Open Probe Hole - CO risk?
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  1. #1
    Join Date
    Sep 2008
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    7

    Open Probe Hole - CO risk?

    Hi,

    Our family recently stayed at a newer home in Maine that used oil heat and hot water. The home had a constant odor of oil combustion, apparently due to heating the hot water, but the odor became very strong when the heat was turned on due to unseasonably cool weather.

    I examined the heating system and observed a hole about ½ inch diameter in the exhaust vent, likely drilled out for a test probe, close to the burner. This was where the odor was coming from.

    The owner insisted the open probe hole was not a cause for alarm, was common practice, and “helped the exhaust gases vent easier” through the exhaust piping.

    I think he is mistaken, and Carbon Monoxide poisoning would be a risk.

    I’d like to hear the experts weigh in.

    Thanks

  2. #2
    Join Date
    Jun 2005
    Location
    The Gray Northwest
    Posts
    661
    If you're smelling "oil combustion", it could be something more involved than a test hole in the stack. You have good reason to be concerned and I would not hazard a guess without actually being there with test equipment in hand.

  3. #3
    Join Date
    Sep 2008
    Posts
    7
    Thanks Big Johnson.

    The rest of the vent pipe and the burner exhaust are all well sealed with high-temp sealant. The open test probe hole seems to be the only spot that emits the smell.

    Is it "common practice" to leave the test probe hole open? And could that be a source of CO?

    The system is ~ two years old, but has seen little use for heating.

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    If the system was venting correctly, air would be sucked IN through the test hole, rather than exhaust gases leaking out...
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Sep 2008
    Posts
    7
    Thanks Mark.

    You could put your hand an inch or so above the test hole and feel the exhaust coming out of the hole. Also, when the burner was started, you would see a puff of smoke come out of the hole.

    Why should the air be sucked IN rather than exhaust gases leaking out? Wouldn't the exhaust pressure at the burner be higher than the pressure at the outside end of the vent pipe?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,611
    You make it hard to determine if the hole is on the flue pipe, or above the burner and combustion chamber.

    Most resi oil burners are negative pressure draft systems, so the hole should be drawing air in at either location. From over fire to breech, its only a .02" difference on most systems.

    Some are positive pressure, and will blow out fumes at either location also.

    I'd say its time thay owner had units serviced.
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  7. #7
    Join Date
    Nov 2007
    Location
    Austin Texas
    Posts
    54
    Quote Originally Posted by erndawg View Post
    Hi,

    Our family recently stayed at a newer home in Maine that used oil heat and hot water. The home had a constant odor of oil combustion, apparently due to heating the hot water, but the odor became very strong when the heat was turned on due to unseasonably cool weather.

    I examined the heating system and observed a hole about ½ inch diameter in the exhaust vent, likely drilled out for a test probe, close to the burner. This was where the odor was coming from.

    The owner insisted the open probe hole was not a cause for alarm, was common practice, and “helped the exhaust gases vent easier” through the exhaust piping.

    I think he is mistaken, and Carbon Monoxide poisoning would be a risk.

    I’d like to hear the experts weigh in.

    Thanks
    Very very very...doubtful. You have a better chance at winning a trillion dollar lotto ticket and being elected in this primary 2008!!! than being killed or injured by this "Probe" hole! It would take about 30 seconds to heat up and all combustibles would go right up the flue! Not out of your Probe hole!....lol LMAO!!!

  8. #8
    Join Date
    Nov 2003
    Location
    Montreal, Qc.
    Posts
    775
    A conventional chimney properly sized and well maintained will draw a negative pressure.
    A good example is when you see a barometric damper on a chimney.
    If you put your hand near it you will see that there is room air being drawn in and no combustion air coming out.
    What type of heating system was this? Warm air or hot water radiators?

  9. #9
    Join Date
    Sep 2008
    Posts
    7
    Hi beenthere.

    The hole is located in an elbow, about 1 foot from the flue connector/boiler vent collar.

    I've never been in a house with such a strong burner smell; that's what prompted me to look at the installation. I could feel exhaust coming right out of that probe hole.

  10. #10
    Join Date
    Sep 2008
    Posts
    7
    Hi thump_rrr.

    There is no chimney in this installation; it is direct vent.

    The system is hot water radiator.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,611
    It should be plugged.
    If the blower is before the hole it will blower out.
    If it uses an inducer, then it shouldn't blow out the hole, and the unit needs service.
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  12. #12
    Join Date
    Jun 2005
    Location
    The Gray Northwest
    Posts
    661
    If your burner and flue are set up correctly, you should not get over 100 ppm of CO ANYTIME during start up, run or shut down. Oil fired boilers are a bit touchy when it comes to nozzle type and spray pattern. There could be a problem with flame impingement if you're seeing smoke and smelling it. Your service tech needs to test for CO and smoke. It's the only way to know what's going on or at least have a starting point.

  13. #13
    Join Date
    Sep 2008
    Posts
    7
    Thanks again Big Johnson.

    I contacted the manufacturer and got this response:

    With any positive pressure vent, an opening in the vent pipe can “spill” flue gases into the home. The test port should be sealed. Health concerns can be an issue if the oil burner combustion is not correct.

    So, DavidInAustin, where's my trillion dollar lotto ticket and my name in the 2008 ballot?

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