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Stinky Furnace Exhaust

cthomas | Posted in Energy, Heating & Insulation on December 14, 2008 10:19am

My furnace exhaust smells pretty bad – sort of an organic smell.  Honestly it smells a bit like propane and rotten grass, or bad toe-jam, or really bad morning breath.

Its a natural gas 90+ efficiency with separate intake and exhaust PVC runs to the outside of the home through the rim joist.

I looked at the flame last night and it was bright blue, so no combustion issues.  The motor and blower seem to be working great.

Anyone have any ideas?

I suppose the next step is to take the exhaust run apart and make sure no little critters crawled in there – but it’s all glued up, so I thought I would post here first…

Thanks in advance…

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Replies

  1. ruffmike | Dec 14, 2008 10:50pm | #1

    Is there a screen on the end of the exhaust run to keep vermin out? Kind of wondering how you are smellng the exhaust, isn't it away from living space?

                                Mike

        Small wheel turn by the fire and rod, big wheel turn by the grace of god.

    1. cthomas | Dec 15, 2008 02:51am | #7

      I was thinking the same thing, and no.  No screen.  (Thus, who knows what type of critter took up residence in there over the summer.)

      The exhaust ends up outside on the back of the home under a deck landing.  It's been smelly all winter so far.  Seems to be getting worse.

      PVC is cheap, so maybe I will just take it all apart and look inside.  The total run is about 20 feet.

      I did think about the water, but with the furnace running and the exhaust being warm, any moisture would evaportate...

       

      Thanks for the thoughts!

       

       

      1. USAnigel | Dec 15, 2008 05:27am | #8

        So this is a new smell.

        disconnect at the furnace and hookup the shop vac to suck it clean!

      2. alwaysoverbudget | Dec 15, 2008 06:26am | #9

        if you think that you truly got something in there stinking,you have a much bigger problem that needs to be dealt with quickly.

        that is if it' s block you could get c.o. in the house! i'd get on this pretty quick and see.if a man speaks in the forest,and there's not a woman to hear him,is he still wrong?

      3. DaveRicheson | Dec 15, 2008 03:18pm | #10

        The exhaust ends up outside on the back of the home under a deck landing.  It's been smelly all winter so far.  Seems to be getting worse.

        Aside from the smell, your exhaust is probably located in an exclusion zone. If you have the installation or owners manual, there should be drawings showing where the exhaust pipe can not be located.

        While I doubt you will spent much time on your deck during the winter months, the wrong location can cause the gasses to carried into your home by eddie currents and drafts. That is why there are exclusion zones around windows, door, soffets, and decks.

        You may even find the drawings on the manufacturers web sit, or contact them and they will send them to you. Play it safe with your families health.

      4. DanH | Dec 15, 2008 03:24pm | #11

        Propane or natural gas?
        The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel

        1. DaveRicheson | Dec 15, 2008 08:28pm | #12

          Forgot to ask that.

          Walked by a big trailer parked in our lot this morning. The exhaust from the propane fuel generator definitely stinks a bunch more than natural gas.

          1. User avater
            Sphere | Dec 15, 2008 08:43pm | #13

            Hey, you geared up for an ICE event? Looking nasty headed our way later.Spheramid Enterprises Architectural Woodworks

            Repairs, Remodeling, Restorations

             

            They kill Prophets, for Profits.

             

             

          2. DaveRicheson | Dec 17, 2008 02:17pm | #17

            Looks like the big ice storm missed us. Kind of split and went north and south of us. I think you all got more than we did.

            I think our contractor spread more salt on the parking lot than the total accumulation of ice in the whole metro area.

            Iike walkin on marbles, and our back entrance has a white "skid mark" all the way to the elevators. That stuff is great on a parque floor.

          3. User avater
            BillHartmann | Dec 17, 2008 06:37pm | #18

            We are getting an freezing rain storm tomorrow. With any "luck" you might be it around Saturday.When I went to Speed I had coop twice at Allis Chalmers in Milwaukee.I remember the same more salt than snow conditions..
            William the Geezer, the sequel to Billy the Kid - Shoe

          4. DaveRicheson | Dec 18, 2008 12:21am | #21

            With any "luck" you might be it around Saturday.

            Gee, thanks for that Bill. I'm on call untill after the holidays. Means I could spending some not so quality time away from the family this season.

            BTW, welcom back.

          5. User avater
            BillHartmann | Dec 18, 2008 12:29am | #22

            With the welcome back I will stand outside tomorrow fanning some plywood to try and deflect the storm.But my aim is not that good..
            William the Geezer, the sequel to Billy the Kid - Shoe

          6. cthomas | Dec 21, 2008 05:37pm | #23

            Furnace update:

            Turns out the secondary heat exchanger was shot.  I am now the proud owner of a   97% efficient, variable speed, modulating burner...

            Maybe I should put racing stripes on it?

            Thanks to all for the insight.  What a great Christmas present...

      5. User avater
        kurt99 | Dec 15, 2008 11:09pm | #14

        For a 90%+ unit to operate properly, the gas leaving the heat exchanger below its dew point so water will condense out in the heat exchanger and it will continue to condense out as it passes through the exhaust line because it continues to cool. It will be wet inside every time the furnace runs. This is perfectly normal but the exhaust line must be installed so it drains back to the furnace without low spots that will trap water.

      6. sledgehammer | Dec 16, 2008 01:16am | #15

        "I did think about the water, but with the furnace running and the exhaust being warm, any moisture would evaportate..."

        No.

  2. alwaysoverbudget | Dec 14, 2008 10:56pm | #2

    before i started dissassembling pvc,unless it's a really short run, i would look at getting a sewr guy out there to run a camera thru there. you can buy one but they are pretty expensive.

    if a man speaks in the forest,and there's not a woman to hear him,is he still wrong?

  3. sledgehammer | Dec 15, 2008 12:00am | #3

    They do put out a fair amount of water. Maybe you have a low spot that's not draining?

  4. USAnigel | Dec 15, 2008 12:30am | #4

    They do smell nasty! My Dad in the UK said the same thing about his 90%+ unit.

  5. 802Mike | Dec 15, 2008 12:38am | #5

    Is this a new install? If not, has it always been like this? Was it set-up with instruments or "plug-n-pray"?

    I've smelled what seemed like burning rubber and it goes away. Figured it was some PVC filings left in the pipe.

  6. DanH | Dec 15, 2008 02:06am | #6

    Propane or natural gas? If propane, check to see if your tank is empty.

    Did the unit just fire up for the first time this winter? It'll take several hours of running time to burn off the odors that seem to accumulate while it's shut down.

    The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
    1. User avater
      Sphere | Dec 16, 2008 01:35am | #16

      When I have stinky exhaust, my wife says it's bad gas.Spheramid Enterprises Architectural Woodworks

      Repairs, Remodeling, Restorations

       

      They kill Prophets, for Profits.

       

       

  7. woodway | Dec 17, 2008 09:19pm | #19

    Many commercial gas supplies come "odorized" so that if there's a leak, you'll be able to smell it. Natural gas and propane are odorless. Usually they put a bit of H2S or sulfur containing organics in called "thiols" which smell and when burned could possibly be the source of your odor.

  8. User avater
    rjw | Dec 17, 2008 09:37pm | #20

    As mentioned, likely a low spot in the exhaust flue and nasties growing in the condensate.

    >>I looked at the flame last night and it was bright blue, so no combustion issues.

    For the record, flame color does not indicate quality of combustion - I've tested plenty of "blue flames" with CO output ay too high.


    "Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."

    Howard Thurman

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