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Fresh Air Intake Vent Smell

mi26
mi26 Member Posts: 3
in Gas Heating
I dropped something on top of furnace in basement. When I reached over to get my nose went across vent in picture. Smelled slight gas. Heater hadn’t come on for about 2 hrs. Had local hvac friend look at it and couldn’t find anything wrong but did notice the slight smell as well. He didn’t do any elaborate testing though. He said it could be gas valve inside furnace not closing all the way leaving some residual gas smell if anything. Or could just be residual gas from the unit running. I’m looking to see if anyone has seen this before ? Leaving gas off. Could it be internal gas valve? Or heat exchanger? Or just residual smell from unit. Links to pics below. One is the vent I smelled gas through. Other are the tubes I was talking about.

https://imgur.com/cSBX783

https://imgur.com/1OWrVAA

Comments

  • RayWohlfarth
    RayWohlfarth Member Posts: 1,656
    I would have it checked by leak testing. If the gas valve is leaking through, it could be very dangerous.
    Ray Wohlfarth
    Boiler Lessons
    delta T
  • mi26
    mi26 Member Posts: 3
    A manometer was used at gas valve and didn’t show anything when unit went off. Soap bubble test was used on gas valve, fittings and orifice as well. Showed no bubbles.
  • HVACNUT
    HVACNUT Member Posts: 6,332
    edited October 2019
    Turn the switch off. Fill a spray bottle with water and some dish soap and spray the joints on the gas piping, outside and inside the furnace. Look for bubbles. Dont spray and electrical components.
    The furnace should be maintained yearly by a qualified tech regardless.
    How large is the equipment room or space that it doesn't need outside combustion air?
    Intplm.
  • mi26
    mi26 Member Posts: 3
    A manometer was used at gas valve and didn’t show anything when unit went off. Soap bubble test was used on gas valve, fittings and orifice as well. Showed no bubbles.

    > @HVACNUT said:
    > Turn the switch off. Fill a spray bottle with water and some dish soap and spray the joints on the gas piping, outside and inside the furnace. Look for bubbles. Dont spray and electrical components.
    > The furnace should be maintained yearly by a qualified tech regardless.
    > How large is the equipment room or space that it doesn't need outside combustion air?
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    Find someone that has a gas sniffer and knows how to use it.


    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    mattmia2
  • JUGHNE
    JUGHNE Member Posts: 11,279
    edited October 2019
    I assume that no one has put a wrench to any piping recently.
    The Mercaptan "smell agent" added to NG remains for years trapped in pipe dope used on threads. Unscrewing fittings will release the smell. Strong enough to smell across the room.
    mattmia2Alan (California Radiant) Forbes
  • mattmia2
    mattmia2 Member Posts: 10,952
    Do you smell it with the valve off?

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