Gas like odor from A/C inside unit but not vents


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Old 07-05-16, 07:36 PM
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Gas like odor from A/C inside unit but not vents

I've recently noticed a gas like odor as I walk by my dual a/c and furnace unit in my basement. I only really notice it when the ac is running or right after. The smell reminds me of natural gas but I had my gas company come out and they checked all the pipes and air and everything checked out. I also have explosive gas and carbon monoxide detectors right by the unit and on all floors so sounds like I'm safe there.

Even weirder is that I only smell as I walk by the unit. If I stop I can't identify the smell. I checked the A coil and although rusty and water looks to be slightly built up, I didn't see any mold or mildew. I was thinking possibly freon but would expect to smell that all the time and I read it's odorless. Also checked my floor drains to make sure the trap wasn't empty. The a/c unit works fine and no smells from the actual vents so I'm starting to think I'm just worrying over nothing or its in my head. Unit is about 14 years old. Any ideas?
 
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Old 07-05-16, 09:41 PM
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Welcome to the forums.

It sounds like the gas shut off valve may be leaking.

Can you remove the burner access door from your furnace, shoot a few pictures and post them here for us? http://www.doityourself.com/forum/el...-pictures.html

Since the gas company was already there and checked.... it may be nothing to worry about.
 
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Old 07-06-16, 02:40 PM
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Thanks! I attached a few pictures. The gas shut off valve is on the outside of the unit. Furnace was replaced this past winter and works great.

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Last edited by PJmax; 07-06-16 at 04:18 PM. Reason: reoriented/enhances first picture
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Old 07-06-16, 04:14 PM
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I enhanced (brightened) your picture of the shutoff valve.

I'd bet the ranch that the gas smell is coming from that old valve. Those type valves are known for that gas smell. I changed a similar valve on my own furnace because it had a tiny odor of gas.
 
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Old 07-06-16, 04:32 PM
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Interesting, it's a house from the 20s so a lot of the piping I would expect to be old. Would you expect to detect a gas leak from that or rather just that it stinks? I know the duke energy guy checked around it pretty good and got a zero reading.

Also, why would it only stink when ac is on? Small amount of gas getting through into blower? Is this something I need to worry about safety wise?

Sorry, new to HVAC stuff so may be asking stupid questions. Thanks for your quick responses!
 
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Old 07-06-16, 04:49 PM
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No such thing as a stupid question.

I would think that if it were an actual gas leak the gas company would have found it. The A/C running shouldn't make a leak smell worse.

I know with my valve I smelled it at random times whether the blower was running or not.

Keep an eye (or nose) on the smell and if it gets worse and does appear to be gas.... call the gas company back.
 
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Old 07-06-16, 04:55 PM
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Thank you. I appreciate your help.
 
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Old 07-08-16, 08:46 PM
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Get yourself a spray bottle of liquid leak detector and soak that ole crappy shutoff valve, you will see some bubbles no doubt. Just not leaking enough for the gas company to find it the Ethyl Mercaptan has a super strong odor, the tiniest amount will trigger a sensitive nose.
 
 

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