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Thread: Combustible gas leak detection
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04-20-2012, 05:18 AM #1
Combustible gas leak detection
I have been using a Tiff8900 and have 3 times this year pointed out leaks to clients that when the HVAC guy arrives says there is no leak. Usually joints, or gas control valves. I have never been there at the time the HVAC guy is there.
Is there a possibility for a false positive? I just bought some bubble leak as a back up. But really, does that make sense? Using a $2 bottle of bubbles to confirm what your $200 tester indicated.
Any thoughts?
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04-20-2012, 05:43 AM #2
Re: Combustible gas leak detection
It does not matter what the bubbles cost, compared to the cost of the electronics. The bubbles are a physical indicator, and the bubbles don't care what your electronic toys have to say. If gas is escaping above atmospheric pressure, the bubbles will form, regardless of what the sniff test says. Maybe the HVAC tech simply does not consider the amount of gas being detected, to be a problem. If the HVAC guy says it's not a problem, recommend the client contact the gas utility for a FREE inspection. In fact, recommend a gas utility inspection as a matter of course, when a leak is detected.
Last edited by Jimmy Roberts; 04-20-2012 at 06:42 AM.
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04-20-2012, 05:44 AM #3
Re: Combustible gas leak detection
Bill, Its not a bad idea to use another method to backup your initial findings! Could you detect a gas smell when you found the leaks?
James Bohac
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04-20-2012, 06:10 AM #4
Re: Combustible gas leak detection
Have the unit tested and calibrated.
' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.
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04-20-2012, 06:13 AM #5
Re: Combustible gas leak detection
About 1/2 the time I did smell gas.
You can't use bubbles on the burner supply fom the gas valve. I sometimes get an indication of gas leaking past the gas control valve. 1 HVAC tech said there will always be a residual amount of gas in the burner supply.
Seem's unreasonable. Thoughts?
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04-20-2012, 05:02 PM #6
Re: Combustible gas leak detection
Residential gas lines usually run about 4 oz of pressure so if the bubble test fails I would say there is a leak.
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04-21-2012, 01:11 PM #7
Re: Combustible gas leak detection
You need to do a search on this site as this has been discussed many times at length. You can get false positives from soap bubbles, pipe dope, thread cutting oil, greasy finger prints, etc.
Keep the fire in the fireplace.
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04-21-2012, 03:36 PM #8
Re: Combustible gas leak detection
My gas leak detector is my nose. I smell gas leaks quite often. At this mornings inspection, I pulled the access panel off off finished wall at the front of the basement and was immediately greeted with a big whiff of gas. The problem (for the home owner) was that the gas line penetrated the foundation wall at ceiling level and the access panel was at the bottom of the finished wall. He was going to have to open as much of the ceiling/wall area as necessary to have the leak fixed.
"It takes a big man to cry. It takes an even bigger man to laugh at that man". - Jack Handey
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04-21-2012, 06:21 PM #9
Re: Combustible gas leak detection
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04-21-2012, 08:56 PM #10
Re: Combustible gas leak detection
It is standard practice to use bubbles to check after the sniffer. I also don't check for leaks while the appliance is running.
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03-16-2015, 08:18 AM #11
Re: Combustible gas leak detection
I use my nose first, then confirm with my Tiff. I will call utility myself if house is vacant.
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03-16-2015, 09:24 AM #12
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03-16-2015, 03:07 PM #13
Re: Combustible gas leak detection
The beatings will continue until morale has improved. mgt.
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03-16-2015, 04:01 PM #14
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03-16-2015, 04:50 PM #15
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03-16-2015, 05:11 PM #16
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03-16-2015, 06:40 PM #17
Re: Combustible gas leak detection
This is what Vern is explaining:
- https://www.youtube.com/watch?v=n4DDnoMAHY8
Generally good information, but incorrect on where to vent the regulator to .
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03-17-2015, 08:23 PM #18
Re: Combustible gas leak detection
ANSI z21.88 allows trace gas leakage at specific rates:
235cc/hr. through the main operator of the valve to the burner at 3/4 psi and 200 cc/hr. through the seals of the valve at 3/4 psi. Note that most gas appliance run at 1/4 psi or less inlet pressure.
Every time the pressure changes the diaphragm moves as it seeks to equalize against atmospheric pressure by the vent. Some trace leakage here is common. It mimics flatulence or a burp. A sustained gas discharge at a vent is a sign of a ruptured diaphragm. In that case, not only should the valve be replaced but the cause determined and corrected or you'll just have to replace another valve.
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Last edited by Bob Harper; 03-17-2015 at 08:31 PM.
Keep the fire in the fireplace.
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03-17-2015, 08:36 PM #19
Re: Combustible gas leak detection
I am finding quite a few (est. 3-5%) MP regulator valves that are installed in attics leaking a small amount at the vent. I don't think I have found any leaking in a crawlspace. The furnace or water heater has not been firing at the time I have noticed the leaks. I can always smell the leak and then verify exact location with sniffer. Is the high temp of the attics causing the diaphragm to fail?
The beatings will continue until morale has improved. mgt.
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03-17-2015, 09:27 PM #20
Re: Combustible gas leak detection
You guys realize this post is 3 years old, right?
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03-18-2015, 03:47 AM #21
Re: Combustible gas leak detection
Bob,
Do you have a reference which addresses the venting pipe when the vent is extended to beyond a combustion/ignition source?
I.e., slope up or down (depends on propane or natural I suppose) or installing a trap in the vent (running across, down, across, back up, etc)
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