Gas smell from furnace

[johnnylighton]

I am having this same problem with my Rheem furnace. After it shuts off, there is a gas smell in a certain part of the house. My electronic detector reported combustible gas where I am smelling it, but its sensitivity is greater than what the gas co. uses. The gas co. did not detect the gas.

dbates, did you ever solve your problem? If so, please let us know how you did it - thanks! :)

[jpsmith1cm]

johnnylighton

I started a new thread for you.

[johnnylighton]

Thanks very much, jpsmith. :)

To fill everyone on this fine site in with my situation, I have the same phenomenon that dbates had and that one other poster also suffered: there is a smell of gas shortly after my furnace, a Rheem, shuts off.

For me, it's mostly in a certain room and is unmistakeable. I purchased a combustible gas detector for $135 from Amazon that detected combustible gas in the places I smell it in that room, in (what the detector reported) was strong concentrations, after the furnace shut off. It also detected gas coming from 4 of the 5 registers. The strongest gas is near the floor in that room. I could not smell it from the registers with my nose.

But the detector I purchased is not in the same class as professional detectors, and there is no way to set the sensitivity. It's much more sensitive than what the gas co. uses. So I asked the gas co. to come out twice when I smelled (and detected) the gas. Their detector did not register gas, so they told me there was no leak. They also shut the valves to all our gas appliances and pressurized the line, and told me we don't have a leak in the line. I returned the detector because I could not set a base sensitivity.

The dbates thread started included a link to a Honeywell PDF that states there is "trace leakage" of gas after some of their valves shut off, and that a slight smell of gas after the furnace turns off is normal. That document is here: http://hphaa.com/knowledge/FAQs/gas-valve-leakage.pdf

But this is more than a slight problem for us, and I worry about the effects of my family continually breathing this gas.

There is also a small possibility that it's some other type of combustible gas. But that wouldn't explain why the smell is there after the furnace shuts off.

Thank you for any suggestions or solutions!

[tostaos]

1. your nose is a better gas leak detector than any gas detector available.
2. A gas valve is allowed to leak, but I would not tolerate it and replace it.

[hvacvegas]

Thanks very much, jpsmith. :)

To fill everyone on this fine site in with my situation, I have the same phenomenon that dbates had and that one other poster also suffered: there is a smell of gas shortly after my furnace, a Rheem, shuts off.

For me, it's mostly in a certain room and is unmistakeable. I purchased a combustible gas detector for $135 from Amazon that detected combustible gas in the places I smell it in that room, in (what the detector reported) was strong concentrations, after the furnace shut off. It also detected gas coming from 4 of the 5 registers. The strongest gas is near the floor in that room. I could not smell it from the registers with my nose.

But the detector I purchased is not in the same class as professional detectors, and there is no way to set the sensitivity. It's much more sensitive than what the gas co. uses. So I asked the gas co. to come out twice when I smelled (and detected) the gas. Their detector did not register gas, so they told me there was no leak. They also shut the valves to all our gas appliances and pressurized the line, and told me we don't have a leak in the line. I returned the detector because I could not set a base sensitivity.

The dbates thread started included a link to a Honeywell PDF that states there is "trace leakage" of gas after some of their valves shut off, and that a slight smell of gas after the furnace turns off is normal. That document is here: http://hphaa.com/knowledge/FAQs/gas-valve-leakage.pdf

But this is more than a slight problem for us, and I worry about the effects of my family continually breathing this gas.

There is also a small possibility that it's some other type of combustible gas. But that wouldn't explain why the smell is there after the furnace shuts off.

Thank you for any suggestions or solutions!

Call a contractor. It's possible that you have a crack in the heat exchanger, and a leaking gas valve. Or just a leaking valve.

Either way, call a furnace man.

[johnnylighton]

Thanks for your responses. I forgot to mention: when we bought the house, the sellers purchased a home warranty. I called for service two times and both times the heating contractor said they could not detect a gas leak from the valve or elsewhere. I asked them to send a different service technician for the second call, so we'd have another set of minds thinking about it. The first time they replaced the pilot assembly because that's what the gas co. told me was wrong initially, and the second time they checked the furnace and said it's fine. This home warranty has since expired.

I think the problem is that there is unburnt gas remaining in the furnace, or continuing to flow into the furnace for a short time, after it turns off each cycle. Somehow this is being vented into the house.

[Mr Bill]

The first time they replaced the pilot assembly because that's what the gas co. told me was wrong initially.

This furnace has a pilot? how old is it, standing pilots went away I think back in 1992/1993 for most mfg.

[johnnylighton]

It's hard to say how old it is. There's a lighting instructions sticker dated 1991 and another dated 1992, so either the furnace itself or the valve only is probably from that time period.

[johnnylighton]

Problem solved! After spending $$$$ and many hours over the last year trying to figure out where the gas smell in our daughter's room is coming from, I was outside yesterday between our house and the house next door. I smelled gas, and it turns out they have good-sized a gas leak coming out of their crawl space where some gas lines are, which carries over to our house and gets trapped against our house. It then goes into our crawl space through the vents, and up into our daughter's room.

When our heater is on, there is positive pressure in her room. After it turns off, the room is no longer pressurized and more gas can seep in from below. That’s why I associated the gas smell with our heater turning off.

I’m glad I know what’s happening now, but rather ticked that I have gone through the time and money dealing with this when it wasn’t even our problem.

Thank you all for being here and for your kind efforts to help solve this problem. :cheers:

[skippedover]

The gas company should have found that problem. Just walking around outdoors they should have found it.