Gas/Combustion Smell from Vents

[subby1000]

We have a 2-year old Trane 80% efficient gas furnace with a 2-stage blower. We notice a gas-like smell from all vents for a short period of time immediately after the burners shut off. The smell is noticable within seconds after the burners shut off and then fades away after 15-30 seconds. That's the only time we smell it. It's not a straight gas smell; it's more of a combustion or slightly rich smell; definitely not normal.

There is no gas smell outside the furnace or anywhere else in the house, and no leak from any of the gas lines. We don't get any readings on our CO detectors, nor have any of the HVAC companies that we've had out, one of which checked the air in the ducts right above the furnace. We've also had the fire department out to check for gas and CO, and they didn't get a reading. The burners are all running fine, so it would not appear to be a crack in the heat exchanger.

Although we've had several reputable HVAC companies out, including the installer, no one can ever smell it, and no one can tell us what may be causing it. We recently learned that the flue piping was not code-compliant because it had two 90-degree elbows immediately after exiting the furnace, and that the return air boot was too small, so we had those items corrected, but the smell remains. I figure some exhaust or unburnt gas must be getting pulled into the air stream after the inducer fan shuts off, but I've checked and don't see any gaps between the blower chamber and the burner chamber. Any thoughts on what this could be? I know it's not sewer gas, but that's about it.

FYI, the furnace is located in a wide open basement and our house is 6 years old. We also have a heat pump, but never smell anything strange when it's running. Any suggestions would be greatly appreciated. Thank you.

[Twilly]

Did Twilli understand you too say no one else has ever smelled it?

[heaterman]

What was the reason for installing a new furnace in a home that was only 4 years old at the time?

[subby1000]

The original furnace was replaced because we had problems with a defective valve and reached a point where we felt the only solution was to replace the whole thing.

We've had family over who have smelled it, but the HVAC people never can.

[Twilly]

Move too Twilli's area cause you need another one, secondly some families just smell better than others.

[Roscoe]

Somehow this don't smell too good,.................. errr sound good either.

What don't any of the reputable HVAC companies have Gas sniffers or Combustion Analyzers, What ?? they smell for gas...........???

[heaterman]

Well, plenty of possibilities here but at any rate, smelling gas or combustion by products is hardly ever a good thing. pay attention to when the odor is most noticable and relay that information to the service tech. Morning or evening after an extended run time when it's cold, windy out side that type of thing.

[phbsales]

Ask your HVAC company about a post-purge kit......................


Or ask Twilli about Coleman furnaces.

[STANCILHVAC]

FOR 1 thing co2 is odorless ,maybe your getting a backdraft from a leaky return and its just musty basement odor,or is it a finished basement,maybe another faulty valve that shuts down sometimes but sometimes dont for awhile causing leaking gas?that would be a hard to remedy online --does the vent go into the chimney or what?

[Twilly]

FOR 1 thing co2 is odorless ,maybe your getting a backdraft from a leaky return and its just musty basement odor,or is it a finished basement,maybe another faulty valve that shuts down sometimes but sometimes dont for awhile causing leaking gas?that would be a hard to remedy online --does the vent go into the chimney or what?

Twilli say for 2 things so is CO

[Twilly]

Also Twill Don't think Twilli would enjoy diet Pepsi without the CO2.

[jpsmith1cm]

Probably not so much with CO. Huh?

[STANCILHVAC]

Also Twill Don't think Twilli would enjoy diet Pepsi without the CO2.

ROWDY SAYS FOR 3 THINGS HE LIKES MT.DEW ANYWAY--SO WHAT DOES IT MATTER--RICHARD OR DICK