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Boddhisattvha's avatar
Boddhisattvha
Explorer
Sep 18, 2013

Furnace Exhaust question

Hey all,
I'm pretty sure I already know the answer to this but there is a lot of really knowledgeable folks on here so I'm looking for a second opinion or suggestions.

1985 Hi Lo and I'm pretty sure the furnace is the original. I didn't use it at all last winter and just started turning it on again recently. I was outside training my black water tank while the furnace was running and I smelled propane. Faint but definitely propane.
Now this is only outside the trailer. There is no smell whatsoever inside and after investigating it is coming directly from the exhaust port of my furnace.

It's a Suburban furnace that lights itself so there's no pilot I can adjust. Is there some other adjustment I can make to it? Is the smell in the exhaust normal? I'm pretty sure I should never smell propane but I could be wrong. Or do I just need a new furnace altogether? I've replaced just about everything else.

Just to be clear
1. Only smells when the furnace is running.
2. Only smells outside the rig
3. Smell is faint but definite.
  • Bumpyroad's avatar
    Bumpyroad
    Explorer
    Sep 18, 2013
    Boddhisattvha wrote:
    Hey all,
    I'm pretty sure I already know the answer to this but there is a lot of really knowledgeable folks on here so I'm looking for a second opinion or suggestions.

    1985 Hi Lo and I'm pretty sure the furnace is the original. I didn't use it at all last winter and just started turning it on again recently. I was outside training my black water tank while the furnace was running and I smelled propane. Faint but definitely propane.
    Now this is only outside the trailer. There is no smell whatsoever inside and after investigating it is coming directly from the exhaust port of my furnace.

    It's a Suburban furnace that lights itself so there's no pilot I can adjust. Is there some other adjustment I can make to it? Is the smell in the exhaust normal? I'm pretty sure I should never smell propane but I could be wrong. Or do I just need a new furnace altogether? I've replaced just about everything else.

    Just to be clear
    1. Only smells when the furnace is running.
    2. Only smells outside the rig
    3. Smell is faint but definite.


    I know nothing about this at all, but sounds like incomplete combustion. have it checked by a professional quickly.
    bumpy
  • WoodGlue's avatar
    WoodGlue
    Explorer
    Sep 18, 2013
    There is a minuscule chance that it could be some burnoff, but I'd still do what bumpy said and have it checked by a professional.

    WoodGlue
  • SWD's avatar
    SWD
    Explorer
    Sep 18, 2013
    "training my black water tank" sounds interesting! Yeah....get your furnace checked out. Shouldnt be smelling propane there.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Sep 18, 2013
    First, one thing I am 100% sure of is you did not smell propane. it is odorless.

    Because it is odorless the propane people add an "odorant" to it, this is what you smell. It is there for your safety and to be honest, this is a good thing.

    Normally. this "Odorant" is completly destroyed by fire when the burner ignights, and thus you do not smell it, however there are several conditions where it might survive and be noticed.

    ONe: if the burner is out of adjustment and not burning hot enough

    Two: If the tank is near empty, sometimes the odorant concentrates

    Three: if the factory (Refinery) put too much in.

    Four through many: Other reasons I do not know well enough to type about.

    That said.. You do need to figure out the cause of the smell and address it.
  • Dave_H_M's avatar
    Dave_H_M
    Explorer II
    Sep 18, 2013
    I think you may have something that is normal there if the exhaust is clean.

    I am gonna sniff mine this winter. :h
  • camperpaul's avatar
    camperpaul
    Explorer
    Sep 18, 2013
    Boddhisattvha wrote:
    -- snip --
    It's a Suburban furnace that lights itself so there's no pilot I can adjust. Is there some other adjustment I can make to it? Is the smell in the exhaust normal? I'm pretty sure I should never smell propane but I could be wrong. Or do I just need a new furnace altogether? I've replaced just about everything else.

    Just to be clear
    1. Only smells when the furnace is running.
    2. Only smells outside the rig
    3. Smell is faint but definite.

    First, propane has no smell,
    Superior Plus Energy Services wrote:

    Clicky Propane is a colorless and odorless gas that is not itself toxic. Because propane has an odor additive (ethyl mercaptan - a scent similar to rotten eggs) you can ...

    This additive does not fully combust and gives an odor to the exhaust, so what you are smelling is the exhaust.
  • Boddhisattvha's avatar
    Boddhisattvha
    Explorer
    Sep 18, 2013
    Thanks all. Apparently I need to be much more specific in my posts. :) I know propane is odorless and that what I smell is the additive. This is however the first time I have seen or heard anyone mention that you could smell the additive without there being excess propane in the air also.
    Bumpy wrote:
    I know nothing about this at all, but sounds like incomplete combustion.

    This was my first thought as well as I had this problem with my water heater before I replaced it. This is why I was wondering if there were adjustments that could be made or not.
    SWD wrote:
    training my black water tank
    Oops, but I actually would like to train it to clean and drain itself out. :)

    way8yxm wrote:
    Two: If the tank is near empty, sometimes the odorant concentrates

    Actually I was scraping the very bottom of one my 30lb tanks. I just noticed that my regulator switched over to the other tank this morning. I will definitely recheck the exhaust tonight when I run the furnace and see if the smell is still present. Thanks for that.

    Camperpaul wrote:
    This additive does not fully combust and gives an odor to the exhaust, so what you are smelling is the exhaust.


    Interesting. So you've noticed this with your rig as well? It sounds reasonable to me anyone wanna second?

    Thanks everyone!
  • dougrainer's avatar
    dougrainer
    Nomad
    Sep 18, 2013
    1. Correctly mixed LP to Air will NOT smell like LP at the exhaust.
    2. You do not state model of furnace, but if the furnace has NEVER been pulled and checked/cleaned in 30 years, the odds are the burner needs cleaned and there may be some insect nests inside restricting the fresh air intake for complete LP air combustion.
    3. Getting low in the LP tank does NOT increase the amount of ethyl mercaptan (LP odorant agent) in the LP system.
    4. If you have the NT series of Suburban, then the cast iron burner is probably clogged with rust. To fix this model burner, you pull the burner and use a Hack Saw blade to clean out the slots in the burner. The NT also has a screw type air adjustment. If running RICH (lack of air) you should also see black soot build up on the outside exhaust vent assbly.
    5. ALL LP sold and produced in the USA and Mexico has the Odorant added at refinement. There is NO LP sold without the odorant. Doug

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