread awhile back regarding smoke from the furnace I think it was newer model trailers and what it was is a loose piece of duck tape touching the furnace and burning off , but this was inside the trailer and did not effect the outside exaust of the furnace , I had this same problem were the duct tape was loose and touching the furnace on my 2012 airstream I guess it was not put on properly at the factory.
Oh and on a new furnace ran for the first time you will smell something burning and its most likely oil coating burning off but don't think this effects you as your trailer is not new ,unless it's a new furnace installed , but exaust will not be black from furnace , maybe what others have suggested could be causing your problem ,mouse ,etc
Don

[idroba]

Originally Posted by jdcamp

Thanks. I put my shop vac up to the exhaust pipe and vacuumed it out. Got a fair amount of soot and a piece of a wasp nest. I then turned the furnace on for awhile and it was better but still some odor and a little lighter colored smoke. I hope I don't have to get the whole thing pulled out and taken apart. Will definitely have to put a screen over the exhaust. Don't know why the don't do that at the factory.

If you got a piece of a wasp nest, and it is still sooting, there most likely is more in there. It may require a removal and disassembly to get it all out.

They don't screen them at the factory because the furnace manufacturer does not sanction any screens over the intake/exhaust pipes and state that in their manuals. The factory can't install things contrary to the furnace manufactures recommendations for liability reasons.

If you decide to screen it after finding the problem, be sure to get the largest external screen available. That will reduce the restriction to a minimum, although still against the furnace makers recommendations.

My personal opinion is that a large basket type screen does not create much if any restriction, and is better than a nest partly obstructing the intake or exhaust.

[TinShack]

You could put a temporary screen in during the summer when insects are active and you don't use the furnace, then remove it when you use the furnace in the winter after the insects die off and before they emerge.

[jdcamp]

Thanks for all the suggestions. A temporary screen for the summer is what I have in mind or maybe just stuff a rag in the exhaust pipe for the summer to keep any wasps or other critters from entering.

[TinTin]

Originally Posted by jdcamp

Thanks for all the suggestions. A temporary screen for the summer is what I have in mind or maybe just stuff a rag in the exhaust pipe for the summer to keep any wasps or other critters from entering.

Potentially dangerous to do this!!!!

[Protagonist]

Originally Posted by jdcamp

Thanks for all the suggestions. A temporary screen for the summer is what I have in mind or maybe just stuff a rag in the exhaust pipe for the summer to keep any wasps or other critters from entering.

Absolutely do not stuff a rag in. You can find screens that attach with spring clips at Camping World, Parts66, Amazon, and others.

This is what I use (though the picture is downloaded, not a picture of mine).

[Gene]

I've used the screens on the water heater and furnace. Be careful with the spring clips because they can be difficult to attach, spring out of your hand and put a nasty scratch in the trailer surface. This is especially sure to happen when your wife is watching. After scratching the aluminum and being told about it, I attached them with mechanic's wire. Mechanic's wire will eventually rust and fall apart, replace the wire every couple of years.

I agree paper wasps or mud daubers are a greater problem than any obstruction caused by the screens. I looked for one for the fridge door, but couldn't find one.

A rag is easy to forget and should not be used, but wouldn't the flame go out when the exhaust is blocked and wouldn't that reduce the danger? Maybe the rag would catch fire if it were stuffed way in, but maybe not. Who wants to try it?

Gene

[Protagonist]

Originally Posted by Gene

I agree paper wasps or mud daubers are a greater problem than any obstruction caused by the screens. I looked for one for the fridge door, but couldn't find one.

The "equivalent opening size" of the screen is larger than the opening size of the furnace exhaust, so it produces no obstruction at all. Unlike do-it-yourself screens that are cut to fit inside the exhaust opening.