"sewer" smell from the ductwork

[Brent Ridley]

It happens to all ages of systems, new and old. It generally happens in the south but I wouldn't rule it out just due to geographical location.

Dirty sock smell happens when swapping from heat to cool. So she says it happens when aux heat is operational - My guess it is happening in defrost which will turn on the aux heat (she sees this displayed) and it shifts into cool momentarily.

When you return, force a defrost and then go sniff around. That's how I duplicate the issue when it's a complaint. I attached a PDF below.

http://wittichen-supply.com/wp-conte...k-Syndrome.pdf

[jtrammel]

I've had dirty socks problems myself, might want to check that. I've also had baked snake, mouse, rats etc on strips trying to stay warm.

[OldSchoolMech]

I'd be looking for something dead.

[palmeri]

Most of the time the strips are downstream of the coil.

True, but most of the time the coil can "see" the strips. Just a thought. I would defintely investigate that coil and pan first.

[kls-ccc]

I'd have to agree with Brent. I had one that would smell when it went through defrost, the rest of the time it was fine. Ended up swapping coils with a dipped coil and the issue went away.

[fro]

Look up dirty sock syndrome. Sound exactly like what you have.

I've been battling it for years in my climate. It's coming from the evap coil. They make special cleaners. I've had about 50/50 success with those. The best solution is just to change the coil.

The smell comes from a bacteria that grows on the coil and you only smell it when swapping from heat to cool (or defrost).

I have had a few dealings with this as well. I know at one point Trane made a special factory "coated" coil to prevent buildup of bacteria. Unfornately this was after a 3k dollar bill from an indoor hygenist.

[pilotlight]

simple check. If the unit is in a basement. look for a floor drain. Sometimes. the water will evaporate from the trap. The smell will not be noticeable with just fan running. Add the air being heated by the strips you have sewer smell every where,.

Or some one pooped or peeed in the duct work

[crmont]

Where there's duct board there's mouse piss.

[Jesjen829]

UV lights claim to get rid of "dirty sock syndrome". A while back I had a air handler in a crawl space and the customer complained of a mold smell. Installed a uv light and she said the smell went away. I personally thought it was in her head but some people are more sensitive to certain smells.